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This Book is the property of the 
 General Electric Company and must 
 be returned to the Assistant General 
 Foreman when you leave the Testing 
 Department. 
 
No. 
 
 Instructions 
 
 FOR 
 
 Testing Electrical Apparatus 
 
 Copyright 1914 
 by General Electric Company 
 
 GENERAL ELECTRIC COMPANY 
 
 TESTING DEPARTMENT 
 SCHENECTADY, N. Y. 
 
 June, 1914 No. Y-435 
 

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 QCU375647 
 
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TABLE OF CONTENTS 
 
 CHAP. 
 
 PAGE 
 
 Introduction 
 
 
 
 
 
 4 
 
 1 Testing Equipment 
 
 
 
 5 
 
 2 The Use and Care of Instruments 
 
 
 
 24 
 
 3 Assembly of Machines for Test 
 
 
 
 58 
 
 4 Preparation of Apparatus for Test 
 
 Inspec 
 
 tion 
 
 
 Wiring; Observations During Operation 
 
 
 98 
 
 5 Testing Records 
 
 
 106 
 
 6 Methods of Conducting Standard Tests 
 
 
 
 108 
 
 7 Direct Current Generators .... 
 
 
 
 136 
 
 8 Direct Current Motors 
 
 
 
 
 
 157 
 
 9 Alternating Current Generators 
 
 
 
 
 
 172 
 
 10 Synchronous Motors 
 
 
 
 
 
 183 
 
 11 Synchronous Converters . 
 
 
 
 
 
 190 
 
 12 Induction Motors 
 
 
 
 / 
 
 
 208 
 
 13 Steam Turbines 
 
 
 
 
 
 227 
 
 14 Marine Engine Sets . 
 
 
 
 
 
 285 
 
 15 General Electric Test Tracks . 
 
 
 
 
 
 300 
 
 16 Blowers 
 
 
 
 
 
 305 
 
 1 < Air Compressors 
 
 
 
 
 
 314 
 
 18 Voltage Regulators . 
 
 
 
 
 
 318 
 
 19 Industrial Control Apparatus , 
 
 
 
 
 
 343 
 
 20 Mining and Industrial Locomotive 
 
 s 
 
 
 
 
 353 
 
 21 Porcelain Insulators 
 
 
 
 
 
 358 
 
 22 Train Control Apparatus 
 
 
 
 
 
 360 
 
 23 Projectors ..... 
 
 
 
 
 
 . 373 
 
 24 Transformer Tests . 
 
 
 
 
 
 . 383 
 
 25 Calculation Sheets 
 
 
 
 
 
 . 421 
 
 Nomenclature .... 
 
 
 
 
 
 . 459 
 
 Index 
 
 
 
 
 
 . 463 
 
GENERAL INSTRUCTIONS FOR TESTING 
 
 Introduction 
 
 This book is intended to give a general outline of the methods 
 and precautions to be followed in test. Every one making tests 
 must become familiar with its contents, and will be held respon- 
 sible for carrying out tests in accordance with the methods 
 and regulations outlined. If, after reading the description of any 
 test, the tester is doubtful about specific points, he should refer 
 the matter to the Head, or Assistant Head of the Section for 
 further instructions before undertaking the work. 
 
 Instructions regarding wiring, starting, and operating 
 machines as given in this book must be followed out carefully 
 and conscientiously, and under no circumstances will deviations 
 be allowed unless permission has first been received from those 
 in authority. The importance of carefulness must be realized 
 at the outset, since practically all accidents likely to happen to 
 men or apparatus are due to. carelessness or lack of appreciation 
 of operating conditions. Any man doing careless work, or taking 
 any risks that may have serious results, renders himself liable 
 to discharge. No one must handle any wiring, connect or operate 
 any switchboard or apparatus unless he is entirely familiar with 
 all the conditions having reference to the test. In addition to 
 being thoroughly familiar with the contents of this book, every 
 one is expected to keep himself informed regarding instructions 
 that are issued from time to time by the Heads of the Testing 
 Department. Such instructions are posted, when issued, on the 
 various section and general bulletin boards provided for that 
 purpose. 
 
 
CHAPTER 1 
 
 TESTING EQUIPMENT 
 
 Electrical Power 
 
 In order to test apparatus under operating conditions it is 
 necessary to provide power at various voltages and frequencies 
 so that either direct current or alternating current apparatus 
 may be readily operated. Direct current power in the Testing 
 Department is obtained either direct from the steam plants in 
 the works located in Building No. 13 and Building No. 61, or 
 from synchronous motor-generator sets installed in the various 
 testing sections, the motors of which operate from the 40 cycle 
 alternating current shop system. The regular direct current 
 shop circuits furnish power at 125 volts, 250 volts and 500 volts. 
 By using other shop generator sets connected in series with the 
 above circuits, intermediate and higher direct current voltages 
 may be obtained where testing conditions so require. These 
 shop generators are commonly known in the Testing Depart- 
 ment as "boosters" or "exciters." These generators alone may 
 be used for furnishing small and moderate amounts of power 
 at variable voltages and where close and variable voltage 
 control is required. The regular shop circuits carry a fluctuating 
 factory and railway load and, therefore, cannot be relied upon to 
 give close voltage regulation. The latter must be used, however, 
 wherever large amounts of power are required, in which case the 
 voltage regulation must be effected by means of shunt boosters 
 in series, the fields being controlled so as to maintain the proper 
 terminal voltage. 
 
 Direct current power above 500 volts is used chiefly for the 
 testing of high voltage direct current railway motors, and is 
 obtained either by boosting the 500 volt shop circuit by an aux- 
 iliary generator or by means of a 1200/2400 volt 1000 kw. three 
 unit set. In all cases when using a "booster" where it is not 
 necessary to have one side of the 1200 volt circuit grounded it 
 should be so wired that there will not be more than 600 volts 
 between either side of the circuit and ground, since the 500 volt 
 shop circuit is permanently grounded on one side. This con- 
 dition can be readily obtained by connecting the boosting gen- 
 erator to the grounded side of the shop circuit. It must be under- 
 stood in this connection that, in all testing work, no ground is to 
 be used as a return circuit; that is, all circuits must be metallic. 
 The 250 volt shop circuit has a grounded neutral; the 125 volt 
 shop circuit is obtained between either side of the 250 volt cir- 
 cuit and the grounded neutral. All direct current shop circuits 
 are wired through circuit breakers and switches permanently 
 mounted on switchboards in each testing section. These circuit 
 breakers and switches control the whole power in their section; 
 they must, therefore, all be opened whenever power is no longer 
 required. 
 
Each of the principal testing sections is equipped with a 
 number of small direct current generators capable of giving a 
 variable voltage for testing work which are known as "exciters," 
 because they are used frequently for field excitation. These 
 generators are direct motor driven, steam turbine driven, 
 engine driven, or belted sets. Turbine driven sets consist of a 
 Curtis turbine driving one or two generators. When the turbine 
 drives two generators, the switchboard is arranged so that 
 the two armatures can be connected in series or multiple. 
 Belted sets are considered as temporary testing sets and are only 
 used in emergency, since their use requires greater care and 
 attention. Their operation is also a possible source of danger, in 
 consequence of the possibility of slipping or breaking belts, etc. 
 
 When an exciter runs in series with a power circuit in order 
 to "boost" or "buck" the voltage the following points require 
 careful consideration. Under no circumstances must the source 
 of driving power be disconnected while the exciter carries load. 
 Therefore, no machine must ever be used in such cases unless it 
 is equipped with a speed limiting device in good working order, 
 which will automatically open the circuit breaker of its armature 
 circuit, should the machine begin to operate at excessive speed. 
 Particular care should always be taken to see that all safety 
 devices, in operation with such machines, are in good working 
 condition before using them. All permanently installed motor- 
 generator sets have a speed limiting device and low voltage 
 release installed on the motors and generators. These are 
 wired in series, so that in case the speed rises suddenly, both 
 motor and generator circuit breakers will be automatically 
 opened and the set shut down. For the same reason, if the 
 power supply from which the sets are driven fails all breakers 
 will be opened automatically. On direct current turbine driven 
 sets the circuit breaker tripping coils are wired so that, when 
 the emergency governor operates, their circuits are broken and 
 the breakers in the generator armature circuit are opened. 
 
 Turbine driven generators should not be used to "buck" the 
 shop voltage, since engine driven and turbine driven sets rely 
 only on their friction and windage losses to prevent their 
 speed from increasing when the direct current generator is 
 "motoring." 
 
 Measurement of ohmic resistance is one of the most common 
 tests and it frequently requires much skill to obtain consistent 
 results. Special measuring booths are located in the various 
 testing sections, fitted with measuring sets provided with 
 D'Arsonval galvanometers. The resistance bridges and resist- 
 ances used are especially adapted to the work. The measuring 
 sets are supplied with storage batteries to furnish current for 
 making the measurements. Care must be taken when charging 
 the batteries to see that they are not charged at too great a rate, 
 also that a high discharge rate does not last for too long a period. 
 Occasionally the battery acid should be tested to see that it 
 maintains the proper specific gravity. This test is made by a 
 hydrometer. 
 
 
In order to prevent vibration, the galvanometers are carried 
 on piers, having no connection with the building foundations. 
 It is essential that the galvanometers be carefully protected 
 from vibration or shock, otherwise, resistance measurements 
 cannot give accurate results. 
 
 Alternating current generators and motor-generator sets are 
 furnished for generating and converting alternating current 
 power at the various voltages and frequencies required in test- 
 ing apparatus. Taps, from the 40 cycle alternating current 
 shop circuit supplying 110 volts, are located in the principal 
 testing sections. These are generally used for supplying power 
 for the excitation of high potential testing transformer sets. 
 As this power is supplied at a constant voltage of 110 volts, a 
 potential regulator is employed with the high potential testing 
 transformer, in order to obtain the high potentials necessary for 
 the various types of apparatus tested. The wiring arrangement 
 of a high potential testing set is shown in Fig. 2. 
 
 wwww-J 
 
 rWVWW-i 
 
 Fig. 2 
 
 WIRING ARRANGEMENT OF HIGH 
 
 POTENTIAL TESTING SET 
 
 The Testing Department uses a 2000 kw. 25 cycle, 13,200 
 volt turbine driven generating set located in Building No. 61 
 for miscellaneous power tests. From this set power is dis- 
 tributed by means of high tension lines to Buildings Nos. 16, 
 12 and 114. This set is also used for supplying power to the 
 railway at Wyatts Crossing and a considerable amount of 
 railway testing is done by its agency. When such work is 
 being carried on, an extensive system of high tension lines is 
 connected to this machine, consequently the circuit has con- 
 siderable capacity. When this circuit is in use, therefore, testers 
 should be cautioned not to come in contact with any part of the 
 circuit, or with the leads attached to it, since its capacity may 
 give rise to a voltage sufficient to produce fatal results. 
 
Fig. 3 
 
 PLUG CONNECTION BOARD FOR SHOP ALTERNATORS FOR 
 
 CONNECTING A, Y or 2 PHASE 
 
 O Indicates front contact 
 ° Indicates back contact 
 
 To Connect 
 
 Plug 
 
 Connecting 
 
 A 
 
 A plugs 
 
 5 to 3, 4 to 6, 2 to 1,7 to 8 
 
 Y 
 
 Y plugs 
 
 2 to 1, 3 to 6 to 7 
 
 2<p 
 
 2 <p plugs 
 
 3 to 7, 6 to 1 
 
 3-phase lines =1,2 and 3. 
 
 o i; no , J phase No. 1=1 and 3 (Line Nos.). 
 *<p lines ^ phase NQi 2 =2 and 4 (Line Nos-)< 
 
 Remove ALL plugs to remove voltage from outgoing lines. 
 
 
No one working on this circuit, or other circuits of high voltage 
 in the Testing Department, should approach nearer than 12 
 inches to the circuit, because actual contact is by no means 
 always necessary in order to receive a dangerous shock. Due to 
 high static capacity and other peculiar conditions, it is extremely 
 important that the Head of the Section investigate thoroughly 
 other sections which have taps to these lines and make sure that 
 
 S 
 
 /ia/f of one phase winding 
 
 Fig. 4 
 
 DIAGRAM SHOWING INTERNAL CONNECTIONS OF PLUG BOARD 
 
 FIG. 3 AND PHASE RELATIONS. PHASE WINDINGS ARE 
 
 PERMANENTLY CONNECTED TO BACK CONTACTS 
 
 AS SHOWN BY NUMERALS 
 
 they are not, and will not be in use, before anyone is allowed to 
 operate this machine. This must be done in order that all taps 
 may be properly protected when not in use, and also that no 
 accidents may occur, due to misunderstandings. No wiring 
 whatever should be done on this circuit while it is alive. In all 
 cases, tests being operated from this circuit must have oil 
 switches interposed between the test wiring and the lines so 
 that connections to the lines may be made through these 
 switches. Wherever temporary switches become necessary they 
 must either be located at such a height or be protected by a 
 
mechanical barrier so that men cannot accidentally come in 
 contact with them. Gil switches, permanently installed in the 
 different testing sections for connecting to the lines mentioned 
 above, must be kept locked open when power is not being 
 drawn from the lines. The Head of the Section is responsible 
 for seeing that these matters are attended to. 
 
 Larger amounts of power may be obtained from the three 
 unit set in Building No. 61 consisting of an ATI-16-5600-300- 
 10,000 volt, 40 cycle synchronous motor driving an ATB 24- 
 6250-300, 4000/2300 volt, 60 cycle and an ATB 10-6250-300, 
 13,200/6600 volt, 25 cycle alternator. (See page 459 for nomen- 
 clature.) By the use of a bank of transformers a wide range of 
 voltages may be obtained and distributed to the various testing 
 sections. This set is very convenient for taking zero power- 
 factor heat runs on large alternators. 
 
 A 1500 kw. three unit set consisting of two MPC 8-750-600, 
 250 volt generators driven by a 40 cycle synchronous motor is so 
 wired that the two generators may be connected in multiple or 
 series for supplying power at 250 or 500 volts. 
 
 In addition to these sets there are others situated in the 
 various sections convenient for power or for "feeding back" 
 tests or for the conversion of direct to alternating current or 
 vice versa. The armature terminals of all alternating current 
 generators are connected to high tension switch panels. By 
 this means, the armatures, when their windings permit, may be 
 readily connected Y or A three-phase, or two-phase. Although 
 such switchboard panels are insulated for 15,000 volts, the same 
 caution, nevertheless, should be observed in operating them 
 as though the lines were bare conductors. The armature coil 
 terminals are each marked on the terminal board. One of the 
 panels is shown in Figs. 3 and 4. 
 
 Steam Power 
 
 A considerable amount, of steam is used for the testing of 
 steam turbines, marine engines and for driving turbine and 
 engine driven exciter sets, steam pumps, etc. Steam is supplied 
 from power houses located in Buildings Nos. 13 and 61 and is 
 conveyed to the Testing Department through underground 
 mains in the yards. The steam pipes are placed overhead in all 
 buildings. These mains are well lagged with asbestos covering 
 and contain a sufficient number of expansion joints to take care 
 of all expansion and contraction. Gate valves are located in the 
 mains at the boiler houses and also just inside the building in 
 which the testing section is located. Motor operated emergency 
 valves are installed in the important mains, so that the steam 
 supply may be shut off by closing a switch in the testing section. 
 Each man working in the steam test should know where these switches 
 are located, so that he may be able to close these valves quickly if 
 necessity arises. These valves must be regularly tested at least 
 once a week to insure certain operation. Steam separators and 
 traps are connected in all mains at the proper points to take care 
 of condensed water. Steam is distributed from the mains to 
 
 10 
 
the various section testing stands by leading off pipe branches. 
 These branches are of sufficient size to test any machine that 
 will be placed in the particular testing stand. At each stand the 
 branch steam mains are fitted with two steam valves, viz: a 
 special Globe Valve, which may be used to throttle steam 
 for machines under test, when necessary, and another valve 
 which is never to be used for throttling. This arrangement 
 prevents any steam leaking through the branch when not in 
 use. Each valve is furnished with a handwheel of sufficient 
 diameter, so that no additional leverage should be necessary 
 in opening or closing. 
 
 All steam valves must be tightly closed, using the hand- 
 wheel fitted to the valve. The handwheel should then be given a 
 slight backward turn in order to free the stem sufficiently to 
 take care of expansion and contraction. If these precautions 
 are observed the valve may always be easily operated by the 
 handwheel. Each branch main valve is furnished with a small 
 by-pass valve. When it is possible to obtain a sufficient supply 
 of steam through these by-pass valves to carry on a test, they 
 should be used in preference to throttling with the large valve. 
 Drip cocks are in all cases located between the main valve and 
 the machine or throttle valve. These drip cocks must always 
 be open when steam is not flowing through the main in which 
 they are located, and should be left open until steam is flowing 
 freely through the main. That is, wherever condensed water can 
 collect in dead-ended mains, a drip should be provided to carry 
 this water away as fast as it collects, in order to prevent a 
 water hammer in the main. A water hammer may produce 
 enormous stresses in a steam main, hence great care must be 
 taken to prevent its development. If water is likely to 
 collect in the main, the supply of steam should be entirely 
 shut off and all water must then be removed before re-opening 
 the steam valve and attempting to use the main again. 
 
 In each section having large steam mains, there are regularly 
 appointed men, whose duty it is to operate all valves with the 
 exception of the throttle valve at the machine under test. 
 The tester should, therefore, ask these men to operate any valve 
 except the throttle valve, which may be operated by the tester 
 himself. Small by-pass valves should also be used in every case 
 gradually to warm up a steam main before allowing steam to 
 flow into it through the opening of the main valve. By using the 
 by-pass valve in this manner, with all drips open, the main can be 
 gradually brought to its running temperature, after which the 
 large valve giving the full flow of steam may be opened. 
 
 All exhaust steam piping is arranged to permit the exhaust 
 steam being passed into the heating system of the factory, 
 into the atmosphere direct, or into surface condensers. Wher- 
 ever possible, condensers should be employed in order to 
 economize steam. Whenever steam heat is required, however, 
 exhaust steam may be passed into the heating system. Steam 
 should only be exhausted into the atmosphere direct in excep- 
 tional cases where it cannot be utilized as just mentioned. 
 
 11 
 
Shop Motors and Generators 
 
 The Testing Department equipment includes a large number 
 of 125, 250, and 500 volt direct current machines of various sizes, 
 which are always available for driving generators under test. 
 They can also be used as a load for motors receiving test, in 
 which case they are run as generators. Many of these machines 
 are shunt wound; a large number, however, are provided with a 
 series field winding and also with commutating poles. Ordi- 
 narily when using such machines as motors, they are operated 
 as shunt machines. Sometimes, however, these motors have 
 to operate in multiple and it is then necessary to use a certain 
 proportion of the series field on one machine in order to give 
 the proper speed equalization. Such cases, however, are special 
 and definite instructions should be obtained before operating 
 the combination. 
 
 When operating as motors, machines should never be sepa- 
 rately excited, unless the test requirements so demand. In such 
 cases, precautions must be taken to prevent loss of motor field, 
 due to the fields being excited from one source and the armatures 
 from another. When shop machines are operated as motors 
 they must have the speed limiting switch mounted on the shaft, 
 connected to the trip coils on the breakers placed in the armature 
 circuit, so that in case a motor begins to run too fast it will 
 automatically be shut down. 
 
 When using direct current machines as compound wound 
 motors, the following precautions must be observed. The series 
 fields must not be connected differentially. They must have 
 only sufficient series field to give the required regulation. Should 
 excessive series field be used and the shunt field adjusted under 
 full load conditions to give normal speed at normal load, the 
 speed may rise to a dangerous point if the load falls suddenly. 
 When machines are so used great care should be exercised in 
 operation to prevent any condition occurring which may give a 
 dangerous rise in speed. When such special conditions occur 
 it must be clearly understood that some one man connected 
 with the test must watch the machine continuously. He is 
 responsible for seeing that accidents, due to excessive speed, 
 cannot occur. 
 
 In all cases the general condition of machines, especially the 
 condition of commutators, brushes, bearings, etc., must be 
 frequently and carefully noted and any defects reported to the 
 Head of Section. 
 
 When using the shop apparatus, it is as important to take 
 the same precautions in wiring and starting for test as are taken 
 in the case of the apparatus for production. These precautions 
 are detailed in the following pages. 
 
 Several of the shop motors used by the Testing Department are 
 alternating current synchronous motors. In most cases, these 
 are permanently connected to a direct current generator. It is 
 often necessary, however, to erect and operate synchronous 
 motors temporarily for production tests. 
 
 12 
 
When starting a synchronous motor the precautions must be 
 observed that are explained in Chap. 11. They must always be 
 run at unity power-factor, unless the special requirements of the 
 test are such that this cannot be done. Since the greater number 
 of these motors are occasionally operated under variable loads, 
 the value of the field current should be watched to see that the 
 armature current is of the proper value for unity power-factor. 
 Should a motor fall out of synchronism, in consequence of exces- 
 sive overload, or otherwise, the armature circuit must be opened 
 immediately to prevent injury to the winding from overheating. 
 When shop generators and motors are being used the lubrication 
 of their bearings must always be inspected at starting and also 
 at definite intervals during operation to keep the bearings cool 
 and prevent overheating. In addition, the instructions on bear- 
 ings given later must be observed. 
 
 Safety Devices 
 
 In a department such as the Testing Department it is 
 essential that proper guards be used in all cases which might be 
 considered as in any way likely to be the cause of an accident. 
 With this in mind special testing equipment which is referred to 
 in other pages of this book has been furnished. Under no cir- 
 cumstances should switches, circuit breakers or other controlling 
 devices be used which are not properly equipped with handles, 
 washers, etc. There is in each testing section a stock of these parts 
 and the Head of Section is responsible to see that none of these parts 
 is missing. 
 
 All circuits, whether high potential or low potential, which are 
 installed permanently are marked so that all can be identified 
 at any time. With very few exceptions current transformers must 
 be used as a matter of safety when taking measurements on high 
 potential circuits. W T henever a connection is made to permanent 
 circuits, proper protection must be afforded by oil switches, cir- 
 cuit breakers or contactors. 
 
 All shaft extensions which are exposed must be guarded. All 
 couplings and belts must be guarded either by a permanent fence 
 constructed of pipe work, or a portable fence designed for this 
 purpose. 
 
 Speed limiting devices (see page 113) must be installed on all 
 shop apparatus in which excessive speed is possible and should 
 be adjusted at least once a week to operate at 10 per cent above 
 normal speed. Whenever speed limiting devices cannot be per- 
 manently installed they must be used temporarily. 
 
 Safety valves and atmospheric relief valves are also per- 
 manently located wherever necessary on permanent steam 
 piping. They should be installed whenever necessary on tem- 
 porary piping in order to insure safety. Great care must be 
 taken in locating these devices in reference to steam mains, air 
 compressor work and air tanks. The tests and apparatus given 
 above are vitally important for the safe* operation of the testing 
 equipment, and the Head of the Section must insist that they 
 be closely followed. 
 
 13 
 
Switchboards and Floor Stands 
 
 Section switchboards are connected to the permanent wiring 
 to obtain flexibility. These are so designed as to minimize the 
 amount of temporary wiring as much as possible. The switch- 
 boards are of two classes; viz. those connected to high voltage 
 circuits (above 600 volts), and the low voltage switchboards 
 (600 volts and below). 
 
 ^LrnmW^^ 9 ^^ 
 
 Mfti&itfiffr fllfMft ^afe tfiftrl 
 
 ^-"^mM 
 
 Fig. 5 
 FRONT OF HIGH TENSION SWITCHBOARD, PLUG TYPE 
 
 The high voltage switchboards consist of a number of slate 
 panels provided with high tension insulators, to which the 
 permanent wiring terminals are attached leading from the 
 permanently installed alternating current generators, trans- 
 formers, and "floor stands." At some distance behind the 
 slate front of the board, a second set of high tension insulators 
 is carried on an iron frame, which are also fitted with terminals 
 connected to horizontal busses running throughout the length of 
 the board. Since with this arrangement, generators, floor stands, 
 and transformer terminals are located in vertical lines, whereas 
 busbar terminals are located horizontally, it is possible to pass from 
 one panel to any other panel on the board by inserting switches 
 between the front and back sets of terminals. The metallic 
 terminals used on these boards form the contact points for plug 
 switches. These plug switches are designed so that having 
 removed or inserted a plug, all live parts are thoroughly 
 protected. 
 
 14 
 
No plug switch must be used for connecting or disconnecting 
 the front and back systems of contacts if there is any voltage on 
 them. The switching system must be considered merely as a transfer 
 scheme and must always be operated as such. 
 
 N 
 
 & ** ^ 
 
 ^ 
 
 SHI-fl-H*-^ 
 
 B— w-fbi 
 |aC+— S~B~fJBt: — - -a 
 
 5f-8--rf - 
 
 un — a — ill 'ii — 
 
 
 mfl^i 
 
 Wr~& -- 
 
 ^ ^ ^ ^ ^' 
 
 < 
 
 o 
 m 
 
 X 
 o 
 
 H 
 
 CO 
 
 O 
 
 »5 
 
 • W 
 
 .*? w 
 
 to fa 
 
 O 
 
 g 
 
 3 
 o 
 & 
 
 (Si 
 
 It will be readily seen by referring to Fig. 5 and to 
 diagram, Fig. 6, that great flexibility is obtained, since any 
 generator connected to a switchboard may be readily trans- 
 ferred to any "floor stand" or to any bank of transformers. 
 Furthermore, any "floor stand" may be immediately connected 
 
 15 
 
with any other "floor stand" by merely inserting plug switches 
 at the board. 
 
 "Floor stands" are so located in each testing section that 
 all high voltage apparatus may be installed near them, thus 
 reducing to a few feet the length of high tension cable which is 
 required for the machine in test. The "floor stands" carry dis- 
 connecting switches and oil switches, through which the final 
 connections can be made between their terminals and the 
 
 Fig. 7 
 FRONT OF HIGH TENSION FLOOR PANEL 
 
 terminals on the high tension switchboard panel. One of these 
 stands is shown in Figs. 7 and 8. 
 
 Green and red "tell tale" lights are located on all switch- 
 board panels and also on the "floor stands." They are auto- 
 matically operated whenever an oil switch on the "floor stand," 
 or a plug switch on the switchboard is opened or closed. When a 
 red lamp is burning either at the "floor stand" or on the switch- 
 board panel, it indicates that the terminals are in use, and 
 
 16 
 
connected to another circuit. If red lights are burning, it is, 
 therefore, necessary to investigate carefully all panel con- 
 nections before making any changes. When, however, a green 
 lamp is burning it indicates that the panel, or "floor stand," is 
 free, and may therefore be used. For example: A red light 
 burning on the "floor stand" indicates that the oil switch has 
 been closed on the corresponding "floor stand" panel and that 
 
 Fig. 8 
 
 HIGH POTENTIAL FLOOR STAND SHOWING 
 
 INTERIOR WIRING AND CONSTRUCTION 
 
 the terminals of the "floor stand" panel are alive. Again, if a 
 red light is burning on the "floor stand" its switchboard panel 
 has been connected by the plug switches to another panel, 
 consequently, the "floor stand" terminals may be alive. Hence, 
 the red light acts as a danger signal. It should never be entirely 
 trusted, however, and the same care should always be taken 
 as though "tell-tale lights" did not exist. 
 
 17 
 
Ais 
 
 Fig. 9 
 HIGH POTENTIAL PEDESTAL AND TESTING TABLE 
 
 Connections are brought out at the top of the "floor stands" 
 through high potential bushing insulators to terminal blocks 
 mounted on the insulators. All this wiring is permanent. 
 From the terminal blocks, temporary lines must be run to 
 the high potential testing table. A second row of insulators is 
 provided on the top of the "floor stands" which must be used 
 only as strain insulators. The temporary cables running to 
 
 18 
 
the testing table must be securely fastened to these insulators. 
 By this means the strain on the connections at the terminal 
 blocks is relieved and wires cannot drop to the floor if they 
 become disconnected. The insulators are arranged so that 
 cables can be taken off at any angle with a safe distance between 
 them. 
 
 If temporary wiring has to be carried some distance, high 
 potential pedestals must be used to support the spans as shown 
 in Fig. 9. 
 
 The testing table shown in Fig. 9 is the standard type of 
 high potential table used in the Testing Department. These 
 tables are constructed so that all high potential wiring is pro- 
 tected, and it is impossible to make contact with it when the 
 table is in use. High voltage and low voltage circuits within 
 the table are placed in separate compartments and insulated 
 from each other. Tables are built of asbestos, wood, angle 
 iron and expanded metal. The a-c. compartments contain 
 an oil switch, potential transformers, and current transformers. 
 
 High voltage connections are made at the top of the table 
 as on high potential "floor stands." The secondaries of the 
 current and potential transformers are connected to binding 
 posts in their respective compartments, forming the terminals 
 of the permanent wiring leading to the instruments on the 
 front or operating side of the test tables. All current trans- 
 formers should have a capacity of 5 amperes for the secondary. 
 Transformer secondaries should be kept grounded on one side 
 when in use. A detailed print of the wiring circuit will be found 
 mounted on each table. All instrument switches and terminals 
 are properly and plainly labeled. All table wiring is permanent 
 and insulated for a maximum working voltage of 15,000. 
 
 The d-c. compartment is wired for all the circuits of two 
 d-c. machines for voltages not exceeding 600 volts. The table 
 is furnished with double-pole 500 ampere 600 volt circuit 
 breakers. For all currents above 300 amperes, terminals are 
 provided for the standard ammeter shunts used in the Testing 
 Department. When using currents above 500 amperes the 
 circuit breaker on the table must be cut out of circuit and 
 breakers of larger capacity wired in the circuit external to 
 the table. When direct currents are read direct, ammeter jacks 
 are provided which allow the insertion or removal of the instru- 
 ment in circuit without interrupting the circuit. 
 
 Though these tables are fitted with safety devices and interlocks, 
 etc., in order to render all protection possible, operators must 
 treat them as if no protection exists. In other words, great attention 
 must be given to all details of operation, and in no case should 
 connections be changed by throwing switches, etc., unless the 
 operator feels certain of the correctness of so doing. 
 
 All d-c. switchboards recently installed are of the plug 
 terminal type, but they differ radically from the a-c. plug 
 boards. The older d-c. boards are equipped with bolted termi- 
 nals. Figs. 10 and 11 show the front and back views respec- 
 tively of a direct current switchboard of the plug type. These 
 
 19 
 
boards carry terminals, circuit breakers and switches for all 
 d-c. shop circuits. Switchboards are interconnected with 
 each other and by means of underground cables are connected 
 to small "pit switchboards" or "posts" or "floor stands' 
 conveniently located. These are generally fitted with plug 
 terminal connections, and are connected permanently to the 
 d-c. switchboards. All exciter sets are also connected to the 
 d-c. switchboards. Hence, any "stand," "pit," "exciter,' 
 etc., can be readily connected to any part of the test desired. 
 
 Fig. 10 
 FRONT OF D-C. SECTION SWITCHBOARD 
 
 In making connections on any of the "plug boards" plugs 
 must not be allowed to strike the slate panels and chip or crack 
 them. See what connections are required, then carefully insert 
 the plug in its receptacle, entering it to the locking position. 
 If these precautions are taken the least damage will be done 
 in case of short circuit. The ampere rating of each switch- 
 board terminal is placed above it. No cables or terminal must 
 be overloaded. 
 
 All field plugs must be carefully locked on insertion so 
 they cannot accidentally be pulled out. 
 
 All "pits" and "stands" must be kept clean and free of 
 rubbish. 
 
 Cables with defective insulation or having defective plug 
 terminals must not be used, but must be sent by the Head of 
 Section to the repair shop as soon as the defect appears. All 
 cables must be kept on cable racks when not in use. 
 
 The following example illustrates, the general procedure to be 
 followed in the wiring of high voltage alternating current circuits. 
 To connect a shop alternator to a high voltage machine on the 
 testing floor near the high potential "floor stand," see that the 
 oil and disconnecting switches are open, then connect . the 
 alternator, at the armature terminal board, to give the proper 
 voltage and phase combination. Connect the machine by 
 temporary wiring to the high potential terminals on the "floor 
 
 20 
 
stand." When the machine is ready to start, a transfer bus should 
 be selected which is not in use on the high potential switch- 
 board. The alternator armature should then be plugged in on 
 the transfer bus, after noting that the alternator oil switch is 
 open. Next plug the panel connected to the proper floor stand 
 to the same bus, and close the alternator oil switch. On closing 
 the circuit at the "floor stand" panel, a red lamp lights up and 
 indicates that the connection of the alternator has been made 
 up to this point. The disconnecting switches should then be 
 
 Fig. 11 
 BACK VIEW OF D-C. SECTION SWITCHBOARD 
 
 closed at the "floor stand." Finally, the oil switch on the "floor 
 stand" should be closed and a red light burns on the correspond- 
 ing panel of the high potential switchboard, showing that the 
 panel is connected through the high potential "floor stand" to 
 the circuit. The oil switch in the test table must be employed to 
 open and close the high tension circuits, if required during the 
 test. In all cases oil switches should be used to "make" or 
 "break" alternating current circuits, where such circuits carry 
 an appreciable amount of current. 
 
 In all high voltage work proper precautions should always be 
 taken to insure against accident in handling circuits. In all cases 
 where temporary circuits of high voltage are used, they must be 
 thoroughly protected by mechanical barriers and danger signals; 
 and white tape should be used wherever it is advantageous as 
 an additional warning. 
 
 Water Boxes 
 
 It is often necessary in testing to dissipate electrical energy 
 through a resistance. When it is necessary to use resistances 
 
 21 
 
as a load for large machines, the water box has been found 
 most convenient. The water box, as used in the Testing Depart- 
 ment, is an iron box mounted on porcelain insulators. Suspended 
 above the box by insulators is a triangular iron blade which 
 can be lowered into the box. When the water box has been 
 filled and the resistance adjusted by the addition of salt, the 
 resistance may be varied by lowering or raising the plate in 
 the liquid which is admirably adapted to close adjustment. 
 
 The box is mounted on porcelain insulators; it should, 
 however, always be considered as grounded. In connecting 
 the boxes to grounded shop circuits, the grounded side should 
 be connected to the cable leading to the box, and the ungrounded 
 side should be connected to the plate. When using water 
 boxes as a load on three-phase circuits, the cables leading from 
 the box should be connected together to form a Y connection, 
 and the phase cables should be connected to the plates. 
 
 Before loading a machine on a water box, the salt solution 
 must be adjusted for the voltage and current required. To 
 do this, apply a low voltage to the box and note the 
 current. If this is not possible add fresh water to the 
 solution until the resistance is sufficiently high to prevent 
 an excessive rush of current when the bottom of the plate 
 enters the solution. 
 
 The majority of water boxes in the Testing Department 
 are equipped with hydraulic cylinders for operating the triangular 
 plate. These consist of vertical cylinders fitted with a piston 
 and piston rod from which the plate is suspended. Water 
 is forced into the cylinder, or released from it by two electrically 
 operated valves, one for raising, and the other for lowering 
 the plate. Small cables run from the electrical valves to a 
 small distributing switchboard, whence leads may be carried 
 to any of the testing tables, and connected to operating switches. 
 Water boxes can be operated from any section by this method 
 of remote control. If it is desired to operate water boxes in 
 multiple, the cables leading to the control valves must be 
 connected in multiple, and a single operating switch will control 
 any number of boxes. 
 
 Unless special permission has been received more than 
 2300 volts must not be connected to water boxes unless they 
 are specially insulated. 
 
 The standard water box used will dissipate 75 kw. continu- 
 ously without excessive heating. If the water in the boxes is 
 allowed to boil, the resistance regulation becomes very unsatis- 
 factory. Arcing may then occur and set up electrical surges. 
 Hence, the temperature of water boxes must always be kept 
 well below the boiling point, either by allowing cold water to 
 run into them continuously while under load, or if necessary 
 by reducing the load. 
 
 To prevent arcs and therefore excessive voltage rises, 
 water boxes must never be used to open alternating current 
 circuits. 
 
 22 
 
Field Rheostats 
 
 The Testing Department is equipped with many wire resist- 
 ance boxes of small and moderate current capacity. These 
 resistances are not grounded upon the frame, but should always 
 be so treated in order to insure safety and freedom from accident. 
 For this reason, the frames should always be insulated from one 
 another and also from ground. All rheostats are marked with 
 their resistance and maximum current carrying capacity, so 
 that the proper resistance for a test can be readily selected. 
 Defective rheostats must never be used in test, but must im- 
 mediately be sent by the Head of the Section to the repair shop. 
 Permanent motors are generally equipped with their own starting 
 resistance. When starting motors for test, series resistances of 
 large current carrying capacity must often be used. In such cases 
 the water box is the best type of resistance. When starting 
 motors with a water box the voltage drop across the box 
 must be reduced to a small value before the motor is thrown 
 directly across the line. 
 
 Transformers 
 
 Each test section is equipped with permanent transformers. 
 Additional transformers are also available for special tests, 
 or for use when the regular transformers are in operation. Per- 
 manently installed transformers should be used whenever 
 possible to save wiring cost and time and to obtain the advan- 
 tages and safety afforded by permanent wiring. On the per- 
 manent banks of transformers the primary and secondary termi- 
 nals are brought out to terminal boards with- the plug switches 
 for making the various transformer coil connections required 
 with the cables leading to and from the bank. The primary 
 terminal boards are insulated for 15,000 volts between 
 lines, and any combination ordinarily desired can be obtained 
 by inserting plugs in the proper terminals. The plug switches 
 must be considered only as a ready method of connecting up 
 the transformer coils. They must not be used for connecting 
 or disconnecting live circuits. The boards are thoroughly insu- 
 lated, but must always be treated as unprotected, when high 
 voltages are used. 
 
 The secondary coils are connected to a low tension plug 
 type switchboard where they may be connected by plug ter- 
 minals to cables running to any part of the test. Each plug 
 terminal is labeled so that no wrong connection should be 
 possible, if ordinary care is observed. 
 
 If temporary transformers are used, they must be properly 
 installed and wired so that safe operation is secured. All cases 
 must be grounded by substantial ground wires or cables, the 
 case and ground terminals must be in good condition and fitted 
 so that they cannot work loose. Never sit or stand on the top 
 of a transformer when connecting or disconnecting it. Always 
 use step ladders for this purpose and see that the transformer is 
 not alive before touching its leads or terminals. 
 
 23 
 
CHAPTER 2 
 
 THE USE AND CARE OF INSTRUMENTS 
 
 Care of Testing Instruments 
 
 All measuring instruments for testing work must be obtained 
 from the general instrument room, or from branch instrument 
 rooms located in several of the testing sections. The instruments, 
 while in this instrument room, are in the charge of a man who 
 is responsible for their condition and calibration before they are 
 given out for testing work. When instruments are taken 
 from the instrument room by the tester he must receipt for 
 them to the man in charge of the instrument room, and be 
 responsible for the proper use and care of them. In all cases, 
 the man signing for testing instruments must be responsible 
 for their return to the instrument room in as good condition as 
 they were received by him. In case instruments are damaged, 
 a report must immediately be made out by the man in whose 
 charge they are and turned in with the instruments to the man 
 in charge of the instrument room. 
 
 All instruments are provided with a mirror under the needle. 
 To eliminate parallax and obtain the correct reading, sight the 
 needle when it exactly covers its mirror image, then without 
 altering the position, read the intersection of the needle with the 
 inner scale circle. It should be remembered that while the scale 
 on most d-c. instruments is equally divided, so that the errors 
 of observation are nearly the same in actual amount in all parts 
 of the scale, the percentage error varies inversely with the 
 deflection. Therefore, when accuracy is required the instrument 
 must not be read at a low point on the scale. 
 
 Before using any instrument it should be carefully inspected 
 to determine whether the needle is free and rests at zero. No 
 instrument which sticks at any part of the scale should be used 
 nor should an instrument be used which has a zero error. In- 
 struments containing permanent magnets should not be carried 
 through strong magnetic fields, as the accuracy of the instru- 
 ment is liable to be affected. 
 
 Nearly all instruments have polished steel pivots and jeweled 
 bearings; dropping the instrument on the table or striking it 
 against another instrument will injure these pivots, causing the 
 needle to stick. 
 
 Curves and certificates should be at hand for correcting the 
 instrument readings before starting a test. 
 
 These precautions apply in general to the use of electrical 
 instruments, but do not include all the precautions which 
 must be taken. Intelligence must always be used when using 
 instruments and measuring devices. Precautions which apply 
 especially to certain types of apparatus will be noted in the 
 following pages referring to various instruments employed. 
 It must be noted that, while the metallic case of a testing instrument 
 is presumably insulated from the terminals and current carrying 
 
 24 
 
parts, it may become accidentally grounded. When using such 
 instruments, therefore, on high potential circuits, the tester should 
 always remember that this condition may occur. He should con- 
 sider that the case is at the same position as its terminals. He 
 should never touch the metallic cases of instruments when they are 
 connected to high potential circuits. If it becomes necessary to tap 
 an instrument case to see if the needle is sticking, small insulating 
 rods must be used. Lead pencils must not be used. 
 
 Phase Rotation Indicator 
 
 The general form of phase rotation indicator is shown in 
 Fig. 12. 
 
 It consists of a laminated iron ring with four windings 
 about 90 deg. apart. 
 
 For two-phase, all four windings are used, while for three- 
 phase but three are used. The terminals are stamped 1, 2, 3, 4, 
 and should be connected to corresponding terminals on the 
 a-c. machine under test. These indicators are intended to run 
 from the residual magnetism of the machine. 
 
 Fig. 12 
 PHASE ROTATION INDICATOR 
 
 The rotor consists of a bar pivoted at the center. This 
 bar should rotate in the same direction as the machine under 
 test. While this is the general principle of the indicator, there 
 are several forms used in the department. They should all 
 be operated, however, from the residual magnetism of the 
 machine. 
 
 The above sketch shows the general construction of the 
 indicator. The phase angles are not absolutely correct but are 
 sufficiently accurate for practical purposes. 
 
 The Compass 
 
 The compass or magnetic needles used for indicating polarity 
 are of the ordinary commercial type. This instrument is not 
 used very frequently in the testing department since there is 
 danger of its polarity being reversed in strong magnetic fields. 
 Care must therefore be taken when using it. 
 
 25 
 
Steam Engine Indicators 
 
 Steam engine indicators are of the standard commercial 
 type and are used to take indicator cards generally oh marine 
 engines. The following points must be considered: The con- 
 necting cord must not stretch, the indicator cylinder must 
 move freely, the paper must be smooth and held firmly on the 
 cylinder, and the pencil must mark plainly and move freely. 
 
 The size of spring used in the indicator must be selected 
 so as to give as large a card as possible. Generally speaking, 
 the larger the card the more accurate the results. The spring 
 must be kept in good condition and must be frequently calibrated 
 in order to insure accurate results. 
 
 A Planimeter should be used to measure the area of indicator 
 cards. 
 
 In using it always set the vernier and scale at zero. The 
 pivot point should be securely located and the tracer moved in 
 one direction around the indicator card back to the starting 
 point. The roller wheel should roll on a flat unglazed surface 
 to secure accurate results. 
 
 Balances and Scales 
 
 In using balances and scales the no-load position should 
 always be noted, as a zero error may exist. Always hold bal- 
 ances, when measuring, by the hook at the top. After using 
 platform scales the beam should always be either dropped or 
 locked to avoid damage to knife edges, which a blow may other- 
 wise cause. All scales and balances used for important readings 
 must be frequently checked against standard weights in order 
 to insure accuracy. 
 
 Manometers and Anemometers 
 
 Manometers are used for measuring low air pressures, i.e., 
 up to 4 or 5 ounces. For measuring pressures up to 2 ounces 
 they consist of two vertical cylinders located parallel to each 
 other upon a proper base through which a connection is made 
 from one leg to the other. The cylinders or "legs" are partially 
 filled with water. In some cases the two legs have a cross 
 section ratio of 10:1. When pressure is applied above the 
 water in one leg the water is forced downward and the water 
 in the other leg rises a corresponding amount. Hence, when 
 the cross section of the legs is the same the pressure is equiva- 
 lent to the difference in level between the water in the two 
 legs, whereas if the ratio of cross sections is 10:1, a water rise 
 in the small leg will measure a pressure equivalent to a water 
 column 1.1 times the height read. Such an arrangement per- 
 mits of accurate observation of pressures. The difference in 
 water levels is generally read on a "hook" gauge provided with 
 a properly arranged screw and corresponding scales. 
 
 The common " U " tube, consisting of a glass tube bent in the 
 form of a letter "U" is frequently employed. One side of the 
 tube carries a scale, by which the difference in height of water 
 in the two legs can be read. In all cases the zero point must be 
 
 26 
 
carefully noted, before applying pressure. This reading must 
 be added or subtracted, as the case may be, from pressure 
 readings. 
 
 Anemometers are used to measure the velocity of air. 
 Such meters are not very accurate even at their best and must 
 not be used where accurate results are desired. In such cases 
 the calibrated orifice or "pitot" tube method of making air 
 measurements must be employed. 
 
 Pressure and Vacuum Gauges 
 
 Pressure gauges must not be subjected to extreme heat, 
 because their accuracy will be affected. With steam pressure 
 gauges, "U" shaped or circular loops must be used in the 
 pressure pipes leading to the gauge. These form a trap that 
 holds sufficient water to fill the operating spring of the gauge, 
 thus protecting it against the high temperature of the live 
 steam and keeping it comparatively cool. Vacuum gauges also 
 
 Fig. 13 
 SLIP INDICATOR 
 
 must not be subjected to extreme heat. All gauges must be 
 regularly checked with standards to make sure they are correct 
 when used on important work. 
 
 The Hydrometer 
 
 The hydrometer is used to measure the specific density of 
 liquids. It is used in the testing department in connection 
 with storage batteries to insure that the electrolyte is kept at 
 the proper density. 
 
 Slip Indicator 
 
 Measurement of the slip of an induction motor at any 
 load is made by means of a slip indicator such as is shown in 
 Fig. 13. This slip indicator is a convenient arrangement for 
 comparing mechanically the angular velocities of two shafts, one 
 
 27 
 
of which is driven at a constant speed by the synchronous motor 
 of the slip indicator and the other at the speed of the motor 
 under test by means of a flexible coupling between them. 
 
 The indicator is mounted on an iron base, fitted with a 
 handle at each end, for carrying or handling it. The synchronous 
 motor is very simple in construction. It has a bipolar stator, 
 and a four-pole rotor without winding. The shaft carries a 
 fly-wheel on one end and on the other a 32 tooth brass gear 
 wheel, which may be made to mesh with any one of a nest of 
 seven gears, mounted on a parallel shaft, by shifting the motor 
 on the brass plate. By loosening two screws passing through 
 slots in the sole plate of the motor, the latter may be shifted 
 to any desired position, exact alignment being secured by dowel 
 pins. The various gears are provided to enable the synchronous 
 motor to drive the parallel shaft at different speeds, thus adapt- 
 ing the instrument for testing motors with various numbers 
 of poles. 
 
 The parallel shaft is equipped at its other end with a bevel 
 gear wheel meshing with two pinions of a differential gear. 
 Meshing with these pinions on the other side is another bevel 
 gear, carried on a shaft the other end of which carries the flexible 
 coupling by which it is connected to the machine in test. A 
 short auxiliary shaft behind the differential gear has, on one 
 end, a gear wheel meshing with the large wheel of the differential 
 gear, and on the other end a small handwheel by which to 
 hold this shaft. 
 
 A clutch, operated by a lever, connects the auxiliary shaft 
 to a cyclometer which registers the number of revolutions of 
 the auxiliary shaft. The gear ratio makes one revolution of 
 the auxiliary shaft equal to one-half revolution of the differential 
 gear. 
 
 The indicator is used as follows: 
 
 With the voltage normal and the speed of the alternator 
 held constant at normal frequency of the motor, the indicator 
 is connected to the induction motor shaft by means of a "split 
 tip." The bevel gear, on the shaft carrying the split tip, is 
 driven at the speed of the induction motor. By holding the 
 large gear of the differential stationary by grasping the hand 
 wheel on the auxiliary shaft, the synchronous motor is mechani- 
 cally brought up to the speed of the induction motor by power 
 transmitted through the other side of the differential and the 
 nest of gears. On closing the line switch on the synchronous 
 motor it will immediately fall into step with the alternators 
 and run at synchronous speed. Should it fail to do so on 
 the first trial, a second or third trial in the same way will 
 usually be successful. With the synchronous motor running 
 and driving one bevel gear of the differential at synchronous 
 speed, and the induction motor driving the other bevel gear 
 at the speed of the induction motor, the large gear of the differen- 
 tial will rotate and drive the auxiliary shaft and cyclometer. 
 In this way, the difference between synchronous speed and 
 the speed of the induction motor is mechanically recorded, 
 
 28 
 
and it is only necessary to read the cyclometer for some definite 
 length of time (usually one minute) "to know the exact number 
 of revolutions by which the two speeds differ. 
 
 In Fig. 13 the gear wheel of the synchronous motor shaft 
 is shown meshed with the gear wheel of the "nest" having the 
 same number of teeth (32). adapting the indicator to test a 
 four-pole induction motor, since the rotor of the synchronous 
 motor has four poles. The other gears of the "nest" have 
 
 Fig. 14 
 STATIONARY TORQUE RECORDER 
 
 16, 48, 64, 80, 96 and 112 teeth, respectively, providing for 
 testing induction motors with the various numbers of poles, 
 commonlv built. 
 
 Stationary Torque Recorder 
 
 Some alternating current motors have a starting torque 
 which varies considerably according to the position of the rotor 
 at starting. In many cases, therefore, the variation of starting 
 torque at different rotor positions must be measured. 
 
 29 
 
This information can be most satisfactorily obtained by 
 using a graphic recording torque meter. Fig. 14 is a sketch of an 
 instrument that is successfully employed in the Testing Depart- 
 ment for quickly and accurately obtaining this torque. In 
 this sketch G represents a form of lever commonly used. It is 
 clamped around the pulley or the shaft of the motor under test. 
 A wooden disk H is provided, of triangular cross section radially. 
 On its conical surface a series of }/% in. grooves is located to 
 accommodate the cord K. This cord rotates the drum £ of a 
 steam engine indicator on which a record of the variations in the 
 torque is traced. The post A supporting the indicator is hollow, 
 and a rod connected to the lever B at the lower end and bearing 
 against the spring of the indicator, transmits any movement of 
 B to the spring, and in turn to the pencil bearing upon the drum. 
 The lever B is provided with a number of holes so that it can be 
 attached to the stirrup R at various distances from the fulcrum 
 S, by which means different leverages can be secured. By this 
 adjustment, and by clamping the complete apparatus to the 
 levqp: arm at different distances from the motor shaft, the 
 maximum travel of the recording pencil on the drum can be 
 kept within the limits normal for the indicator spring used. 
 The shaft and crank F are supported at right angles to the lever 
 B by an iron pipe frame not shown in the sketch. The spring 
 balance L is used only in calibrating the apparatus and is then 
 disconnected and the rope Z connected directly to the stirrup R. 
 The calibration of this instrument should be made as follows: 
 With no tension on the rope, pull the cord K and revolve the 
 drum E, thus recording the zero line on the paper record. Raise 
 the outer end of the lever above the horizontal position and with 
 the cord K in that groove on H which gives the proper rotation 
 to the drum E, slowly lower the lever by means of the crank F to 
 a position considerably below the horizontal plane passing 
 through the axis of the motor. This line gives the value W — F. 
 Where W is the weight of indicator lever arms, etc., tending to 
 rotate the rotor and F is the friction of the motor bearing. The 
 lever is now slowly raised to a position correspondingly above 
 the horizontal plane and a third line obtained on the indicator 
 drum, measuring the value W-\-F. The lever is now blocked 
 and held in a horizontal position and the crank F turned until 
 the spring balance reads 10 lb. By means of a cord, the drum 
 is rotated and a line drawn upon it correspondingly to 10 lb. pull. 
 This may be repeated and the indicator card calibrated through 
 the range required. 
 
 After the indicator calibration record has been made the 
 spring balance, is removed and the rope Z connected directly to 
 the stirrup R. Having determined the direction of rota- 
 tion of the motor when supplied with power, the line switches 
 may be closed, using about one-half normal voltage on the 
 motor. By means of the crank F and the rope Z the lever arm is 
 rotated through an arc equal to that employed in obtaining the 
 friction curve and a record made. Make a similar record while 
 lowering the lever through the same arc. While the lever is 
 
 30 
 
ascending, the record measures the value W-\- F-\-T, where T is 
 the torque of the motor under test ; % descending, the record gives 
 W — F-\-T. From the five curves* so obtained, the torque at 
 any position is readily obtained. 
 
 On these motors the cycle of torque variation usually repeats 
 itself regularly during a revolution. It is, therefore, only nec- 
 essary to continue the record throughout one of these cycles. 
 The indicator card has blanks for recording the machine rating, 
 number, and all other information necessary in connection with 
 this test. These cards should always be filled out clearly before 
 being sent to the Calculating Department. 
 
 The Ballistic Galvanometer 
 
 The Ballistic Galvanometer when used to measure magnetic 
 flux or electric quantity must be supported on a pier to elim- 
 inate vibration. It may be located either beside the apparatus 
 under test, if a pier is available at that place, or at a distance, 
 usually in the laboratory. 
 
 In measuring magnetic flux an exploring coil, usually of a 
 few turns only, is employed enclosing the flux at any convenient 
 point. As the exploring coil voltages are ordinarily very low, 
 no particular care is required for insulation except to guard 
 against mechanical abrasion. 
 
 The method for obtaining the necessary change of flux may 
 be either by withdrawing an exploring coil, by reversing the 
 current producing the flux, or by making or breaking the current. 
 For permanent magnets the first is the only way possible. 
 For electromagnets the second method is the more usual, the 
 exploring coil being wound permanently in place. If the current 
 is broken without reversal, the measurement is subject to an 
 error due to residual magnetism; which in a continuous iron 
 circuit (no air gap, as in a stack of ring punchings) sometimes 
 gives a remainder of over three-quarters of the whole flux (as 
 may be seen in a hysteresis loop). Similarly if the current is 
 made, an error occurs if the flux does not start from zero 
 value. 
 
 The expression for computing the flux is F = kRD/ N, where 
 k is the constant of the galvanometer, R the resistance (external 
 -fgalvanometer resistance), D the observed deflection, N the 
 number of turns of the exploring coil. If the galvanometer is 
 one with considerable damping, k will vary greatly with the 
 resistance, being constant only at high resistances, and the 
 curve or table giving the k values must be referred to. If only 
 relative values of flux are required, for instance, the variation 
 of flux with generator field current, no value of k need be 
 obtained, the flux being proportional to RD, the product of 
 resistance and deflection. 
 
 In computing the flux it is necessary to note carefully 
 whether, as is usually the case, the constant of the galvanometer 
 is given for a reversed current, and whether the observations 
 correspond. For instance, in calibrating, the current is usually 
 reversed, and flux observations of a permanent magnet made 
 
 31 
 
by withdrawing the coil must always be multiplied by two, if 
 the ordinary k of the galvanometer is used. 
 
 When observing quantitatively, see that the whole flux 
 change occurs before the galvanometer coil has moved through 
 any considerable portion of its swing. This is readily tested by 
 waiting a fraction of the galvanometer period, perhaps a second 
 or two, before pressing the key, after which there should be no 
 deflection. 
 
 The swing of the galvanometer coil is stopped either by 
 short circuiting through a proper key, if the galvanometer is 
 damped considerably, or by a counter torque obtained by 
 applying in the proper direction a small fraction of the voltage of 
 a cell through a suitable reversing key. 
 
 The calibration of the ballistic galvanometer is usually 
 accomplished by reversing the current in a long air solenoid 
 with an exploring coil surrounding the middle. The flux at the 
 middle of the solenoid is 4irnAI/10, where n is the number of 
 turns of the solenoid per cm., A the area and / the current 
 (in amperes). 
 
 SPEED AND FREQUENCY 
 
 The primary standard for speed is an accurate speed counter 
 and a reliable chronometer. The Company's chronometer is 
 checked by Washington time, as time record is made on the 
 laboratory through a special wire, daily at noon. 
 
 Secondary or Working Standard 
 
 The Company's working standard is a liquid tachom- 
 eter having a scale 36 inches long and graduated from 300 to 
 1200 revolutions per minute. This tachometer is coupled to a 
 small variable speed motor, to the other end of which is con- 
 nected through a nest of gears the tachometer to be tested. By 
 means of these gears the tachometer' under test can be run in 
 either direction and at speeds which are multiples of the range 
 of the standard. This working standard is checked weekly by 
 the standard speed counter and a watch which has been com- 
 pared with the chronometer. 
 
 The working standard for the vibration frequency indicator 
 is a current interrupter of the vibration type, operated by the 
 working standard tachometer and motor. For the Thomson 
 station type, a machine running at the required frequency, 
 checked by a speed counter and watch, constitutes the working 
 standard. 
 
 Tachometers 
 
 The Company has in use the following types of tachometers: 
 Veeder Liquid, Schaeffer and Budenburg portable, Niagara 
 portable, Dr. Horn portable, Hopkins' electric portable and 
 Frahms vibration portable. 
 
 All portable tachometers should be checked running in both 
 directions, as it is frequently found that they differ somewhat in 
 their calibration whether run clockwise or counter-clockwise. By 
 
 32 
 
"clockwise" is meant clockwise rotation of the tachometer shaft 
 looking at the spindle end. 
 
 Tachometers like the S.&B., Niagara and Dr. Horn types 
 when run continuously need oiling every 3 or 4 hours. The best 
 grade of clock oil only should be used on them. This type, 
 although it is apparently strong and compact, is nevertheless 
 a delicate instrument and should be handled as carefully as any 
 other measuring instrument. 
 
 The Veeder liquid tachometer- is a centrifugal pump arranged 
 to pump the liquid from a small reservoir into a glass tube, the 
 height of the liquid in the tube rising or falling with the speed. 
 This type of tachometer has a small plug that can be screwed 
 into or out of the reservoir, changing the level of the liquid in 
 the reservoir and tube by displacing some of the liquid in the 
 reservoir and thereby adjusting the zero. In the later types of 
 Veeder tachometers, the zero is the lower surface of the inverted 
 cone at the foot of the glass tube in the reservoir. The meniscus 
 of the liquid in the column should be level with the lower surface 
 of this cone. The liquid used is grain alcohol slightly colored 
 with red aniline dye. Wood alcohol should not be used as it 
 corrodes the shaft, causing the bearings to leak. If the tachom- 
 eter leaks, it should be returned to the Standardizing Labo- 
 ratory to be repacked. 
 
 The Hopkins electric tachometer consists of a small magneto 
 which generates about 200 millivolts at full speed and is used 
 with a portable millivoltmeter or, where permanently installed, 
 with a station instrument. 
 
 There are two kinds of vibration tachometers; one is tuned 
 to respond to the vibration of the machine, due to the speed; 
 the other is an electromagnetic type. The former, however, is 
 not satisfactory where more than one machine is running, as the 
 reeds respond to the vibration of a machine adjacent to the one 
 being tested. The electromagnetic type can be used conveniently 
 when an accurate speed measurement is required at some distance 
 from the machine. Not more than the rated voltage should be 
 applied, as excessive voltage will cause a burn out. 
 
 Frequency and Speed Indicators 
 
 G-E Type H frequency and speed indicators are of the switch- 
 board type and are convenient for use on testing stands. The 
 two instruments differ in the scale only, one being graduated to 
 read frequency and the other the normal speed and a certain 
 high and low percentage of the machine speed on which it is 
 used. In using these instruments, adjustments for wave shape 
 must be made by shifting the arms on the resistance box used 
 with the instrument before beginning a test. This can be done by 
 measuring the speed of the machine by means of a speed counter 
 and watch, and moving the arms until the instrument reads 
 correctly. Both of these types are iron clad (shielded) instru- 
 ments, and, therefore, they are not affected by stray fields. 
 
 Frahrri 's system vibration frequency indicators and Hartman 
 and Kempf frequency indicators are similar to the electrically 
 
 33 
 
operated vibration tachometers but are graduated to read fre- 
 quency. They have a voltage range of from 250 to 50 volts and a 
 frequency range of from 90 to 223^ cycles. In the former 
 (Frahm) the voltage adjustment is made by means of four taps 
 on the resistance ; the binding posts being marked +, 65, 100, 130, 
 180 and 250. In the latter type (H and K) a, small button is 
 provided on the end for cutting in or out resistance when the 
 instrument is first connected to the circuit. This button should 
 always be in the 250 volt position, and after connection has been 
 made, the button should be turned until the right amount of 
 resistance has been cut out to correspond to the voltage applied. 
 
 These instruments possess important advantages over 
 tachometers in that they may be located at the testing table so 
 that the instrument readings may be observed and the speed 
 controlled by one man. They can be read more accurately and 
 are not influenced by the direction of rotation. They may also 
 be used to read the speed of d-c. machines or machines which 
 are under-excited. For this purpose a current interrupter is 
 provided on the shaft of a centrifugal tachometer. This inter- 
 rupter is provided with binding posts which must be connected 
 in series with the frequency indicator and a 125 volt d-c. circuit. 
 They are also provided with disks having several contact points. 
 For a disk having four contact points the frequency indication 
 would be the same as that of an eight pole alternator. 
 
 It is not safe to use these frequency meters for measuring 
 the speed of a machine under test when it is first started, since 
 they cannot always distinguish between 20 cycles or 40 cycles 
 in consequence of the fact that both a 20 cycle and a 40 cycle 
 reed will vibrate at 20 or 40 cycles. The speed should be roughly 
 set to that desired, by reading the tachometer dial, after which 
 it can be exactly adjusted by the frequency meter. Due to the 
 many advantages of these instruments they should be employed 
 wherever possible, in place of the ordinary tachometer for 
 testing work. 
 
 WAVE SHAPES 
 
 The term wave shape is used to denote the generator e.m.f. 
 wave, at no load. The voltage from a potential transformer 
 secondary is transmitted to the Standardizing Laboratory, 
 where the oscillograph is connected in. As the oscillograph 
 current is only about 0.2 ampere, the load on the potential trans- 
 former is inconsiderable. 
 
 Generator potential waves at various loads of unity or 
 other power-factors are sometimes required. When a series of 
 waves is taken, the oscillograph is brought near to the generator 
 or apparatus under test, and is in charge of an operator from the 
 Standardizing Laboratory. 
 
 Current waves are taken with the oscillograph connected 
 across a shunt (similarly to a millivoltmeter). The resistance 
 of the shunt should be selected to give a shunt potential drop of 
 at least 0.2 volt. A current transformer of suitable rating may 
 be used with a small shunt in the secondary. 
 
 34 
 
The flux distribution on generator or motor pole faces is 
 determined by obtaining the potential wave of a narrow exploring 
 coil, usually of only a few turns, on the armature. In d-c. 
 generators or motors the wave of potential between commutator 
 bars is sometimes taken. Where temporary slip rings are used 
 duplicate brushes should be placed on each ring to avoid the 
 effects of chattering. 
 
 When two waves, or three waves, are required together, 
 taken in their proper phase relation, such as the potential and 
 exciting current waves of a transformer, they are recorded 
 together by two elements or three elements in the oscillograph. 
 
 The Oscillograph 
 
 The oscillograph, on account of its short period (about 
 1 6000 second) can be applied in a great variety of tests where 
 a knowledge of rapidly varying currents or voltages is required. 
 
 For the oscillograph a d-c. circuit of about 8 amperes is 
 required to operate the arc, field, shutter, and film-driving 
 motor: the source is usually the 125 volt shop circuit. 
 
 The oscillograph current proper is small; about 0.2 ampere. 
 For current curves a shunt potential drop of at least 0.2 volt is 
 required, as the resistance in the oscillograph is 1 to 2 ohms. 
 One, two or three oscillograph elements may be used, the instru- 
 ment being regularly built as a three-element oscillograph. The 
 insulation between the elements is sufficient to stand several 
 times the ordinary 110 volts. 
 
 The oscillograph indication is adapted to the voltage by 
 adjustable resistance. 
 
 Its use for wave shapes is considered in preceding paragraphs. 
 
 For currents and voltages on opening or closing a circuit 
 the oscillograph is placed near the point of operation so that 
 the operation may be effected during the period of exposure of 
 the oscillograph. Where the operation is in response to a signal 
 it is usually not practicable to make the exposure much less 
 than a second. If it is necessary to have the record to a larger 
 time scale so that the film must be driven faster than 60 rev. 
 per min. for a shorter exposure than a second, the operating 
 mechanism and the oscillograph shutter are actuated by one 
 operator, or are connected together either mechanically or 
 electrically. In some tests the exposure can include more than 
 one revolution of the film, that is, the record may go more than 
 once along the film. In some cases the film revolves much more 
 slowly, to give an exposed record of several seconds or even a 
 minute or more. 
 
 For short-circuit tests of alternators, three-phase, quarter- 
 phase or single-phase, two oscillographs are usually used together, 
 one on the armature, and one on the field. If the record ends 
 before the transient is over, an auxiliary exposure is sometimes 
 made a few seconds later to obtain the permanent short-circuit 
 condition of the alternator. It is customary to connect a 
 resistance load across the exciter in parallel to the generator 
 
 35 
 
field. For three-phase short circuits, shunts are connected in, 
 one in each phase, on the ground side of the switch. 
 
 Where the duration is required, and is not otherwise given, 
 as frequently occurs in d-c. tests, one oscillograph element can 
 record on an alternating current timing wave of known fre- 
 quency; for instance, the 40 cycle shop circuit. 
 
 Visual inspection on the screen, sometimes with the help 
 of a moving mirror, is made for adjustment to a suitable scale, 
 where practicable, before the formal photographic record is 
 taken. 
 
 RESISTANCE MEASUREMENTS 
 
 Unit Employed 
 
 The unit employed is known as the "International Ohm." 
 It is represented by the resistance offered to an unvarying 
 electric current by a column of mercury at deg. C, 14.4521 
 gm. in mass, of a uniform cross-sectional area, and 106.3 cm. 
 in length. The cross-sectional area of this column is approx- 
 imately 1 sq. millimeter. 
 
 Primary Standard 
 
 The Company's primary standards consist of two 1 ohm 
 units of the Bureau of Standards form and two 1 ohm units of 
 the Reichsanstalt form, which are compared with the Govern- 
 ment Standards at Washington and certified to by the Bureau 
 of Standards. These certificates give the temperature at which 
 the units are correct and the temperature coefficient, if any; 
 i.e., the correction factor to apply when the temperature of the 
 unit differs from the standardizing temperature. 
 
 The Company has also other units of the same forms varying 
 in resistance from 0.0001 to 10,000 ohms which are used as 
 standards in connection with the 1 ohm units. 
 
 Working Standards 
 
 These consist of several current carrying units of various 
 current capacities and resistance values. They are frequently 
 compared with the primary standards referred to and also 
 with each other. 
 
 CLASSES OF RESISTANCE MEASUREMENTS 
 
 There are three general classes into which resistance measure- 
 ments may be divided. These are "Medium," covering a 
 range from 1 to 100,000 ohms; "Low," covering a range below 
 5 ohms; and "High," covering a range above 50,000 ohms. It 
 will be noted that the division line between the classes is not 
 very definite, i.e., the several ranges overlap each other. 
 
 Medium Resistance Measurements 
 
 For the measurement of medium resistance the "Wheat- 
 stone Bridge" and the "Slide Wire Bridge" are used. 
 
 36 
 
 
WHEATSTONE BRIDGE 
 
 Two types are in use, the "Post Office" pattern and the 
 "Decade" type. Both operate on the same principle. In the 
 ''Post Office" type the resistances composing the rheostat are 
 all connected in series and the reading is obtained by adding 
 all the values of the plugs that are out when a balance is obtained. 
 In the "Decade" type (also the dial type) only one plug is 
 used for each decade, and the reading is obtained directly, by 
 noting the values against the plugs that are in when a balance 
 is obtained. It is, of course, understood that in both cases 
 proper account must be taken of the ratios as plugged in the 
 "arms" of the bridge. Also, in both cases, only one plug in 
 each arm must be used and the values must be taken from the 
 plugs that are in. The following remarks will apply to both 
 types of bridge. 
 
 Good Contacts 
 
 All plugs and other contacts should be kept clean and 
 bright. The plugs should be cleaned every time the bridge is 
 used or, if in constant use, at least every day. This may be done 
 by wiping them with a piece of soft cloth or waste applied with 
 the finger. Never use emery cloth or polishing powder. The 
 key contacts may be cleaned by putting a piece of heavy paper 
 between them, pressing the key and pulling the paper out. 
 If very much corroded, a piece of worn crocus (not emery) cloth 
 may be used. 
 
 It is essential that all plugs should be tight. It is not neces- 
 sary to use much force, in fact this should not be done. The 
 plug should be given a slight rotary motion, at the same time 
 applying a gentle pressure. In removing the plugs, give them 
 a rotary motion in the same direction as when they were inserted. 
 The rotary motion should be in a clockwise direction, to prevent 
 unscrewing the plug heads. 
 
 Using Keys 
 
 To operate the keys (if they are in proper condition) only a 
 firm steady pressure is necessary. Pounding the keys must not 
 be allowed, since it ruins them. This applies to all testing keys, 
 as well as to bridge keys. 
 
 Choice of Ratios 
 
 In using the Wheatstone Bridge, it is best that the resistance 
 in the arms and the resistance in each of the four bridge arms 
 should be as nearly equal as possible, as this gives the most 
 sensitive arrangement. 
 
 Most bridges have a capacity of 1 to 9999 or 10,000 ohms 
 in the rheostat, with ratios for multiplying or dividing the 
 rheostat plugging by 1000. It is not advisable where other 
 means are at hand to use the 1/1000 or 1000/1 ratios, except 
 on a bridge of unusually accurate resistance adjustments, as 
 the 1 ohm coils are not as accurate as those of greater resistance. 
 Avoid using 1 ohm coils as far as possible. 
 
 37 
 
Temperature Coefficient 
 
 For ordinary bridge work in the factory and in general work 
 (outside of the laboratory) the temperature coefficient of the 
 bridge may be neglected, as it is too small to be appreciable 
 within the limits of the work under consideration. The temper- 
 ature coefficient of the material in test, however, must always 
 be considered; if an allowance for it is necessary to secure the 
 desired accuracy, it should be made. Apparent disagreement 
 between different departments frequently arises which on investi- 
 gation will often be found to be due to a disregard of the tem- 
 perature coefficient of the material under test. 
 
 Should it be necessary to make a temperature correction 
 for the bridge, great care must be taken to measure the temper- 
 ature of the bridge coils correctly. A thermometer placed in the 
 bridge box often does not nearly indicate the correct temperature 
 of the^ coils, especially if the surrounding temperature is rapidly 
 changing. The bridge should be kept in a nearly constant 
 temperature and the indications of the thermometer in the box 
 should remain substantially constant for at least one hour, 
 preferably for two or three hours. 
 
 SLIDE WIRE BRIDGE 
 
 This is a modification of the Wheatstone Bridge, the slide 
 wire forming two arms of the bridge and corresponding to the 
 ratio arms in the Wheatstone. 
 
 Ohmmeter 
 
 The so called "Sage" ohmmeter is essentially a slide wire 
 bridge arranged for portable use where approximate values are 
 sufficient. 
 
 This instrument is useful for special jobs and is found very 
 convenient, especially on outside work, i.e., where no fixed 
 bridge is available, such as in a power station, car barns, etc. 
 Its sensitiveness and consequently its degree of accuracy is 
 largely dependent on the hearing of the observer and the con- 
 dition of the dry cell batteries forming a part of the instrument 
 and supplying the necessary current for making a measurement. 
 A telephone receiver of the "watchcase" pattern is used on 
 this bridge in place of a galvanometer to determine when balance 
 is obtained. 
 
 • Instructions already given regarding contacts and plugs 
 apply. In addition the slide wire and "contact finger" should 
 be given proper attention. The wire can be wiped off with the 
 finger or a soft cloth when dirty. The contact finger may be 
 cleaned with crocus cloth. 
 
 Under no circumstances use any emery or crocus on the slide 
 wire as this will ruin the bridge. The bridge should be tested 
 before starting on an outside job, to see if it is in working order, 
 as the batteries deteriorate even when standing idle. Never leave 
 the bridge connected, as metallic dirt or conducting material 
 sometimes collects in the plug holes which may short circuit 
 and spoil the battery if the receiver switch is not in working 
 
 38 
 
order, as occasionally happens. This switch should receive 
 occasional attention. 
 
 The so called Weston ohmmeter is a low range voltmeter 
 with a scale graduated to read in ohms. It will give fairly 
 
 
 5 H3 
 
 w 
 o 
 
 < 
 
 . CO 
 bo h 
 
 E Pi 
 
 o 
 (J 
 
 to 
 
 O 
 
 § 
 Pi 
 <5 
 
 accurate results if the potential employed is constant and its 
 value properly taken into account. The inverse ratio of de- 
 flections of the instrument without and with the unknown 
 
 39 
 
resistance connected in series is a measure of the resistance in 
 ohms. It is further described under the section on " High Resist- 
 ance by D-C. Voltmeter." 
 
 The "Evershed" ohmmeter is a true ohmmeter, because the 
 scale readings are directly given in ohms and are independent 
 of the current or voltages used. This outfit is not to be discussed 
 here as its use has not been adopted. It is a valuable device 
 for certain purposes; for further information refer to the 
 makers or agents. 
 
 A comparison of the Evershed with the methods used in the 
 Sage and Weston ohmmeters show why the latter two are not 
 true ohmmeters. The Evershed apparatus is also used for high 
 and insulation resistances. 
 
 Low Resistance Measurements 
 
 Under this heading are included the "Thomson Bridge," 
 sometimes called "Double" Bridge, and the "Drop Method," 
 using an ammeter and voltmeter or their equivalents. Fig. 
 15 shows the wiring for a special application of the drop method. 
 This is used where the outfit can be permanently installed and 
 a special operator employed; therefore, further explanation will 
 not be given here. 
 
 THE THOMSON BRIDGE 
 
 This is a modification of the Wheatstone Bridge and is 
 suitable for use with low resistances, as its arrangement removes 
 the objection to the former, viz., the resistance of connections 
 and plugs. It is also a modification of the "Drop Method" 
 discussed later, but the accuracy of the results is not directly 
 dependent on the value of the current employed. As this device 
 is in the nature of a permanent fixture and a special operator is 
 generally employed for its use, further explanation is not con- 
 sidered necessary. 
 
 The instructions, already given, in reference to contacts, 
 plugs, slide wire, etc., also apply here. If a slide wire bridge 
 is not provided with a roller the contact must not be moved 
 until it is released from the wire. Failure to observe this will 
 soon ruin the wire, especially if it is of small diameter. 
 
 DROP METHOD (DIRECT CURRENT) 
 
 For this method current and potential measuring instruments 
 of suitable ranges are required, simultaneous readings being 
 taken on each; from these readings the resistance is calculated by 
 
 E 
 Ohm's Law (i?= — ). 
 
 The Current Standard must be connected in series with the 
 resistance to be measured, and, where practicable, a suitable 
 adjustable resistance for controlling the current. The volt 
 standard is connected across the resistance to be measured, so 
 as to measure its potential drop. A non-inductive resistance 
 may be connected in series with the voltmeter to alter its sen- 
 
 40 
 
sitiveness if required. This resistance should have a current 
 capacity equal to that of the voltmeter. 
 
 The instruments should be so chosen that the deflections 
 obtained are reasonably large, in order to reduce the error of 
 observation as much as possible. The current used should be 
 sufficient to give a good deflection on the ammeter. It must not, 
 however, be great enough to heat the resistance under test 
 and thereby change its resistance. This point is very important 
 and frequently overlooked; the greater the temperature coeffi- 
 cient of the material of the resistance the more important it 
 becomes. If the current employed in making the measurement 
 is not steady, two observers should take observations, one 
 reading the ammeter and the other the voltmeter. Simul- 
 taneous readings should be taken, each reading being repeated 
 several times, the average reading being used to determine the 
 final result. Neglect in considering the ratio of the resistance 
 of the voltmeter used to that of the apparatus under test some- 
 times introduces errors. If the ratio is large (2000 or more) the 
 
 r y =/OOor/ 
 /feac/zng onV=0. Svo/£ 
 
 law of divided circuits can be neglected and the result obtained 
 from Ohm's Law as previously stated. If the ratio is small, 
 allowance must be made, since a part of the current is shunted 
 through the voltmeter, which is also measured by the ammeter. 
 To illustrate this point take the following example, as per 
 Fig. 16: 
 
 Bv Ohm's Law R v = ' —=0.005 ohms. Whereas 
 
 100 amperes 
 making the allowance for shunted current through V (where r v 
 = 100 ohms) we get £* = 0.00500025 or 0.005 per cent, a differ- 
 ence too small to consider for this class of work. This is found 
 as follows: 
 
 The current i v through V is equal to the drop across R x or 
 
 -4 d V f S =0-005 amperes. Now i x = I-i v or 100-0.005 
 r v 100 ohms 
 
 E 0.5 
 = 99.995. Since the value of R x is equal to " 7 " = qq~qq = 
 
 = 0.00500025, the value as given above. Again supposing r v = l 
 and following the same reasoning we get R x = 0.005025 or 0.5 
 per cent, a difference which is too large to be neglected. 
 
 41 
 
High Resistance Measurements 
 
 Under this heading, "High Resistance D-C. Voltmeter," 
 "Insulation Resistance Measuring Sets" and "Meggers" are 
 considered. 
 
 HIGH RESISTANCE D-C VOLTMETER 
 
 A high resistance instrument (50,000 ohms or more) is gen- 
 erally used for high resistance measurements. For lower 
 resistances, lower voltages and a lower resistance voltmeter 
 may be used. The Weston ohmmeter belongs to this class. 
 In these cases on the voltmeter, the deflection is directly pro- 
 portional to the current flowing through it, and inversely 
 proportional to the resistance of the circuit with constant 
 potential across it. 
 
 A constant potential of about 500 volts is usually employed. 
 This voltage reading is determined by connecting the terminals 
 of the supply directly to the voltmeter. The resistance to be 
 measured is then connected in series with the voltmeter and a 
 second reading made and noted. The resistance X is then given 
 
 by the formula ir^=^; Then R m + X = ^ 
 
 where R m = resistance of the voltmeter used; D m the deflection 
 of the voltmeter with resistance in series; V the voltage of the 
 supply when taking reading D m , and X is the resistance sought. 
 
 If the value of X is large relative to R m it is not generally 
 necessary to subtract R m to get X, and this is not usually done. 
 
 In making these measurements do not attempt to use a 
 voltmeter which reads lower than the voltage of supply, as in 
 case the resistance is omitted the instrument is likely to burn 
 out. Do not try to get results by this method unless the supply 
 is steady and constant or a second voltmeter is connected directly 
 to the line all the time with a second observer for taking simul- 
 taneous readings. When two instruments are used do not get 
 their resistance values mixed; the resistance of the instrument 
 reading the voltage is immaterial. 
 
 A suitable reflecting galvanometer calibrated to read in volts 
 may be used in place of the voltmeter. The method and cal- 
 culations are the same as described above. 
 
 INSULATION RESISTANCE TESTING SETS 
 
 The principle of operation is similar to that of the d-c. 
 voltmeter, a shunt box being added to increase the range of the 
 galvanometer which is used in place of the voltmeter in the 
 other method. 
 
 The galvanometer constant K = and the re- 
 
 10 X c 
 re- 
 sistance = 77- c where D = deflection of galvanometer when 
 
 taking constant; D 2 when making observation; S = multi- 
 plying factor for shunt; R = resistance in ohms in series when 
 taking constant ; C and C 2 = number of cells used when taking 
 constant and observation respectively. 
 
 42 
 
Complete instructions are furnished with the portable outfit 
 when sent out. The permanent outfits work on the same 
 principle and are generally installed with other testing apparatus 
 where a special operator is available. 
 
 The following points should be mentioned. The various 
 parts of the entire outfit, including the connecting wires (both 
 internal and external), must be properly insulated from each 
 other and from earth to prevent leakages. If this is not done, 
 leakage currents may pass through the galvanometer and not 
 through the resistance being measured, thus falsifying the 
 results. 
 
 If the resistance being measured lies between the earth and 
 some conductor, as is the case with a lead covered cable, one 
 side of the galvanometer should be connected directly to earth, 
 taking precaution to insulate the rest of the circuit well. To 
 form an earth, a bare wire may be used grounded to earth, to 
 which one side of the galvanometer is connected. With this 
 arrangement, if any leakage occurs, the leakage current is 
 shunted by the galvanometer and does not affect the readings. 
 Where possible, leakage should be eliminated, but reasonably 
 correct results can be obtained by testing, changing over the 
 connections and averaging the results. 
 
 When making insulation measurements on cables installed 
 underground, tests should be made for earth currents. To do 
 this, disconnect the battery and short-circuit the terminals to 
 which the battery was connected. Then, connect to ground and 
 to line and observe the galvanometer deflection. If there is no 
 deflection no earth currents exist, if there is a deflection of 
 constant direction and amount a dead resistance equal to the 
 internal resistance of the battery can be substituted in place of 
 the short-circuiting wire and the amount and direction of the 
 galvanometer deflection can again be observed. This deflection 
 is added to or subtracted from the deflection obtained when 
 making the test, before dividing into the constant. Since the 
 battery resistance is small compared to the resistance under test, 
 it can usually be neglected and the deflection used as obtained 
 with the short-circuiting wire. If the earth currents are very 
 appreciable or unsteady in amount or direction, the test should 
 not be taken until the conditions are more suitable. 
 
 Chloride of Silver Dry Cell Batteries are generally used to 
 supply the current for these resistance measurements. 
 
 These cells are very quickly ruined by short-circuiting or 
 using them on too low a resistance. The cells should never have 
 less than 5000 ohms per cell connected in series with the circuit 
 connected to them. 
 
 Never put into the battery covers wires or other material 
 which could short-circuit the cells. The space between the 
 covers and cell tops may seem to be a convenient place to 
 carry spare wire but this practice causes trouble. Abrasion of 
 the insulation on the lead wires supplied with the batteries may 
 short-circuit the cells, and must be watched. 
 
 43 
 
The cells should be tested before using to see that they are 
 in good order (giving about 0.8 to 1 volt). In any case the e.m.fs. 
 of the cells must be sufficient to allow the operator to get correct 
 results. The resistance of the voltmeter used should be at least 
 5000 ohms, or if several cells in series are tested at once, the 
 voltmeter resistance in ohms must be at least 5000 times the 
 number of cells tested in series. 
 
 It frequently happens that some of the cells in a battery 
 give only a fraction of their proper voltage; in such cases the 
 voltage of each individual cell must be considered when making 
 a test, and the total voltage must not be estimated merely from 
 the number of cells in use, but actually measured. 
 
 Wherever possible, cells below normal voltage should be 
 rejected and replaced by new cells. 
 
 The " Marcuson Portable Testing Battery" is used when 
 an outfit is permanently installed. As this is a form of storage 
 cell it will stand an appreciable amount of current as compared 
 with the Chloride of Silver Dry Cell Battery. The voltage is 
 also more dependable and being about twice as much per cell 
 requires only half the number of cells. 
 
 The galvanometer shunt boxes and series resistances are 
 marked with different units from those used on the portable 
 outfits and a slightly different formula is used but the principle 
 and general arrangement are the same. As there is a special 
 operator where more sets are installed, further mention will not 
 be made here. 
 
 MEGGER 
 
 This instrument, developed by Sidney Evershed, of London, 
 combines, in one convenient case, both the measuring instru- 
 ments and the current supply apparatus. The current is fur- 
 nished by a magneto generator operated by a hand crank. 
 Those in use by this Company are known as "Constant Pres- 
 sure Meggers," and the drive is through a slip device so that the 
 proper speed is maintained after having once been reached. 
 The proper speed can easily be determined after a few trials. 
 It is only necessary to turn the crank fast enough, as the gener- 
 ator cannot be driven at too high a speed. 
 
 The insulation to be measured is connected between the 
 two terminals, the crank turned, and the insulation resistance 
 read directly from the scale while the crank is being operated. 
 If one of the conductors surrounding the insulation is earth, 
 this should be connected to the terminal on the megger marked 
 "earth." 
 
 Before a measurement is taken all leads should be discon- 
 nected and the index set to "infinity." This is done by turning 
 the crank and bringing the index to read "infinity" by operating 
 the index adjuster. 
 
 These instruments are made in several capacities ranging 
 from 40 to 2000 megohms full scale deflection and should be 
 selected according to the resistance to be measured. 
 
 The magneto in these instruments generates a voltage as high 
 as 1000 and a very uncomfortable shock may be received. Care 
 
 44 
 
should therefore be used in handling the leads or touching the 
 terminals when the magneto is in operation. 
 
 The instrument is very conveniently portable and for outside 
 work is generally to be preferred to the insulation resistance sets. 
 
 MEASUREMENT OF ELECTROMOTIVE FORCE 
 
 The unit of electromotive force is the international volt. 
 This is the electrical pressure, which, when steadily applied to 
 a conductor the resistance of which is one international ohm, 
 will produce a current of one international ampere. Weston 
 Standard Cells whose e.m.f. is certified to by the National 
 Bureau of Standards are used as a primary standard of e.m.f. in 
 the Standardizing Laboratory. 
 
 The Potentiometer 
 
 To compare an e.m.f. directly with the standard, the poten- 
 tiometer is used. The e.m.f. of the standard cell is balanced 
 against the drop of potential caused by passing current through 
 the potentiometer shunt from a storage cell. This shunt consists 
 of a series of adjusted resistance coils and a slide wire marked 
 to scale. By setting the contacts of the circuit containing the 
 galvanometer and the standard cell at scale points indicating the 
 exact voltage of the standard cell, and adjusting the storage 
 battery current until the circuit balances and the galvanometer 
 reads zero, the potentiometer becomes direct reading. Any 
 external d-c. voltage not exceeding 1.5 volts may then be read 
 by balancing it against the drop across a suitable part of the 
 potentiometer shunt. For extreme accuracy, a small correction 
 is made to allow for known differences in the resistance of the 
 various sections of the slide wire. To measure higher voltages 
 a multiplier is used which will reduce 15, 150 or 750 volts to the 
 1.5 volts required for the potentiometer. 
 
 Voltmeters 
 
 For a working standard of direct voltage a G-E laboratory 
 standard d-c. voltmeter is used, and for alternating voltage 
 a G-E laboratory standard a-c. voltmeter. These are frequently 
 calibrated to the primary standard. In the case of the a-c. 
 instrument, reversed readings are made in calibration, to insure 
 agreement between the a-c. and d-c. calibrations. The instru- 
 ments to be calibrated are compared with the working standards 
 by means of a system of multipliers which give the necessary 
 range to the working standard. 
 
 For the measurement of direct voltages, G-E Type DP2 
 D'Arsonval voltmeters are used. There are also a few Weston 
 instruments still in use. These give a range from 1 to 750 volts 
 with full scale reading, and, by means of multipliers, up to 3000 
 volts. These instruments operate by the torque produced on a 
 movable, current-carrying coil located in the field of a permanent 
 magnet. A very powerful stray field may partially demagnetize 
 or cross-magnetize the instrument and permanently change its 
 calibration. The DP2 instruments are shielded; some of the 
 
 45 
 
Weston instruments are not. The unshielded instruments are 
 easily affected by stray fields. These instruments are also made 
 up as millivoltmeters with low resistances, with low scale read- 
 ings from 200 millivolts up. 
 
 Never connect any instrument marked " Millivoltmeter " or 
 "Special Meter" across higher voltage than it reads, otherwise 
 the instrument will burn out. To measure voltage higher than 
 the capacity of the instrument a multiplier may be placed in 
 series with it. Then if E is the corrected reading of the volt- 
 meter, V the voltage to be measured, R v and R m the resistances 
 of the voltmeter and of the multiplier, 
 
 V = EX Rv ~t Rm 
 
 Rv 
 
 or, two voltmeters may be placed in series and careful simul- 
 taneous readings taken; the sum of the two corrected readings 
 is the voltage to be measured. One of the two voltmeters may be 
 considered as a multiplier for the other; then if E\ and £2 are the 
 corrected readings on the two instruments at one point, and E 
 is the corrected reading on the first instrument at any other 
 point, 
 
 For both a-c. and d-c. instruments the Standardizing Lab- 
 oratory furnishes a curve and sometimes a certificate. On these 
 curves the correction to be added to or subtracted from the 
 instrument reading is plotted against the indication of the 
 instrument. The certificate shows the comparison of the read- 
 ings of the instrument with those of a correct standard. These 
 curves and certificates should be used to correct readings and 
 to determine the proper reading for any voltage required. 
 
 The Laboratory also furnishes a constant, A~, for d-c. instru- 
 ments which are used in the Testing Department. This con- 
 stant K is such that if V = corrected voltage and E = reading of 
 of the instrument, 
 
 V = KXE 
 V 
 From this E =-^ 
 A 
 
 Therefore, to obtain the reading on the instrument which 
 corresponds to the voltage required, divide the correct voltage 
 by the constant of the instrument. Since these constants are 
 never far from unity, the equation 
 
 E = (2-K) X V= V+(l-K) X V 
 is nearly true. This is the most convenient method for getting 
 the proper reading. 
 
 Illustration : 110 volts required, K = 1.003 
 E=V + (l-K)XV 
 
 = 110 + (1-1. 003) XI 10 
 = 110-0.003X110 
 = 109.67 
 
 46 
 
This constant should be used only to make an approximate 
 correction and should not be used where an accuracy of 0.5 per 
 cent or better is desired. 
 
 D-C. voltmeters should be disconnected from field circuits 
 while the field switch is being opened, because of the inductive 
 kick, which frequently bends the needle. They should also be dis- 
 connected from synchronous motor or synchronous condenser 
 fields, while the machines are starting from the a-c. side because 
 of the high alternating voltage developed by transformer action 
 in the field windings during starting. This voltage will some- 
 times puncture or burn out a voltmeter. 
 
 A voltmeter should always be connected through a double- 
 pole switch, and should be kept out of circuit when not in use, 
 as its readings may change with long continued heating. The 
 cover glass should never be rubbed before reading on account of 
 the electrostatic effect on the needle. If a cover glass shows 
 electrification, it may be discharged by moistening it with the 
 breath. No moisture should be allowed to reach the inside of 
 the instrument. 
 
 Two types of Thomson voltmeters are generally used for 
 the measurement of alternating voltage, — Type P and Type P3. 
 The P3 instrument may also be used on direct voltage without 
 sensible error, but the P instrument must not be so used for 
 accurate work unless nearly full scale readings are taken. These 
 instruments have a range of from 15 to 750 volts full scale read- 
 ing. 
 
 On account of the spreading of certain parts of the scale, an 
 a-c. voltmeter cannot be used with accuracy as low on the scale 
 as a d-c. instrument. In general a P instrument should not 
 be used below }/$ its maximum reading. The P instruments, 
 containing no permanent magnets or shields, are also sensitive 
 to the action of stray fields, especially if this field alternates at 
 the same frequency as the voltage applied to the instrument. 
 They should, therefore, be kept away from masses of iron and 
 from cables carrying heavy currents, and should be placed at 
 least two feet from other instruments. The P3 instruments 
 are much less sensitive to stray fields, and may be placed within 
 two inches of one another without sensible error. 
 
 Cables carrying heavy currents, whether direct or alternating 
 current, should be kept close together. They must never pass on 
 opposite sides of a machine standing on an iron floor. If an instru- 
 ment reads alike in four positions 90 deg. apart, it is unaffected 
 by stray fields. Protection from stray fields for an unshielded 
 instrument is sometimes obtained by placing the instrument 
 in an open topped iron box. The accuracy of the indication, 
 however, may be slightly changed by the proximity of the iron 
 to the field of the instrument. 
 
 Care should be taken that voltage leads are always connected 
 to the points between which the difference of potential is to be 
 read. Thus, in reading volts across the armature on a com- 
 pound wound d-c. machine, the leads should be attached to the 
 brushes, while in reading volts across the machine thev should 
 
be attached to the outer end of the series field and the brush 
 ring of opposite polarity. In any circuit where voltage drop is 
 measured, the resistance of an extra connection in the main 
 current circuit included between the voltmeter contacts is often 
 sufficient to cause serious error. Only the voltmeter current 
 should flow through the voltmeter leads. 
 
 Potential Transformers 
 
 For most commercial alternating voltages a 130 or 150 volt 
 voltmeter is used in connection with a potential transformer. 
 The transformer voltages given in the following table are in 
 common use. In addition to this list of standard transformers, 
 there are in the Testing Department a few transformers of 
 other descriptions for special uses. 
 
 STANDARD POTENTIAL TRANSFORMER VOLTAGES 
 
 Primary Volts Secondary Volts 
 
 OIL INSULATED, IRON CASE 
 
 13200 
 11000 
 
 110 
 110 
 
 ■ 
 
 DRY INSULATED, IRON CASE 
 
 
 6600 
 5500 
 
 110 
 110 
 
 DRY INSULATED, MARBLE BASE 
 
 » 
 
 3300 
 
 2200 
 
 1100 
 
 550 
 
 220 
 
 110 
 110 
 110 
 110 
 110 
 
 DRY INSULATED, PORTABLE, WOODEN CASE 
 
 1100/2200 
 550/1100 
 
 110/220 
 110/220 
 
 Most of these transformers are designed for use at any fre- 
 quency from 25 to 60 cycles. They are tested with a load of a 
 single instrument at from 80 to 120 volts secondary and should 
 not be loaded with more than two instruments nor used outside 
 this range of voltage or frequency except when special arrange- 
 ments have been made with the Standardizing Laboratory and 
 
 48 
 
the transformers have been checked under the proper conditions. 
 The transformer primary must be connected to the line and the 
 secondary to the instruments. 
 
 In the portable type there are four primary and four second- 
 ary terminals, from which three voltage ratios may be obtained; 
 viz., series multiple, multiple multiple or multiple series con- 
 nection. For series connection, the two inner terminals are 
 connected and the lines or instrument leads are connected to the 
 two outer terminals. For multiple connection, the two terminals 
 on one side are connected to one line or lead and the two on the 
 opposite side are connected to the other. The cases of the iron 
 potential transformers should always be grounded. No changes 
 should ever be made in connections with the high potential on. 
 
 MEASUREMENT OF CURRENT 
 
 The primary standard of current is the silver voltameter 
 which is used for comparison occasionally. The practical 
 standard used is a set of very accurate standard current-carrying 
 resistances. The voltage drop across these resistances is meas- 
 ured by the potentiometer. The current value is then obtained 
 by multiplying the voltage by a constant depending on the 
 resistance used. 
 
 A G-E laboratory standard millivoltmeter used in connection 
 with a multiplier and set of shunts constitutes the working 
 standards of direct current. The working standards for alternat- 
 ing current include a series of Kelvin balances covering a wide 
 range of currents. ! The working standards are calibrated from 
 the potentiometer, reversed readings being used for the balances. 
 The portable instruments are compared with the working 
 standards. 
 
 For the measurement of direct current, G-E Type DP2 
 ammeters and some Weston ammeters are used. The DP2 
 instruments are self-contained with full-scale readings from 
 150 milliamperes up to 30 amperes. The Weston instruments 
 are self-contained up to 200 amperes. The DP2 millivoltmeters 
 of 200 millivolts full scale are used with G-E portable shunts 
 from 30 to 3000 amperes capacity. For higher ranges manganin 
 oil-cooled shunts are used in connection with the same millivolt- 
 meter. There are also some 500, 1000, and 2000 ampere shunts 
 of 400 millivolts drop at rated current which are used in con- 
 nection with 400 millivolt Weston instruments. For heat runs 
 where high accuracy is not required, Thomson station shunts 
 ranging up to 15,000 amperes are used with DP2 millivoltmeters 
 of 60 millivolt full scale. This combination has an appreciable 
 temperature coefficient, and should not be used for accurate 
 measurements without special instructions from the Standard- 
 izing Laboratory. 
 
 In reading a millivoltmeter attached to a shunt, assume the 
 end of the scale to represent the rated amperes of the shunt, and 
 read the result accordingly. To correct for instrument error, 
 multiply by the instrument constant, or use the certified values. 
 In case the millivoltmeter and shunt have been certified as a 
 
 49 
 
unit, the correction shown in the certificate includes errors of 
 both instrument and shunt. If the instrument error is separately- 
 certified, correction may be made for the shunt error by multiply- 
 -p 
 
 ing by -=r=, where E= rated volts drop of the shunt, / = rated 
 
 current of the shunt, and R = actual resistance of the shunt. 
 
 This correction is very small, and may usually be neglected. 
 
 For measuring current beyond the capacities of the instru- 
 ments at hand, two ammeters may be placed in multiple; but 
 both instruments must be read simultaneously at every point. 
 If two shunts are used in multiple, millivoltmeters must be con- 
 nected to each and readings taken on both. 
 
 For the measurement of alternating current, Types P and P3 
 ammeters are used. The general statements as to voltmeters 
 apply equally to ammeters of the same type. The ammeters are 
 somewhat more likely to produce stray fields, especially the high 
 current instruments. Ammeters should be protected by a short- 
 circuiting switch, which is kept closed except when reading. 
 
 The usual method of measuring high alternating currents is 
 by using current transformers in connection with low reading 
 ammeters. The standard commercial G-E transformers have 
 a 5 ampere secondary. These are used in the Testing Depart- 
 ment for all purposes. Current transformers have a core and 
 windings like a low voltage, high current power transformer, but 
 are insulated to stand considerable voltages, but they should 
 never be used on circuits whose voltage exceeds that given on 
 the nameplate. The ratio given by the Laboratory for a point 
 is accurate at that point, but the ratio varies somewhat for lower 
 or higher currents. The secondary should not carry more than 
 two instruments. The secondary circuit of a current trans- 
 former must never be open while current flows through the 
 primary. If this precaution is not taken, there is danger of 
 the transformer overheating and thereby breaking down the 
 insulation. There is also danger to anyone handling the second- 
 ary, owing to its high voltage. Opening the secondary while 
 current flows in the primary also magnetizes the transformer 
 core, which causes a change in the ratio of currents and in the 
 phase angle between them. The transformer should, if subjected 
 to this high magnetization, be carefully demagnetized before 
 being relied on for precision work. 
 
 Demagnetization may be carried out by putting at least one- 
 half load primary current through the transformer with 10 ohms 
 or more connected to the secondary, in series with the instru- 
 ments to be used. This resistance should then be gradually 
 reduced to zero, by steps of one ohm or less. All these trans- 
 formers can be used on circuits operating at 25 to 125 cycles. 
 
 To measure the currents in a three-phase circuit, two equally 
 rated current transformers and three ammeters are necessary. 
 The primaries of the two transformers are placed in two of the 
 lines; the secondaries are connected with like polarities together 
 (straight connection); a common connection is added so as to 
 short-circuit both secondaries. One ammeter is placed in each 
 
 50 
 
separate transformer secondary circuit; the third ammeter goes 
 in the common line, and reads the current in the third phase. 
 Where both voltage and current are small, as in the testing of 
 small induction motors, three similar current transformers should 
 be used to avoid unbalancing the circuit. 
 
 MEASUREMENT OF POWER 
 
 There is no primary standard of electrical power in practical 
 use. Wattmeters for general use are tested on direct current; 
 for special accuracy, particularly under low power conditions, 
 alternating current is used for the test. In the d-c. test, 100 
 volts, as given by a laboratory standard voltmeter is applied to 
 the potential circuit of the wattmeter, and current, measured 
 on a laboratory standard ammeter, is sent through the watt- 
 meter current circuit. The product of the volts and amperes 
 gives the true watts. Readings are taken direct and reversed 
 and the average is used as the true a-c. value. When the a-c. 
 test is made, the wattmeter is compared directly with a cali- 
 brated dynamometer. If a test at low power-factor is desired, 
 the phase position of the voltage supplied to the potential 
 circuits of the instrument and the standard is controlled by a 
 phase shifting transformer. 
 
 P and P3 instruments are used in the Testing Dept. Their 
 potential circuits are for 150 volts, with current circuits ranging 
 from 1 to 200 amperes. The full scale readings range from 150 to 
 20,000 watts. The P instruments are the more sensitive to stray 
 fields. 
 
 Never apply more than the rated voltage to the potential 
 circuit. The current circuit will carry up to three times the 
 rated amperes for a short time. The accuracy of the wattmeter 
 depends but slightly on the ratio of current and potential 
 applied. W T attmeter readings may be corrected by reference 
 to curves or certificates as previously stated for voltmeters. 
 Current and potential transformers may be used with wattmeters 
 where the current or potential is larger than the wattmeter 
 rating. The secondaries of current transformers used on poly- 
 phase circuits with wattmeters should not be interconnected. 
 
 When wattmeters are used with current or potential trans- 
 formers, the potential circuit, current circuit, and case of the 
 wattmeter should be connected together with a light fuse wire, 
 to prevent differences of potential between the coils and case. 
 
 If R w is the corrected reading of the wattmeter, C the certified 
 ratio of the current transformer, and P the certified ratio of the 
 potential transformer, 
 
 True watts =PXCXRw 
 
 When reading a small power at a moderately high voltage 
 on a wattmeter, the wattmeter reading may be affected by the 
 losses in the instrument itself. If the current flowing in the 
 voltage circuit of the wattmeter passes also through the current 
 coil, the wattmeter reads the losses in its potential coil. If a 
 voltmeter is similarly connected, the wattmeter reads its losses 
 
 51 
 
also. If E is the applied voltage and R the resistance of the loss 
 circuit, then, since the circuit is practically non-inductive, 
 
 loss=iT 
 
 If the wattmeter and voltmeter are so connected as to 
 prevent the current in the potential circuits from flowing through 
 the current coil, the wattmeter reads the losses in its current 
 coil, and the voltmeter reads the drop through the wattmeter 
 current coil in addition to the voltage across the load. These 
 errors are nearly always negligible. If the wattmeter reads the 
 losses in potential circuits, a measure of the amount of the losses 
 may be had by reading the wattmeter, after opening the load 
 circuit so as to leave all instruments connected to the main 
 lines. This is called reading stray power, and is a good check 
 for leakage losses. 
 
 In measuring the watts in a two-phase circuit, each phase 
 should be considered as a separate single-phase circuit. The 
 sum of the readings on two wattmeters gives the total watts. 
 
 In a three-phase three-wire circuit two wattmeters should be 
 used. The current coils should be placed in two of the phases 
 and each potential coil connected from that phase in which its 
 current circuit is placed, to the third phase. The algebraic sum 
 of the wattmeter readings gives the total watts. The higher 
 reading wattmeter is always positive; the lower reading is posi- 
 tive if the power-factor is above 0.5, negative if it is below 0.5. 
 To determine by test whether the reading is positive or negative, 
 open the phase to which the wattmeter in question is not con- 
 nected. This leaves a single-phase circuit on the wattmeter; 
 if the wattmeter still reads forward, it will give positive values on 
 the three-phase connection. If it reads backwards, it gives 
 negative readings on three-phase. 
 
 To read the watts in a three-phase four-wire circuit, three 
 wattmeters should be used. The current coils should be con- 
 nected in the three-phase lines, and each potential coil should 
 be connected from the line in which its current coil is placed to 
 the neutral line. The total watts equal the, sum of the corrected 
 indications of the three wattmeters. The same method may be 
 used on a three-phase three- wire system by connecting the 
 potential circuit of the three instruments in Y, thus forming a 
 neutral point for the instruments. The instruments must have 
 equal resistances in the potential circuits. If potential trans- 
 formers are used with the primaries connected in Y on a three- 
 phase three-wire circuit, the secondaries should be connected 
 in delta to the potential circuits of the wattmeters. 
 
 If a wattmeter potential circuit is not absolutely non-inductive 
 the current in it will have a slight phase displacement relative to 
 the voltage across the wattmeter terminals. This is equivalent 
 to a change in the phase angle between the voltage and current 
 of the main circuit as read on the wattmeter. Hence, wattmeters 
 are subject to an error, from which ammeters and voltmeters 
 are free. If a current and a potential transformer are used 
 
 52 
 
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 54 
 
there is usually a further phase difference between primary and 
 secondary current in the former, and between primary and 
 secondary voltage in the latter. The result of these three 
 angular changes is a change in the phase relation in the watt- 
 meter. The total change rarely exceeds 2 degrees, and is fre- 
 quently less than 30 minutes. At or near unity power-factor its 
 effect on the reading is inappreciable; but at a very low power- 
 factor large errors may result. 
 
 Correction for Phase Angle 
 
 Correction of wattmeter readings for errors due to phase 
 angle of wattmeter, current transformers, and potential trans- 
 formers, may be made as follows: — 
 
 A — Single-phase circuits. 
 
 (1) Correct all instruments for scale error. 
 
 (2) Obtain a, the equivalent phase angle of the wattmeter, 
 from the certificate. (This is very small for the P and P3 watt- 
 meters, and can usually be neglected.) 
 
 (3) Select £, the phase angle between the primary and 
 (reversed) secondary currents of the current transformer, from 
 the certificate, using the reading of the ammeter in series with 
 the wattmeter. 
 
 (4) Select 7, the phase angle between the primary and 
 (reversed) secondary voltages of the potential transformer from 
 the certificate, using the reading of the voltmeter in parallel 
 with the wattmeter. 
 
 (5) Determine cos 2 , the apparent power-factor from the 
 
 readings of the ammeter, voltmeter and wattmeter (corrected 
 
 according to Xo. 1) by the formula 
 
 ^ , . Watts 
 
 Power-factor = — - w 
 
 volts X amperes 
 
 (6) Add algebraically a, /3 and 7, using the signs as given 
 in the certificates. 
 
 (7) Select the correction factor from Tables 1 or 2. In 
 these tables a series of values of ( a-\-(5-\-y) is given in the left 
 hand column; in the first line across the top of the columns is 
 given a set of values of the apparent power-factor (cos 02-) 
 The correction factor is found in the column under the proper 
 apparent power-factor in line across the page from the proper 
 value of ( a +0+7). For values lying between those given in the 
 tables, interpolation will give sufficient accuracy for most cases. 
 
 Table 1 should be used when ( a + +7) is a positive angle 
 and the power-factor of the circuit supplying the wattmeter 
 is lagging, or when ( a +/3 +7) is a negative angle and the power- 
 factor of the circuit is leading. 
 
 Table 2 should be used when ( a +/3 +7) is a positive angle 
 and the power-factor is leading, or when ( a +/3 +7) is a negative 
 angle and the power-factor is lagging. 
 
 (8) True watts = wattmeter reading corrected according to 
 (1) X certified ratio of current transformers X certified ratio of 
 potential transformer X correction factor for phase angle. 
 
 55 
 
If the greatest accuracy or values outside the limits of the 
 table are required, the following method may be used: 
 
 Follow (1), (2), (3), (4) and (5) as given herewith. If cos 6 
 represents the true power-factor of the circuit, being considered 
 a positive angle for lagging current and a negative angle for lead- 
 ing current, 
 
 0=02 + (a+/3+ 7 ) 
 Then 
 
 True watts = wattmeter reading corrected according to 
 (1) X certified ratio of current transformer X certified ratio 
 
 of potential transformer X — 
 
 cos 6 2 
 
 — is the correction factor given in Tables 1 and 2. 
 
 Co$ 02 s 
 
 B — Three-phase three-wire circuits with currents and voltages 
 balanced. 
 
 When two wattmeters or a polyphase wattmeter are used 
 with similar current transformers whose secondaries are equally 
 loaded and not interconnected the total watt reading may be 
 corrected for phase angle by the same method as on single-phase, 
 using the apparent power-factor of the three-phase circuit which 
 is 
 
 Total wattmeter reading 
 3 X volts (delta) X amperes of one line 
 instrument corrections being applied as per (1). 
 
 C — Other polyphase circuits. 
 
 On three-phase four-wire circuits, three-phase three-wire 
 circuits, whose currents or voltages are unbalanced, and two- 
 phase circuits each wattmeter should be treated as a separate 
 single-phase instrument obtaining the apparent power-factor 
 from its reading and of the voltmeter and ammeter in the same 
 phase, consequently using a different correction factor for each 
 wattmeter. On a three-phase three-wire circuit using the two- 
 wattmeter method, it should be noted that the current is fre- 
 quently leading in one wattmeter and lagging in the other. 
 
 MEASUREMENT OF POWER-FACTOR 
 
 Watts 
 
 The power-factor of a single-phase circuit = . , 
 
 b ^ volts X amps. 
 
 It is usually obtained by using the readings of the voltmeter, 
 ammeter and wattmeter. 
 
 In a balanced three-phase circuit, the power-factor may be 
 obtained from the two wattmeter readings. If a is the phase 
 angle, the power-factor = cos a, and R is the ratio of the smaller 
 to the greater wattmeter reading, 
 
 Tana=—~y/3 
 
 56 
 
The principle of the General Electric Company balanced 
 three-phase power-factor meter uses this fact. The elements 
 are so combined into one instrument that the position of the 
 pointer depends on the ratio of the watts. The instrument is 
 quite accurate, and independent of frequency. 
 
 The volt-amperes in a balanced three-phase circuit are 
 equal to the product of the amperes per line, the volts between 
 lines, and the square root of three. 
 
 57 
 
CHAPTER 3 
 
 ASSEMBLY OF MACHINES FOR TEST 
 
 HANDLING MATERIAL 
 
 When erecting large apparatus for test, methods of handling 
 and transportation are of prime importance. Each piece of 
 apparatus must of course be handled with reference to its 
 special construction. Practically all of the handling of the larger 
 machines and parts is done by the crane men and crane followers, 
 but each test man should become familiar with the correct 
 methods of handling such material and see that such work is 
 carried on in the approved manner. 
 
 There is a great difference between ropes and slings used for 
 hoisting. In ropes the wear can always be seen by the strands 
 becoming frayed, loose, or cut. A chain, except for a few 
 bruises, will not show any signs of weakness, even though, at 
 the same time, it may be full of small cracks which cannot be 
 seen by the naked eye, or it may be much crystallized by long use. 
 
 Care should be used in every case to see that satisfactory 
 slings and ropes are used to lift apparatus. 
 
 There are many varieties of hitches and knots, some of 
 which are shown on the following pages. 
 
 Wire cable slings occupy a very important place in hoisting 
 and have been found very satisfactory when carefully used. 
 
 In using slings of any kind care should be taken to see that 
 one section does not lie on top of another and thus put an undue 
 strain on the outer section. 
 
 It often happens when a rope sling is used double that the 
 ends of the rope are passed through the double part. Unless this 
 is done carefully the effect of only one part will be obtained 
 instead of two. 
 
 Increased Stresses Due to Angle of Slings 
 
 When a weight is lifted by two or more slings connected to 
 the crane hook and making an angle with each other, the increase 
 in the stress of the individual slings must be considered. On 
 account of this angle between the two sets of slings the stresses 
 on each set is greater than half the total load, and increases very 
 rapidly as the angle between the sling and the work is decreased. 
 An angle of 45 degrees between the sling and the work makes 
 the stress in each sling % of the total weight, and the collapsing 
 force between the two points of attachment to the work is equal 
 to Yi the weight. This collapsing force acts in a direct line 
 between the two points of attachment. If the work is ring 
 shaped, it would tend to deform the ring. A spreader of suffi- 
 cient stiffness should be used between these two points to resist 
 this collapsing force. It will be seen that eyebolts are not 
 suitable for attaching the slings to the work unless a spreader 
 is used to relieve them of this side pull, which would put a 
 heavy bending moment on the shank of the bolt. 
 
 58 
 
Reducing the angle between the sling and the work to 30 
 degrees makes the stress in each sling equal to the total weight 
 and the collapsing force is also equal to the total weight. Such 
 a small angle should never be used if avoidable. 
 
 The following tables show how the safe load becomes very 
 much smaller when the slings are used at an angle instead of a 
 straight pull. 
 
 SAFE LOAD IN LB. ON MANILA ROPES AND SLINGS 
 
 
 Two Part Sl/ng 
 
 Two Part Sling 
 
 Two Port Sling 
 
 Two Port Si in g 
 
 Rope 
 
 i 
 
 i 
 
 A 
 
 
 
 Diam. 
 
 
 
 / \ 
 
 y/\ 
 
 
 in In. 
 
 
 
 / \ 
 
 / \ 
 
 ^^\^ 
 
 
 Vertical Looc/ 
 
 60° Angle 
 
 45"Ang/e 
 
 xn"Angle> 
 
 V?. 
 
 500 
 
 435 
 
 355 
 
 250 
 
 % 
 
 1000 
 
 870 
 
 710 
 
 500 
 
 Vx 
 
 1500 
 
 1300 
 
 1065 
 
 750 
 
 V* 
 
 2000 
 
 1750 
 
 1420 
 
 1000 
 
 1 
 
 3000 
 
 2600 
 
 2125 
 
 1500 
 
 IK 
 
 4000 
 
 3475 
 
 2830 
 
 2000 
 
 IV? 
 
 5000 
 
 4340 
 
 3540 
 
 2500 
 
 1U 
 
 8000 
 
 6940 
 
 5665 
 
 4000 
 
 2 
 
 10000 
 
 8680 
 
 7080 
 
 5000 
 
 2H 
 
 13000 
 
 11285 
 
 9200 
 
 6500 
 
 2V 2 
 
 16000 
 
 14880 
 
 11325 
 
 8000 
 
 SAFE LOAD IN LB. ON WIRE CABLE OR SLINGS 
 
 
 Two Port Sling 
 
 Two Part Sling 
 
 Two Part Sling 
 
 Two Port Sling 
 
 Wire 
 
 i 
 
 i 
 
 A 
 
 
 
 Cable 
 Diam. 
 in In. 
 
 
 
 A 
 
 /\ 
 
 /^ 
 
 
 Vertical Load 
 
 60 "Angle 
 
 45°Angre 
 
 30°Angle 
 
 V?, 
 
 4000 
 
 3470 
 
 2830 
 
 2000 
 
 % 
 
 6500 
 
 5625 
 
 4590 
 
 3250 
 
 u 
 
 9000 
 
 7800 
 
 6350 
 
 4500 
 
 Vh 
 
 12000 
 
 10400 
 
 8500 
 
 6000 
 
 1 
 
 16000 
 
 13870 
 
 1 1300 
 
 8000 
 
 IK 
 
 24000 
 
 20800 
 
 17000 
 
 12000 
 
 iy 2 
 
 38000 
 
 32900 
 
 26900 
 
 19000 
 
 w 
 
 50000 
 
 43300 
 
 35300 
 
 25000 
 
 2 
 
 64000 
 
 55500 
 
 45250 
 
 32000 
 
 59 
 
SAFE LOADS FOR EYEBOLTS 
 
 When it is necessary to use eyebolts for lifting loads no 
 greater strain should be allowed than given in the table on 
 page 61, which gives the safe load in pounds up to and including 
 bolts 2 3^ in. in diameter. 
 
 It should be understood that to obtain the greatest strength 
 from an eyebolt, it must fit reasonably tight in the hole into which 
 it is screwed, and the pull applied in a line with the axis of the 
 screw. 
 
 Eyebolts should never be used if considered the least faulty. 
 They should never be painted when used for miscellaneous 
 lifting, as paint is very apt to cover up flaws. They should be 
 tested occasionally by tapping gently with a hammer but not 
 sufficient to bend or to otherwise injure them. If it does not 
 impart a good ring one of two things is the reason. It may fit 
 too loosely in the hole, or there may be a flaw. 
 
 Where a bolt is to be used for anything like its maximum 
 load it should be screwed in tight with a bar and given a gentle 
 tap with a bar or hammer to see if it imparts a solid feeling. 
 If not, it should not be used. 
 
 The strains set up in an eyebolt when used at an angle 
 are very severe, due to the bending action of the bolt, and it 
 is very liable to break where it is screwed into the work. This 
 is shown very clearly by the table on page 61, that gives the safe 
 load when used for a direct pull, and also shows how the strength 
 of the bolt rapidly decreases according to the angle that may 
 be used. 
 
 SAFE LOAD ON ROPES AND CHAINS 
 
 The tables on page 62 give the safe loads which may be put 
 on manila rope, wire cables, and chains. The first column gives 
 the diameter of the rope or chain, the second column gives the 
 safe load which the rope or chain is to carry singly. In a sling 
 where the strain is carried by two ropes or chains, the load 
 given in third column should be used. In a sling where four 
 parts of the rope or chain carry the load, the figures in the fourth 
 column should be used. Figures are in tons of 2000 lb. each. 
 
 The figures given in the above table are for cases in which 
 the slings are in constant use and subjected to ordinary shop 
 practice. Where cables of known high tensile strength are used 
 these figures may be increased proportionately. 
 
 The loads for manila rope should be used only when the rope 
 is in fairly good condition; when badly chafed or worn the load 
 should be reduced in proportion. 
 
 As there are a great many different kinds of material to handle 
 in the various parts of the Works, and in order to familiarize 
 those engaged in the actual handling of these materials, a short 
 table of the weights of the various materials is given on page 62. 
 
 The weights of cast iron, steel, copper and lead are given 
 in pounds per cubic foot. The weights of wood, concrete, stone, 
 earth, brick, mortar and marble are also given in pounds per 
 cubic foot. 
 
 The weight of shafts is given per lineal foot. 
 
 60 
 
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 0000 
 
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 61 
 

 SAFE LOAD IN 
 
 TONS, VERTICAL LOAD 
 
 
 MANILA ROPE 
 
 WIRE CABLE 
 
 CHAINS 
 
 Dia. 
 of 
 
 Safe Load 
 in Tons 
 
 Dia. 
 
 of 
 
 Rope 
 
 in In. 
 
 Safe Load 
 in Tons 
 
 Dia. 
 
 of. 
 
 Chain 
 
 in In. 
 
 Safe Load 
 in Tons 
 
 Rope 
 in In. 
 
 Single 
 
 Two 'Four 
 
 Single Two 
 
 Four 
 
 Single 
 
 Two Four 
 
 Rope 
 
 Part Part 
 
 Rope 
 
 Part 
 
 Part 
 
 Chain 
 
 Part i Part 
 
 V2 
 
 H 
 
 h\ a 
 
 y 2 
 
 1 
 
 2 
 
 y 
 
 y 
 
 % 
 
 iy 
 
 b A 
 
 % 
 
 A: % 
 
 % 
 
 m 
 
 SH 
 
 sy 
 
 % 
 
 i 
 
 m 
 
 3 
 
 % 
 
 % 
 
 %\ Wa 
 
 %. 
 
 2y 
 
 ±y 
 
 9 
 
 y 
 
 2 
 
 sy\ e 
 
 H 
 
 A 
 
 1 i 2 
 
 % 
 
 sy 
 
 6 
 
 12 
 
 % 
 
 3 
 
 5 1 9 
 
 1 
 
 Va 
 
 iy 2 \ 2y 2 
 
 i 
 
 4 
 
 8 
 
 16 
 
 Va 
 
 5 
 
 9 15 
 
 lfc 
 
 1 
 
 2 3 
 
 IX 
 
 6 
 
 12 
 
 24 
 
 y 
 
 6 
 
 IOH'18 
 
 \y. 
 
 IX 
 
 2H\ 4 
 
 \y, 
 
 10 
 
 19 
 
 36 
 
 i 
 
 8 
 
 14 24 
 
 1% 
 
 2 
 
 4 6 
 
 i% 
 
 13 
 
 25 
 
 48 
 
 iy 
 
 11 
 
 19 
 
 33 
 
 2 
 
 2X 
 
 5 8 
 
 2 
 
 16 
 
 32 
 
 60 
 
 iy 
 
 13 
 
 23 
 
 39 
 
 2U 
 
 SA 
 
 6^11 
 
 
 
 
 
 iy 
 
 18 
 
 32 
 
 54 
 
 zy 2 
 
 ±A 
 
 8 13 
 
 
 
 
 
 
 
 
 
 WEIGHTS OF VARIOUS MATERIALS 
 
 Material 
 
 Weight per 
 Cu. Ft. in Lb. 
 
 Weight per 
 Cu. In. in Lb. 
 
 METALS 
 
 Cast iron 
 Steel 
 Copper 
 Lead 
 
 450 
 489 
 552 
 709 
 
 0.26 
 0.28 
 0.32 
 0.41 
 
 WOOD 
 
 Ash 
 Pine 
 
 45 
 38 
 
 MISCELLANEOUS 
 
 Concrete 
 
 Stone 
 
 Earth 
 
 Brick 
 
 Mortar 
 
 Marble 
 
 155 
 180 
 72 to 110 
 100 to 150 
 100 
 180 
 
 SHAFTING 
 
 Diameter 
 in In. 
 
 6 
 
 8 
 10 
 12 
 14 
 16 
 
 Weight of Shafting in Lb. 
 per Lineal Ft. 
 
 95 
 169 
 264 
 368 
 517 
 676 
 
 62 
 
Approved Methods of Handling 
 
 Fig. 17 to 39 show some of the approved methods of 
 handling apparatus in the factory. 
 
 iSL 
 
 __* 
 
 Fig. 17 
 TWO CRANE EQUALIZER 
 
 Used with two cranes of different lifting capacities, when 
 lifting a load of greater weight than the safe capacity of one 
 crane. For example: in the case of a weight of 90 tons, which 
 is to be lifted by two cranes; one having a capacity of 60 tons, 
 and the other a capacity of 30 tons. The hooks of the equalizer 
 should be located so as to bring the center of the weight one- 
 third of the length of the beams away from the end attached to 
 the 60 ton crane. This arrangement brings two-thirds of the 
 weight on the 60 ton crane and one-third of the weight on the 
 30 ton crane. 
 
 i 
 
 Fig. 18 
 ONE CRANE EQUALIZER 
 
 63 
 
Fig. 19 
 BLACKWALL HITCH 
 
 Exceedingly useful where material is to be drawn along the 
 floor, or for hauling cars on a level, or where the hitch is to be 
 made quickly, or where a change is frequently required. 
 
 64 
 
xvvs 
 
 Fig. 20 
 CLOVE OR DOUBLE HALF HITCH (METHOD;OF.MAKING) 
 
 Fig. 21 
 CLOVE OR DOUBLE HALF HITCH 
 
 Very useful in the hands of a trained rigger, but, except for 
 hauling, should not be generally used where other slings are 
 available. 
 
 65 
 
Fig. 22 
 BOWLINE KNOT 
 
 First position necessary in making a bowline knot. 
 
 Fig. 23 
 BOWLINE KNOT 
 
 Second position necessary in making a bowline knot. 
 
 Fig. 24 
 BOWLINE KNOT 
 
 Third position and completed bowline knot. If properly 
 made this knot cannot slip. 
 
 66 
 
Fig. 25 
 BOWLINE ON A BIGHT 
 
 The "bight" of a rope is that part which is doubled. There 
 should be very little occasion for using this knot outside of the 
 riggers' department. 
 
 67 
 
Fig. 26 
 SQUARE OR REEF KNOT 
 
 slip. 
 
 Used only for joining two ropes together. This knot cannot 
 
 68 
 
Fig. 27 
 STUDDING SAIL HITCH 
 
 May be used very properly for hoisting timber or such 
 material. 
 
 Fig. 28 
 SHEET BEND IN EYE 
 
 Generally used for an adjustable sling. It can be adjusted 
 quickly, and is a safe and useful sling in the hands of trained 
 riggers. 
 
 69 
 
Fig. 29 
 TIMBER HITCH 
 
 Used principally for hoisting rough lumber. 
 
 Fig. 30 
 TIMBER AND HALF HITCH 
 
 Very useful for hoisting shafts or timbers in a vertical 
 position. 
 
 70 
 
Fig. 31 
 SPLICED ROPE SLING 
 
 Fig. 32 
 LIFTING BLOCKS 
 
 A method of protecting the cable on sharp corners is by 
 means of the corner blocks shown. 
 
 71 
 
Fig.133 
 WIRE CABLE SLING 
 
 Proper way of using in connection with a hook. 
 
Fig. 34 
 LIFTING REVOLVING FIELD 
 
 Two or more double slings should be used, depending upon 
 the weight, the slings to be placed behind two adjacent arms 
 and protected by means of padding. 
 
 73 
 
Fig. 35 
 
 PROPER WAY TO LIFT AND TURN REVOLVING FIELD 
 
 (FIRST POSITION) 
 
 A double set of slings should be used on the main hoist to 
 lift the field high enough for turning; padding being used wher- 
 ever necessary to protect the slings from sharp corners. 
 
 74 
 
Fig. 36 
 
 PROPER WAY TO LIFT AND TURN REVOLVING FIELD 
 
 (SECOND POSITION) 
 
 The field having been hoisted high enough for turning, a 
 piece of timber or scantling should be placed through the bore 
 of the field, the other end of the scantling to be connected to the 
 "small hoist" by the sling; then by lifting on the "small hoist" 
 and lowering on the "main hoist" the work is turned over. 
 Great care should be used, especially against chafing or cutting 
 of the slings. 
 
 75 
 
Fig. 37 
 LIFTING MOTOR-GENERATOR SETS 
 
Fig. 38 
 LIFTING A BASE WITH STANDARDS 
 
 Frequently a base and standard are lifted and no provision 
 is made for any lateral strains that may occur; tending to place 
 an unnecessary strain on the bolts fastening the standards to the 
 base. When such a lift is to be made a piece of timber should be 
 placed between the bearings to relieve the strain, as shown. 
 
 77 
 
Fig. 39 
 METHOD OF LIFTING ARMATURE TO ASSEMBLE 
 IN BEARINGS 
 
 78 
 
ERECTING MACHINES FOR TEST 
 
 Blocking — General Remarks 
 
 The cast iron bases, blocks, rails, etc., used for temporary 
 foundations for machines in test are called "blocking." 
 
 In setting up a self-contained machine, that is, one with its 
 own base, shaft and bearings, the only blocking necessary is that 
 required to allow the stator to clear the floor and it should be 
 placed so that the bearings and frame are well supported. 
 
 The blocking, in all cases, should be as low as possible and 
 the necessary height should be obtained with the least number 
 of sections. Many machines come to test without base, shaft 
 or bearings, and the test blocking must be arranged to meet such 
 conditions. 
 
 All blocking must be securely clamped or bolted in place, 
 the latter method being preferable. The height of blocking 
 necessary is found by measuring the distance from the supporting 
 foot to the bottom of the stator. If the machine has a base, 
 the thickness of the base should be subtracted from this measure- 
 ment. 
 
 Shafts 
 
 All self-contained machines are tested on their own shafts. 
 The assembling of the shaft in the rotor will be discussed later. 
 
 Machines without base, shaft or bearings require the use 
 of a temporary or shop shaft and bushings of the right size to 
 fit the shaft and the bore of the rotor. 
 
 Shop shafts should be frequently tested in a lathe to be sure 
 that all parts of the shaft run true. The bushings should also 
 be carefully inspected to see that they are free from burrs and 
 are not worn either on the inside or outside. In assembling 
 shafts in rotors care must be taken to see that the shaft and bore 
 are clean and free from burrs. 
 
 Lubricate the shaft and bore thoroughly with a mixture of 
 white lead and lard oil. 
 
 If bushings are to be used, slip one bushing on the shaft and 
 introduce the shaft into the rotor and slip the other bushing 
 into the other end of the rotor hub. 
 
 When bushings are used on a shop shaft the rotor is held in 
 position by a collar on each side of the hub. Where a shaft is 
 used without bushings there will be pressure enough obtained 
 to hold the rotor in position without the use of collars. The 
 collars should not obstruct the air passages of the armature. 
 
 In pressing shafts into the rotors of self-contained machines 
 great care must be exercised to see that the rotor is located on 
 the shaft in the exact position called for on the drawing, other- 
 wise the end play will be defective. 
 
 The most accurate method of locating the rotor on the shaft 
 is as follows: 
 
 From the shaft drawing lay off the distance on the shaft 
 from the center of a journal to the center line of the rotor; 
 measure back from this point the distance from the center line 
 
 79 
 
of the rotor to the back end of the hub. When the rotor is in the 
 correct position on the shaft the end of the hub will be at this 
 point. 
 
 In measuring from the center of the rotor to the end of the 
 hub several different points on the circumference of the punch- 
 ings should be taken, as owing to the unevenness of the punch- 
 ings one distance might be a little greater or less than the 
 average distance, and the average distance is the one that should 
 be used. 
 
 The shaft is usually started into the bore with a heavy ram 
 swung from the crane, a piece of heavy fiber being held between 
 the end of the shaft and the ram to prevent injury to the shaft. 
 The shaft is then placed in the hydraulic press and forced in. 
 As soon as the rotor reaches the correct point on the shaft the 
 power must instantly be released. 
 
 The pressure usually required between shaft and bore is 
 five (5) tons per inch of diameter of shaft on horizontal machines. 
 A pressure of four (4) tons per inch will pass, but below this 
 amount the pressure obtained should be reported to the proper 
 superintendent who will decide whether it will pass. 
 
 The bore is usually scraped to a standard pin gauge and the 
 allowance for pressure is made on the shaft. 
 
 Bushings 
 
 Bushings one-half (%) inch or less in thickness are usually 
 made of steel. The thicker ones are made of cast iron. 
 
 In order that the bushings may go on the shaft and into the 
 bore without excessive ramming which would soon destroy them, 
 they are bored from 0.001 to 0.003 in. larger, and turned from 
 0.001 to 0.003 in. smaller than standard. 
 
 This will make a comparatively loose fit between the shaft 
 and rotor and the rotor must be held in position by some form 
 of clamp or set-screw collar. 
 
 This looseness though immaterial on most large machines 
 is sometimes troublesome on small ones, especially small high 
 speed direct current machines as it may cause unbalancing, or 
 it may cause the commutator to run eccentric and thus cause 
 poor commutation. For this reason, a shaft without bushings 
 should be used whenever it is possible. 
 
 Couplings 
 
 Shop couplings are required to be driven on and off shafts 
 easily; they therefore do not have a very tight fit and so must be 
 held in place with a set-screw the same as used with a pulley. 
 
 Whenever a flange coupling is put on a shaft it should be 
 faced off either in a lathe or in its own bearings to insure that the 
 face runs in a plane perpendicular to the center line of the shaft. 
 The set screw should be tightened before facing the coupling. 
 
 If a coupling has been faced off and then removed from the 
 shaft it will probably run out of true when it is re-assembled 
 on the shaft, so it is better to test a coupling every time it is 
 assembled on a shaft. In facing off a coupling on a shaft in a 
 
 80 
 
lathe it is of the greatest importance to see that the journals 
 run true when the shaft is turning on center because when the 
 shaft is in its bearings it is the journals that determine how the 
 coupling runs and not the lathe centers. 
 
 In connecting two shafts with a flange coupling the face of 
 each half of the coupling must revolve in a plane perpendicular 
 to the center line of the shaft and the center line of one shaft 
 must be a continuation of the center line of the other. 
 
 The first condition is assured by facing off the couplings as 
 described above, and the second condition is obtained in various 
 ways. 
 
 For example, the bearings in which the shafts turn may be 
 located and aligned by stretching a fine wire between the centers 
 of the two outboard bearings and adjusting the position of the 
 other bearings to this line. In this case, allowance must be 
 made for the natural sag of the line, which depends on the length 
 and tightness of the line. For tables of sag and method of 
 using steel wire for aligning shafts, see article by A. H. Nourse 
 in the American Machinist of March 5th, 1908. 
 
 The usual method of aligning two shafts with flange couplings 
 is to bring one coupling up to the face of the other and as nearly 
 into the correct position as can be judged by the eye, and then 
 to move the pillow block by a bar or jack until the faces of the 
 couplings are exactly parallel to each other. This condition can 
 be determined by gauging the distance between the faces. If 
 a gauge can just be inserted in the space between the coupling 
 at several different points, the faces are parallel. The height can 
 be adjusted very readily as it is usual to have the couplings made 
 with a projecting ring on the face of one half and a corresponding 
 recess in the face of the other one. Care should be taken to see 
 that the coupling bolts are a good fit in the holes, otherwise each 
 bolt may not be equally stressed and some bolts may shear off. 
 
 Several designs of flexible couplings exist; but two types 
 are much used in the works. One coupling consists of two parts 
 of four arms each, the arms of one part interlocking with those 
 of the other. These arms are separated by rubber buffers. The 
 other type has its two parts laced together by a leather belt. 
 
 In flexibly connecting two shafts the shafts need not be 
 exactly in line, although they should be so adjusted as closely as 
 possible, without spending too much time on the alignment. 
 
 Assembly 
 
 Apparatus delivered from the Manufacturing Department 
 can be divided into two general classes, viz., self-contained 
 machines which are delivered completely assembled; and 
 machines which may or may not be self-contained, but which are 
 delivered to test partially or wholly dismantled. It is usually 
 the practice to align and center in the machine shop before 
 delivery to test, all machines having their own bases, whether 
 they are delivered completely assembled or not. It is, therefore, 
 important to consider the precautions and methods which have 
 been found necessary in assembling apparatus for test. 
 
 81 
 
Cast iron bases, especially those used in connection with 
 medium size and large apparatus, do not possess the necessary 
 stiffness to allow them to be erected without proper support 
 on the iron floor or testing blocks. Care must, therefore, be 
 taken when setting machines in the testing stand to see that 
 there are no chips, or lumps, under the blocking or base which 
 may spring the base or destroy the alignment. It is well to 
 measure the distance between pillow blocks after the base and 
 lower half of frames are in place (in the case of split frame 
 machines), before the rotating parts are placed in the bearings. 
 
 All reference marks or assembly marks (usually numbers) 
 on machines, except on those of the vertical type, will be found 
 at the right hand side of the machine when facing the com- 
 mutator or connection end. When the machine, therefore, is 
 properly assembled, all marks should appear on that side. 
 
 Before placing the shaft in its bearings, the surface of bear- 
 ings and journals should be well oiled. After the shaft carrying 
 the rotating parts has been assembled, a measurement should 
 be made of the air gap. If the air gap is not uniform, or does 
 not agree with the drawings of the machine, the trouble must 
 be rectified. The gap can be equalized on top and bottom by 
 inserting shims under the frame feet. If the gap does not 
 equalize laterally it is usually corrected by shifting the frame 
 and redoweling the frame feet to the base. 
 
 Air Gap 
 
 The measurement of air gaps is important on all apparatus. 
 Air gaps on direct current machines are measured in the follow- 
 ing manner: With the armature stationary, the gap should be 
 measured at both the commutator and pulley ends, the measuring 
 scale being inserted under each pole tip, without including the 
 chamfer of the tip. A mark should then be placed on the 
 armature circumference under the center of a given pole and the 
 armature revolved through one pole span. The air gap measure- 
 ment should be taken at the new position at the commutator 
 end and so on for successive poles. The first set of measure- 
 ments is known as the "stationary gap"; the second set as the 
 "revolving gap." 
 
 An eccentricity test of the armature is made by marking 
 a point on one pole piece and measuring the air gap between 
 this point and several equally space points around the surface 
 of the armature punchings. These readings at once show if 
 the armature will run true. If the armature will not run true 
 the matter should immediately be reported to the office. 
 
 On commutating pole machines the air gap measurement is 
 taken under the center of the commutating pole. It is also 
 necessary to measure the distance between the tip of each com- 
 mutating pole and the adjacent tip of the main pole. The 
 maximum allowable variation in this measurement is p- in. 
 Should this amount be exceeded the matter should be referred 
 to the office for instructions before proceeding with the test. 
 
 Air gap measurements are taken on alternating current 
 machines with the revolving field stationary, and also by 
 
 82 
 
revolving it in a similar manner to that given above for "station- 
 ary " and "revolving gap" on direct current machines, except 
 that the air gap measurement on a-c. machines is taken at 
 the center of the pole piece both on the front and back ends. 
 In measuring the "revolving gap" it is not necessary to take 
 the air gap measurement under each pole. The measurement 
 need only be taken at points spaced 45 mechanical degrees 
 apart. That is, eight (8) sets of measurements are required 
 for the "revolving gap." 
 
 The average gap as taken must check with the requirements 
 as given on the Engineering Instructions. Fifteen (15) per cent 
 variation is allowed between the maximum and minimum read- 
 ings when measured from iron to iron and 20 per cent variation 
 is allowed when measured over the binding wire. On machines 
 using shims the average gap must be as close to Engineering 
 instructions as can be obtained with a 14 mil shim. 
 
 vSince the air gaps of induction motors are small, and since 
 a uniform gap is important, they are measured by special 
 gauges provided for that purpose. In using these gauges they 
 are passed completely through the motor air gap from end to 
 end of the punching. This gap measurement is taken at sev- 
 eral points about the circumference of the rotor with it station- 
 ary and revolving in a similar manner to that indicated above. 
 
 Testing instructions which are issued from the office, in 
 the case of special machines, give the length of air gap required 
 for a particular machine, hence, the length of air gap measured 
 should be checked against this information. If discrepancies 
 exist, the matter should be immediately referred for instruc- 
 tions, before starting the machine for test. When air gap 
 measurements are made, a critical inspection should be made 
 of the clearance between the rotor and windings or other parts, 
 to insure that it is sufficient to allow the machine to operate 
 without any surfaces striking or rubbing together. This may 
 occur if the windings project unnecessarily and in no case must 
 clearances be so small as to be unsafe. Should such cases 
 occur, the trouble must be corrected and the proper clearances 
 obtained before the machine is started for test. 
 
 Air gap measurements should be made from iron to iron 
 whenever possible and never from the wooden wedges of the 
 armature. 
 
 Brushes 
 
 In preparing commutating machines for test, the brushes 
 must be equally spaced around the commutator, 180 electrical 
 degrees apart. The brushes on a stud must align properly 
 with each other, and with the commutator bar from the front 
 to the back end of the commutator. To space the brushes 
 place a strip of paper tape around the commutator and mark 
 the paper where the ends overlap. Remove the paper tape 
 and divide it with a scale, or dividers, into as many equal divi- 
 sions as there are poles on the machine. Then replace the paper 
 around the commutator and paste the overlapping ends to- 
 
 83 
 
gether. Space the brushes by the marks on the paper, taking 
 care that the holders are clamped to the stud in the proper 
 position. 
 
 In some cases brushes are run trailing and in others leading, 
 with reference to the direction of rotation. Radial brushes 
 are also sometimes used. 
 
 When the brushes have been set, fit them to the commutator 
 surface. To do this, use a strip of sandpaper between the corn- 
 
 Fig. 40 
 RADIAL, LEADING AND TRAILING BRUSHES 
 
 mutator and brush face. Coarse sandpaper is used first to 
 obtain an approximate fit. Follow with very fine sandpaper. 
 A close and accurate fit with the commutator is essential to get 
 good commutation tests. When sandpapering, the sandpaper 
 must be held close to the commutator to prevent rounding the 
 tip of the brush when drawing the sandpaper away. The sand- 
 paper should be drawn in the direction of rotation. These 
 instructions apply also to fitting carbon brushes on collector 
 rings. When the sandpapering of the brushes is finished, the 
 resulting carbon dust must be blown from the armature or 
 rotating part. The air blast should be directed away from the 
 rotating part, so that the carbon dust is carried completely 
 away and cannot drift into the windings. The leading, trailing, 
 and radial brush setting is shown in Fig. 40. 
 
 84 
 
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 O /O eo 30 40 SO GO 70 30 £>0 /00 
 Pressure /6s. £><?/- sg.//?. J Droj.&/'ea 
 
 Fig. 41 
 
 OIL RING BEARING, STILL AIR, ROOM 
 
 TEMPERATURE 25° CENT. 
 
 SO 
 
 /O 20 30 40 ^O 60 70 0O &0 /OO 
 /^r&sst/re /£>. pe/~s<z-//7 prv/\ area 
 Fig. 42 
 OIL RING BEARING, WELL VENTILATED 
 ROOM TEMPERATURE 25° CENT. 
 
 85 
 
In case copper gauze brushes are used a form and file, or 
 emery paper, must be used to fit them to the commutator 
 or collector ring. Copper brushes are now seldom used on com- 
 mutators. Copper leaf brushes, as used on synchronous con- 
 verters, are so constructed that no special fitting is required. 
 They must, however, be properly adjusted in the holder to make 
 good contact upon the slip ring. 
 Bearing Lubrication 
 
 When oil-ring lubrication is used, the lubricating oil must 
 not be allowed to get so low in the oil well that the ring does 
 
 '§ 280 
 
 ^ 240 
 
 200 
 
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 r ar//7gs 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4>0 
 
 N £V0 400 £0O dOO /OOO0PO /600 2000 
 
 Rubbing Speed in feet per minute 
 
 Fig. 43 
 SAFE MAXIMUM PRESSURE ON BEARINGS FOR EACH SPEED 
 
 not dip into it. If this instruction is observed satisfactory 
 lubrication will be obtained for all ordinary bearing pressures 
 and rubbing speeds. For high bearing pressures, or high speeds, 
 some form of forced lubrication is used. The oil is forced into 
 the bearing either on the bottom, or the lower quarter and 
 enters the bearing at a point such that the revolving shaft 
 draws the oil under the shaft. Oil from forced lubricated bear- 
 ings is usually returned to an external cooling tank, where 
 its temperature is reduced before being again pumped into 
 the bearing. Oil rings and forced lubrication are occasionally 
 used on the same bearings, so that if the oil pressure fails the 
 rings supply enough oil to prevent danger, until the oil pres- 
 sure can be restored. 
 
 A properly designed bearing may run hot from the following 
 causes: Oil rings sticking; scarcity or poor quality of lubricating 
 oil; excessive local pressure in the bearing; insufficient relief 
 on the sides of the bearings; improper alignment and exces- 
 sive belt pull, or current flowing from frame to shaft. 
 
 The remedy for the greater part of these troubles is obvious. 
 In the case of excessive local pressure in the bearing, or insuffi- 
 
 86 
 
cient relief on the side of the bearing, the remedy is to remove 
 the high spots on the babbitt or bearing metal with a scraper 
 and increase the side clearance. 
 
 Allowable bearing pressures, speeds, etc., are given in Figs. 
 41, 42 and 43. 
 
 Before starting a machine all bearings must be filled with 
 the proper amount of oil. Bearings should be inspected to 
 see the}* have not been carelessly filled, viz., that oil has not 
 been spilled on the bearing housing, or bearing shell, or upon 
 other parts associated with the bearing, otherwise, a false 
 impression may be obtained as to oil leakage or throwing when 
 under test. To give the bearing a critical test for oil leaking 
 
 Fig. 44 
 TYPES OF OIL GAUGES 
 
 or throwing, the dividing line between cap and bearing pedestal 
 and between bearing brackets, should be painted with whit- 
 ing. The end of the commutator or field spider adjacent 
 to the bearing should also be given a white coating, so that 
 it is possible to detect, after a comparatively short run, the 
 slightest leakage or throwing of oil. 
 
 Bearings with the end of the bearing shell visible should 
 be filled with oil until it touches the lower part of the shell 
 at the end of the bearing housing. Where the end of the bearing 
 shell cannot be seen the bearing should be filled to within Y% in. of 
 the top of the visible portion of the oil gauge glass; in the case 
 of sight gauges to within 3^8 in. of the top of the gauge. In the 
 case of overflow gauges having no glass, a record of the distance 
 of the oil level from the top of the gauge must be made, in 
 every case, upon the Testing Record. Gauges with glass tubes 
 so placed as to show the oil level (Fig. 44a) are used on bearings 
 of large machines, and stand pipe gauges (Fig. 44b) on small 
 and medium size machines. Overflow gauges (Fig. 44c) are 
 those with the top of the stand pipe fitted with a hinged cap. 
 
 Oil gauges on most induction motors are of the overflow 
 type, and should be filled to within tV in. of the overflow. As 
 
 87 
 
already stated, no oil must be spilled upon the bearing parts. 
 In filling bearings a funnel must be used and the oil inserted 
 through the sight holes for the oil rings, or through the opening 
 above the shaft at the end of the bearing housing. 
 
 During test no oil should be allowed to leak or be thrown 
 from the bearings upon the rotating parts, or windings. This 
 is especially true with reference to commutating machines, 
 where it is important that lubricating oil be kept away from 
 the commutator, brushes and fittings. Should oil-leaking or 
 throwing on these parts be detected during the test, the test 
 should immediately be discontinued and the cause of leakage 
 removed. If bearings under test rise in temperature 40 degrees 
 cent, or more, above the room temperature, it should be reported 
 to the office as a defect, since no properly designed bearing 
 should heat above 40 degrees rise under normal conditions. It 
 will usually be found that a greater temperature rise is due to 
 a faulty bearing. 
 
 Thrust Bearings 
 
 There are two classes of thrust bearings; those which depend 
 upon a film of oil between two flat plates, and those which have 
 either hardened rollers or balls rolling between two hardened 
 surfaces. The first class may be sub-divided into (a) those 
 which are supplied with oil under pressure and (b) those which 
 revolve in a bath of oil. In both these classes the bottom plate 
 is stationary and the top one rotates with the shaft. 
 
 In the pressure thrust bearing the two plates are recessed 
 for about half their diameter and the remaining annular ring is 
 scraped or ground to a true surface. Scraping is perhaps pref- 
 erable to grinding as in a ground plate there is a possibility of 
 particles of the abrasive becoming imbedded in the surfaces and 
 causing them to cut. The bottom plate usually rests upon a 
 spherical surface which allows the plates to align themselves 
 in their proper relative positions. The oil is led from the pump 
 or accumulator to the recess between the plates and the pressure 
 raised until the plates separate and the oil passes out between 
 the plates and up along the shaft to the overflow where it escapes 
 and returns to the pump or cooling tank. 
 
 It is obvious that the pressure per sq. in. required to separate 
 the plates is a function of the superincumbent weight and the 
 area of the bearing plates. The limit of allowable pressure per 
 sq. in. on this type of bearing is the capacity of the pumps or 
 accumulator, as the friction is purely fluid friction and the plates 
 do not come in contact with each other. If an accumulator is 
 not used it is necessary to interpose between the pump and the 
 thrust bearing some form of baffler which will cause a back 
 pressure on the pump above that required to separate the plates 
 of the thrust bearing. This difference in pressure between the 
 two sides of the baffler should be from 25 to 40 per cent of the 
 pressure required to lift the plates. For example; if it requires 
 1000 lb. per sq. in. to separate the plates, the pump should show 
 a pressure of from 1250 to 1400 lb. per sq. in._ This insures a 
 uniform flow of oil through the plates, which condition is 
 
 88 
 
absolutely necessary for correct operation of this class of thrust 
 bearing. 
 
 The amount of oil which should be passed through a pressure 
 thrust bearing varies with the diameter of the plates and this 
 amount in gallons should be about 100 per cent of the diam- 
 eter of the plates in inches. Thus a 20 inch thrust bearing 
 requires about 20 gallons per minute. 
 
 In operating this kind of a thrust bearing some reserve 
 source of oil pressure, such as a spare pump, should be at hand 
 in case of the failure of the one in service. Both pumps should 
 be on the line constantly and each pump should be capable of 
 supplying the necessary amount of oil to the bearing. If one 
 pump fails the other can carry the load while repairs are being 
 made. A check valve should be placed in the line from each 
 pump so that the oil cannot escape if a valve or some other 
 vital part of the other pump should fail. 
 
 The other style of plate bearing revolves in a bath of oil and 
 is grooved in such a way that the top plate draws a film of oil 
 between itself and the bottom plate. 
 
 A type of thrust bearing of this kind is a segment bearing. 
 The novel feature of this bearing is a series of adjustable surfaces 
 mating with a continuous thrust collar. The parts carrying these 
 adjustable surfaces are referred to as "shoes" or "segments" 
 and are free to adjust themselves, thus bringing about uniform 
 distribution of load over the entire bearing surface and, further, 
 and more important, adjust themselves at a slight angle with 
 the collar and thus glide or skim over the oil film which adheres 
 to it. 
 
 The "shoes" consist of heavy steel blocks faced with babbitt, 
 their upper faces forming the adjustable bearing surfaces. 
 Each "shoe" fits into a recess in the body casting and is mounted 
 on a spherical topped block in contact with another spherical 
 topped block below, which provide the adjustment to running 
 conditions. 
 
 Below each shoe seat is an adjustable wedge for raising and 
 lowering to bring about a uniform distribution of load. 
 
 Machines equipped with bearings of this type require a con- 
 siderable amount of power to start, consequently, they are 
 usually assembled in the Testing Department with a pressure 
 step bearing underneath them so that they may be easily 
 started. The "step-block" is then lowered until the machine 
 is supported from the upper thrust bearing. 
 
 Unusual care should be exercised in first starting bearings 
 of this type and the machine should be brought to speed very 
 slowly to be very certain that the bearing is operating properly. 
 
 ROLLER BEARINGS 
 
 The roller type of thrust bearing (see Fig. 45) consists of 
 several hardened steel rollers held in a brass retainer and arranged 
 radially to the shaft. The rollers revolve between hardened 
 and ground steel plates, one of which is stationary and the other 
 revolving with the shaft. In this form of bearing the oil is not 
 
 ' 89 
 
under pressure but must be supplied quite liberally. The oil 
 must enter as close to the shaft as possible so that the centrifugal 
 force may throw the oil out across the surface of the disks. 
 Rapid starting of a new roller bearing often causes trouble by 
 scoring or drawing the temper because the hardened steel plates 
 as they come from the grinder are not in proper condition for a 
 bearing surface. This trouble can be avoided by lapping the 
 plates or by running several hours at slow speeds thus giving the 
 plates a chance to smooth themselves. The amount of oil that 
 should pass through a bearing of this type is very indefinite. 
 
 Fig. 45 
 VERTICAL ROLLER THRUST BEARING 
 
 The sole function of the oil is to keep the bearing cool and just 
 what this amount may be for a particular bearing is hard to 
 predict but will probably be from 10 to 14 gallons per minute 
 on bearings up to 30 in. diameter. In any special case it is better 
 to be guided by the advice obtained direct from the manu- 
 facturers of the roller bearing in question. 
 
 Roller bearings have been made as large as six feet across the 
 disks and carry 2,500,000 lb. 
 
 Balance of Rotating Parts 
 
 Static Balance 
 
 Rotating parts are usually balanced by putting them on 
 a shaft and laying the shaft on two parallel rails called balance 
 ways. The balance ways must be carefully leveled and well 
 supported to prevent deflection from the weight of the piece 
 to be balanced. After the correct amount of balance weight has 
 been determined, a suitably formed weight is made and securely 
 
 90 
 
fastened to the inside of the rim, or at a point at the same 
 distance from the center as that at which the temporary weights 
 were supported. The weights should be so fastened that they 
 will not produce a shearing stress on the bolt or other fastening 
 holding them in place. In revolving fields the weight should 
 be placed on the inside of the rim. In this case the bolt has 
 only to keep the weight from falling out when the machine is 
 at rest. 
 
 On d-c. armatures, pockets are generally provided into 
 which melted lead is poured and hammered into place. 
 
 On slow speed machines it is not necessary to get accurate 
 balance, especially on heavy fields. On a 2000 or 3000 kw. 
 field running about 120 rev. per min. an unbalanced weight of 
 50 lb. would probably not be noticed. Vertical machines must be 
 more accurately balanced than horizontal ones. 
 Dynamic Balance 
 
 A field with good static balance will not necessarily be in 
 good balance when running. It is often necessary to rebalance 
 a rotor dynamically after the machine is assembled. 
 
 The shaft must be straight before any balancing is done. 
 This can be determined by holding a pointer or pencil to the 
 shaft and revolving the shaft slowly. If the pointer touches all 
 points, the shaft is straight and the work of balancing may 
 proceed. If it does not touch all around, the shaft is sprung 
 and must be straightened before the rotor is balanced. On 
 very heavy rotors it is not possible to balance them statically 
 as a whole, because their weight will press the shaft sufficiently 
 into the ways to prevent the rotor from taking its natural 
 position. In this case the parts are balanced separately as 
 carefully as possible and the whole is afterwards dynamically 
 balanced, if necessary. 
 
 To locate roughly the position proper for balancing, hold a 
 pencil or chalk so that the high side of the shaft strikes it as 
 the shaft revolves at normal speed. On a rigid shaft this mark 
 will indicate the heavy side, but on a flexible shaft it will prob- 
 ably show the light side of the rotating part. Put some weight 
 on the side opposite the mark and try again. If the balance is 
 better, the weight is in the proper place and the mark will 
 be found to extend further around the shaft. If the balance 
 is worse, the weight is on the wrong side. If the mark is found 
 to have moved, weight should be added at the new point. If 
 the mark is found on just the opposite side, too much weight has 
 been added. 
 Pulleys 
 
 Pulleys are made of various materials such as cast iron, steel, 
 steel rims with cast iron centers, wood rims with cast iron 
 centers, paper rims with cast iron centers, etc. Paper pulleys 
 are in common use, especially in the smaller sizes and when 
 not subjected to dampness, they are preferable to cast iron or 
 steel on account of their higher coefficient of friction. Steel 
 pulleys have the advantage over cast iron in that they will 
 stand a higher speed, are much lighter and are not liable to 
 
 91 
 
have hidden cracks or flaws. A pulley should be made with 
 a bore of such size that it will go on the shaft without pressure 
 and should be held in place with set screws. All pulleys, especially 
 cast iron ones, should be rigidly inspected frequently for cracks 
 or other flaws. A speed of 5000 ft. per min. produces a tensile 
 stress of about 1200 lb. per sq. in., which is the usual working 
 stress allowed for cast iron pulleys. There are men detailed 
 in the Testing Department whose business it is to inspect all 
 pulleys after they are put on machines and again before machines 
 are started. The practice of having pulleys inspected each time 
 before a machine is started, must be rigidly adhered to. It is very 
 essential that the shaft extend clear through the hub of the 
 pulley. This will give the pulley a maximum working strength 
 and will insure its not coming off the machine while it is running. 
 The set screws in these pulleys must be inspected to see that they 
 are in good condition, that the threads are not damaged, and 
 that they extend through the hub to the key in the shaft. 
 
 Flange pulleys are cast iron pulleys with a steel center. These 
 are readily adapted to any machine by first fitting a coupling 
 to the shaft and then bolting this flange pulley to the coupling. 
 New centers are readily obtained for these pulleys so that they 
 may be easily kept in first class condition. It is good practice 
 to operate pulleys between 4000 and 5000 ft. per min. When 
 not in use, they must be placed in the store-house provided for 
 that purpose. 
 
 Belts 
 
 Leather belts are much used in the Testing Department and 
 a considerable amount of power is transmitted by them. In 
 no case, however, should a belt carry more than 400 kw. When- 
 ever possible, endless belts must be used, as they are stronger 
 and do not cause fluctuations in the electrical instruments as 
 do laced belts. Laced belts must be examined very carefully 
 before starting a test to see that the lacings are in first class 
 condition, and all belts must be inspected before being used to 
 see that they are riveted properly and in no way defective. The 
 size of belt to be used must be carefully calculated by the Head 
 of Section, and in no case should it be left to the judgment of 
 the shop men. The belts must never be wider than the pulley, 
 nor be allowed to run with one end overlapping the edge of the 
 pulley, as this will surely injure the belts. They should be run 
 with the tight side on the bottom if possible, and must be kept 
 free from oil as this reduces the capacity very much and causes 
 slipping on the pulley. Quarter turns in belts must be avoided 
 if possible as this stretches the belts on one side and greatly 
 reduces their capacity. Under no conditions is a belt to be 
 overloaded; if it breaks it may seriously damage apparatus or 
 injure men working in the vicinity. Belts, must, therefore, be 
 regarded as sources of danger and possible accident. When not in 
 use they must be returned to the store-house where they will be 
 inspected and repaired by a man employed for that purpose. 
 
 Whenever belts are running near an aisle, or passage way, 
 guards must be so placed that men cannot fall, be thrown, or 
 
 92 
 
drawn into them. The testing tables should never be set in a line 
 with a running belt and work should be so arranged that an 
 employee must not work continuously in line with belts, unless 
 proper mechanical guards are provided. Whenever a belt is found 
 defective, it must be returned to the repair shop for repairs. 
 
 HP KM 
 
 3e/t /6 20 24 28 32 36 
 W/'dth -2oly- 3p/y 
 
 44 48 32 36 60 64 68 72 76 80 inches 
 4-p/y 4« 3p/y ~ 
 
 Fig. 46 
 WIDTH OF LEATHER BELTS 
 
 Fig. 46 and the data on page 94 show the carrying capacity 
 of leather belts of various widths and thicknesses "when running 
 at speeds of from 1000 to 5000 ft. per minute. It is not per- 
 missible to operate a belt in the Testing Department at a higher 
 velocity than 5500 ft. per minute. 
 
 When a belt is started for the first time it must be very 
 carefully watched to see that it runs properly on the pulley, 
 
 93 
 
and has the proper tension. Under no circumstances must an 
 employee lean against, sit or stand upon, or pass through a 
 belt even though it is not running. It is equally important 
 that neither tools, nor articles of any description be laid upon 
 belts after they are placed on the pulleys. 
 
 DATA IN CONNECTION WITH WIDTH OF LEATHER BELTS 
 
 The curves in Fig. 46 have been plotted from the following 
 data: 
 
 Coefficient of friction =0.4. 
 
 Arc of contact = 165°. 
 
 Weight of leather belting = 56 lb. per cubic foot. 
 
 Centrifugal force =0.012 F 2 (with velocity in ft. per second.) 
 
 7\ = 1. T 2 =0.316. 
 
 Ratio tight over slack side=-^- 
 
 ■L 2 
 
 3.1643. 
 
 Torque or pull = Ti- T 2 =0.684. 
 Greatest tension = T x +0.012 F 2 . 
 Average thickness per ply = tf in- 
 Working tension per sq. in. =275 lb. for laced belting. 
 H.p. or kw. per inch in width of f% in. thick. 
 
 1.05 
 
 1.56 
 
 2.03 
 
 2.46 
 
 2.855 
 
 3.18 
 
 3.447 
 
 3.63 
 
 3.73 
 
 .783 
 1.163 
 1.514 
 1.835 
 2.129 
 2.372 
 2.57 
 2.71 
 2.78 
 
 Width of Belt 
 
 Up to 6 in. 
 6 in. to 20 in. 
 20 in. to 40 in. 
 40 in. to 60 in. 
 60 in. to 80 in. 
 
 Up to 2 in. 
 
 2 in. to 5 in. 
 
 5 in. to 10 in. 
 10 in. to 36 in. 
 Above 36 in. 
 
 Up to 2 in. 
 
 2 in. to 5 in. 
 
 5 in. to 10 in. 
 10 in. to 24 in. 
 24 in. to 36 in. 
 Above 36 in. 
 
 for 1000 ft. per minute, 
 for 1500 ft. per minute, 
 for 2000 ft. per minute, 
 for 2500 ft. per minute, 
 for 3000 ft. per minute, 
 for 3500 ft. per minute, 
 for 4000 ft. per minute, 
 for 4500 ft. per minute, 
 for 5000 ft. per minute. 
 
 Curves Plotted with the Following Thickness 
 
 1 ply belting varying from ^ in. to •& in. 
 
 2 ply belting varying from ^ in. to ^f in. 
 
 3 ply belting varying from -jjf in. to f| in. 
 
 4 ply belting varying from f| in. to §J in. 
 
 5 ply belting varying from f£ in. to l-^- in. 
 
 Belts are to be Used in the Following Widths 
 
 varying by \i in. 
 varying by Yi in. 
 varying by 1 in. 
 varying by 2 in. 
 varying by 4 in. 
 
 Pulley Face to Exceed Width of Belt 
 
 + h 
 
 + y 2 
 + ^ 
 
 74 
 
 + 1 
 
 +iy 2 
 
 + 2 
 
 94 
 
Before starting a test, the man responsible for the test must 
 see that no one is in contact with the belt, and that nothing 
 has been left lying upon it or where it may fall into it, while 
 running. 
 
 Truing Commutators 
 
 The condition of a commutator determines to a great extent 
 the satisfactory operation of the unit in service. A true periphery 
 and a perfectly smooth surface are two requisites to satisfactory 
 service. 
 
 To secure these conditions is the aim of all commutator 
 truing devices. There are two methods now recognized for 
 truing commutators, viz., a turning tool and slide rest, sup- 
 plemented by sandpaper, or some form of commutator grinder. 
 
 In turning commutators some sort of a slide rest with a tool 
 holder must be provided. In the Testing Department there 
 are several sizes built on the same general plan, but differing 
 principally in the length. The slide rest is held rigidly in such 
 a position that the point of the tool is about on a level with the 
 center of the commutator and movable parallel to the surface 
 thereof. A very sharp diamond-point tool and a fine feed 
 should be used. The cutting speed should be about 350 ft. per 
 min. The end play must be eliminated by some means, usually 
 by tying a board in such a position that it holds the armature 
 securely against one oil deflector. After the commutator has 
 been trued up as carefully as possible with the tool the final 
 finish is obtained with either sandpaper or carborundum paper. 
 Emery in any form should never be used because of the metallic 
 particles which it contains. 
 
 The objection to turning commutators is: first, that the cutting 
 tool breaks the mica instead of cutting it; second, because of 
 the different densities in mica and copper, the tool does not give 
 a perfectly uniform surface and leaves the commutator bars 
 a little higher in the center than on the edges; third, it is neces- 
 sary to take a deep cut with the tool to get the required "bite" 
 for cutting; fourth, the tool must be supplemented with sand- 
 paper; fifth, the tool wears rapidly and must be replaced by 
 another or re-ground during the process of turning. This is 
 especially true when turning a commutator when the machine 
 is run as a motor. When a tool is replaced in the middle of a cut 
 it is difficult to prevent a score or a slight ridge being left where 
 the new cut begins which can be removed only by taking another 
 cut off the whole length of the commutator. This results in 
 great waste of copper and decreases the life of the commutator. 
 In truing a grooved commutator, that is, one from which the 
 side mica has been cut out, it is very difficult to keep from carry- 
 ing the copper across the slots when using a turning tool. This, 
 of course, would necessitate cutting out the bridges of copper 
 which on a commutator of any size means a considerable loss of 
 time. 
 
 The other, and perhaps the better method of truing com- 
 mutators is with a commutator grinder. This consists essentially 
 
 95 
 
of a small motor geared to a spindle which carries an abrasive 
 wheel, the whole being carried on a slide rest similar to that used 
 in turning commutators. The advantages of a commutator 
 grinder over a turning tool are many; there is only one dis- 
 advantage. The commutator can be ground with the machine 
 running at normal speed and carrying full voltage. The grinder 
 does not have to be so rigidly supported as the turning tool, 
 and there is no danger of gouging the commutator as is the case 
 with a turning tool. Grooved commutators can be ground with 
 practically no bridging of the copper between bars. A com- 
 mutator grinder can be installed, and the commutator ground 
 without shutting down the machine. The commutator grinder 
 produces an absolutely true surface from the fact that the 
 grinding is done when the armature is running at normal speed. 
 It is often the case that a commutator which runs true at slow 
 speed will run eccentric at normal speed. 
 
 Another important feature of the commutator grinder 
 is the arrangement for catching all the copper dust. This 
 consists essentially of a hood enclosing the grinding wheel 
 leaving just enough opening for the wheel to come in contact 
 with the commutator. A discharge pipe fitted with an ejector 
 using compressed air produces a vacuum sufficient to draw all 
 the chips away from the wheel and deposit them in a bag which 
 is fastened to the end of the suction pipe. 
 
 The disadvantage of a grinder is that it cannot remove 
 copper as rapidly as a turning tool, and if the commutator has 
 been allowed to become deeply grooved by the wear of the 
 brushes, time would perhaps be saved by turning it, rather than 
 grinding it. On the other hand, if the commutator is given the 
 attention due it and attended to before the grooves become of 
 appreciable depth, it will not only be better for the commutator 
 to be ground, but it will prevent the necessity of removing a 
 large amount of copper as would have to be done if the com- 
 mutator were turned. 
 
 Correcting End Play 
 
 If a machine is properly leveled the rotor will revolve without 
 rubbing either oil deflector when there is no field on the machine. 
 If this is found to be the case, but that when field is put on the 
 rotor pulls either one way or the other, it shows that the magnetic 
 center of the field and armature do not lie in the same plane. 
 This may be caused by the rotor being out of place on the shaft, 
 or by the stator being out of its proper position on the base. 
 It is evident that the defective end play may be corrected by 
 moving either the rotor or frame. Whichever is found wrong 
 should be made right, although perhaps it might be cheaper 
 to move the stator than the rotor. 
 
 The stators of the larger machines are not doweled till after 
 the machines have been set up and tried out for both air gap 
 and end play. 
 
 If the machine were being installed outside where there were 
 no facilities for pressing the shaft in or out of the rotor, the best 
 
 96 
 
and certainly the cheapest way of correcting end play would 
 be to move the frame on the base and redowel. 
 
 If there is not sufficient clearance between the frame holding- 
 down bolts and the holes in the feet, the holding-down bolts 
 could have the body turned down as far as the depth of the 
 thread, the reduced part being made of a length about Y± in. 
 greater than the thickness of the foot and measured from the 
 under side of the head. This will allow a much greater move- 
 ment of the stator and w^ill not weaken the bolt if it is not 
 reduced below the root of the thread. This method of correcting 
 end play is sometimes used in the Testing Department, but 
 after test the defect is always remedied by the shop, so that the 
 proper position of the stator may be obtained without the use 
 of the reduced bolts. 
 
 97 
 
CHAPTER 4 
 
 PREPARATION OF APPARATUS FOR TEST ; 
 INSPECTION; WIRING; OBSERVA- 
 TIONS DURING OPERATION 
 
 Preliminary Inspection 
 
 It is the aim to have all apparatus delivered to the Testing 
 Department from the manufacturing department in a completed 
 condition including fittings and all other parts. 
 
 When apparatus is delivered, the man in whose charge it 
 has been placed should make a very careful inspection for 
 mechanical defects and should see that all parts as assembled 
 check with the Testing Instructions. 
 
 The following are some defects which may appear: Copper 
 bridges formed between the bars over the side mica of the com- 
 mutator, due to improper turning; bent end conductor or com- 
 mutator leads; improper brush staggering; damaged insulation 
 of armature and field spools; broken insulating boards on 
 fields; insufficient clearance between bare electrical terminals or 
 conductors and ground; poor joints between electrical conductors; 
 loose terminals; bus rings or other connections improperly sup- 
 ported; brush pigtails too long or touching the armature risers; 
 too little clearance between a brush stud or various parts of 
 fittings and ground; incorrect spring pressure; defective spacing 
 of collector ring taps; defective spacing of lubricating brushes, 
 etc. It should be noted that laminated pole tips are not bent 
 and that cast pole tips are of approximately uniform thickness 
 on all the main poles of the machine. All oil rings in each bearing 
 should be visible through the bearing cap oil cover and the 
 bearings should be properly filled with oil as described on page 
 87. See that the brushes on collector rings ride properly on 
 the rings and do not overlap. 
 
 In fact a test man should place himself in the position of 
 the customer and if anything about the machine does not 
 appear right he should report it to the Head of Section. 
 
 It is the duty of the Head and Assistant Heads also to look 
 over the apparatus, but the man in charge of the machine will 
 be held directly responsible. The Head or Assistant Head of 
 Section must place the brushes of d-c. machines on the mechanical 
 neutral and sign the Testing Record to that effect. 
 
 The above inspection should also be made on all machines 
 upon which changes have been made by the shop to make sure 
 that no foreign material has lodged in the machine. 
 
 Wiring 
 
 Though a great deal of the wiring in testing work is tempo- 
 rary, it must always be done as neatly as possible, due regard 
 being paid to safety. All circuits should be protected by signs 
 or barriers, where there is danger of any one coming in contact 
 
 98 
 
with them. Conspicuously lettered danger signs are used to 
 indicate the nature of the circuit. In addition to this, white 
 tape is used around cables or apparatus carrying high voltages. 
 After a tester has completed the wiring of a machine, he should 
 notify the Head of Section, or Assistant Head of Section, to 
 inspect the same. The Head of Section, or Assistant Head of 
 Section, must then assure himself that it is satisfactory, and 
 if so, enter his approval upon the Testing Record sheet and 
 sign his name. 
 
 The following general rules should always be followed in 
 wiring apparatus for test. First, procure the print of connec- 
 tions, which will be furnished by the Head of Section. 
 The apparatus must then be connected up in accordance there- 
 with. A copy of this print is sent to the customer with the 
 apparatus, to help him in its installation. 
 
 Checking the wiring during test serves the double purpose 
 of detecting errors in the print, or wrong connections in the 
 apparatus. It is consequently of considerable importance. 
 
 In wiring apparatus for test, all the wiring should be com- 
 pleted before any of the circuits are connected to the source 
 of power, to prevent the necessity of handling live circuits 
 while wiring. Where possible, one hand only should be used 
 for connecting or disconnecting low voltage live circuits 
 where an intervening switch cannot be used for making final 
 connections. It must always be remembered that any circuit 
 may become grounded and that some circuits are permanently 
 grounded. The 125, 250, and 500 volt direct current shop 
 circuits are permanently grounded. Hence, in all cases, circuit 
 breakers must be wired on the positive side of the "125 volt" 
 and "500 volt shop" circuits. As the "250 volt shop" is a part 
 of the three- wire system with grounded neutral, a circuit breaker 
 must be used on each side. 
 
 Opening direct current motor and synchronous motor 
 fields is likely to break down the insulation of the apparatus, 
 and in the case of a d-c. motor, the motor will run away. Wher- 
 ever binding posts and connectors, as used for rheostats and 
 small fields, are employed, a length of unbroken insulation 
 should be stripped from the end of the temporary field wire, 
 so that the portion stripped can be passed through the binding 
 post and bent back over the terminal. A complete loop is thus 
 formed which prevents the circuit being broken, even though 
 the clamping screw in the binding post or terminal works loose. 
 It is not safe to insert in the binding post the bare end of a 
 wire which has previously been used, since it may be fractured. 
 
 When a motor field is wired through the field ammeter 
 switch, the wire leading to the switch terminal and thence to 
 the ammeter should be continuous, the switch simply serving 
 to short-circuit the leads near the ammeter terminals. Motor 
 field circuit breaking switches must be located so that they 
 cannot be opened accidentally. The field switches must be 
 provided with a holding clip, or other fastening. Single-pole 
 switches must always be used in all field circuits. 
 
 99 
 
In all cases, circuit breakers must be used for breaking 
 direct currents of appreciable value. Oil switches must like- 
 wise be used on all alternating current circuits, when currents 
 and voltages of any magnitude are in question. Never break 
 an alternating current circuit either by water box, or by 
 an ordinary air-break switch, otherwise abnormal voltages 
 may be produced and strain the insulation of the apparatus. 
 All direct current generator and motor armature circuits must, 
 therefore, contain a circuit breaker of sufficient capacity to 
 open the maximum current delivered by the machine under 
 test. When "feeding back" tests are made on direct current 
 machines, two circuit breakers must be used, one in the supply 
 circuit, and one in the motor-generator circuit through which 
 the load energy is exchanged between the machines. 
 
 All transformers with iron cases must have their cases 
 grounded by a substantial wire, or cable, leading to ground. 
 This lead must be substantially connected to the transformer 
 case and to ground, so that it cannot be accidentally discon- 
 nected. 
 
 Temporary switches, circuit breakers, etc., should never 
 be attached to a test table or switchboard which is permanently 
 equipped. They should be mounted on rheostat stools, or 
 temporary stands. All temporary cables and wiring must 
 be properly insulated from iron floors, frames, and ground. 
 High voltage alternating current lines must be carried at a 
 sufficient height so that they cannot come in contact with 
 men walking under them. This also applies to disconnecting 
 and oil switches. Cables must be kept a sufficient distance 
 apart to take care of the potential difference between them. 
 They must be mechanically supported so they cannot drop 
 from their fastenings to the floor. High tension wires must be 
 carried to the testing table from the rear. They must not be car- 
 ried over the heads of men working at the test table. All wires 
 and circuits carrying more than 600 volts, must be regarded 
 as high voltage. No one must approach closer than 1 foot to 
 high voltage circuits, since many circuits possess sufficient 
 capacity or voltage to arc over before contact is made. 
 
 Starting Up 
 
 Before starting a machine for the first time, the tester must 
 assure himself that all instructions contained in Chapter 3, 
 and in the preceding paragraphs have been rigidly followed in 
 reference to the mechanical and electrical conditions, the wiring 
 of the various circuits, lubrication, etc. The belt lacings must 
 be watched to prevent them opening during test. Pulleys must 
 be inspected by the regularly appointed Pulley Inspector 
 to make sure they are securely fastened on the shaft and that 
 they are mechanically strong. All keys, set screws, or other 
 rotating parts which may catch in the clothing, or injure others 
 must be properly protected. All keyways must be provided 
 with covers or guards. All shafts carrying one-half of a solid 
 coupling must have that part boxed in, so that workmen may 
 
 100 
 
not come in contact with the sharp edges which usually exist. 
 No loose articles must be allowed inside any rotating or station- 
 ary parts. All belts must be guarded by substantial guards. 
 
 If a machine has been standing for any length of time, 
 before it is started again the same precautions must be observed. 
 These points are strongly emphasized in reference to all ver- 
 tical apparatus, where the danger of dropping things into a 
 machine, while running, or of workmen leaving tools in danger- 
 ous places on or about the machine is very much greater than 
 with horizontal apparatus. 
 
 When apparatus is first started it should be brought to 
 speed very slowly and carefully watched to see that every- 
 thing is correct as the speed increases to normal value. Reliable 
 tachometers, or speed indicating devices must be used in starting 
 to prevent a dangerous increase of speed. Oil rings must be 
 examined at slow speed to see if they are carrying sufficient 
 oil to the bearings. In the majority of cases, oil rings should 
 turn when the machine is running at 34 normal speed, and 
 should properly lubricate the bearings. 
 
 The balance of the rotating parts should be carefully noted 
 until the machine has reached its normal rated speed. If the 
 apparatus does not run without vibration the matter should 
 be reported as a defect. The vibration must be remedied 
 before the test proceeds. Vibration due to the running of the 
 machine may indicate lack of balance, whereas it may be really 
 due to improper alignment, or to springing of the shaft. When 
 unbalancing occurs in operating machines running above 1200 
 rev. per min. correction must be made by dynamic balancing 
 as in Chapter 3. 
 
 Preparation for Heat Runs 
 
 Heat runs are taken primarily to determine the amount of 
 temperature rise on the different parts of a machine while run- 
 ning under a specified load. This rise in temperature is measured 
 either by the rise in resistance of the current carrying parts or 
 by means of thermometers, or both. The results obtained by the 
 rise in resistance, as a general rule, are used only as a check on 
 the results obtained by reading thermometers placed on the 
 different parts, the temperature rise of which it is desired to 
 determine. Guarantees, except in special cases, are always 
 based on the rise by thermometer. 
 
 Thermometers should be carefully examined for broken 
 mercury columns before being placed on a machine. They should 
 not be inverted and in no case should they be placed on a 
 machine so that the bulb is on a higher level than the 
 other end. 
 
 Before starting a heat run thermometers should be placed 
 on the stationary accessible parts of the machine indicated by 
 the Testing Record. Each thermometer should be attached with 
 the bulb in contact with the part of which the temperature 
 is required and should have the bulb covered with a sufficient 
 amount of putty to secure it to the machine and to shield it 
 
 101 
 
from being affected by the surrounding air. Extreme care must 
 be exercised regarding the amount of putty so used, as too much 
 putty is as bad as too little. Just enough should be used to 
 do the work required. There should be no restriction of 
 the natural windage of the machine or radiation from the coil 
 whose temperature is being measured. 
 
 Thermometers which are to register the temperature of air 
 ducts should be so placed that the bulbs cannot make contact 
 with the iron laminations while the machine is running. Ther- 
 mometers which are liable to be shaken off by continued action 
 of windage, or slight vibration, should be securely fastened to 
 the machine. 
 
 When placing thermometers on field coils, care should be 
 taken tosee that they are not placed on the fiber strips protecting 
 the outside terminals. These fiber strips run from one terminal 
 to the other and form a non-conducting wall between the coil 
 and its outside insulation, and thus do not represent the true 
 temperature of the coil. Coils above the horizontal center 
 line of the machine should be used as the top of the machine 
 is usually somewhat hotter than the bottom. On small machines 
 two thermometers will be sufficient on the coils, but larger 
 machines should have at least four. 
 
 One thermometer will be sufficient on the frame of small 
 machines, but two or more should be used on the large units. 
 At least two thermometers should be used on the laminations 
 ard ducts of small machines, and at least four should be used 
 on larger machines. 
 
 Any large machine requiring a considerable floor space 
 should have the room temperature taken at four or more different 
 near-by points, and at a sufficient distance away so as not to be 
 affected by the windage and radiation of the machine. 
 
 The machine should be shielded from currents of air coming 
 from adjacent pulleys, belts and other machines, as unreliable 
 results are obtained when this is not done. A very slight current 
 of air will cause great discrepancies in the heating results, con- 
 sequently a suitable canvas screen should be used to screen the 
 machine under test, or the machine causing the draught should 
 be shut down. Great care must be used, however, to see that 
 such screen does not interfere with the natural ventilation of 
 the machine under test. Care must always be taken to see that 
 sufficient floor space is left between machines to allow free 
 circulation of air. 
 
 During the progress of the heat run the different parts of the 
 machine should be carefully watched for excessive heating of 
 any part, including the bearings. A sufficient number of ther- 
 mometers and amount of putty should be made ready to take 
 all the final temperatures of the revolving parts after the machine 
 is shut down, and the man in charge of the machine, if it is a 
 large one, should obtain temporarily several extra men to help 
 apply the thermometers and record the results. 
 
 On shutting down, thermometers should be placed on all the 
 revolving parts as specified on the Testing Record. 
 
 102 
 
All small commutators should have at least two, and large 
 ones at least six thermometers applied at different points 
 extending the whole length of the commutator from the arma- 
 ture risers to the outer end. 
 
 The thermometers must be applied as speedily as possible, 
 and the resistances of the various circuits measured immediately 
 after the machine stops. If any thermometer shows an un- 
 usually high temperature as compared with others it must be 
 immediately checked by placing other thermometers on the 
 same part. Reliable results depend directly upon promptness 
 and speed, and nothing should be allowed to interfere with the 
 carrying on of this work. To avoid repetitions of runs the 
 machines must be shut down quickly. 
 
 Readings should be taken of all thermometers every two 
 minutes until they begin to fall. 
 
 In calculating the rise of temperature the room temperature 
 should be taken as the average of the last two readings recorded 
 during the heat run. 
 
 Temperature Coils 
 
 In order more accurately to determine the temperatures of 
 the inaccessible windings of large machines, coils of small wire 
 known as "temperature coils" are sometimes imbedded in the 
 slots with the main winding. The rise in temperature of the 
 main winding is found from the rise in resistance of these tem- 
 perature coils and, consequently, accurate measurement of the 
 cold resistances of these coils is of the utmost importance. 
 During the heat run, readings should be taken of the resistances 
 of these coils at the same time that the thermometer readings 
 are taken. All readings must be very carefully made as a small 
 error made in the resistances of these coils makes a very appre- 
 ciable difference in the final temperature obtained. The rise 
 in temperature mav be calculated from the formula given on 
 page 112. 
 
 OBSERVATIONS AND COMMENTS DURING OPERATION. 
 REPORTING AND CORRECTING DEFECTS 
 
 On all Testing Records a number of questions are given 
 concerning the operation and condition of the machine during 
 the test, which should be intelligently answered by the men 
 conducting the test. 
 
 A close watch should be made for undue heating of bearings. 
 While running under load, no bearing should rise more than 40 
 deg. cent, above the room temperature. In case such a rise 
 occurs, the bearing should be scraped and the test repeated. Any 
 machine showing a bearing temperature rise of 25 deg. cent., 
 during an "equivalent load" run, should have the run continued 
 till bearing temperatures are practically constant, unless the 
 temperature continues to rise rapidly. In any case, note should 
 be made if the bearing temperatures rise above these limits and 
 the fact should be reported as a defect. 
 
 103 
 
A record should be made of any oil throwing or leakage 
 during test, and the matter reported at once. In the case of 
 oil throwing on d-c. machines, the test should be discontinued 
 until the defect is remedied. 
 
 All covers must be assembled in place so that it is impossible 
 for any foreign matter accidentally to get into the machine. 
 
 All staging around machines must be substantial and secure. 
 
 End play should be tried both with and without field on 
 the machine. This matter should be recorded on the Record 
 Sheet. If the end play is. defective it may be repaired as given 
 on page 96. 
 
 During a heat run, machines set upon shop blocking should 
 have the blocking and holding-down bolts examined at least 
 every 24 hours to prevent the machine from pulling over or the 
 bearings from loosening. 
 
 Any connections not checking with the connection print or 
 wiring diagram should be reported. 
 
 All machines should be carefully watched for any unbalanc- 
 ing or change in alignment. A defect of this nature may appear 
 after the machine has been running for some time even though 
 the balance and alignment may have seemed perfect at the 
 beginning of the run. 
 
 Record should be made of binding bands, commutator 
 shrink ring or any other part running out of true. 
 
 Commutators sometimes become noisy during operation, 
 due to brush friction. This may be remedied by a slight occa- 
 sional lubrication of the commutator surface. The noise may 
 be due to the brushes chattering, in which case no lubrication 
 must be used, but the defect reported at once. Chattering 
 may be caused either by poor commutator surface or an improper 
 setting angle of the brushes. 
 
 One or two brushes may glow and become very hot on a 
 stud carrying a number of brushes, while the other brushes run 
 cool and without sparking. This is known as selective com- 
 mutation and is due to difference in brush pressure, composition 
 or contact resistance which cause some of the brushes to carry 
 more than their share of the current, thus overheating them and 
 giving poor commutation. In order to remedy this difficulty, 
 it is usually necessary to change either the brushes or brush 
 pressures, or possibly both. 
 
 The brushes should be examined to see that they do not 
 stick in their holders. 
 
 Collector rings with rough joints, eccentric collector rings 
 or ones running out of true should be reported at once. 
 
 Unless the line circuit of a machine or the circuit supplying 
 excitation to the fields is grounded, grounds developing in the 
 armature, fields, or fittings during test may not at once become 
 apparent. During the high potential test any defect of this 
 nature is readily shown, however, and should be reported at 
 once in order that repairs may be made immediately. 
 
 The spacing and alignment of field poles, especially in the 
 case of com mutating pole machines, should receive the most 
 
 104 
 
careful attention. Poor alignment is usually indicated when 
 the air gap is measured. 
 
 The checking of polarity (see page 111) at once indicates 
 the reversal of any field coils. 
 
 In three-phase machines the reversal of any phase will 
 cause a considerable unbalancing in the voltage across phases. 
 The reversal of one coil will be shown in a similar manner, 
 but the unbalancing is not so pronounced. In quarter-phase 
 machines these defects will be shown by the phase rotation 
 test only. See page 172. The test of balancing voltage and cur- 
 rent and of phase rotation should, therefore, be carefully taken. 
 
 Stationary Apparatus 
 
 The instructions already given in reference to rotating 
 apparatus very largely apply to stationary apparatus. The 
 following points must also be carefully observed in testing the 
 latter, including transformers, regulators, compensators, switches, 
 relays, etc. 
 
 Careful inspection must be made for mechanical or elec- 
 trical defects when preparing stationary apparatus for test. 
 The precautions already given in reference to wiring should be 
 followed. All valves, tripping devices, contacts and insulation 
 should be examined. 
 
 Wherever cases or receptacles are oil filled for insulation 
 purposes, see that the proper amount of oil is put into them 
 before test. During the test the tanks and receptacles must 
 be carefully inspected for oil leakage, due to blow holes in 
 castings, oil plugs, oil gauges, or due to siphoning through the 
 leads. Adjustments of springs, weights, contacts, gauges and 
 air gap clearances must be made before testing, so far as is 
 practicable. Xo metallic particles must be allowed to drop or 
 be thrown into transformers, regulators, etc., during test; 
 otherwise breakdowns of insulation may result. 
 
 When testing stationary apparatus, it is rarely possible to 
 tell from inspection whether the apparatus is "alive" or not. 
 Hence there is all the more reason, on high voltage apparatus, 
 to make use of signs and barriers, to eliminate danger and pre- 
 vent shocks. 
 
 105 
 
CHAPTER 5 
 
 TESTING RECORDS 
 
 For the purpose of recording the results of standard tests, 
 various Testing Records are used to suit the different classes 
 of apparatus. Before a standard test is made, the tester must 
 provide himself with one of the Testing Records. He should 
 immediately fill in all blanks and headings, with all the data 
 concerning the machine which can be entered before the test 
 is started. All entries must be made at once upon the Testing 
 Record and never on "scrap paper." These Testing Records 
 (which should contain all the results of the standard test) 
 must be checked at the conclusion of each test to insure con- 
 sistency of readings and that full and complete explanations 
 have been made concerning the machine under test. 
 
 One man is appointed in each section to approve the results 
 of each individual test immediately upon its completion. In all 
 cases the written approval of this man must be obtained for 
 each test before the next test is started. 
 
 The completeness of these records is of the greatest impor- 
 tance, since they are used when passing the machine for ship- 
 ment and are finally filed in the Data Department, where they 
 are accessible for reference for the Designing Engineer and 
 others who desire to know the characteristics of the particular 
 machine. It is, therefore, necessary to make accurate, neat 
 and orderly entries on the Testing Record, and supplement 
 them with sufficient data fully to inform any one who has not 
 personally taken part in the test. Then, if reference is made to 
 them afterwards, no question can arise as to the meaning of 
 any of the readings or observations made. 
 
 In general, the Testing Record is intended to be a complete 
 and accurate history of the individual machine while in test 
 and, therefore, every effort must be made to carry out this 
 idea. 
 
 Special tests must be recorded on special Record Sheets. 
 As these tests are special and often involve new or peculiar 
 conditions, careful notes and explanations, with diagrams if 
 necessary, should be entered to make clear the conditions under 
 which the test was conducted. 
 
 The date of making the test, together with the name of the 
 individual making it must always be recorded on all Testing 
 Records and Record Sheets. In addition, whenever exhibition 
 tests are made for our own Engineers, or for a customer's Engineer 
 the Record Sheet must give the names of the Engineers who 
 witness the test. Records of tests taken under the direction 
 of a customer's Engineer must be plainly marked so that they 
 may be distinguished from any other tests which may be taken 
 on the machine. It is frequently necessary to furnish the cus- 
 tomer with "certified copies" of tests in lieu of his sending an 
 Engineer to witness the tests and check up the guarantees. 
 Wherever Engineering instructions request "certified copies" 
 
 106 
 
of the test, all the necessary tests and information must be 
 recorded on the Record Sheet so that "certified copies" can be 
 made, demonstrating that all guarantees have been met. 
 
 The reasons for all check tests should be plainly stated on the 
 Testing Record. 
 
 When tests have been finished, all records in reference to 
 them are sent to the Calculating Room, and such calculations 
 made as required. Curves showing the characteristics of machines 
 are plotted and filed with the corresponding Record Sheet. It 
 is the function of the Calculating Room also to check up results 
 on the Testing Records with those of duplicate machines already 
 shipped; and, where necessary, to refer Testing Records on 
 newly designed machines to the Engineering Department for 
 their approval before passing the machine for shipment. As 
 soon as the Calculating Room is assured, that the test proves 
 that a given piece of apparatus is satisfactory and has the 
 characteristics required for our guarantees, it approves the 
 Testing Record and the machine is listed on the "Daily Test 
 Report." 
 
 The "Test Report" is issued daily, copies being sent to all 
 persons interested in the shipment of the machine. It is the offi- 
 cial notification that the apparatus is satisfactory in all respects 
 and may be shipped. 
 
 The majority of apparatus tested is listed upon this "Test 
 Report." Certain small mechanisms and parts which only 
 require a slight electrical test are passed for shipment, bearing 
 the Testing Department stamp only, to show that they have 
 been officially tested. 
 
 Since the system of passing apparatus is largely founded 
 on the test records, it is essential that these records be com- 
 plete in every detail. 
 
 107 
 
CHAPTER 6 
 
 METHODS OF CONDUCTING STANDARD 
 TESTS 
 
 In the manufacture of armatures and fields for electrical 
 apparatus, many of the "faults and weaknesses" of material 
 and errors of workmen can be disclosed by what may be termed 
 "stationary testing." Faults and weaknesses may arise as 
 follows: Through a wrong application of insulation, or through 
 mechanical, faults in it. The use of wrong material for con- 
 ductors, leads, etc. Wrong assembly or connections — workmen's 
 mistakes. 
 
 Direct current armatures are tested for grounds, short-cir- 
 cuits, open -circuits, and high resistance joints before being 
 sent to the Testing Department. In testing for grounds a 
 high potential is applied between winding and core; the potential 
 depending upon the class of apparatus tested. When a ground 
 develops in test, if it cannot be located by inspection it must 
 be referred to the Armature Department. In no case is it to 
 be located by smoking the insulation. 
 
 /K 
 
 -0-31 
 
 Fig. 47 
 TESTING FOR GROUNDS 
 
 If a low resistance ground has developed it may be quickly 
 and accurately located by the following method: A low voltage 
 current is passed through the armature winding from a com- 
 mutator bar to the one adjacent to it, which is sufficient to 
 give a readable deflection on a galvanometer or milli- voltmeter 
 (as shown in Fig. 47). A line is connected to a galvanometer 
 to ground, the other galvanometer connection being placed 
 on one of the commutator bars. Then pass the supply and 
 galvanometer leads from segment to segment, until a full 
 deflection is obtained and zero reading when the leads are 
 moved one segment further. The grounded coil then lies 
 between the bars, for which full deflection was obtained. 
 
 108 
 
A "bar to bar" test is usually made to disclose short-circuits 
 open-circuits, and other similar faults. For this test the wind- 
 ings connected to two adjacent commutator segments have 
 their resistance measured by the "drop of potential method," 
 as indicated in Fig. 48. Storage batteries should be used and 
 a special electro-magnetic D'Arsonval galvanometer. With this 
 arrangement readings can be obtained rapidly, as the instrument 
 is "dead beat." 
 
 Measuring the ohmic resistance of the winding will some- 
 times reveal a wrong connection, which, on a bar to bar measure- 
 ment, would give a uniform deflection all around the commutator. 
 Series or wave windings may sometimes have all the conductors 
 joined in series, but in the wrong order, so that the armature 
 is inoperative. In the case of multiple or lap windings, double, 
 triple or even quadruple spiral re-entrant windings are possible, 
 whereas a single spiral is required. In taking a resistance 
 measurement for brush to brush or a running resistance of 
 the armature, see that the measurement is made from the 
 proper commutator segments. For multiple or lap windings, 
 the resistance measured from diametrically opposite points 
 divided by half the number of poles squared will give the true 
 running resistance, while with a series or wave winding the 
 
 W 
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 Fig. 48 
 TESTING FOR OPEN CIRCUIT 
 
 resistance should always be taken at points 180 electrical degrees 
 apart. For example, take a four-pole armature with a lap 
 winding and 360 commutator segments. This should have 
 its resistance measured between bars Xo. 1 and No. 181. The 
 resistance divided by four will give the running resistance. 
 With a wave winding on the same armature, the resistance 
 measurement should be taken between bars No. 1 and No. 91, 
 this resistance being the true running resistance. 
 
 Alternating current armatures and fields are similarly tested 
 for grounds, short-circuits, open- circuits, wrong connections, 
 polarity, etc. In testing for grounds the same methods and 
 similar apparatus are used as for direct current machines, 
 except that with alternating current the voltages generated 
 and used are usually higher and, consequently, the testing 
 
 109 
 
voltages are correspondingly higher and greater care must be 
 taken in testing. All high potential tests must be made with 
 carefully calibrated electrostatic voltmeters that have been 
 checked with a spark gap. The testing equipment should be 
 as near the apparatus as possible, since the additional capacity 
 of testing lines may raise the voltage at the receiving end much 
 above that at the generating end. Unless this precaution is 
 taken, excessive voltages may be applied which may damage 
 the insulation. In case a ground develops a resistance measure- 
 ment will generally locate the point at which it occurs, unless 
 each phase has two or more multiple circuits. In the latter 
 case it may be more readily located by opening one or more 
 cable joints and separating the circuits. 
 
 A measurement may then be taken in the following manner: 
 First, measure the resistance of the grounded circuit or phase. 
 Second, measure the resistance to ground by connecting one 
 line to ground. Third, measure the other end of the resistance 
 to ground, by connecting one measuring line at the other ter- 
 minal of the phase and one to ground. If all measurements 
 have been accurately made the sum of the second and third 
 will be equal to the first, and the location of the ground will 
 be as far from one terminal as the measured resistance from 
 that terminal to ground is of the total resistance of the circuit. 
 
 This test is shown in Fig. 49, which represents a single 
 circuit, or phase, of an alternating current machine, with a 
 
 I 
 
 
 Fig. 49 
 TEST FOR GROUNDS ON AN A-C. ARMATURE 
 
 ground as shown. If the resistance between A and B is one 
 ohm, between A and G 0.35 ohm and between B and G 0.65 
 ohm, the location of the ground is 35/100 of the distance 
 between A and B, from A. As 10 coils are in the circuit the 
 measurements show that the fourth coil is grounded, counting 
 from A. 
 
 In the case of an alternating current winding the ohmic 
 resistance measurement will not always detect a wrong con- 
 nection, such as a reversed coil, pole section, or phase; since, 
 although the copper resistance would be measured correctly 
 the total winding might be partly reversed and, therefore, 
 inoperative. Such faults may be discovered by a polarity or 
 impedance test, with alternating current. For this purpose a 
 :single-phase current can be used, since a reading may be taken 
 
 110 
 
on the different circuits, or between pairs of terminals succes- 
 sively by shifting the testing lines until the whole windings 
 have been tested. 
 
 Short-circuited coils on moderate size machines can be 
 readily tested by using a wound electro-magnetic yoke excited 
 with alternating current. This yoke is dropped over a portion 
 of the armature coil after the coils have been placed in their 
 slots. The yoke and armature form an alternating current 
 transformer, "with the yoke winding as primary, and the arma- 
 ture coil as secondary. If there is a short-circuited turn, layer 
 or coil in the armature, the magnetizing current in the yoke 
 winding rises. If the current is maintained a short time, the 
 insulation on the short-circuited section will warm up appreci- 
 ably, or burn sufficiently to indicate the defective coil. 
 
 On larger size alternator armatures, tests may be made for 
 short-circuits by passing alternating current through the 
 armature coil itself. In this case it is usually necessary to 
 increase the reactance of the coil by placing a magnetic bridge 
 over its armature slots after it has been assembled in the core. 
 
 The above tests may be made with the apparatus at rest. 
 The Armature Department, therefore, uses them for detecting 
 faults and correcting them before delivering the parts to the 
 Testing Department. These faults can be more readily cor- 
 rected when apparatus is being wound, with a resulting saving 
 in time and cost. It is, however, sometimes necessary to test 
 by these methods, after apparatus has been received in the 
 Testing Department, in order to locate faults which have 
 developed later. 
 
 As soon as the spools are assembled on a machine and before 
 the frame is taken from the spool assembly stand the windings 
 should be tested electrically for resistance and high potential. 
 They should also be tested for polarity of the poles by exciting 
 the field coils. These tests check the assembly of spools and 
 their position upon the frame. In testing field coils for polarity 
 all field windings must be tested separately to ascertain that the 
 series, shunt and commutating pole windings are wound and 
 assembled so as to give the required polarity. Polarity may be 
 tested by use of a compass, but the compass must not be carried 
 too near to the poles, as it may be demagnetized, or even reversed. 
 To test for the opposite polarity of alternate poles, bridge two 
 pole tips with a piece of soft iron. If the polarity of the poles 
 differs the piece will be strongly attracted, whereas if the poles 
 are of the same polarity much less attraction will be exerted. 
 
 Drop on Spools 
 
 With a given current flowing through the field the voltage 
 drop on any one spool of a direct current machine should in 
 no case be more than 4.5 per cent higher or lower than the 
 average drop, and on alternating current machines no spool 
 should vary more than 7 per cent either way from the average. 
 If the drop is outside of these limits, the matter should be 
 referred to the office for instructions. The field spools for 
 
 111 
 
alternating current apparatus are assembled on the field spider 
 in the Armature Department, hence it is necessary to take only 
 a resistance measurement per spool before using them for a 
 test. In recording drop on the spools of alternating current 
 machines, they should be numbered in a clockwise direction 
 facing the collector end, and beginning at the spool next to the 
 opening in the field for spool No. 1. 
 
 In direct current machines spool No. 1, either main or corn- 
 mutating is always the top spool or the next adjacent in a clock- 
 wise direction facing the commutator end. 
 
 Resistance 
 
 When testing a machine a very careful record must be kept 
 of the resistances of all windings. Most armatures when 
 delivered to test are fitted with equalizer rings which make it 
 impossible to obtain the true armature resistance. The Arma- 
 ture Department's tag attached to the armatures when received 
 in the Testing Department gives the armature resistance which 
 was obtained before the connection of the equalizer rings. The 
 tester must, therefore, record on the Testing Record the measure- 
 ment of resistance from this tag. The armature resistance is 
 rarely measured in the Testing Department. Such cases are 
 specified when required. The shunt field resistance is obtained 
 by the "drop method," using an ammeter and voltmeter. This 
 measurement is required on each machine before a test is started. 
 For measuring the series field resistance a special galvanometer 
 measuring set must be used, with which the various testing 
 sections are provided. As a considerable amount of the resist- 
 ance of a series field may consist of the contact resistances 
 between the spools, all connections must be carefully cleaned and 
 clamped tightly together, before taking the resistance. 
 
 After the heating test on any machine, the resistances of 
 the various parts are again measured and the rise in temperature 
 may be calculated by the following method: 
 Let Rh = hot resistance of copper measured at the temperature 
 
 h- 
 Rti = cold resistance of copper measured at the temperature 
 
 h. 
 
 Then * 2 = (238+*i) -^7 -238 
 Kt\ 
 
 The rise obtained from this formula should then be corrected 
 
 according to the standard rules of the A.I.E.E. for variations 
 
 from 25 deg. cent, in the observed room temperature. 
 
 Insulation Resistance 
 
 A measurement of the insulation resistance is occasionally 
 taken upon direct current machines and alternators. The 
 government requires this measurement in most cases. An 
 insulation resistance measurement is frequently taken on 
 alternators of 2300 volts and above. On commercial apparatus 
 generally, the measurement of insulation resistance, however, 
 is unnecessary, since the materials used have ample dielectric 
 
 112 
 
strength and the slight leakage which a low insulation resist- 
 ance would indicate is unimportant. This test when required 
 is taken by the "d-c. voltmeter method of measuring high resist- 
 ance" as given on page 42. In case the insulation resistance is 
 lower than required, due to dampness, the machine should be 
 baked either by the method described for making equivalent 
 load tests (page 144) or by placing the machine in a baking oven. 
 
 High Potential Test 
 
 This test is taken by applying an alternating voltage between 
 the various windings of a machine and from the current carrying 
 parts to ground. Fig. 2 shows the connections for one of the 
 standard high potential testing sets. Unless otherwise specified 
 all high potential tests should be taken as given on the Standing 
 Instructions for the machine in question. When the high poten- 
 tial test is applied to a moderate or large sized machine or piece 
 of apparatus, such machine must be entirely surrounded by 
 white tape and should have placed on it in a conspicuous place 
 the standard high potential signs to make doubly sure that no 
 one comes in contact with it. A sufficient number should stand 
 guard around it to make sure that no one is injured. 
 
 On small apparatus the standard high potential signs should 
 be used and but one man need stand as guard. Small machines 
 need not be surrounded with white tape. 
 
 After finishing the high potential test all oil and disconnecting 
 switches must be opened before the high potential testing cables 
 leading to the apparatus are handled. All temporary and high 
 potential testing cables must be disconnected from the testing 
 transformers or high voltage source at the conclusion of the test. 
 
 Adjustment of Speed Limiting Device 
 
 Many d-c. machines are equipped with a device for limiting 
 the speed in case of loss of field or any other condition which 
 might cause excessive speed. These devices must be adjusted 
 to operate at 15 per cent above the normal speed of the machine 
 under test (10 per cent for shop machines). This device is a 
 centrifugal device in which a revolving weight acts against a 
 spring and operates a switch connected in the circuit of the low 
 voltage trip coil of the circuit breaker. 
 
 Figs. 51a and 51b give diagrammatic views of the latest type 
 of this device. In order that it may operate properly the follow- 
 ing adjustments must be made: 
 
 With the weight moved outwards to the maximum distance, 
 a clearance of ye in. as shown in Fig. 51b must be allowed between 
 the centrifugal weight and the link when the switch is open. 
 This clearance must be allowed in order to prevent the weight 
 from hammering the switch after it has been forced open. 
 With the switch blade wide open and with the weight at its 
 maximum distance outwards, there must be y& in. clearance 
 between the nearest point of the switch and the centrifugal 
 weight. A clearance of 34 in. must be allowed between the 
 switch blade and the clips when the switch blade is in its extreme 
 "out" position, as shown in Fig. 51b. 
 
 113 
 
The adjustments of the clearance of the switch and centrif- 
 ugal weight can be obtained by finishing their respective stops 
 (on the short end of the switch and the hook shaped stops on 
 the ring), to the proper dimensions. If too much material has 
 already been removed from the stop, it may be drilled and tapped 
 for a screw or plug which can then be finished to the proper 
 dimensions. 
 
 All of the clearances given are the minimum that are obtained 
 when the weight is rotating. 
 
 After these clearances have been adjusted, the spring should 
 be adjusted, if necessary, so that the centrifugal weight strikes 
 the switch and forces the switch blade from the clips when the 
 speed has reached the specified limit. The springs are adjusted 
 
 Fig. 50 
 SPEED LIMITING DEVICE (EARLIER TYPE) 
 
 so that the weight operates on the switch when the speed has 
 risen 15 per cent above normal. The method of spring attach- 
 ment and therefore of adjustment will be clear from the figures. 
 
 The switch shown in Fig. 50 is arranged to short-circuit the 
 low voltage trip coil of the circuit breaker and should be adjusted 
 with the clearances shown in Figs. 52a, b, c. In this case the 
 revolving weight drives the switch blade into the switch con- 
 tacts. 
 
 Figs. 52a, b, c also show diagrammatically a type of 
 switch which is adjusted by varying the notch in which the 
 loose end of the spring is placed. The number of the notch in 
 
 114 
 
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 Fig. 51a 
 
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 Fig. Sib 
 DETAILS OF SPEED LIMITING DEVICE (LATER TYPE) 
 
 115 
 
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 Fig. 52b 
 
 Fig. 52c 
 DETAILS OF SPEED LIMITING DEVICE (OLD TYPE) 
 
 116 
 
which correct adjustment is obtained must be recorded, and 
 the speed at which it trips; also the tripping speed and number 
 of the notch on each side of the correct one. The notches are 
 numbered beginning at the one nearest the pivot. 
 
 In adjusting any speed limiting device several check readings 
 must be taken at the final position to make certain that the 
 device is set at the proper point. 
 
 Adjustment of End Play Device 
 
 Many machines, especially synchronous converters, are 
 equipped with an end play device to cause an even wearing of 
 bearings, commutator and collector rings. These devices are 
 
 Fig. 53 
 MAGNETIC END PLAY DEVICE 
 
 of two types, viz., magnetic and mechanical. Before any adjust- 
 ments are made great care must be used to see that the machine 
 is perfectly level, that it floats in the mid position of its end 
 play with field on, and that it has the correct amount of end 
 play. 
 
 The magnetic end play device, see Fig. 53, causes the armature 
 to oscillate by the same principle as is used in an electric bell. 
 It should be wired as shown in Fig. 54, using a source of supply 
 whose voltage equals the normal voltage of the machine under 
 test. To adjust the device set contact (A) by means of the 
 thumbscrew (T) until it firmly touches contact (B). This 
 is done with the armature in the mid position of its end play. 
 When the contacts come together the circuit is closed through 
 the coil and the electromagnet pulls the end of the shaft toward 
 it. When the shaft comes toward the magnet it pushes the rod 
 
 117 
 
(R) against the arm carrying contact (B) which opens the 
 circuit, releasing the magnetic pull on the end of the shaft so 
 that the armature is pulled back in the other direction by the 
 field of the machine. The momentum of the armature carries 
 it beyond the mid position of the end play and the contacts 
 come together again. The pull of the electromagnet is not 
 exerted fully until the armature has traveled away from the 
 device some distance beyond the mid position. The pull is 
 then established and causes the armature to return to mid 
 
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 Fig. 54 
 CONNECTION DIAGRAM FOR MAGNETIC END PLAY DEVICE 
 
 position. This cycle is then repeated. A rheostat is provided 
 to adjust the magnetic pull of the device to that of the fields, 
 so that the armature may oscillate the full distance of end play 
 allowed without bumping the bearings. After final adjustment 
 has been obtained, the amount of resistance included in the 
 rheostat should be measured and recorded on the Testing Record. 
 
 A condenser is connected across the contact to suppress the 
 spark when the circuit is opened. 
 
 The bushing through which the push rod passes should not 
 be lubricated, as it is provided with specially prepared graphite 
 for self-lubrication. 
 
 The mechanical end play device is shown in Fig. 55, and 
 consists of a ball running in a raceway held in a block which is 
 held in a shell. This shell is screwed into a three armed casting 
 which is bolted to the end of the pillow block of the machine. 
 This ball makes contact with a plate on the end of the shaft 
 
 118 
 
of the machine. The shell in which the raceway block is held 
 should be screwed into the position at which the ball will just 
 make contact with the plate when the armature is in the mid 
 position of its end play. The ball must be in its lowest position 
 and the spring which" is in the shell must not be set up tight 
 but must have sufficient play to take up the force of the end 
 thrust. As the center line of the raceway block is at an angle 
 
 Fig. 55 
 MECHANICAL END PLAY DEVICE 
 
 with the center line of the shaft, the friction between the ball 
 and plate will cause the ball to be carried up and during the 
 revolution it will throw the shaft its full distance. The ball 
 will then fall back and the pull of the field will cause the arma- 
 ture to return and the cycle to be repeated. Adjustment should 
 be made of the tension of the spring so that the armature will 
 swing through the range of its end play and yet not bump the 
 bearings. It may be necessary to change springs. When the 
 exact position of the ball has been determined, the shell may 
 be held in place by screwing down the plug in the side of the 
 three armed spider. 
 
 Saturation 
 
 In order to ascertain the characteristics of the magnetic 
 circuit, a test known as "saturation" is made. The character- 
 istic curve may be obtained by either of the following methods: 
 "generator saturation," or "motor saturation." 
 
 119 
 
Generator Saturation 
 
 The test usually made is "generator saturation." To 
 obtain a saturation curve by this method, the machine is driven 
 as a generator, preferably at normal speed. If, however, 
 a set of readings is known for one speed, they can be obtained 
 for any other by direct proportion. Hence a saturation curve 
 taken at any constant speed at once gives the saturation curve 
 at any other speed. The brushes of direct current machines 
 should always be set on the neutral point and the machines 
 run preferably at no-load speed when taking a no-load saturation 
 curve. 
 
 In taking a saturation curve on polyphase alternating cur- 
 rent generators, a reading of the voltage across each phase 
 must be taken at normal field current, to see if the phases 
 are properly balanced. If they do not balance, they must be 
 made to do so. On synchronous converters careful readings 
 must be taken of the direct voltage, as well as the alternating 
 voltage between all phases with the field excitation giving 
 normal voltage. The phase voltages must also be closely 
 balanced. 
 
 The usual method of taking a generator saturation curve 
 is to hold the speed constant, and then increase the field current 
 step by step until at least 125 per cent of the normal voltage 
 of the machine is reached, taking readings at each step simulta- 
 neously, of volts armature, volts field, and amperes field. After 
 reaching the maximum value of the field current, without open- 
 ing the field, reduce the current gradually in four or five steps, 
 and again take readings to determine the value of the residual 
 magnetism at various points along the curve. Special care 
 must be taken to insure accurate readings at and above normal 
 voltage, since with alternating current generators, this is the 
 portion of the curve used for calculating the regulation under 
 load. Whenever saturation curves are taken, a record of the 
 air gap from iron to iron must be made upon the Record Sheet, 
 together with the armature and field specifications. 
 
 Motor Saturation 
 
 When it is inconvenient or impossible to drive the machine 
 as a generator, a "motor saturation " may be made. In this case 
 the machine is operated as a free running motor. The driving 
 power must be furnished from a variable voltage circuit. A 
 certain voltage is impressed upon the armature and the motor 
 field weakened or increased in the case of direct current machines 
 to give normal speed, and a record made of the volts armature, 
 amperes armature, amperes field, volts field, and speed. The 
 starting voltage should be at least 50 per cent lower than 
 the normal voltage of the apparatus. The applied voltage 
 at the armature should be increased by steps to 25 per cent 
 above normal value, and the field increased correspondingly to 
 keep the speed constant, the same readings being recorded at 
 the various steps as before. Readings should also be taken at 
 
 120 
 
three or four points as the impressed voltage and field current are 
 lowered to approximately the values at the beginning of the test. 
 Care should be taken when testing direct current apparatus, 
 as unstable electrical conditions may develop, and excessive 
 speeds result. The circuit breaker in the armature circuit of 
 the motor driving the machine must, therefore, be accessible 
 to the tester reading the speed. 
 
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 SATURATION CURVE ON A 500 KW., 600 VOLT, 20 POLE, 360 R.P.M. 
 
 3-PHASE, 60 CYCLE, A-C. GENERATOR 
 
 On alternating current apparatus, the machine is run as 
 a motor and the impressed voltage varied as already described. 
 The speed is independent of the motor field in this case, and 
 instead of regulating the motor field for speed it should be 
 regulated to give mimimum input current at each voltage. 
 Readings should be taken of voltage impressed, amperes arma- 
 ture, amperes field, and volts field. With induction motors it is 
 only necessary to impress variable voltages at constant fre- 
 quency and record readings of impressed volts armature, 
 amperes armature, and speed. 
 
 121 
 
The calculation of saturation tests is very simple, as it 
 consists only in applying instrument correction factors and 
 ratios, and plotting upon coordinate paper, volts armature 
 as ordinates and amperes field as abscissae. Fig. 56, and Calcu- 
 lation Sheet No. 1, show the results of a saturation test made 
 by either of the above methods. 
 
 Core Loss 
 
 Three methods are used to measure the core losses on rotating 
 direct current apparatus and alternating current synchronous 
 apparatus. They are known as follows: "running light core 
 loss," "belted core loss," and "deceleration core loss." 
 
 The following conditions must be obtained with direct current 
 apparatus in order to give satisfactory results: Brushes must 
 be shifted on the commutator to the mechanical neutral point. 
 They must have their normal tension and the commutator 
 must be clean, so that the normal operating commutator and 
 brush friction values are obtained. This test, wherever pos- 
 sible, must be made after all the others have been finished, 
 in order to have a glossy commutator with its surface in good 
 operating condition. The driving power should be supplied 
 from a variable voltage circuit that is not subject to sudden 
 fluctuation. Readings must not be taken when the rotating 
 parts are accelerating or decelerating. 
 
 Running Light 
 
 This test is made by running the machine free as a motor. 
 It is made on most d-c. generators and motors which are given 
 a running test and occasionally on alternating current syn- 
 chronous apparatus. 
 
 When "running light" tests are made on direct current 
 generators, the observations must be made with full load field 
 flux. The potential applied to the armature must be equal 
 to the normal rated voltage of the generator increased by the 
 IR drop in the armature at full load. With this voltage im- 
 pressed, the field current is varied until normal speed is obtained, 
 when careful readings must be made of armature current, 
 armature voltage, field current, field voltage and speed. 
 
 If the machine in test is a direct current motor, the voltage 
 applied to the armature should be equal to the normal rated 
 voltage of the motor, less the IR drop in the armature under 
 full load. The field current is then adjusted to give normal 
 speed and electrical and speed readings taken, as outlined 
 above for direct current generators. 
 
 The power supplied to machines running free will equal 
 that absorbed in bearing friction, brush friction, windage, 
 and core loss, when the armature PR losses have been sub- 
 tracted. 
 
 In making records of these tests, the Testing Record must 
 clearly show whether the running light current consists of the 
 armature current plus the shunt field current, or whether it 
 is the armature current alone. To check this point, open 
 
 122 
 
the armature circuit with the shunt field circuit closed, and 
 note whether any current is indicated on the ammeter reading 
 the power supplied. If no current is indicated, the reading 
 indicates the armature current alone, otherwise, the running 
 light current is equal to the sum of the armature and field 
 currents. To obtain ''running light" core loss tests, only a 
 single field winding must be used for excitation; this must be 
 a shunt field winding. 
 
 In the case of series wound motors the field should be sepa- 
 rately excited and extreme care should be taken to see that the 
 motor does not lose its field. 
 
 In order to obtain running light core loss upon alternating 
 current synchronous machines (in which class synchronous 
 converters are not included as the core loss test on these ma- 
 chines is similar to that on direct current machines), they should 
 be operated as synchronous motors at the proper frequency and 
 rated voltage. For the best results, both frequency and voltage 
 must have a steady value. 
 
 With normal voltage on the armature, the direct current 
 field should then be varied until minimum armature current 
 is obtained. Readings should then be taken of amperes and 
 volts of all the phases. At minimum input current unity 
 power-factor is obtained and, therefore, the power to drive such 
 machines will be the volt-ampere input. Wattmeters may 
 be used in addition to check the volt-ampere readings. This 
 measurement includes friction and windage losses, together 
 with open-circuit core loss, plus the I 2 R loss in the armature. 
 If the value of the core loss need not be separated from the other 
 losses, the test is useful for checking up full load efficiencies. 
 
 Belted Core Loss 
 
 By means of the ' ' belted core loss' ' method the core loss can be 
 separated from the bearing friction, brush friction and windage. 
 A small direct current motor is used to drive the machine under 
 test as a generator at its rated speed. A belt drive between these 
 machines is most commonly used, but wherever great accuracy 
 or a high speed is necessary, direct drive by means of a coupling 
 is often used. 
 
 The driving motor for this test should be such that good 
 commutation is obtained for all loads required by the core loss 
 test with a fixed setting of the brushes; and with the maximum 
 volts on the machine under test, it should carry not more than 
 50 per cent of its normal rated capacity. Ordinarily a good rule 
 to follow is to select a motor, the rated capacity of which is 
 approximately 10 per cent of the rated output of the machine 
 under test. When the brush setting to give the best possible 
 commutation at all loads has been obtained, the brushes should 
 be left in that position throughout the test. The commutator 
 surface should be in first class condition and should have the 
 brushes closely fitted to it. 
 
 The belt should be of minimum width and weight to carry 
 the load without slipping. When testing motor-generator sets, 
 
 123 
 
synchronous converters and other machines that do not require 
 belts in practice, the tension of the belt must be kept as low as 
 practicable so that the bearing friction is not increased on account 
 of belt pull. Endless belts should always be used in preference 
 to laced belts. 
 
 The diameter of the pulleys should be so selected that the 
 driving motor will run at or near its rated speed when the 
 machine under test is running at its normal speed. 
 
 The driving motor should have its field separately excited 
 from a constant source and other wiring so arranged that readings 
 may be taken of amperes armature, volts armature, amperes 
 field and speed. The volt-wires should be firmly attached to 
 brushes on two adjacent studs. The brushes so used should be 
 insulated from the holders so that the true volts armature may 
 be obtained. Previous to starting the test, careful resistance 
 measurements must be made of the armature of the driving 
 motor. 
 
 The machine under test should be wired as a separately 
 excited generator with provision for reading volts armature, 
 volts field, amperes field and speed. 
 
 The test should then be carried out as follows: The field 
 of the driving motor should be adjusted to about normal value 
 and held constant, and the speed regulated by varying the 
 voltage applied to the armature terminals. Careful readings 
 should be taken to make sure that no belt slipping occurs. This 
 is done by taking simultaneous readings of speed of both the 
 driving motor and the machine under test: (a) with no field on 
 the machine under test, (b) with normal field excitation. The 
 two readings of speed should be identical. The machines 
 should be run a sufficient length of time to allow the friction 
 to become constant. This will be the case when the input to 
 the driving motor becomes constant when driving the machine 
 under test without any field excitation. 
 
 Throughout the entire test, readings must be taken at abso- 
 lutely constant speed when the rotating parts are neither accel- 
 erating nor decelerating. 
 
 Readings should be taken as follows: 
 
 (a) Take the input to the driving motor with no field on the 
 machine under test and with all brushes down on the commu- 
 tator. 
 
 (b) Take the input with field on the machine under test 
 to give normal volts with all brushes down on the commutator. 
 
 (c) Take the input with all brushes raised from the com- 
 mutator and with the same field current in the machine under 
 test as for the preceding reading. 
 
 (d) Take the input with all brushes raised and with no field 
 on the machine under test. 
 
 The difference between the first and fourth readings is brush 
 friction. The difference between the second and first readings 
 and also the difference between the third and fourth readings is 
 core loss. The core loss should be the same with the brushes 
 down as with the brushes up, and the two results obtained 
 
 124 
 
should check within 6 per cent before proceeding with the test. 
 Starting with zero field on the machine under test observations 
 of the input to the driving motor should be made at various 
 values of the field up to that which will give 125 per cent normal 
 voltage, and at least half the readings should be taken between 
 90 per cent and 110 per cent of the normal voltage. 
 
 The "friction, reading" with zero field excitation on the 
 machine under test should be repeated at least three times during 
 the progress of the test; namely, at the beginning, again near 
 the mid point of the curve and finally at the end of the test. 
 
 
 
 
 
 ' 
 
 
 | 
 
 j : 
 
 ! 
 
 
 
 
 
 
 
 
 
 
 
 1 ' "' 
 
 
 
 
 
 
 
 
 
 
 i 
 
 
 
 
 
 
 
 tt ~\ 
 
 
 
 
 
 
 
 It 
 
 
 
 
 
 
 
 
 t7 ^ 
 
 
 
 
 
 1 1 1 
 
 
 
 
 
 
 
 
 
 A 
 
 
 
 
 
 
 
 
 
 
 
 
 
 f\ 
 
 
 
 
 
 
 
 
 
 
 , 
 
 
 
 
 / 
 
 it in 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 rl 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 ^o 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 * <? 
 
 
 
 
 
 
 
 
 
 
 
 y 
 
 
 
 • i 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 ! 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 w 
 
 
 
 
 
 ! 
 
 
 
 
 
 
 
 
 
 Nj> 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 _ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 o 
 
 
 i 
 
 ft 
 
 y 
 
 TT^ 
 
 * 
 
 y 
 
 ^ 
 
 J 
 
 V 
 
 h- 
 
 <=>? 
 
 yj 
 
 44- 1 
 
 Fig. 57 
 
 OPEN CIRCUIT CORE LOSS ON A 500 KW., 600 VOLT, 20 POLE, 360 R.P.M. 
 
 3-PHASE, 60 CYCLE, A-C. GENERATOR 
 
 As the amperes field of the machine under test are increased 
 the volts armature of the driving motor should also increase 
 because of the increased IR drop in the armature. 
 
 The driving motor should then be unbelted and a "running 
 light " reading taken on it as follows: Without changing the brush 
 shift hold the same amperes field as was held during the core loss 
 test and take a reading of the input to the motor to give the 
 same speed as was read on the driving motor at the beginning 
 of the test. The volts armature should be lower than for anv 
 reading taken during the core loss test. 
 
 To check the results of the core loss as the test proceeds the 
 power input to the driving motor required bv the core loss at 
 a given excitation should be plotted agains't volts armature 
 generated. This should give a curve similar to Fig. 57. 
 
 Correcting the motor input at the various field strengths 
 by deducting the PR loss in the armature of the driving motor 
 and subtracting the power input to the driving motor with zero 
 field on the machine in test, the core loss is left corresponding to 
 
 125 
 
By subtracting the "running light " 
 input to the driving motor from the input with zero field on the 
 machine in test, the bearing friction and windage losses of the 
 machine under test are obtained. 
 
 No pulsation or sudden variations must occur in the arma- 
 ture current of the driving motor which might vitiate the power 
 readings. It is advisable to wire an inductive winding in series 
 with the armature of the driving motor in order to steady the 
 motor armature current. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 f 
 
 O 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 J 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 -4000 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 SOOO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1/ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 r 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 y 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ,> 
 
 V' 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 /ooo 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 s 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 >1 
 
 s\ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 /oo 
 
 200 
 
 SOO too SOO 
 
 6O0 
 
 700 
 
 Fig. 58 
 
 SHORT CIRCUIT CORE LOSS ON A 500 KW\, 600 VOLT, 20 POLE 
 
 360 R.P.M., 3-PHASE, 60 CYCLE, A-C. GENERATOR 
 
 In making out reports of core loss the following data regarding 
 the machine under test should be recorded on the Testing 
 Records in addition to the electrical readings already mentioned: 
 viz., circumference of commutator; circumference of shunt and 
 series field spools; height of shunt and series field spools; number 
 and width of commutator bars; size and material of brushes; 
 number of studs and brushes per stud; brush pressure per brush; 
 rating of driving motor together with its armature and frame 
 number; type and rating and serial number of the machine 
 under test. 
 
 On series motors core loss tests should be taken at several 
 different speeds covering the range of the speed curve. The 
 method used is identical with that described above and will be 
 considered in connection with railway and series motor tests. 
 
 126 
 
Synchronous alternating current machines generally have 
 loss measurements taken as outlined above on open-circuit (see 
 Calculation Sheet No. 2), and also with the armature of the 
 machine under test short-circuited. In the latter case the 
 increase in power supplied by the driving motor over that 
 required by the friction loss is plotted as ordinates against 
 the amperes armature as abscissas, or the open-circuited arma- 
 ture voltage due to a given excitation. A curve is obtained 
 
 /O 20 30 40 50 60 70 SO SO /OO //O /20 
 Seconcfs 
 
 Fig. 59 
 
 DECELERATION CURVES ON A 3000 KW., 2300 VOLT, 720 R.P.M. 
 
 60 CYCLE, 3-PHASE, A-C. GENERATOR 
 
 similar in character to the open-circuited core loss curve. Such 
 test is commonly known as "short-circuited core loss." Fig. 58 
 shows the results of such tests after all correction factors have 
 been applied. In making this test careful measurements must be 
 made of the resistance of the short-circuited armature circuit 
 including all leads, before and after the test, since to obtain the 
 true short-circuited core loss the PR loss must be subtracted. 
 Observations should be made with the short-circuited armature 
 current at least 200 per cent of its normal full load value. (See 
 
 127 
 
Calculation Sheet No. 3.) Care must be taken not to overheat 
 the windings. 
 
 Deceleration Core Loss 
 
 It is often necessary to determine the core loss, friction 
 and windage losses of large machines when it, is impracticable 
 to employ the "belted core loss" method. The "running 
 light" reading alone does not allow the separation of the core 
 loss from friction and windage. A method known as the 
 "deceleration core loss" is used for this purpose. Such tests 
 
 90 
 80 
 70 
 60 
 
 X40 
 
 20 
 10 
 
 _L 
 
 t 
 
 / 
 
 f 
 
 7 
 
 
 7 
 
 7- 
 
 / 
 
 / 
 
 jT 
 
 y 
 
 s^ 
 
 ^^ 
 
 ^.^^ i 
 
 *" r ~* 
 
 
 
 "800 
 
 J200 /600 2000 
 Vo/ts /Ir/nati/re 
 
 2400 
 
 Fig. 60 
 
 OPEN CIRCUIT CORE LOSS CURVE FROM 
 
 DECELERATION CURVES IN FIG. 59 
 
 are employed regularly on turbine-driven units, and it is very 
 convenient to use them in connection with certain vertical 
 waterwheel-driven generators, and other exceptionally large 
 horizontal alternators and direct current machines with a 
 considerable flywheel capacity. 
 
 A running light reading at normal speed and normal voltage 
 should be taken to give the driving power necessary under 
 that condition. Where this is not practicable, the moment 
 of inertia of the rotating part must be known. This can be 
 very accurately calculated for the majority of machines from 
 their mechanical dimensions, as given by the working drawings. 
 
 The test is as follows : First drive the machine with no field 
 at a little above normal speed, and then suddenly cut off the 
 driving power and observe the deceleration, then do the same 
 
 128 
 
thing with full field on the machine. In the first case the decelera- 
 tion is due to the retarding force (friction and windage), in 
 the second case due to these factors plus core loss. Readings 
 of the speed of the rotating parts should be taken at sufficiently 
 frequent intervals to obtain a uniform and reliable curve. 
 A set of these curves is shown in Figs. 59 and 60. With the 
 aid of these curves together with a "running light" test, or 
 a calculation of the kinetic energy of the rotating parts, a 
 determination of the value of the core loss, and also of the 
 friction and windage, is readily made. The following is a brief 
 derivation of the formulae used in calculating such results by 
 either method. 
 
 If W = weight. 
 
 r = radius of gyration. 
 Si = speed in r.p.m. at time 7\ 
 Sa = speed in r.p.m. at time TV 
 Wr 2 = flywheel effect. 
 
 Then the kilowatts loss may be found from the following: 
 
 *2308 (S^-Sf) 1 . . . , , .. , o , c. 
 
 — — Wr- - _ = kw. lost in decelerating from Si to S 2 
 
 with any particular field excitation. 
 
 * This formula gives the average power loss from Si to Sz and may be 
 derived as follows: 
 
 If M = mass 
 
 v =linear velocity at radius of gyration 
 03 = angular velocity 
 
 5 = speed in r.p.m. corresponding to angular velocity 
 g =32.2 ft. per sec. per sec. 
 £ = kinetic energy at speed 5 and time T 
 Ei = kinetic energy at speed Si and time Ti 
 Ei = kinetic energy at speed S2 and time Ti 
 P = power 
 
 1 W 
 
 The kinetic energy of a moving body at any instant is — Mv 2 . M = — and 
 
 for a rotating body v=ru> and co =— — . 
 
 b(J. 
 
 1 W W / ?7rS\ 2 
 
 Hence E =-- M& = ^-(raj2) =~ I r =^) =0.00017 Wr*S*. 
 I Ig Ig \ oU / 
 
 £1 =0.00017 Wr 2 Si 2 (1) 
 £•2=0.00017 Wr°- S2 2 (2) 
 
 The energy consumed between Ti and T2=Ei—Ei but for (1) and (2) 
 £1 -Ei =0.00017 Wr* (Si 2 -S2 2 ) in foot lb. 
 Energy 
 
 Power 
 
 Time 
 
 .-. P=|i-^- 2 = 0.0001 7 Wr* ( ;!f y? ft. lb. per sec. 
 
 /« — il (J2 — i l) 
 
 Multiplying by the proper constants to reduce to kilowatts we have 
 
 kw .0.00017 W,: ^M x^| Xi -^ Wr-- ^=^ which is 
 (T2 — T1) 1000 00O 10 10 (T2 — T1) 
 
 the average power loss for speeds from Si to S2. 
 
 (Continued on page 130) 
 
 129 
 
If T z and T* are respectively the times at which the speeds 
 S\ and 52 occur with no excitation on the machine, then in this 
 
 rt. 1 "I 2308 W 2 W-Sf) 
 
 case the loss m kw. = ■ Wr 2 -?= , _ T , 
 
 §The kw. core loss is then the difference between the results 
 obtained from the above two formulae. 
 
 With deceleration core loss records the same data must be 
 entered upon the record sheets that are required in connection 
 with the belted core loss method. Calculation Sheets 2 and 3 
 show the standard method of calculating test results, open- 
 circuited and short-circuited, taken by the belted core loss 
 method. Calculation Sheet 4 shows the method employed in 
 calculating results of deceleration core loss, either by using the 
 value of Wr 2 , or the running light test. 
 
 Input- Output Test 
 
 It is sometimes required that the efficiency of a machine, or 
 motor-generator set be measured by the input-output method. 
 The measurement of the power input to the motor or the output 
 from the generator is then required. The efficiency of the set 
 will then equal 
 
 To find the loss at any particular speed use the following method: 
 
 E =0.00017 Wr 2 S 2 . If ds is the infinitely small change of speed during the 
 infinitely short time dt then 
 
 f . "p-moi;™* ) _ . 00034 Wr , s « or a _ KS is 
 
 dt dt dt dt dt 
 
 But — =- is a rate of change of energy or power and -3- =P 
 dt dt 
 
 Having obtained a deceleration speed-time curve we can get. P for any 
 
 value of 5. Since -r - is the slope of the curve and can be obtained by drawing 
 
 at 
 the tangent to the curve where 5 has the desired value. Substituting values of 
 
 5 and -7- in the above equation gives the value of P. 
 dt 
 
 § If the kw. ' 'running light " has been obtained, 
 
 , .. • r ..,, 2308 _. . (Si* -52*) v WrKSt-Sf) 
 kw "running light" =- T7 r- Wr 2 -y= 7F -^- = Ki 
 
 Wr 2 = 
 
 10'° (T2-T1) (T2-T1) 
 
 kw. "running light " (7^2 — Ti) 
 
 also kw. friction = 
 
 Ki(5i2-5 2 2 ) 
 KiWr 2 (Si 2 -S2 2 ) 
 
 (Ti-Tz) 
 or substituting for Wr 2 
 
 kw friction =7^ =rr Xkw. "running light." 
 
 {Ti— Ta) 
 
 Hence knowing the "running light," the friction can be calculated and the 
 core loss separated from the "running light." 
 
 130 
 
Total output of generator 
 total input to motor 
 The efficiency of the generator equals 
 Total output of generator 
 input to motor — motor losses 
 The efficiency of the motor equals 
 
 Output of generator +generator losses 
 input to motor 
 
 In the case of induction motors, input-output test is some- 
 times taken by the string brake method, which is discussed 
 in Chapter 12." 
 
 The input-output method of measuring efficiency is one 
 of the most difficult tests which the Test Dept. is called upon 
 to make, and is subject to considerable inaccuracy. 
 
 This method of the direct measurement of the efficiency of a 
 machine should preferably be made by using a duplicate machine 
 for power or for load. This is especially true of motor-generator 
 sets. The two sets should be wired up for feed back test and the 
 electrical losses supplied to the direct current machine, unless 
 it is possible to secure a source of alternating current whose 
 wave form is identical with that of the alternating current motor 
 under test. 
 
 Great care must be exercised in wiring the machines for 
 this test. The voltmeters, reading the voltage of the input and 
 the output, should be wired as near to their respective machines 
 as possible. 
 
 The secondaries of the current transformers should be wired 
 directly to the instruments and not through any switches or 
 contacts of any kind, and the wiring must be continuous, i.e., 
 without an}' splices. The alternating current wattmeters, 
 reading the input, must be placed some distance apart. All 
 instruments should be carefully tested for stray fields. If the 
 machines have series fields, these must be disconnected. 
 
 Before the machine is started the wiring must be thoroughly 
 inspected by the Head of the Section or one of his assistants. 
 The complete set of instruments, transformers, etc., must be 
 specially calibrated before this test is commenced. No reading 
 should be taken until the instrument pointers are steady and 
 extreme care must be taken to have all readings simultaneous. 
 Xo man should read more than two instruments and preferably 
 there should be one man for each instrument reading directly 
 the input and the output. 
 
 The resulting errors from the input-output method are likely to 
 be large, since any inaccuracy in instruments, or personal errors in 
 reading, influence the results directly. The errors in reading the 
 instruments maybe partially eliminated by taking several readings 
 at each load and using the average of all these readings. Even 
 with the best conditions for making the input-output test it is 
 still much more preferable to ascertain efficiency by measuring 
 the losses directly. By adding all the losses to the output at any 
 
 131 
 
load the input at that load may be obtained, The output 
 divided by this result gives the per cent efficiency. The same 
 per cent errors in instruments or instrument readings in loss 
 measurement test influences the results of the efficiency calcula- 
 tions only indirectly; consequently the latter method is superior 
 for ordinary testing. 
 
 Shunt F/'e/d 
 
 vvw 
 
 Tora6/ea/?d 
 -+- Exc/tat/o/7 
 
 OCo/T?fmi£at/ng/ye/d 
 * 'WWW 
 
 Commutat/f?0 
 —F/<?/d 
 
 ToExc/tatbn 
 
 Fig. 61 
 CONNECTIONS FOR LOAD LOSS TEST 
 
 To Exc Station 
 
 Load Loss Test 
 
 As stated in the section on input-output tests it is much 
 more desirable to ascertain the efficiency of a machine by 
 measuring the losses directly. However, there are some machines 
 which when loaded show a loss which cannot be measured or 
 calculated directly from the no-load test. This additional loss 
 is known as "load loss." 
 
 To obtain the efficiency of a machine under load without 
 making the input-output test, the method of measuring the PR 
 loss by means of a booster and observing the input to a separate 
 driving motor which supplies the rotation and core losses is used. 
 This test requires two similar machines coupled and wired 
 together, as shown in Fig. 61. The driving motor should prefer- 
 ably be direct connected so as to eliminate the belt loss. 
 
 132 
 
After the machines have run a sufficient time under load 
 to reach constant temperatures they should be shut down and 
 the IR drop between the two machines taken at the terminals 
 of the machines at currents corresponding to the loads at which 
 the load loss is to be observed. These readings will give the 
 approximate booster voltages required for the different loads. 
 
 The machines should then be run until the friction is constant. 
 Then take several core loss readings on each machine with the 
 voltage varying from 75 to 125 per cent of normal. Also take 
 careful readings of the input to the driving motor with both 
 machines excited to give normal voltage. The difference between 
 the motor input (less its own losses) for normal voltage on the 
 machines and for friction (less the driving motor losses) is the 
 core loss at normal voltage. 
 
 Readings should then be taken at various loads holding the 
 voltage on the generator constant at normal, and the booster 
 supplying voltage at 10 per cent below the normal drop as 
 obtained at standstill; at normal drop; and at 10 per cent above 
 normal drop for each load. As the booster and the driving motor 
 are furnishing all the losses the sum of the power supplied by 
 these two machines should be practically the same for the above 
 readings for any given load. This variation in booster voltage 
 is made in order to check each point under slightly different 
 instrument readings. 
 
 When a complete set of readings is taken the machines should 
 be shut down and the IR drop again observed for the various 
 currents used in taking the IR drop at the beginning of the test. 
 Take the average resistance obtained from the drop at the- 
 beginning and at the end of the test and use this for calculating 
 the PR to be deducted from the power supplied the two machines 
 under the different loads. 
 
 The load loss for two machines will then equal the total 
 power supplied by the booster and the driving motor minus the 
 PR loss of the circuit minus the PR loss of the driving motor 
 armature minus the driving motor input at no-load normal 
 voltage on both generators or motors under test. 
 
 As this method gives a fairly accurate measurement of the 
 total losses under full load, or at any per cent of full load it is a 
 direct method for measuring the load loss and the efficiency. 
 However, it requires the most accurate work. The same amount 
 of care in the calibration of instruments and transformers, in 
 the wiring of the machines and in reading the instruments is 
 required as is necessary for the input-output test. The effect 
 of brush shift on the load loss is very noticeable. The load loss 
 may also be affected by the condition of the brush contact 
 surface and by the condition of the commutator. It is, therefore, 
 important not to disturb the brushes or commutator after the 
 tests have been commenced. 
 
 Maximum Output 
 
 The maximum output of direct current compound wound 
 generators is dependent upon their commutation, or heating 
 
 133 
 
limitations, hence, the maximum output test on these machines 
 is usually a commutation test, which will be described later. 
 As in shunt wound generators the voltage falls with the load at 
 constant field excitation, the maximum output is not always 
 limited by commutation. It is not usual to make maximum 
 output tests, however, on the above machines, since they 
 possess little practical interest. 
 
 In the case of induction motors, the maximum output, or 
 breakdown point, is a matter of considerable importance. If 
 sufficient power is available, the motor is loaded in successive 
 steps, beginning at zero load up to the breakdown point. During 
 this test readings of volts armature, amperes armature, speed, 
 and motor output are taken and plotted. It is essential that 
 the voltage and frequency of the power circuit from which 
 the motor is operating be held constant. It is also important 
 that readings be taken quickly at overload currents, and that 
 the motor be allowed to cool between such readings, or it will 
 overheat. Where sufficient power is not available to take a 
 breakdown test with normal voltage impressed on the armature 
 of the motor, a voltage considerably below normal is used, viz: 
 z /i, Y2, or even }/i voltage. It is then necessary to calculate the 
 full voltage results from those obtained at the lower voltages. 
 This may be done by increasing the power output proportionally 
 to the square of the ratio of normal voltage to the lower voltage. 
 
 All maximum output tests on synchronous motors, unless 
 stated to the contrary, should be made with a field excitation 
 giving minimum input armature current for a given load. 
 Readings must, therefore, be taken of volts armature, amperes 
 armature, amperes field and volts field with various loads 
 from no load to that load which will cause the motor to break 
 from synchronisn, adjusting the field strength for each reading 
 to give minimum input. The speed of a synchronous motor 
 will be constant until the point of breakdown is reached, whereas 
 that of an induction motor will decrease from no load to the 
 breakdown point. 
 
 In case sufficient power is not available to make a maximum 
 output test upon a synchronous motor at its normal rated 
 voltage, its voltage may be reduced below normal, as described 
 for induction motors. If the minimum input is obtained when 
 the readings are taken, the output of the motor at normal 
 voltage may be determined in the manner described for induc- 
 tion motors. 
 
 The wiring for this test must be arranged so that the arma- 
 ture circuit of the motor can be opened immediately when it 
 breaks from synchronism. 
 
 Wave Form — Potential Curve Between Brushes 
 
 In the determination of wave form of a d-c. machine the 
 following method should be used: The machine should be run 
 at normal speed and voltage. A pair of voltmeter leads separated 
 a distance equal to the width of one commutator bar is placed 
 on the commutator under the center of one pole and moved from 
 
 134 
 
bar to bar over to the center of the next pole of like polarity, 
 the voltage being read at each step. In this way the voltage 
 between bars is obtained for a complete cycle of 360 electrical 
 degrees. 
 
 The readings should be corrected and plotted as ordinates 
 against the number of the corresponding bars as abscissae and 
 a sketch showing the position of the poles should be made on 
 the same sheet in conjunction with the curve obtained. 
 
 Wave form on alternators is obtained by the use of the 
 oscillograph. 
 
 Over-Speed Test 
 
 Very often the Testing Department is called upon to take 
 tests on a machine with the revolving part running at a specified 
 speed above normal to test for mechanical strength. 
 
 On all large machines this test is always taken with the rotor 
 placed in a large pit and driven mechanically at the designated 
 speed. Careful measurements are taken by the Mechanical 
 Inspectors of definite parts of the rotor under test and the test 
 then started. The machine should be shut down and check 
 measurements taken at normal speed and at 22, 41, 58, 73, and 
 87 per cent over normal to see that there is no stretching of the 
 metal or loosening of the different parts. 
 
 Xo over-speed test should be started unless an especially 
 appointed man is present to witness the test. 
 
 Small machines are usually run inside the building after being 
 covered with heavy castings as a precaution against accident. 
 
 135 
 
CHAPTER 7 
 
 DIRECT CURRENT GENERATORS 
 
 The tests on direct current generators may be divided as 
 follows: Preliminary tests; short commercial and adjustment; 
 heating tests; special tests; input-output tests; over speed 
 test; and wave form. 
 
 Preliminary tests consist of drop on spools; polarity; cold 
 resistance measure; air gap; checking of armature and field 
 specifications; brush and equalizer spacing; brush alignment; 
 commutating pole spacing; and preliminary inspection, all of 
 which have been explained in preceding chapters with the excep- 
 tion of equalizer spacing. 
 
 Equalizers consist of rings or cross connections tapping into 
 equi-potential points on the winding of multiple wound arma- 
 tures between each pair of poles. These rings prevent inequali- 
 ties in voltage between brushes of equal potential due to 
 inaccurate centering of the armature. They allow alternating 
 current to flow from the stronger to the weaker pole pieces, which 
 slightly demagnetizes the former and magnetizes the latter, thus 
 equalizing the voltage at the brushes. Not only do these rings 
 prevent an interchange of heavy cross-currents between brushes 
 but they also compensate for inequalities at the pole pieces 
 tending to bend the shaft or overheat the bearings. These rings 
 must be examined carefully to see that the taps are equally 
 spaced and that the connections are tight. 
 
 General Instructions 
 
 After checking up all of the above points the machine should 
 be turned over slowly and the eccentricity of the commutator 
 carefully measured. If it is eccentric more than 0.005 in. it must 
 be trued according to the method given in Chapter 3, page 95. 
 
 The man in charge of the machine should obtain the sheet 
 of Testing Instructions from the Head of Section. The machine 
 should be wired according to the correct wiring diagram obtained 
 from the Head of Section who should then see that the wiring 
 is inspected and checked. The different methods for obtaining 
 load are described in subsequent pages. 
 
 It is absolutely necessary that the machine operate correctly 
 when connected according to this print, and any discrepancy in 
 operation should immediately be referred to the Head of Section. 
 
 Make provision for reading volts and amperes line, volts 
 and amperes field, and speed. 
 
 Using the precautions mentioned in Chapter 4, page 100, the 
 machine may then be started. The brushes should first be set 
 on the mechanical neutral by the Head or Assistant Head of 
 Section, by shifting the brush-holder yoke until the brushes 
 are in line with the center of the pole pieces. This position can 
 be located accurately enough by sight on machines without 
 commutating poles. On commutating pole machines a more 
 accurate method is used which is described later. 
 
 136 
 
If the machine has been assembled and connected correctly 
 it should "build up" when the shunt field switch is closed and all 
 resistance is cut out. To make sure that all the resistance 
 has been cut out of the field circuit, the field boxes may be short- 
 circuited by a short piece of wire temporarily held against the 
 terminals. If it does not build up, the connections should again 
 be checked with the wiring diagram and the polarity and resist- 
 ance of the shunt field, and the different specifications re-checked. 
 If these prove to be correct, the field switch should be opened 
 and the residual armature voltage noted. If, upon again closing 
 the switch, this decreases or drops to zero, it shows that the 
 machine is not wired properly and that the current tends to flow 
 in the wrong direction through the field. This condition should 
 be referred to the office, as the only way to remedy it would be to 
 change the connections. If, however, upon closing the field 
 switch the residual armature volts do not diminish it may be 
 necessary to "flash the field" by sending a current through it 
 in the proper direction from some external source. 
 
 The building up of a series generator is a more complicated 
 operation. The load increases with the voltage and great care 
 must, therefore, be taken in obtaining the correct external 
 resistance to prevent the voltage from increasing rapidly. As it is 
 practically impossible to decrease the external resistance enough 
 (i.e., put the blade of the water box in far enough) to allow 
 the generator to pick up, the usual method is to put the water 
 box blades in and short-circuit one of the boxes with a fuse 
 wire, then close the circuit breaker and switches. If the machine 
 then starts to pick up, and the voltage decreases as soon as 
 the fuse wire burns away there is too much resistance in the 
 water boxes. They should, therefore, be salted (to decrease 
 the resistance) and the operation repeated. Should the resist- 
 ance in the boxes be too low the load will increase very rapidly 
 and the breakers may have to be opened to prevent the machine 
 arcing over between brushes. 
 
 MACHINES WITHOUT COMMUTATING POLES 
 
 SHUNT ADJUSTMENT 
 
 After the machine builds up in the proper manner a saturation 
 curve should be taken as described in Chapter 6, page 120. 
 
 The machine should then be compounded according to the 
 Testing Instruction sheet. This test is very important and the 
 results must be passed by the Head, or Assistant Head of 
 Section. The machine must first be adjusted for good com- 
 mutation. No fixed rules can be laid down for judging com- 
 mutation, but Fig. 62 shows a chart covering the various grades 
 of commutation and should serve as a guide in judging this 
 question. The machine should be loaded by one of the methods 
 described under "Actual Load Test" described later. 
 
 In order to obtain good commutation on generators without 
 commutating poles, it is necessary to shift the brushes from 
 the mechanical neutral in the direction of rotation to a position 
 
 137 
 
that will give satisfactory commutation at both no load [and full 
 load. It is not usually possible to obtain sparkless (No. 1) 
 commutation on generators without commutating poles, but 
 it should not be worse than No. 2, as shown in Fig. 62. If it is 
 impossible to obtain satisfactory commutation by shifting the 
 brushes, the matter should immediately be reported to the Head 
 of Section. 
 
 After satisfactory commutation has been obtained the posi- 
 tion of the brush-holder yoke should be marked with a chisel 
 and the machine then given a cold compounding test as follows: 
 
 A/OJ 
 
 A/o./i 
 
 L 
 
 A/oJg 
 
 No.2 
 
 No .3- 
 
 No.4 
 
 c 
 
 Fig. 62 
 VARIOUS DEGREES OF GENERATOR AND MOTOR SPARKING 
 
 The voltage should be adjusted at no load with a falling field, 
 that is, the voltage should be brought considerably above 
 normal and gradually reduced to normal by "cutting in" the 
 field rheostat. Then without changing the position of the field 
 rheostat normal load should be put on the machine with the 
 speed held constant and a reading taken at full series field 
 of volts armature, amperes, volts and amperes field and speed. 
 The volts armature should rise considerably above the rated 
 full load voltage of the machine. If it does not rise but falls, 
 the series field is either weak or reversed. If the whole series 
 field opposes the shunt field it may be easily checked by tracing 
 
 138 
 
out the direction of the current after it leaves the armature. 
 All field spools are wound in the same direction so that only 
 the general direction around the frame need be traced. 
 
 The series field may be wound in an opposite direction to 
 the shunt field. To test this, reverse the series field leads. 
 Should the machine over-compound with the series field in the 
 reversed direction from the shunt field, the test should 
 immediately be discontinued until the spools are changed. A 
 report of this defect should be made to the Head of Section. 
 
 
 
 ^-^ 
 
 ^^ 
 
 .4? 
 
 ^<^ 
 
 *zs -T 
 
 -**4 
 
 JZ* 
 
 S7 
 
 sy 
 
 /_/ 
 
 /_/ 
 
 /Z? 
 
 s_7 
 
 /-£ 
 
 y / 
 
 
 / / 
 
 7 7 
 
 Z 7 
 
 1 _r 
 
 _/ 7 
 
 t J 
 
 t^ 
 
 * 
 
 % 
 
 _i 
 
 / Futtload 
 
 ^Amperes Mac/?//?e 
 
 Fig. 63 
 SERIES CHARACTERISTIC 
 
 It may be that only a part of the series field is reversed. 
 In locating a reversed series spool it is best to excite the series 
 field up to 20 per cent of full load current, then either try for 
 polarity or take a potential curve using the series field as a 
 source of excitation. Extremely low voltage will appear on the 
 potential curve, both in front of and behind the reversed spool. 
 
 If the machine overcompounds correctlv, a shunt should be 
 placed on the series field and adjusted until the specified com- 
 
 139 
 
pounding is obtained. The no-load point should be taken with a 
 falling field as above, then, without touching the field rheostat 
 the load should be applied gradually until full load is reached. 
 A reading should then be taken as above. This process should be 
 repeated until the shunt has been so adjusted that a full load 
 voltage is obtained about one per cent above that specified. 
 This will allow for voltage drop in the armature due to heating. 
 The shunts for the series field are usually made up of cast iron 
 grids as specified in the Engineering Notice. 
 
 Machines that are for direct connection to steam engines, 
 etc., should have allowance made for the drop in speed from no 
 load to full load, due to engine regulation. 
 
 The shifting of brushes on series generators necessitates 
 good judgment. The brushes should first be given a little 
 more lead with full load than is necessary for commutation. 
 The load should then be gradually reduced, and the commutation 
 noted until zero voltage is obtained. Should sparking occur 
 at any point, a readjustment of the brushes should be made by 
 shifting them back towards the neutral point, provided that 
 full load commutation will so allow. 
 
 A series characteristic is taken on all series wound generators. 
 This is done by increasing the load by small steps until full 
 load is obtained, amperes line and volts machine being recorded 
 at each step. The load is then reduced by small steps to no 
 load, the same readings being taken. A curve is then plotted 
 between amperes as abscissae and volts machine as ordinates. 
 See Fig. 63. 
 
 In the case of series machines forming part of booster sets, 
 the guarantee sometimes does not allow this curve to deviate 
 by more than a certain percentage from a straight line. The 
 curve should be taken in all cases with the German Silver shunt 
 in place, if the latter is necessary. 
 
 HEATING TESTS 
 
 Two methods may be used for making heating tests, i.e., 
 Actual Load Tests and Equivalent Load Tests. 
 
 ACTUAL LOAD TEST 
 
 Several different means for obtaining actual load test may be 
 employed, such as the "water box," "feeding back" and 
 "circulating current" methods. 
 
 Water Box Method 
 
 The "water box" method familiarly known as the "dead 
 load" method, as its name implies, consists in driving the 
 machine by a motor or other means and loading it directly upon 
 a water box. See Fig. 64. This method entails considerable 
 expense, since all the power generated is lost. On large machines 
 requiring a considerable amount of power to be dissipated, 
 several water boxes are connected in multiple. The standard 
 water box used in the Testing Department is designed to 
 
 140 
 
dissipate 75 kw. continuously and care should be taken to 
 have the circulating water in the water boxes so adjusted that 
 violent boiling will not occur, as it is difficult to hold the load 
 constant when this occurs. The load should be evenly divided 
 between the different water boxes. 
 
 _R&/si4fkrf 
 
 
 f^S-Resfctance 
 
 Sfr/fj/7f/d 
 
 %5/?unt ® \V7/ 
 
 &5/?unt 
 ffekt 
 
 -^-a 
 
 water 
 
 &0X 
 
 Fig. 64 
 CONNECTIONS FOR LOADING D-C. GENERATOR ON A WATER BOX 
 
 Feeding Back Methods 
 
 To obviate the loss of power and reduce the cost of testing 
 the "feeding back" method is used when possible, especially 
 with large d-c. machines or motor-generator sets. In this 
 method the total machine losses are supplied either mechanically 
 or electricallv from an external source. 
 
 Fig. 65 
 CONNECTIONS FOR MECHANICAL LOSS SUPPLY FEED BACK 
 
 In the mechanical loss supply method, two machines of the 
 same size and voltage should be belted or direct connected 
 together and mechanically driven by a motor large enough to 
 carry the losses of the set. Connections are made as in Fig. 65. 
 If the machines have series fields the one to operate as a motor 
 should be so connected that it will run as an accumulative 
 compound wound motor. The voltage of each machine should be 
 brought up as in a generator and the machines thrown together 
 
 141 
 
by closing the switch between them when the voltage across it is 
 zero. One machine is then adjusted to act as a motor by weaken- 
 ing its field. This lowers its generated voltage and causes current 
 to flow through the machines which should be adjusted to the 
 required value. The speed is held constant by the loss supply 
 motor. After running at the proper load for the specified time, 
 the heat run should be taken off and tests finished according to 
 the standard requirements. 
 
 In the method of electrical loss supply, two machines are 
 direct-connected or belted together, and the losses supplied 
 electrically. See Fig. 66. The machine acting as a generator 
 should be run under normal operating conditions of voltage 
 and current. The speed is held by varying the field of the motor. 
 It may be necessary to connect the motor field in series-multiple 
 to obtain the required condition. 
 
 7&WFJ? 
 
 .c 
 
 yssr Jjr^L 
 
 Shunt 
 FFeM 
 
 Fig. 66 
 CONNECTIONS FOR ELECTRICAL LOSS SUPPLY FEED BACK 
 
 When Compound Wound Generators are being tested by 
 this method the series field of the motor must be included or 
 the load will be unstable. 
 
 Another method of "Feeding Back," often used, is to run 
 the entire .load back on the main supply circuit from which 
 the motor is run which drives the generator in test. If the 
 main supply circuit is likely to vary in voltage, it may be neces- 
 sary to insert resistances between the generator and supply. 
 It sometimes happens that the no-load voltage of the generator 
 is below that of the supply. As changing the line resistances 
 will have no effect at no-load, the generator voltage must be 
 increased until it is equal to that of the main supply circuit. 
 Having previously calculated the full-load field current from 
 the no-load current, and the ratio of compounding voltages, 
 the machines are thrown together and full load put on the 
 generator by cutting out the variable resistance. 
 
 Two similar motor-generator sets can be tested very readily 
 by the "Feeding Back" method. 
 
 142 
 
As an illustration, suppose each set consists of an induction 
 motor and a d-c. generator. In this case, connections are made 
 as in Fig. 67. The a-c. and d-c. ends of the respective sets 
 are connected together, one set being run normally and the 
 other inverted. The induction generator feeds back on the 
 induction motor, both taking their exciting current from the 
 alternator (A) which supplies the losses. They are started 
 one at a time from the a-c. end, and the d-c. ends adjusted 
 by means of a voltmeter across switch (P). The d-c. motor 
 field is weakened until the ammeter in the d-c. line indicates 
 that normal current is flowing. The weakening of the motor 
 field allows the speed of the inverted set to increase just enough 
 to load the induction generator while it also decreases the 
 counter e.m.f. of the motor a sufficient amount to allow full 
 load current to flow in the d-c. circuit. This load must be 
 
 Fig. 67 
 CONNECTIONS FOR INDUCTION MOTOR-GENERATOR SET FEED BACK 
 
 closely watched as it is unstable. Load instability is a rather 
 common occurrence in "Feeding Back," due either to variations 
 in shop voltage or speed. 
 
 Circulating Current Method 
 
 It will be noted in the "Feeding Back" tests described 
 that it is necessary to weaken or strengthen one of the fields to 
 obtain the load. To conduct the test with the same field excita- 
 tion on both machines the armature of a separately excited 
 booster may be connected in series with the armatures of the 
 two machines being tested. The machines, connected so that 
 they run at the same speed, are brought up to normal speed 
 by means of the motor supplying the losses. The connecting 
 switch is then closed and the booster field strengthened until 
 normal current flows in the armature circuit, the field current 
 being adjusted to give the same excitation on both fields. The 
 voltage is held across the motor terminals by varying the speed 
 of the loss supply motor. 
 
 143 
 
EQUIVALENT LOAD TEST 
 
 Very often it is found impossible to run actual load tests, 
 especially on large machines on account of limited facilities. 
 Equivalent load tests have consequently been devised in which 
 the heating of a machine at a certain load may be closely 
 ascertained without actually loading it. 
 
 A direct current machine may be satisfactorily tested in this 
 manner by short-circuiting the armature upon itself or through 
 the series field connected so that it will not build up as a series 
 generator. The shunt field is separately excited from an external 
 source until the required current flows through the armature, or 
 armature and series field. This method is the one usually used 
 for baking and settling the commutator. Amperes armature 
 and field, and volts field should be read throughout the run. 
 When this test is run for a commutator bake, the final tem- 
 perature of the commutator should be recorded. 
 
 A similar method of making an equivalent load run consists 
 in running the generator under reduced kilowatt output by 
 lowering the voltage and keeping the current normal. In this 
 case the fields are all wired in and all readings taken as during 
 a full load run. 
 
 NORMAL LOAD HEAT RUN 
 
 After the machine has been properly compounded the heat 
 run may be started. Before going ahead with this test, the 
 tester should read carefully all the instructions contained in 
 Chapter 4, regarding the location of thermometers and reading 
 of temperature, etc. 
 
 In addition, the brushes and commutator should be in first 
 class condition and under no circumstances should a heat run 
 be started until the brushes have at least a 90 per cent fit. The 
 brushes should be carefully watched to see if they pick up 
 copper, and if such is the case the commutator while running 
 should be cleaned with a piece of canvas and the copper wiped 
 off the brushes. This should be repeated until the trouble is 
 entirely eliminated and the commutator shows a tendency to 
 take on a smooth surface. No heat run should be started if the 
 commutator tends to become gummy, as satisfactory commuta- 
 tion cannot be maintained for any length of time. 
 
 During the heat run all conditions should remain normal and 
 the line current, voltage and speed be held as specified on the 
 testing instructions. Amperes and volts field should be read. 
 Readings of all instruments and thermometers should be taken 
 and recorded every half hour. Commutation should be noted 
 and recorded at every reading during the run. The amperes 
 field should increase slightly during the run and the volts field 
 should increase an amount corresponding to the higher tem- 
 perature of the field coils. When the machine reaches constant 
 temperature, as shown by thermometers, it should be shut 
 down and final temperatures taken of all parts and the hot 
 resistances of the various circuits carefully measured. The rise 
 
 144 
 
of temperature by the rise in resistance should be calculated 
 by the formula given on page 112. 
 
 OVERLOAD HEAT RUN 
 
 All overload heat runs require considerable attention. The 
 machine should first be brought to normal load temperatures 
 before the overload is applied. The overload should be carried 
 only for the specified time, since in many cases the temperature 
 rises rapidly throughout the whole period of the run; hence 
 lengthening or shortening this period a few minutes may cause 
 several degrees difference in the final temperatures obtained. 
 As a general rule, readings of all instruments and thermometers 
 should be taken every fifteen minutes. If the voltage should 
 fall below the rated full load value with normal field, it should 
 be raised to and kept at the rated amount during the run. The 
 amperes and volts field will increase during the duration of the 
 overload. 
 
 MISCELLANEOUS TESTS 
 
 High Potential Test 
 
 After the necessary heat runs and while the machine is still 
 warm the wiring should be removed and the high potential test 
 applied. 
 
 Compounding Curve 
 
 After the heat runs have been taken and final temperatures 
 recorded, a hot compounding curve should be taken. The hot 
 compounding test is similar to the cold compounding test 
 described on page 138, except that the compounding must be 
 adjusted very close to the value specified on the testing instruc- 
 tions. When this has been done a complete curve should be 
 obtained with readings taken in the following order: No load, 
 full load, 3 i load, H load, 34 load, no-load, and 125 per cent load. 
 The field rheostat must not be moved from the position for the 
 no-load setting. A curve should be drawn with load as abscissae 
 and volts armature as ordinates. 
 
 Rheostat Data 
 
 After the heat runs, rheostat data should be taken in the 
 same manner as saturation, with the exception that the brushes 
 are placed at the running position instead of the neutral point. 
 
 On machines which do not require heat runs, only two points 
 need be taken on the curve, namely, at full voltage and half 
 voltage. 
 
 Shunt Regulation 
 
 Shunt regulation should be taken on shunt wound generators 
 when requested by the Engineers. A reading should be taken 
 first at no-load normal voltage. Without changing the rheostat, 
 l /i load should be thrown on and a reading taken of amperes 
 
 145 
 
armature, volts armature, amperes field and volts field. Holding 
 34 load, the voltage should be brought up to normal and the 
 same readings taken. The load should now be increased to Yi 
 full load, with the rheostat in the same position, similar readings 
 being repeated. This test is repeated for z /i and full load. With 
 full load on the machine the voltage should then be brought up 
 to normal. With the field rheostat in this position the load is 
 then taken off the machine and the rise in voltage observed. 
 All these entries should be made on the Record Sheet. A curve 
 should be plotted with amperes armature as abscissae and volts 
 as ordinates. See Fig. 68 and Calculation Sheet 28. 
 
 If the voltage should drop to zero when 34 load is put on 
 the machine, the load should be applied in smaller increments. 
 Speed should always be kept constant throughout the test. 
 
 300 400 SOO 
 
 /7/7?peres Line 
 
 Fig. 68 
 
 SHUNT REGULATION CURVE ON A 6-POLE, 100 KW., 
 
 600 R.P.M., 125 VOLT GENERATOR 
 
 Running Light 
 
 Running light readings should be taken before the machine 
 is stripped out. This test is described in Chapter 6, page 122. 
 
 Field Compounding 
 
 Field compounding is taken when called for by the Engineers. 
 From its results is obtained the additional ampere turns field 
 necessary to overcome armature reaction and IR drop in the 
 machine from no-load to full load. The test is made by sepa- 
 rately exciting the field of the machine under test, in order to 
 hold the voltage at its terminals constant as the load is increased 
 from no load to full load. Readings of amperes field, volts 
 field, amperes armature, volts armature and speed are taken at 
 no load and at least three intermediate points between no 
 load and rated load. It is generally required, and usually 
 advisable, to take an observation at 25 per cent overload, 
 if the power is available. All readings should be made with 
 a rising field current. Fig. 69 shows a curve of field compounding 
 in which is plotted amperes field or ampere-turns field as ordi- 
 
 146 
 
nates, and amperes armature as abscissae. See also Calculation 
 Sheet Xo. 5. 
 
 Stud Potential Curve 
 
 This test is sometimes taken on machines equipped with 
 multiple wound armatures which are not furnished with equalizer 
 rings and is obtained as follows: 
 
 All the brushes except those on two adjacent studs are 
 raised from the commutator, the voltage is then raised to 
 normal and the field current noted. This field current and the 
 speed must be held constant for all other points on the curve. 
 The brushes on stud No. 3 should now be lowered, those on 
 Xo. 1 raised and the voltage read between studs No. 2 and 
 Xo. 3. This should be continued until voltage readings have 
 been taken between each pair of studs. The test should be 
 
 r 
 
 r 
 
 /oo 
 
 200 
 
 SOO <400 soo 
 
 Amperes /Ir/natt/re 
 
 eoo 
 
 Fig. 69 
 
 FIELD COMPOUNDING CURVE ON A 150 KW., 250 VOLT, 225 R.P.M. 
 
 6 POLE D-C. GENERATOR (6 BAR BRUSH SHIFT) 
 
 made with the field current rising. The maximum voltage 
 variation permissible is 4 per cent of the average value. This 
 test, although similar in name, should not be confused with 
 the bar to bar potential curve taken to determine the wave 
 form of a d-c. machine and described in Chapter 6. 
 
 SPECIAL TESTS consist of saturation and core loss, shunt 
 adjustment, compounding and commutation tests. These have 
 all been previously described. 
 
 INPUT-OUTPUT TEST, OVER-SPEED TEST, and WAVE FORM 
 have been described in Chapter 6. 
 
 COMPLETE TEST consists of normal and overload heat runs, 
 saturation and core loss, compounding and commutation tests. 
 
 STANDARD EFFICIENCY TEST is made by the method of losses. 
 Page 430 and Calculation Sheet 11 give the method for calculat- 
 ing the efficiency of a d-c. generator. See Fig. 70. 
 
 THREE-WIRE GENERATORS 
 
 Some direct current generators are provided with collector 
 rings for operation on Edison three-wire circuits. The series 
 field is usually divided and one-half placed on each side of the 
 
 147 
 
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 Fig. 70 
 
 EFFICIENCY AND LOSSES ON A 100 KW., 6 POLE, 275 R.P.M. 
 
 525/575 VOLTS, COMPOUND WOUND D-C. GENERATOR 
 
 148 
 
armature, as shown in Fig. 71. Tests are made as on other d-c. 
 generators with the following additional special points: 
 
 In compounding a machine, care should be taken to have 
 the shunts in each half of the series field of approximately the 
 same size, and when the correct compounding has been obtained 
 "shunt balance readings" should be taken as follows: 
 
 Remove the shunt from one side of the series field and take 
 readings at no load and full load. Replace this shunt and repeat 
 the readings for the other half of the series field. The line voltage 
 obtained on these two readings should check. 
 
 -vV\AAA/W 
 
 Shunt 
 Ffrkt 
 
 
 Fig. 71 
 THREE- WIRE GENERATOR 
 
 Unbalanced Readings 
 
 If unbalanced readings are required, a compensator should 
 be wired as in Fig. 71. A reading should be taken at no load 
 normal voltage. With no change in the field and holding con- 
 stant speed, \i load should then be thrown on one side of the line 
 and the voltage read from the neutral to each side of the line. 
 Volts and amperes line, volts and amperes field should also be 
 read. One-quarter load should then be put on the other side of 
 the line, giving a balanced load, readings being taken as before. 
 The load should then be increased to 3^ load on one side, this 
 procedure being continued until 125 per cent balanced load is 
 obtained and readings taken at each step. Instructions some- 
 times call for 50 per cent unbalancing, in which case the load is 
 increased 50 per cent at each step instead of 25 per cent. 
 
 Revolving Compensator 
 
 One type of three-wire generator has its compensator 
 mounted directly on the shaft at the back of the armature and 
 is equipped with only one slip ring. 
 
 COMMUTATING POLE GENERATORS 
 
 General Notes 
 
 The general instructions covering mechanical inspection, 
 measurement of air gaps, drop on spools, etc., applying to all 
 other generators must be followed in testing machines with 
 
 149 
 
commutating poles. The function of the commutating pole is 
 to improve commutation and in testing, commutation is, there- 
 fore, important. The pole spacing should check within -^ in. 
 as specified on page 82. 
 
 The commutating poles produce the necessary flux for 
 neutralizing the effect of armature reaction. This flux prevents 
 the shifting of the neutral point between no load and full 
 load which occurs in d-c. machines not equipped with them. 
 In addition it aids the current reversal in the armature coils at 
 commutation. To obtain the proper reversal without sparking 
 at normal current requires a definite number of ampere turns 
 in the commutating field.. The brushes are placed on the 
 mechanical neutral, and if the machine is properly com- 
 pensated the mechanical neutral will check with the electrical 
 neutral. 
 
 Baking Commutators 
 
 Commutators of commutating pole machines are baked 
 according to the method on page 144. The brushes must never 
 be shifted under load, so as to produce sparking and heating. 
 They must always be shifted at no-load to insure their not 
 being set beyond the safe limit of no-load commutation, thus 
 rendering it possible for the machine to flash over if the load is 
 suddenly removed. In all cases, the Head of Section or his 
 assistant must be consulted before the brushes on any com- 
 mutating pole machine are shifted far from the neutral. 
 It must also be remembered that the armature must not be 
 short-circuited through the commutating pole winding when 
 baking a commutator, as in this case the majority of machines 
 will build up as series generators, and the armature current can- 
 not be controlled. 
 
 Locating the Neutral 
 
 Referring to Fig. 72, one armature coil contained in a pair of 
 slots in the armature core and the corresponding commutator 
 segments are marked for the convenience of the Testing Depart- 
 ment. The coils are marked with red paint, and the ends of the 
 corresponding commutator bars are stamped with the letter " O. " 
 In a machine with full pitch winding the two red marked arma- 
 ture conductors (A) forming a coil will come one pole arc apart, 
 and in setting the brushes these conductors should be placed 
 directly under the centers of the commutating poles as shown, 
 and the brushes shifted until the center of the brush rests on the 
 center line of the commutator segment corresponding. On a 
 fractional pitch winding the two red conductors will not span a 
 full pole arc, and hence they should be so located that they are 
 equi-distant from the center of their respective" poles as shown by 
 the dotted lines B-B, and the brushes set as above. If there is 
 more than one coil per slot, there will be a corresponding num- 
 ber of commutator segments stamped O-O, but the middle one 
 should be used. After the brushes are set the usual tests for 
 building up, saturation, etc., may be continued. 
 
 150 
 
Shunt Adjustment 
 
 It is the aim of the Engineers to design the commutating 
 field so that it will operate without a shunt; however, it is some- 
 times necessary to shunt out some of the current to obtain the 
 proper compensation for satisfactory commutation. A thorough 
 trial should be made, however, with full commutating field. In 
 adjusting for commutation, a compound wound machine may be 
 
 Fig. 72 
 DIAGRAM SHOWING MARKING OF ARMATURE AND 
 COMMUTATOR FOR LOCATING MECHANICAL 
 NEUTRAL 
 
 run with full series field. If the commutation is not satis- 
 factory at full commutating field about ten per cent of full load 
 current should be shunted. If the commutation is improved 
 more current should be shunted until sparkless commutation 
 (Xo. 1, see Fig. 62) is obtained at all loads up to fifty per cent 
 overload unless otherwise specified. 
 
 If the commutation is not improved by shunting current 
 the Head of Section should be notified. Sometimes a slightly 
 better effect is obtained by shifting the brushes forward or 
 backward from the neutral point. This, however, should only 
 
 151 
 
be done after all other adjustments have failed, and permission 
 has been obtained from the Head of Section. 
 
 If none of these methods gives satisfactory results the 
 trouble may be due to a weak field. This can be ascertained by 
 separately exciting the commutating field and sending a larger 
 current through it than would otherwise be obtained with 
 normal load on the machine. If such procedure improves the 
 commutation the fact must be referred to the Engineers to have 
 changes made. 
 
 The iron grid shunts used on the larger machines should 
 be placed so that the edges of the grids are in a vertical position 
 and as near as possible to the position they are to occupy when 
 in actual operation. Care should be taken to see that they 
 contain ample current carrying capacity and do not heat up. 
 If they are allowed to heat excessively the amount of current 
 shunted changes, and thus destroys the commutation of the 
 machine. 
 
 When the final brush position has been determined it should 
 be marked with a chisel. On the larger machines a trammel 
 should be made by the shop to assist the customer to assemble 
 the brushes in a correct position. This trammel consists of a 
 steel bar pointed on the ends and of the correct length to mark 
 the distance from two points in the magnet frame to the point 
 on the commutator on which the brushes on one stud should be 
 placed. 
 
 After the proper adjustment has been obtained an ammeter 
 should be wired in and the amount of current shunted carefully 
 measured. 
 
 Inductive Shunt 
 
 Any condition which would suddenly under-excite the corn- 
 mutating field or make it inactive would make the machine 
 sensitive and cause bad sparking at the brushes. If the corn- 
 mutating field is equipped with a grid or German Silver shunt 
 and the machine becomes short-circuited, the inductance of the 
 commutating field forces the instantaneous heavy overload 
 current through the non-inductive shunt and leaves the com- 
 mutating field without sufficient excitation to neutralize the 
 armature reaction. The electrical neutral immediately shifts 
 and bad commutation results. 
 
 To eliminate this trouble an inductive shunt is sometimes 
 used across the terminals of the commutating field in series with 
 the non-inductive shunt. This shunt will be used only when 
 called for by the Engineers, but when so specified it should be 
 in circuit while the commutating field is being adjusted for com- 
 mutation. The inductive shunt is of low resistance, and is de- 
 signed to have an inductance greater than the commutating field. 
 
 If the machine has an inductive _ shunt and flashing or 
 violent sparking is produced by throwing a heavy load on and 
 off quickly, try adjusting the air gap of the inductive shunt. 
 With a given winding on the core, the inductance of the shunt 
 may be varied by changing the air gap and the relative induc- 
 
 152 
 
tance of the shunt and commutating winding be thus altered. 
 If the current read on the meter in the shunted circuit quickly 
 falls to zero when a heavy load is thrown off by tripping a 
 breaker, and the brushes show sparking, there is too little 
 inductance in the shunt and its air gap should be decreased. 
 The air gap should be adjusted so as to give minimum sparking 
 when the machine is operating with a highly fluctuating load. 
 
 Motor Operation 
 
 Some machines are required to run as motors as well as 
 generators. When such operation is specified they are equipped 
 with a switch for reversing the series field, so that they may run 
 as accumulative compound wound motors. Such machines 
 should be tried under load as motors and have shunts adjusted 
 as specified above. If possible the same shunt should be used 
 for motor operation as was obtained when the machine was 
 operating as a generator. In no case should a machine be 
 passed for both motor and generator operation unless it will 
 operate satisfactorily under both conditions without changing 
 the brush position. 
 
 Compounding, Etc. 
 
 After satisfactory commutation has been obtained the 
 machine should be compounded and other tests taken as des- 
 cribed for generators without commutating poles. 
 
 THREE-WIRE COMMUTATING POLE GENERATORS 
 
 Commutating pole machines equipped for three-wire oper- 
 ation should be adjusted similarly to the above. Care must 
 be taken to see that the shunts on each half of the commutating 
 field are approximately equal. 
 
 EXCITERS 
 
 Exciters are tested in the same manner as other direct cur- 
 rent generators, as previously explained. All 125 volt exciters 
 must give at least 175 volts with full shunt field at no load. 
 Most 125 volt compound wound exciters are compounded at 
 both the rated voltage and at 80 volts. On small exciters the 
 brushes are usually shifted ahead of the neutral point to obtain 
 the compound at 125 volts and a shunt placed across the series 
 field for the 80 volt condition. The latter is only an approxi- 
 mate setting and no attempt is made to get extremely accurate 
 results. 
 
 Stability Test 
 
 Direct connected exciters should be given a Stability Test. 
 With rated no-load voltage on the alternators, raise and lower 
 the speed 2 per cent above and below normal, noting and 
 recording the voltage change in each case. The change in 
 voltage should not exceed 6 per cent of normal no-load voltage 
 in either case. The no-load voltage setting should always be 
 made with a rising field. 
 
 153 
 
THREE- WIRE BALANCER SETS 
 
 In the operation of three-wire circuits the load often tends 
 to become heavier on one side than the other with a consequent 
 unbalancing of the voltage. To obviate this, small motor- 
 generator sets called "balancer sets" are used. 
 
 In its most common form the balancer set. consists of two 
 similar machines on one shaft or with their shafts coupled 
 together and their armatures connected in series across the out- 
 side mains. Each machine is wound for one-half the voltage 
 between the outside mains, and their combined rating in amperes 
 is made equal to the probable difference in load between the two 
 sides of the system. This unbalanced load is carried by the 
 neutral wire taken from the balancer at the point where the 
 two armatures are connected. 
 
 When the load on the system is balanced, the two machines 
 run as motors in series across the outside lines, no work is done, 
 and the only current used is that necessary to overcome the 
 losses of the machines running free. As soon as one side of the 
 system becomes more heavily loaded than the other, the drop in 
 voltage on this side will be the greater and the voltage impressed 
 on the machine on this side reduced. The other machine, 
 having the higher voltage, will tend to run faster than the first 
 and drive it as a generator. The machine operating as a motor 
 will act as a load on its side of the system, lowering the voltage 
 on that side, while the generator will supply current to and raise 
 the voltage on the heavily loaded side. The combined current 
 of the two machines equals the unbalanced load of the system 
 and the total effect is to restore the voltage balance of the system. 
 As the unbalanced load on the system may shift from one side 
 to the other, this action of the balancer must also shift. Either 
 machine may at any instant be operating as a motor and the next 
 instant as a generator. As the direction of rotation is always 
 the same it is impossible to tell, without knowing how the load is 
 balanced, which is the motor and which the generator. 
 
 Balancer sets are adjusted by loading one side at a time with 
 the required current in the neutral wire. 
 
 Fig. 73 shows the connections for a compound wound, corn- 
 mutating pole balancer set connected for loading in the Testing 
 Department. These sets may be shunt wound, shunt wound with 
 commutating poles, or compound wound with commutating poles. 
 
 Balancer sets should receive the same preliminary inspection 
 and tests as d-c. generators and motors, and after being wired 
 according to the correct diagram, should be adjusted for com- 
 mutation, field balance, speed and compounding. 
 
 Commercial and Adjustment test consists of balancing tests 
 and the operation of the set to demonstrate that it is a duplicate 
 electrically of machines of the same type already shipped and 
 that it is free from manufacturing defects. 
 
 Balancing tests consist of adjusting both machines of the set 
 so that the voltage across each machine shall always be balanced 
 within 2 per cent. The sum of the two voltages will be equal 
 to the applied voltage. The wiring on balancer sets must be 
 
 154 
 
done as carefully as that for motors as either end of the set may 
 be operating at any time as a motor. The same precautions, 
 therefore, must be exercised as when operating a motor. 
 
 
 for/ob/e rT&s/s to/ice 
 
 TC/rca/i 
 Greater 
 
 ^yVWVWVW— ' 
 
 Fig. 73 
 WIRING DIAGRAM FOR TESTING BALANCER SET 
 
 VL = Impressed volts line 
 VA, VAi = Volts machine A and Ai 
 VF, VFi = Volts shunt field A and Ai 
 AL = Amperes line 
 
 AA, AAi = Amperes armature A and Ai 
 AF, AFi = Amperes shunt field Aand Ai 
 AN = Amperes neutral 
 
 Shunt Wound Sets 
 
 On shunt wound sets the fields are cross connected and should 
 be adjusted and the brushes shifted to such a position that the 
 proper voltage balance is obtained. One side of the set is 
 loaded at a time as shown in the figure. Satisfactory com- 
 mutation and speed must also be obtained, and when such condi- 
 tion has been established with one side running as a generator. 
 
 155 
 
the set should be reversed and the other side adjusted to cor- 
 respond. When both sides have been properly adjusted the 
 set should operate with either end running as a motor. 
 
 Shunt Wound Sets with Commutating Poles 
 
 If the set is equipped with commutating poles, it should be 
 adjusted with the brushes placed on the mechanical neutral 
 as on other commutating pole machines. After good com- 
 mutation has been obtained (by adjusting a shunt in the com- 
 mutating field, if necessary), the proper voltage balance should 
 be obtained. It should not be necessary to shift the brushes from 
 the mechanical neutral, but if a balanced condition cannot other- 
 wise be obtained the Head of Section should be notified im- 
 mediately. 
 
 Compound Wound Sets with Commutating Poles 
 
 On these sets, the commutating field should be adjusted for 
 commutation and the shunt and series fields adjusted for the 
 proper voltage balance, after satisfactory commutation has 
 been obtained. It should be noted that on a compound wound 
 balancer set the machine operating as a motor runs as a dif- 
 ferentially wound machine while the other acts as an accumula- 
 tive compound wound generator. Therefore, care should be 
 taken in adjustment as the set may have enough series field to 
 cause it to speed up to a dangerous point. 
 
 HEAT RUNS, ETC. 
 
 After the set has been adjusted the heat runs should be 
 taken by loading one side for the specified time with the required 
 current flowing through the neutral wire. All readings of voltage 
 and current should be carefully checked to see that they are 
 consistent. 
 
 Saturation may be taken by operating each machine as an 
 individual generator. 
 
 Core loss may be taken on a set with three or more bearings 
 by the method of belted core loss previously described, the belt 
 being run over the coupling between the machines. 
 
 On two bearing sets the core loss is obtained by a series of 
 "running light" readings on each machine as follows: 
 
 With one end operating as a shunt motor read the input 
 with no voltage on the other (a) with brushes down, (b) with 
 brushes up; then (c) with normal voltage on the generator end 
 with brushes down. These readings should then be repeated 
 with the set reversed. From these the core loss of the set may 
 be calculated. 
 
 SPECIAL TESTS consist of saturation, core loss, input-output, 
 commutation and field balancing tests. 
 
 INPUT-OUTPUT TEST consists of taking careful measurement 
 of the input and output of the set when connected .as during the 
 heat runs. 
 
 COMPLETE TEST consists of field balance and adjustment, 
 normal and overload heat runs, core loss or input-output, and 
 commutation tests. 
 
 156 
 
CHAPTER 8 
 
 DIRECT CURRENT MOTORS 
 
 The tests on direct current motors may be divided in the 
 same manner as for generators. 
 
 Preliminary Tests are practically the same as those taken 
 on d-c. generators and the instructions included in Chapter 7 
 should be carefully followed. 
 
 When the machine has been wired according to the correct 
 print, the wiring should be checked by the Head of Section, or his 
 assistant, and it is absolutely necessary that the machine should 
 operate in the proper direction of rotation when so connected. 
 Make provision for reading volts and amperes line, volts and 
 amperes field and speed. Direct current motors may be loaded 
 by the methods given in Chapter 7 or by belting to generators. 
 
 Starting 
 
 After setting the brushes on the mechanical neutral and 
 observing instructions contained in Chapter 4, page 98, the 
 machine may be started. You must be absolutely certain that 
 there is a full field on any motor before attempting to start it. On 
 starting, the speed of the machine must be carefully followed 
 with a tachometer and the circuit breaker must immediately 
 be opened if the speed rises above the prescribed limits. 
 
 With the starting rheostat, or water box in the "off" posi- 
 tion the terminals of the rheostat or box must be attached across 
 the open main switch AFTER the circuit breaker has been 
 closed. The lower terminal should be attached first. The 
 resistance across the main switch may then gradually be cut 
 out, and if the speed of the motor is all right, should be entirely 
 cut out and the main switch closed. If the motor tends to run 
 above normal speed, the circuit breaker must be opened and the 
 motor shut down. The connections should be carefully checked 
 to see that the field is wired properly. It may be that the field 
 has been connected directly across the main switch. If such is 
 the case the field current will fall rapidly as the starting resist- 
 ance is cut out and the motor will speed up. To test for incorrect 
 connections in the field, observe the volts field during starting. 
 These will drop if the field is incorrectly connected. Trouble 
 may also be experienced due to reversed polarity, etc., which 
 may be traced out as noted under d-c. generators. 
 
 MOTORS WITHOUT COMMUTATING POLES 
 Adjustment for Speed and Commutation 
 
 After the motor has been started it should be adjusted for 
 commutation by shifting the brushes back of the mechanical 
 neutral. This shift is necessary as the electrical neutral of a 
 motor is shifted by the armature reaction in a direction opposite 
 to the direction of rotation. When shifting brushes for com- 
 mutation the speed of the motor must be carefully watched. 
 With no-load normal voltage and full field a speed reading should 
 
 157 
 
be taken, the brushes being shifted so that when full load is on, 
 the speed is not less than 7 per cent below nor more than 3 per 
 cent above normal rated speed. With the machine hot the 
 speed must not vary more than 5 per cent either way from the 
 normal rated speed, consequently the full load speed with the 
 machine cold must be within the limits as given above. The 
 same precautions regarding brush fit and the condition of the 
 commutator should be used as for d-c. generators. 
 
 All compound wound motors should be adjusted with full 
 series field. If this cannot be done, the fact should be referred 
 to the Head of Section. The speed must come within 4 per cent 
 of the rated speed when the machine is hot. Differentially com- 
 pound wound motors should be loaded with care since the series 
 field may be strong enough to overcome the shunt field and cause 
 the machine to speed up and run away. The no-load speed of 
 accumulative compound wound motors should be carefully 
 watched as it may be considerably higher than the rated speed. 
 When the correct running position has been found it should be 
 marked with a chisel and the number of bars shift from the 
 neutral point recorded on the Testing Record. 
 
 Speed Regulation 
 
 Speed regulation may be defined as the ratio of the drop in 
 speed from no load to full load divided by the full load speed. 
 On a load run this regulation must not exceed 6 per cent. 
 
 Heating Tests 
 
 After the correct adjustment has been obtained the heating 
 tests may be started. The general instructions in Chapters 4 
 and 7 should be followed carefully. Motors may be loaded by 
 belting to generators, feeding back, or by the circulating current 
 methods described in Chapter 7. 
 
 In using the method shown in Fig. 65, if the machines are 
 motors, the same connections should be made and the machines 
 thrown together. The voltage of the system must be held by 
 the machine running as a generator. The only correct way of 
 obtaining load is by changing the speed of the set, the brushes 
 having previously been set in the running position. Usually 
 the speed will have to be decreased and the difference between 
 full load and no-load speed will be the normal drop in speed 
 for the motors. Cases have occurred where the speed of the 
 motor, due to armature reaction, increased during the load. 
 In "feeding back," this fact is shown by the motor taking an 
 overload at no-load speed in which case the speed of the loss 
 supply must be increased. 
 
 In using the method shown in Fig. 66, if two shunt motors are 
 being tested, one machine should be run at normal voltage, 
 current, speed and with full field; the other should be run as a 
 generator with a little higher current and slightly stronger 
 field than it would have under normal condition. The fields of 
 the generator may have to be connected in multiple. The 
 motor should be started first from the electrical loss supply 
 circuit and its brushes shifted for commutation and speed. 
 
 158 
 
After exciting the field of the generator and adjusting the voltage 
 between the machines to zero the circuit may be closed. 
 The machines should then be loaded by increasing the field cur- 
 rent of the generator. The brushes must always be shifted 
 carefully while the machines are under load, for a slight change 
 in shift will at once change the load. During the heat run the 
 speed will rise and the field current will fall. After the heat run 
 has been finished and all motor readings taken, the wiring should 
 be changed and the motor readings taken on the machine which 
 ran as a generator. 
 
 The circulating current method is used particularly in the 
 testing of series or railway motors. In the latter case the 
 machines are geared to the same shaft. 
 
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 Fig. 74 
 SPEED CURVES D-C. MOTORS 
 Running Light 
 
 Running light test should be taken on all motors at hot full 
 load speed. The armature current required for running light 
 must not be over 5 per cent of the full load current. 
 
 SPECIAL TESTS consist of core loss, adjustment, commutation 
 tests and speed curves. 
 
 If special tests are required a hot speed curve should be 
 included. From no load to full load, and including several 
 intermediate points, the speed should be carefully read, the 
 
 159 
 
voltage being held constant at all loads. A curve should then 
 be plotted with speed as ordinates and amperes as abscissae. 
 No load and full load points of a cold speed curve should also be 
 
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 Fig. 75 
 EFFICIENCY AND LOSSES ON A 70 H.P., 6 POLE, 850 R.P. 
 500 VOLT D-C. MOTOR 
 
 160 
 
taken. See Fig. 74. Some motors with a considerable armature 
 reaction give a speed curve which rises as the load increases. 
 All cases of rising speed curve must be referred to the Head of 
 Section. 
 
 COMPLETE TEST consists of normal and overload heat runs, 
 saturation and core loss, speed curves and commutation tests. 
 
 INPUT-OUTPUT TEST and OVER-SPEED TEST are taken in a 
 similar manner as for generators. 
 
 STANDARD EFFICIENCY TEST is made by the method of losses. 
 Page 433 and Calculation Sheet 12 show the method used in 
 calculating the efficiency of a d-c. motor. See Fig. 75. 
 
 COMMUTATING POLE MOTORS 
 
 Adjustment for Commutation 
 
 The brushes of commutating pole motors should be placed 
 on the mechanical neutral as explained under d-c. generators. 
 The electrical neutral at no load should then be located by 
 running the machine in both directions of rotation with the 
 same field current, shifting the brushes, if necessary, until 
 the speed comes the same in each direction. The machine should 
 then be loaded with full commutating field and the commutation 
 and speed carefully noted for each direction of rotation. If 
 the commutating field is of the proper strength, commutation 
 should be No. 1 (see Fig. 62). The full load speed of commutating 
 pole motors when hot must be. within 5 per cent of the rated 
 speed, and consequently the speed obtained on the above 
 reading should not be less than 7 per cent below nor more than 
 3 per cent above the rated speed, allowing for a 2 per cent rise 
 in speed when the machine heats up. 
 
 If the commutation is not satisfactory, or if the speed should 
 increase from no load to full load, the commutating field should 
 be shunted until black commutation and satisfactory speed is 
 obtained. If with full commutating field the speed falls below 
 the limit given above, the fact should be referred to the office, 
 as no amount of shunting of the commutating field will bring 
 the speed within the limit. With black commutation the motor 
 should show a falling speed characteristic from no load to full 
 load. If the speed rises more than one per cent within this range 
 of load the fact should be referred to the Head of Section. 
 
 If satisfactory adjustment cannot be obtained by shunting 
 the commutating field, it may be that the field is too weak. In 
 this case it should be separately excited with a current higher 
 than that which would normally be obtained. If satisfactory 
 adjustment is obtained under these conditions the fact should 
 be referred to the Engineers to have changes made. 
 
 After the correct adjustment has been obtained, the brush 
 position should be chisel-marked and a cold speed curve taken. 
 The speed and commutation in both directions of rotation up 
 to the amount of overload specified in the testing instructions 
 should be read and recorded. On DLC and RLC motors the 
 brush-holder yoke should be securely doweled in position after 
 tests are finished. 
 
 161 
 
Some commutating pole motors show a tendency to "hunt" 
 with full commutating field, but this can usually be eliminated 
 by shunting the field. In all cases a notation should be made on 
 the Testing Record regarding this point of stability. 
 
 After the final adjustment, an ammeter should be wired in 
 and the amount of current shunted recorded on the testing 
 record. The machine may then be given the heat runs called 
 for and after these have been taken and while the machine is hot, 
 a hot speed curve should be taken using the same range of load 
 as in the cold speed curve. 
 
 Other tests are taken as previously described. Running 
 light readings may be taken without disconnecting the series or 
 commutating field, as the extra current required will be small. 
 
 Motor and Generator Operation 
 
 Quite frequently commutating pole machines are sent 
 out as part of a motor-generator set, and required to operate 
 as either a motor or generator. All such machines must have 
 shunt adjustments made for both methods of operation while 
 the machine is in test. Since the brushes are set on the no-load 
 electrical neutral on almost all machines the same shift is 
 proper for both motor and generator operation. The majority 
 of machines, however, require a different adjustment of the 
 commutating field shunt, for motor operation, to insure the 
 proper speed characteristic. On the majority of commutating 
 pole motors too strong a commutating field will cause the 
 speed to increase as the load increases. This is never permissible. 
 Current must be shunted from the commutating field till the 
 speed at full load and overload is less than that at no-load, 
 giving the motor speed a drooping characteristic. 
 
 If a drooping characteristic and good commutation cannot 
 be obtained with the same adjustment, notify the Head of 
 Section at once, so that the proper steps may be taken to 
 correct the trouble. Inductive shunts are used on both motors 
 and generators, and the adjustment of the shunt is obtained 
 in the same way in each case. In adjusting the commutating 
 field shunt of a motor, however, the speed must be carefully 
 noted, as well as the commutation after any change in the 
 shunt is made. 
 
 VARIABLE SPEED MOTORS 
 
 The variations in speed of variable speed motors may be 
 obtained by either armature or field control. 
 
 Two methods of armature control may be used. The first 
 consists in varying the resistance in the armature circuit and 
 is used in work requiring no inherent regulation or constant 
 load. The economy and inherent regulation by this method 
 of control is poor. 
 
 The second method of armature control consists in varying 
 the voltage impressed on the motor armature only, the field 
 remaining constant at its full value. The efficiency and regu- 
 lation obtained by this method of control is good. 
 
 162 
 
In the method of field control the brushes are set to give 
 the best commutation at both speed limits. The variations 
 in speed are then obtained by varying the field. 
 
 Commutating pole variable speed motors must have the 
 shunt in the commutating pole field adjusted for the highest 
 rated speed. Speed curves and running light tests should be 
 made at both speed limits. 
 
 Shunt wound variable speed motors should have the brushes 
 set for commutation at the speed limits. Speed curves and 
 running light tests should be made at both these speeds. 
 
 Some compound wound variable speed motors are not 
 designed to run light, consequently before starting, the smallest 
 load the motor is designed to carry should be ascertained. The 
 Engineering Notice usually specifies the load at which the 
 motor should start. Commutation should be adjusted at the 
 speed limits and the speed carefully recorded. Speed curves 
 should be taken at the speed limits. Running light should be 
 taken at the various speeds. 
 
 DIRECT CURRENT SERIES AND RAILWAY MOTORS 
 
 The principal type of series motor is the railway motor. 
 Other types, however, are built for use with hoists, air com- 
 pressors, pumps, etc. As all these motors are designed for 
 intermittent service, the test, unless otherwise specified in the 
 Engineering Notice, is of one hour's duration at full load, 
 the brushes being on the neutral point. The load must never 
 be taken off a series motor unless the armature circuit is first 
 opened, otherwise the motor will run away. For the same 
 reason a series motor should always be started under load. 
 All running light tests must, therefore, be made with the field 
 separately excited. 
 
 The speed of railway motors and other series motors when 
 hot should never vary more than 3 per cent from the normal 
 rating. 
 
 As the tests on railway motors are very complete and their 
 general method applies to any series motor, the tests on rail- 
 way motors will be discussed more or less in detail. Hot and 
 cold resistances must be taken on all railway motors. The 
 cold resistances, when corrected to 25 deg. cent., must not vary 
 more than 5 per cent from the standard resistance. 
 
 High potential must always be applied while the motor 
 is cold and hot. There are Standing Instructions specifying 
 the degree of high potential to be applied to all parts of the 
 different types of motors. 
 
 GENERAL TESTS consist of sufficient preliminary tests to war- 
 rant Engineering approval for production. It is impossible to 
 define, definitely, the heading, since the tests may include only a 
 few minor tests, or they may include Complete and Special Tests. 
 For instance, it may be necessary to make slight changes, 
 either in the construction or design of a standard motor in 
 order that it may meet special requirements due to peculiar 
 operating conditions, etc. After these changes have been made, 
 
 163 
 
tests are conducted to insure the motor meeting such condi- 
 tions satisfactorily. These tests are included under the general 
 tests. If, after completion, they are found to be satisfactory, 
 Engineering approval is given for the production of the machine 
 in question. 
 
 COMPLETE TESTS consist of special tests, thermal character- 
 istics, commutation and input-output. With the exception of 
 commutation, the other tests under this heading will be con- 
 sidered separately. 
 
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 Fig. 76 
 
 CORE LOSS AND SPEED CURVE OF A 50 H.P., 500 VOLT 
 
 RAILWAY MOTOR 
 
 200 240 
 
 Commutating tests on series railway motors should be 
 made by holding normal voltage and operating the machine 
 at loads varying from 33 ^ per cent to 200 per cent normal 
 load. 
 
 On series commutating pole motors, Interruption Tests 
 are taken. These consist in opening and closing the motor 
 circuit, while the machine is running at various loads and speeds. 
 The machine should stand such tests without arcing over at a 
 
 164 
 
line voltage as high as 125 per cent normal. The loads are 
 varied from 33 }/& per cent to 200 per cent normal. Mill motors 
 are tested for commutation by suddenly reversing the direction 
 of rotation under various loads. 
 
 DEVELOPMENT TESTS consist of General Tests and Special 
 Tests, and are made when an entirely new type of machine is 
 being developed. 
 
 SPECIAL TESTS consist of speed curves, core loss, and satura- 
 tion tests. 
 
 In taking a speed curve two similar motors are mounted on 
 a testing stand, the pinion of each meshing in the same gear 
 on a shaft. One motor drives the other as a separately excited 
 generator and is run loaded until the motor is heated to about 
 50 deg. cent. rise. The speed curve is then taken on the motor 
 rotating in both directions, the voltage being held constant. The 
 resistance of both armature and field should be measured both 
 before and after taking the curve. 
 
 Core loss should be taken as on any other machine by the 
 belted method, except that the test should be made at about 
 five speeds. Fig. 76. The lowest speed should correspond 
 to about 175 per cent full load amperes (taken from speed 
 curves) and the highest at about 200 per cent full load speed. 
 During this test the machine is separately excited. 
 
 A saturation curve may be taken as on any other machine 
 by separately exciting the field. Saturation curves at different 
 speeds mav be obtained from data taken during the core loss 
 test. 
 
 The speed curves, core losses and saturation are calculated 
 as previously explained. The speed curves and core losses 
 should be plotted on the same sheet against amperes line as 
 abscissae and rev. per min. and watts as ordinates. From these 
 two sets of curves another can be developed, which will give the 
 core loss of the motor at any speed or current. 
 
 The Thermal Characteristic should be obtained by making 
 a series of heat runs at varying amperes, allowing sufficient time 
 to get a temperature rise of 75 deg. cent, on any part except the 
 commutator. Each run should be made at the same constant 
 voltage, the current value for each run varying from 50 to 150 
 per cent normal. If a sufficient number of heat runs be taken 
 on a sufficient number of motors of the same class, type and 
 form, the horse-power rating for 75 deg. cent, rise may be 
 obtained for any length of run from one-half hour to continuous 
 running. Before starting a heat run, cold resistances and tem- 
 peratures should be taken. After the motor has run continuously 
 for the allotted time, amperes and volts having been held 
 constant with all covers off, and all openings unrestricted, it is 
 shut down, hot resistances measured, and all temperatures 
 taken. The results of the thermal heat run should be plotted, 
 one curve for armature and one for field, against time in hours 
 as abscissas and degrees cent, rise as ordinates. Through zero 
 and the plotted points corresponding to the different loads, lines 
 should be drawn. The intersections of these lines with the line 
 
 165 
 
of 75 deg. cent rise gives the time the motor takes to attain 75 
 degrees rise with the load corresponding to the plotted point 
 through which the line was drawn. From these curves another 
 curve should be plotted with time as abscissa? and amperes load 
 as ordinates. This is an ampere time curve for 75 deg. cent. rise. 
 
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 70 
 
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 it / 
 
 
 \ 1 j 
 
 
 
 
 3 4 
 
 /SO 
 
 %/60 
 
 /40 
 
 /ZO 
 
 /00 
 80 
 60 
 40 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 v 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 s, 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 \ t 
 
 
 
 V 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 <> 
 
 p 
 
 k 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 *m 
 
 n 
 
 /Ts\y 
 
 
 
 
 
 
 
 *%r 
 
 
 
 
 
 
 
 
 
 
 
 
 
 n- 
 
 
 
 
 
 
 
 
 
 
 
 4Z 
 
 
 
 
 
 
 
 /i./z 
 
 'Ovfot/t 
 
 
 
 
 
 
 
 
 
 
 
 
 
 01 
 
 L £// 
 
 <S> 
 
 
 
 -fff~ 
 
 
 2 3 <4 
 
 /ioctrs /?un 
 
 Fig. 77 
 
 THERMAL CHARACTERISTICS OF A 100 H.P., 600/1200 VOLT 
 
 RAILWAY MOTOR 
 
 On the same sheet as the ampere time curve is plotted, a curve 
 should be drawn with time as abscissae and horse power as 
 ordinates, the horse power being calculated from the standard 
 75 deg. cent, characteristics. See Fig. 77. 
 
 166 
 
In loading railway motors, as in the Speed Curve, two 
 motors are geared together on the same shaft (see Fig. 78), 
 one running as a motor at the rated voltage and full load current 
 and driving the other as a separately excited generator. The 
 separately excited field of the generator is in series with the 
 motor field, thus giving a normal full load excitation. The 
 armature of the generator is connected to a water box, the 
 resistance of which is varied until full load on the motor is 
 obtained. The run is made for one hour, after which temper- 
 atures are taken. 
 
 Motor 
 
 [=|)j^a^j: JT==rt =#=) 
 
 Generator 
 
 "&O-0OOOO0O" 
 
 fte/a 1 
 
 Fig. 78 
 CONNECTIONS FOR LOADING TWO RAILWAY MOTORS 
 
 Resistances are measured and high potential applied both 
 before and after the test, and, before starting, the speed should 
 be checked in both directions of rotation. 
 
 The circulating current method is often used in making this 
 test. 
 
 One out of every fifty of all types of motors should receive 
 the one hour load run. All 600 volt commutating pole motors, 
 excepting those receiving the one hour load run, should be run 
 under load for ten minutes in each direction of rotation. Other 
 motors having their characteristics well established should 
 receive commercial tests. 
 
 COMMERCIAL TESTS consist in running a motor light for a 
 short period. It is the practice to run four motors in parallel, 
 the fields being connected in series and separately excited by 
 
 167 
 
a current equal to full load current of the motor. (See Sketch 
 of Connections in Fig. 79.) 
 
 With normal voltage held constant across the armatures, the 
 motors are run light for five minutes in each direction of rotation, 
 readings of speed, armature and field current being recorded. 
 
 With rated voltage across the motors, the fields should be 
 weakened until about twice normal speed is attained. Under 
 these conditions the machine should be run in each direction 
 for five minutes, the same readings as above being recorded. 
 
 Resistance measurements cold only are taken. High poten- 
 tial tests must be made after this run. 
 
 Booster 
 
 <& 
 
 F/W/ F/e/SJ FMJZ Fi6>M4\ 
 
 Fig. 79 
 CONNECTIONS FOR RUNNING LIGHT ON RAILWAY MOTORS 
 
 Care must be taken that the resistance at 25 degrees cent, 
 and speed come within the prescribed limits already mentioned. 
 
 STANDARD EFFICIENCY TESTS on all series motors with the 
 exception of railway motors are made by the method of losses and 
 the calculation is identical with that of any other motor. In 
 this case, of course, the amperes armature equals amperes line. 
 See page 433. 
 
 In making an INPUT-OUTPUT TEST the motors are geared 
 and connected as for the Load Heat Run and are usually run 
 under full load for one hour up to ordinary working temperatures 
 and to get the bearings in good running condition. Before 
 the load is put on, a careful measurement of the armature and 
 field resistances of the motor, and of the armature of the gener- 
 
 168 
 
ator is taken by the drop in potential method. Three differen 
 measurements of each should be made with as many different 
 values of current, which should be near the normal load current. 
 Holding constant normal voltage, 12 or 15 different loads 
 ranging from as low as possible to 150 per cent load should 
 be put on, the direction of rotation being such that the motor 
 tends to lift from its bearings. Readings at each load should 
 be taken of the amperes, volts armature and speed of the motor 
 and amperes and volts armature of the generator. The direction 
 of rotation should then be changed and several check points 
 taken in speed and amperes, after which the machine should 
 be shut down and hot resistance measurements made. 
 
 /300 \ 
 /200 .Vi 
 J/OO ^ 
 
 /ooo /oo 
 
 900 30 
 800 30 
 7O0 70 
 
 600 60 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 s, 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 s 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 -%Cc 
 
 
 >Li 
 
 KC 
 
 
 
 
 
 
 
 
 
 
 . %c?/?. 
 
 
 
 
 
 
 
 
 
 -f 
 
 %<Jec 
 
 tr 
 
 C7/X 
 
 l> 
 
 i 
 
 ct 
 
 Vo 
 
 n 
 
 
 
 
 
 
 
 
 
 
 
 
 j 
 
 
 1 
 
 ^ 
 
 > 
 
 
 
 
 s 
 
 s , 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 V 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 ^f. 
 
 ft 
 
 
 
 
 
 
 
 
 I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 30 
 
 /20 
 
 Fig. 80 
 INPUT-OUTPUT CURVES ON A 100 H.P., 600 VOLT, RAILWAY MOTOR 
 
 Tractive effort 
 
 The Calculation Sheet 8 and Fig. 80 show the method 
 
 of working and plotting the data obtained from the input-output 
 
 test. Unless otherwise specified the tractive effort and miles 
 
 per hour are calculated for 33 in. wheels. The formulas used 
 
 are: 
 
 ,,.. , R. p. m. X diameter of wheels in inches X-n- 
 
 Miles per hour = — ■= : ,^„^ 
 
 Gear ratio X 1056 
 
 Amps. X volts X efficiency X 252 
 
 Miles per hour X 500 
 
 The gear ratio is that between the gear and pinion. 
 
 From these characteristics new ones should be plotted, 
 as shown in Fig. 81, the PR being corrected for 75 deg. cent, rise, 
 and the gear loss assumed as 5 per cent at full load. If the gear 
 loss from test has to be changed at full load, it should be changed 
 in the same ratio throughout the curve. (See Calculation 
 Sheet 9.) 
 
 COOLING OFF TESTS are made by running the motor under 
 full load, with covers off, for one hour, shutting down and reading 
 temperatures as the machine cools down. For the first hour 
 
 169 
 
after the machine is shut down, the following temperatures 
 are read every fifteen minutes: the armature, commutator, 
 field, frame, air in the motor, and room temperatures. After 
 the first hour temperatures should be taken every half hour 
 until the temperature of the hottest point is not more than 25 
 degrees cent, above the surrounding atmosphere. 
 
 The results of the cooling off test should be plotted to time as 
 abscissas and degrees centigrade rise as ordinates. The curves for 
 armature, field, commutator, frame and air in the motor, should 
 all be plotted on one curve sheet. 
 
 
 
 
 
 ' uu ""rag 1) L, %c?/? 
 
 
 
 = = = = = ~ — 
 
 % * v 
 
 s' 
 
 & 2^ v 70 25^ 
 
 ^ 7 
 
 £ S h f S 
 
 A*' 
 
 
 3M 
 
 
 «&£ 
 
 v fe §u t ^ d 
 
 6& 
 
 ^ 1 ^ f "■-- 
 
 T&- 
 
 ^2000 K 2/7^ 40 \- 
 
 ^ >£**&,<».- 
 
 
 
 5? ?> ^ 
 \ S* 30 ^ 
 
 
 £ ?!* ^ 7 
 
 
 &/OO0^ /O 20 4L 
 
 
 
 
 -j ** 
 
 
 t **" 
 
 
 o o /?U-I^ 
 
 
 /20 /GO 
 
 Amperes 
 
 200 
 
 260 
 
 Fig. 81 
 
 SPEED, TRACTIVE EFFORT, EFFICIENCY ON A 100 H.P., 600 VOLT 
 
 RAILWAY MOTOR 
 
 DYNAMOTORS 
 
 Dynamotors are used to supply current at one-half the line 
 voltage of a system and consist of an armature having two 
 distinct windings and commutators rotating inside a common 
 magnetic circuit, having a shunt winding and also a series 
 winding so connected that it is active only during the period 
 of starting. The tests ordinarily taken consist of dynamic 
 balance of the armature in a special frame, a one hour heat run 
 at rated output and running light readings with normal con- 
 nections (but with the ground connection removed) and also 
 at reduced voltage with the series field only. After these tests 
 are finished the dynamotor should be thrown directly on the line 
 and starting characteristics and commutation noted. 
 
 Core loss when called for, should be taken by the method of 
 motor core loss. Calculation Sheet 27 shows results of a motor 
 core loss on this type of machine. 
 
 170 
 
Input-output efficiency is calculated from the readings taken 
 with the machine connected as for a heat run. Calculation Sheet 
 26 shows results of such test. 
 
 VENTILATION TESTS 
 
 Ventilation tests are sometimes taken on Railway Motors. 
 The double pitot tube method is ordinarily used and the velocity 
 and quantity of air delivered calculated using the weight of the 
 standard air. In this cas e 
 
 V=401oV h 3 at the center of the pipe. 
 
 Q =3654^4 V I13 using the average velocity as given 
 in Chapter 16, page 313. 
 
 17 
 
CHAPTER 9 
 
 ALTERNATING CURRENT GENERATORS 
 
 The tests on Alternating Current Generators may be divided 
 as follows: Preliminary tests, commercial tests, heating tests, 
 special tests, input-output tests, over-speed test, wave form, 
 location of keyway, voltage regulation and static tests. 
 
 Preliminary Tests consist of drop on spools, resistance 
 measurement, air gap and fitting of collector brushes. The pre- 
 cautions specified in Chapter 4 should be carefully followed. 
 
 COMMERCIAL TESTS consist of excitation and other readings 
 at no load necessary to demonstrate that the machine is a dupli- 
 cate of the same type already shipped and that it is free from 
 manufacturing defects. 
 
 After the machine has been started a saturation curve should 
 be taken as described in Chapter 6, page 120, the curve being 
 taken up to full excitation voltage on the field. Care should be 
 used to see that the voltages in the various phases are balanced. 
 
 Synchronous impedance may then be taken. The object 
 of this test is to determine the field current necessary to produce 
 a given armature current when the machine is running short- 
 circuited. Since the regulation of the machine is calculated from 
 the impedance and saturation curves, care should be taken that 
 consistent results are obtained. 
 
 The armature . should first be short-circuited; then with 
 the machine running at normal speed and a weak field current, 
 the current in each phase should be read. The field current 
 should be increased gradually until 150 per cent normal arma- 
 ture current is reached, readings being taken simultaneously 
 of amperes armature and field and volts field. Care should be 
 taken not to overheat the windings. 
 
 Although the speed in this test should be held normal a 
 
 small variation therefrom will not affect the curve, because 
 
 e.m.f. -E 
 
 in the formula, current = = '— A = / „ ^ ^et the term R 2 
 
 Impedance VR 2 +L 2 W 2 
 
 is small compared with L 2 W 2 , and as E and W vary propor- 
 tionally to the speed, the current remains practically constant. 
 In the calculation of synchronous impedance all readings 
 should be corrected for the constants of instruments and ratios 
 used and a curve plotted on the same sheet as the saturation 
 curve, amperes or ampere turns field being plotted as abscissae 
 and amperes armature as ordinates. See Calculating Sheet 
 7 and Fig. 82. 
 
 Phase rotation should be taken after these tests are finished 
 by using a "Phase Rotation Indicator" described in Chapter 2, 
 page 25. See Fig. 12. The terminals of the machine under test 
 whether three-phase or quarter-phase should be connected 
 to the corresponding terminals of the indicator. The indicator 
 should operate on the residual voltage of the alternator but if it 
 will not, a small field current should be applied to the machine 
 
 172 
 
under test and the voltage should gradually be brought up to a 
 small amount and the magnet of the meter should revolve in the 
 same direction as the rotor of the machine under test when 
 facing the head end. Be careful not to burn out the indicator. 
 If it rotates in the opposite direction (a) for a quarter-phase 
 machine, a phase is reversed; (b) for a three-phase machine, either 
 a phase is reversed or the wrong leads have been brought out. 
 The head end of a machine is the end at which the coil to coil 
 
 /OOO 
 
 
 
 
 
 
 
 
 
 
 S 
 
 900 
 
 
 
 
 
 
 
 
 
 
 _ f 
 
 
 
 
 
 
 
 
 
 
 / 
 
 BOO 
 
 
 
 
 
 
 
 
 
 
 ./ 
 
 
 
 
 
 
 
 
 
 
 r 
 
 l**> 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 *m 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 r 
 
 / 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 y 
 
 ' 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 \300 
 §200 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 /oo 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 °t 
 
 / 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 A 
 
 
 
 2 
 
 s4/n 
 
 
 'pert 
 
 s / 
 
 JO 
 %vfc 
 
 f 
 
 <U) so 
 
 Fig. 82 
 
 SYNCHRONOUS IMPEDANCE CURVE ON A 500 KW., 600 VOLT 
 
 360 R.P.M., 3-PHASE, 60 CYCLE, A-C. GENERATOR 
 
 armature connections are made. Figs. 83 and 84 cover every 
 type of standard connection block, and will assist in numbering 
 the machine terminals for the phase rotation indicator. If the 
 block is on the side of the machine facing the bearing, or on the 
 outside of the frame proper and at right angles to the shaft, the 
 numbers should read 1-2-3 in a clockwise direction. If the block 
 is in any other position, as on the side facing the bearing with 
 the numbers running radially, or on the frame proper with the 
 numbering parallel to the shaft, the same sequence of numbers 
 should exist, but the block has been given a quarter turn in a 
 clockwise direction. In the case of revolving armatures the 
 numbering is always from the inside ring toward the outer. 
 
 Magnetic leakage sometimes causes a small e.m.f. to be 
 generated which causes an alternating current to flow through 
 
 173 
 
the frame of the machine to the shaft, resulting in the pitting 
 and marring of the latter inside the bearing. A reading should 
 be taken on all alternators of 200 kv-a. and above to ascertain 
 
 \ Load End 
 
 ( 
 
 
 \ 
 
 i 
 
 m 
 
 )N 
 
 
 "tT 
 
 w/ 
 
 Load End 
 
 1 2 J 
 O O O 
 
 
 
 / 2 
 » o . o 
 3 a. 
 o o 
 
 
 Clockwise 
 
 
 
 1 2 
 o o 
 
 3 d 
 
 o o 
 
 
 13 
 I • 
 
 3 . 
 
 4 4 
 
 Commutator Collector 
 For A 3 or A Moch/r>QS wrth' 
 Revolving Shunt 
 
 Connect -Studs land 3 to the some Phase on I Q and QB 
 Connect Stud 3 to beginning of Phase / 
 Connect Stud 4 to beginning op Phase 2 
 
 Fig. 83 
 CONNECTION BLOCKS 
 
 whether there is any appreciable current flow from this source. 
 A high reading a-c. ammeter should be connected to low resist- 
 ance leads, one of which is in contact with the revolving shaft, 
 and the other securely fastened to the frame of the machine.. 
 
 174 
 
If an appreciable reading is obtained on the instrument, the fact 
 should be reported as a defect to be remedied by insulating 
 the bearing-standard from the base. 
 
 V 
 
 d Lead End 
 
 J 
 
 i 
 
 ^ 
 
 uuu 
 Lead £nd 
 
 } 
 
 I 3 5 7 
 
 ?z:zz--s 
 
 A O Machines 
 With Revolving Shunt 
 
 5 ■ -^H 
 
 s - 
 
 Commutator Col lee tor for 
 A T Machines Col lector Studs 
 hove odd numbers, Commutator 
 Studs have ever, numbers 
 
 Fig. 84 
 CONNECTION BLOCKS 
 
 All machines rated 1000 kv-a. and above must be furnished 
 with insulation under the bearing pedestal. 
 
 HEATING TESTS 
 
 Before starting these tests instructions in Chapter 4 regarding 
 thermometers, etc., should be carefully followed. The heating 
 
 175 
 
tests on a-c. generators may be divided into two parts; 
 load tests and equivalent load tests. 
 
 actual 
 
 ACTUAL LOAD TESTS 
 
 Actual load tests may be taken by the water box method or 
 feeding-back method. 
 
 The water box method is similar to that described for d-c. 
 generators. Boxes must be used in each phase and care must 
 be taken to keep the currents in the various phases balanced. 
 The boxes in the different phases of a three-phase machine 
 should be connected in "Y", and the leads from the generator 
 under test should be run to the blades. Not more than 2300 
 volts should be applied to the standard water box. Machines 
 requiring a higher voltage than this should have transformers 
 placed in the line. In the various sections there are several 
 water boxes good for more than 2300 volts and these should 
 be used whenever possible, rather than transformers. 
 
 Fig. 85 
 
 GRAPHICAL DETERMINATION OF CURRENTS 
 
 FOR A POWER-FACTOR HEAT RUN 
 
 Very often it is required to load an a-c. generator at a 
 specified power-factor. In such case a synchronous motor should 
 be connected across the terminals of the generator under test 
 in multiple with the water boxes and should ordinarily be run 
 light, having its field excited to give the required leading or 
 lagging current in the armature circuit of the generator under 
 test. If the latter machine is to be run at leading power-factor 
 the field of the synchronous motor must be excited with a 
 current above its normal excitation for unity power-factor. 
 The machine under test is accordingly run below normal excita- 
 tion. If a lagging power-factor is specified the conditions are 
 reversed. Wattmeters must be used to determine the power- 
 factor of the circuit. The amount of current to be held in the 
 armature circuit of the synchronous motor floating on the line 
 may be determined graphically as follows. Referring to Fig. 85: 
 
 Let AB = full load current of the generator under test (for 
 a normal load heat run.) 
 
 176 
 
Draw angle BAC=the angle whose cosine is the power- 
 factor to be held. 
 
 Draw BC perpendicular to AC. 
 
 Lay off CD = minimum input current for the synchronous 
 motor running light. 
 
 Then BD is the current to be held in the armature circuit 
 of the synchronous motor and AD is the amount of current to 
 be carried by the water boxes. Thus, by holding the synchro- 
 nous motor current at BD (varying the field if necessary) and 
 loading the generator under test on the water boxes until AD 
 amperes are obtained the load of the specified power-factor is 
 obtained and the heat run may be taken. 
 
 OV 
 
 Fig. 86 
 SHIFTING OF PHASES SHOWN DIAGRAMMATICALLY 
 
 "Feeding Back" Method 
 
 Two similar alternators may be tested under actual load 
 by direct connecting their shafts and supplying the losses 
 mechanically. It is, however, necessary to shift the stators 
 with respect to each other so that the machines will remain 
 continually out of phase with each other. The vector difference 
 of the voltages thus generated by the two machines will cause 
 a current to flow which may be varied by changing the relative 
 positions of the stators. For example, consider a three-phase 
 machine the phases of which are shown diagrammatically in 
 Fig. 86. The machines should be run at normal speed, with the 
 fields separately excited to a value corresponding to the load 
 at which it is desired to make the test. The value of this excita- 
 tion should be calculated from the saturation and synchronous 
 
 177 
 
impedance curves. With points a and a r connected together 
 the voltage across b and b' should be read, the circuit closed 
 and the value of the current flowing observed. Knowing the 
 voltage between phases a-b, a'-b', and between b and b', the 
 angle of phase displacement may be readily obtained. Should 
 the armature current be considerably greater or less than that 
 desired a further trial will be necessary. 
 
 The current value will vary nearly as the angle of dis- 
 placement so that an approximate value of the angle desired 
 can be found from the value of current and angle previously 
 ascertained. When the value of this angle has been ascertained, 
 the phase displacement should be changed, so as to obtain it 
 as closely as possible. With the machines still connected together 
 as they were originally, the angle of phase displacement pre- 
 viously found will be increased 120 electrical degrees by con- 
 necting a' and b. If a' and c are connected, a still further 
 displacement of 120 degrees is obtained. If with any of these 
 connections, the field of one machine be reversed, a still further 
 displacement of 180 degrees is made. With the connection which 
 gives the nearest value of armature current to that required, 
 a further adjustment may be made by shimming the stator of 
 either or both machines up on one side and taking shims out on 
 the other side. The circuits should then be closed and the heat 
 run made for the specified time. Even with the angles of phase 
 displacement possible with -the various combinations of con- 
 nections and field reversals it may not be practicable to get the 
 desired armature current. In this case, unbolt the coupling 
 and shift the rotor of one machine around one or more 
 bolt holes. The "cut and try" operation should then be 
 repeated. 
 
 Although thus "cut and try" method is not the best one to 
 use it gives very satisfactory results, especially where it is 
 necessary to make an actual full load test. 
 
 Two frequency changer sets consisting of a-c. generators 
 and synchronous motors may also be given an actual load run 
 by shifting the phases of the generators or motors with respect 
 to each other. The losses in the sets should be supplied electri- 
 cally from the synchronous motor end. The stators of the gener- 
 ators or motors are usually held in cradles, so that they may 
 be rotated to run in phase with other machines, consequently 
 it is necessary only to turn the frames in their cradles to obtain 
 the proper shift. Each different load of course requires a 
 definite relative position of the two stators. The fields should 
 be excited with the field currents necessary for the test as found 
 from the saturation and synchronous impedance curves. One 
 set will operate direct and the other inverted. 
 
 If a run is required at a specified power-factor the generator 
 of the set operating inverted should have its field excited at such 
 a value that the specified power-factor is obtained on the gener- 
 ator of the set operating normally. Wattmeters should be 
 used to determine the power-factor. 
 
 178 
 
EQUIVALENT LOAD TESTS 
 
 Equivalent Load Tests may be subdivided into "Open 
 Circuit Heat Run," "Short Circuit Heat Run," "Open Delta 
 Heat Run" and "Zero Power-Factor Heat Run." 
 
 The Open-Circuit Heat Run as its name implies consists in 
 running the generator at no load and with a field current which 
 gives a predetermined percentage over normal voltage. The 
 run should be continued until the temperatures are constant 
 and the machine then shut down and the final temperatures 
 recorded. The resistance of the field should be measured care- 
 fully both before and after the run. Volts armature and speed 
 should be held constant and readings taken of volts and amperes 
 field. 
 
 The Short-Circuit Heat Run consists of running the machine 
 until temperatures are constant with its armature terminals 
 short-circuited through an ammeter and with sufficient excitation 
 in the field to obtain a given percentage over normal current in 
 the armature. Amperes armature and speed should be held 
 constant and readings taken of amperes and volts field. Final 
 temperatures should be recorded and the resistance of the 
 armature both before and after the run carefully measured. 
 
 The Open Delta Heat Run is sometimes made on large three- 
 phase alternators. The phases of the machine should be 
 connected in delta, one side of which is left open. The 
 machine should be run up to speed, the field excited and 
 the voltage across the opening in the delta measured with a 
 potential transformer and voltmeter. This voltage should be 
 approximately zero. The armature should then be wired to a 
 source of direct current sufficient to supply the amount necessary. 
 One side of the open delta should be grounded to protect the 
 armature of the direct current machine from static strain. 
 The other armature terminals should be carefully insulated. 
 Due to harmonics which may exist in the legs of the delta, an 
 alternating cross-current may flow in the winding. This should 
 be measured by an a-c. ammeter and current transformer (if 
 necessary) inserted in the armature circuit. The amount of 
 circulating direct current necessary is then found as follows: 
 
 Let / = normal rated current of machine under test. 
 V = normal rated voltage of machine under test. 
 
 ^ T rated kv-a. 
 
 then / = ;= 
 
 V3 V 
 Let I\ = amount of cross current found with field excited as 
 specified above. 
 
 h= amount of direct current required. 
 Then P = Ii>+I 2 * 
 I 2 2 =P-Ii 2 
 When this value has been determined the voltage of the machine 
 supplying the circulating direct current should be increased 
 until the desired current is obtained. The field of the alternator 
 under test should then be excited to the value necessary to give 
 normal no-load voltage, and the run continued until tempera- 
 
 179 
 
tures are constant. Careful record should be made of volts 
 armature, volts and amperes field, direct- and alternating- 
 current amperes armature, and speed. 
 
 /oo 
 
 90 
 BO 
 70 
 
 \eo 
 % 
 
 20 
 
 /o 
 
 
 
 11- -4- -4- ■ 
 
 ~~-W- — X X ^ 
 
 ^ v J_ J_ i 
 
 y\. _J_ J. _|_ .3. 
 
 Z .«_ >§ ">5i ^ ^ 
 
 J. yL. A_ 
 
 / 't 
 
 r 
 
 
 H 
 
 I 
 
 I 
 
 r 
 
 f 
 
 t 
 
 . 
 
 
 
 
 
 eo so 
 
 /20 
 
 /40 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 220 
 
 
 
 
 
 | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 j 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1- 
 
 ZOO 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 t 
 
 
 
 
 
 
 \ 
 
 
 
 
 
 
 
 
 
 J_ 
 
 
 
 
 
 lot 
 
 M 
 
 
 
 
 
 
 i- 
 
 
 
 
 >»- 
 
 
 
 /eo 
 
 
 
 
 
 i 
 
 
 
 
 pt 
 
 t 
 
 
 
 
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 r 
 
 
 
 
 
 
 
 
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 s_ 
 
 
 
 
 N» 
 
 
 
 
 "W 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 4- 
 
 
 
 
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 ?r 
 
 ei 
 
 o 
 
 ss 
 
 
 
 
 
 
 
 
 
 
 
 
 
 MO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \/20 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 X/00 
 
 eo 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 eo 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 <*o 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 fr/ct/o/j 
 
 7/1 
 
 c/ 
 
 Mb 
 
 da 
 
 'J*' 
 
 
 
 
 
 
 
 
 
 
 
 20 
 
 
 ¥r\ 
 
 A 
 
 r#^ 
 
 
 
 
 
 
 
 
 ^T 
 
 
 
 
 
 
 
 
 
 
 L 
 
 
 £f 
 
 A 
 
 
 
 
 
 
 / 
 
 0/7C 
 
 
 OS 
 
 
 
 
 
 
 zo 
 
 <40 
 
 /ZO 
 
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 60 eo /a 
 
 Fig. 87 
 
 EFFICIENCY AND LOSSES ON A 5000 KW., 11,000 VOLT, 257 R.P.M. 
 
 60 CYCLE, 3-PHASE A-C. GENERATOR 
 
 The Zero Power-Factor Run is another excellent method of 
 making an equivalent load run and is often used where two 
 machines of approximately the same rating are available. The 
 
 180 
 
generator under test is run as a synchronous motor with its 
 field excited to give full load current. The field is usually over- 
 excited, but there may be cases when under-excitation is specified 
 or a test may be called for in which the field will be intermittently 
 over- and under-excited. Readings should be recorded of amperes 
 armature, volts armature, amperes and volts field and speed, 
 and the run continued until all temperatures are constant. 
 Final temperatures should then be taken and the resistances 
 of both field and armature carefully measured. 
 
 SPECIAL TESTS consist of saturation, synchronous impedance, 
 open- and short-circuit core loss and wave form. On turbine 
 driven generators air readings will be taken to determine the 
 pressure and amount of air circulating in the various parts of the 
 machine. 
 
 INPUT-OUTPUT TEST, OVER-SPEED TEST and WAVE FORM 
 have been described in Chapter 6. 
 
 COMPLETE TEST consists of special tests and heating tests. 
 
 STANDARD EFFICIENCY TEST is made by the method of losses. 
 Page 437 and Calculation Sheet 14 and Fig. 87 show the method 
 of calculating and plotting results. 
 
 LOCATION OF KEYWAY 
 
 It is often required that two machines whose revolving parts 
 are on the same shaft, or are to be direct connected shall operate 
 in series or multiple. In such case the generated voltages must 
 be in phase with each other, and in order to make sure of this 
 fact the key-ways of the machines must be definitely located 
 with respect to each other. This is done by connecting the 
 fields of the two machines in series and exciting them from the 
 same source of power. The revolving parts are then adjusted 
 and the keyways so located, that upon suddenly opening the 
 field switch, no "kick" is obtained upon a voltmeter connected 
 across any particular phase of either machine. This position 
 can best be determined in the following way: Set the rotating 
 part of the first machine with respect to the stationary part so 
 that no "kick" is obtained on a voltmeter across any one phase 
 when the field circuit is suddenly opened. Then set the other 
 machine so that zero "kick" is obtained on that phase which is 
 to be connected to the phase of the first machine on which zero 
 "kick" was obtained. A definite marking should be made upon 
 the machines so that the shop may cut the key-ways in such 
 position that the relative position of the rotors will always 
 remain the same. 
 
 VOLTAGE REGULATION 
 
 A test of the voltage regulation of alternating current gener- 
 ators is sometimes made, but more frequently is calculated from 
 the saturation and synchronous impedance curves. In actually 
 determining the regulation, the machine is subjected to normal 
 load with normal voltage held on the armature. With the field 
 excitation held constant, the load is suddenly thrown off and the 
 armature voltage observed. The difference between this 
 voltage and normal voltage divided by the normal voltage is 
 
 181 
 
the per cent voltage regulation. Very often, especially on large 
 machines, it is found impossible to run the machine at actual 
 load on account of limited facilities. In such cases it becomes 
 necessary to calculate the voltage regulation from the saturation 
 and synchronous impedance test. This is done as follows: 
 Let V = normal line voltage. 
 
 / = normal line amperes 
 
 R =hot resistance between lines. 
 
 r . ^ , , . rated kv-a. 
 I for three-phase machines = 7^ 
 
 Vs v 
 
 T , , , . rated kv-a. 
 
 I for two-phase machines = -r-== 
 
 2V 
 
 = voltage drop in armature for three-phase 
 
 machines. 
 
 v = IR = voltage drop in armature for two-phase 
 machines. 
 
 Let ai = amperes field on saturation curve corresponding 
 to(F+»). 
 
 a 2 = amperes field on synchronous impedance curve 
 corresponding to J. 
 
 The amperes field required to produce n ormal ra ted voltage 
 with full load on the generator will be a s = var+^2 2 . 
 
 Let Fi=the voltage on the saturation curve corresponding 
 
 to a 3 . 
 
 Vi — V 
 Then per cent regulation = — ^ — 
 
 If it is desired to calculate the regulation of the machine at a 
 
 power-factor less than unity then I becomes- — ? — - — 
 
 per cent power-factor 
 
 and as becomes Vai 2 +a 2 2 — 2a x a 2 sin where = the angle whose 
 cosine is the power-factor. 
 
 STATIC TESTS 
 
 Some perfectly standard a-c. generators are given what is 
 known as "Static Test." The resistance and polarity of the 
 field spools are measured and the stationary armature is con- 
 nected to an alternator of the correct frequency and the voltage 
 necessary to overcome the impedance of the winding is measured 
 at several different current values up to 200 per cent normal. 
 Care should be taken not to overheat the windings. For this 
 test the machine is not assembled in bearings, but the field 
 is placed inside the armature and the air gap measured, after 
 which, the field is removed and the impedance test taken. 
 
 WAVE FORM 
 
 Wave form is taken with the oscillograph and ordinarily at 
 no load. The Engineers may, however, specify a full load test. 
 In this case the machine is usually "dead-loaded" to eliminate 
 the effect of the wave form of other machines. 
 
 182 
 
CHAPTER 10 
 
 SYNCHRONOUS MOTORS 
 
 The tests on synchronous motors may be divided as follows: 
 Preliminary Tests; Commercial Tests; Heating Tests; Special 
 Tests; Input-Output; Over-Speed; Wave Form; and Torque Tests. 
 
 Preliminary Tests consist of drop on spools, resistance 
 measurement, air gap and fitting of collector brushes. The 
 instructions in Chapter 4 should be carefully followed. 
 
 When a machine is run as a synchronous motor extreme care 
 should be used in starting it to see that the field circuit is open 
 and that the voltmeter switch is not closed. The special switch 
 designed for this case must always be used. The field of the 
 synchronous motor acts as the secondary of a transformer, and 
 the voltage induced across the rings at starting may be enough 
 to cause serious injury As the machine comes to synchronism 
 this induced voltage falls to zero and the field switch may then 
 be closed. 
 
 COMMERCIAL TESTS consist of excitation and other readings at 
 no load necessary to demonstrate that the machine is a duplicate 
 electrically of machines of the same type already shipped and 
 that it is free from manufacturing defects. 
 
 Synchronous motors are ordinarily run as a-c. generators 
 when commercial tests are taken. 
 
 HEATING TESTS 
 
 Heating Tests on synchronous motors as on other machines 
 consist of actual load tests and equivalent load tests. In 
 making an actual load test the machine is usually excited with 
 a current to give minimum input on the armature as found from 
 the phase characteristic curves which are taken as follows: 
 
 PHASE CHARACTERISTIC 
 
 The machine must be operated from some a-c. source of 
 correct frequency and at constant voltage. A reading of amperes 
 input on all phases should be taken with zero field on the motor, 
 where possible. Starting with a weak field and reading volts 
 and amperes armature and volts and amperes field, the field 
 should be increased by small steps until the point of minimum 
 input armature current is found. Increasing the field current 
 beyond this point increases the amperes armature. On a no-load 
 phase characteristic curve, the watts input at the lowest point 
 should check very closely with the sum of the core loss, friction 
 and windage losses, since the power-factor is unity on synchro- 
 nous motors at this point and the amperes field must equal that 
 found for normal voltage on the saturation curve. These points 
 must be checked with each other to see that they agree. With a 
 weak field the current is lagging and with a strong field it is 
 leading. In taking a no-load phase characteristic the current 
 should rise to a value of at least 50 per cent of full load alter- 
 nating current. 
 
 A load phase characteristic should be taken in a similar 
 manner to the no-load. The output is held constant and the 
 amperes load recorded in addition to the readings noted above. 
 
 183 
 
Care must be taken not to overheat the windings. It is 
 impossible to obtain a zero field point during the full load 
 characteristic, since the current would be so large as dangerously 
 to heat the machine and the torque not sufficient to carry full 
 load output. 
 
 /oo 
 
 90 
 
 GO 
 
 X 
 
 70 
 
 % 
 
 40 
 
 JO 
 
 /O 
 
 X 
 
 \ 
 
 X 
 
 \ 
 
 \ 
 
 X 
 
 X 
 
 x 
 
 
 \ 
 
 \ 
 
 Xl 
 
 t 
 
 / 
 
 i 
 
 f 
 
 t 
 
 R 
 
 t 
 
 m 
 
 i 
 
 M 
 
 t 
 
 W- 
 
 i 
 
 /O £0 
 
 30 4-0 
 
 GO 
 
 Fig. 88 
 
 PHASE CHARACTERISTIC CURVES ON A 187 KV-A., 2300 VOLT, 
 
 720 R.P.M., 3-PHASE, 60 CYCLE, SYNCHRONOUS MOTOR 
 
 All readings should be corrected for instruments and shunt 
 ratios and a curve plotted between amperes field as abscissae 
 and amperes armature as ordinates. See Calculating Sheet 10 
 and Fig. 88. 
 
 184 
 
ACTUAL LOAD TESTS 
 
 The actual load test on a synchronous motor is usually made 
 by belting or direct connecting the motor to a d-c. shop generator 
 and exciting the field of the motor for minimum input as found 
 above. 
 
 In taking a power-factor heat run, the field of the synchronous 
 motor should be over-excited to give the required power-factor 
 unless otherwise specified. Wattmeters should be used to 
 determine the power-factor. 
 
 Synchronous motors which are parts of Frequency Changer 
 sets may be given an actual load run as explained under a-c. 
 generators. 
 
 EQUIVALENT LOAD TESTS 
 
 Synchronous motors are usually run as a-c. generators when 
 being given equivalent load test. 
 
 Sometimes a synchronous motor is given an equivalent load 
 run by loading it on a d-c. generator and running at reduced 
 voltage, having the load brought up to cause full load current 
 to flow in the armature, and having the field held at the value 
 which may be specified. 
 
 SPECIAL TESTS 
 
 On synchronous motors consist of starting test, saturation, no 
 load and full load phase characteristics, synchronous impedance, 
 core losses and wave form. 
 
 Saturation, synchronous impedance, core losses and wave 
 form are taken as for a-c. generators. 
 
 Starting Tests 
 
 Starting tests are taken as follows: If the motor is of a new 
 type and rating, starting tests should be made both with and 
 without a compensator. In all cases, however, the motor should 
 first be tested without the compensator. 
 
 The center line of one pole should be placed in line with the 
 center line of the frame. At the head end of the motor a distance 
 of 180 electrical degrees should be marked off in a clockwise 
 direction from this line. The total length of the scale used should 
 be %$ of the distance between the center lines of adjacent poles 
 for three-phase machines, 3^ for two-phase machines and ^i for 
 six-phase machines. The scales should be divided into five equal 
 parts, each division line being numbered. On each one of these 
 scale divisions the center line of the marked pole should be placed 
 and the motor started. Thus five tests are made to insure that 
 the motor will not stick in any position. See Fig. 89. 
 
 With one pole moved to position No. 1 and the machine 
 at rest, sufficient current should be sent through the armature 
 to give a reasonable reading of amperes and volts on the various 
 phases and induced volts on the field. The induced volts field 
 should be read with a potential transformer and a-c. voltmeter. 
 The readings with the machine at rest are taken to determine 
 which phase gives the maximum readings of current and voltage 
 so that the latter can be read at the moment of starting. 
 
 185 
 
With the instrument switches adjusted to give the maximum 
 reading, the armature current should be increased until the motor 
 starts. Volts armature, amperes armature and induced volts 
 field should be read simultaneously. The starting volts should 
 now be held constant until the motor comes to synchronism, 
 the time required to reach this point being recorded. The 
 machine attains synchronism when the induced -volts on the 
 field fall to zero. Then the machine should be shut down and 
 the tests repeated from each of the other four positions. 
 
 Enough time must be allowed between readings so as not to 
 overheat the machine and the current must be left on only so 
 long as is necessary to obtain a reading. 
 
 "1*^ 
 
 Pole, 
 
 Fig. 89 
 
 METHOD OF DIVIDING POLE ARC FOR STARTING TEST ON A 
 
 3-PHASE MACHINE 
 
 If a motor shows a tendency to remain at half speed the 
 alternating voltage should be increased until the motor breaks 
 from half speed and comes up to synchronism. The voltage 
 required to break the motor from half speed should then be held 
 and recorded until full speed is reached. 
 
 All starting tests should be recorded on a special record sheet 
 provided for the purpose and a sketch made showing the starting 
 positions. If the motor sticks at half speed a record should be 
 made of this fact. 
 
 If the test is required with a compensator, the motor should 
 be set with its field in the position where the highest starting 
 current is taken and allowed to rest in that position for at least 
 six hours until the oil is well pressed out of the bearings. This 
 is done in order to obtain the worst starting conditions likely 
 to occur in normal operation. Connections should then be made 
 to the lowest tap of the compensator and with normal voltage 
 held on the line, the starting switch of the compensator should 
 be closed. If the motor fails to start, the voltage must at once 
 be switched off and connections made with the next higher taps 
 on the compensator and so on until the motor starts. Readings 
 
 186 
 
2000 VO 
 
 /aoo so 
 /600 so 
 
 J400 
 
 -'O 
 
 . /ZOO %60 
 
 %*/O0O si SO 
 ^ <v 
 
 <^ aoo $\40 
 
 600 ^30 
 
 400 20 
 
 200 /O 
 
 O O 
 
 SO 
 45 
 AO 
 35 
 %30 
 
 FE:==ii::£"t::5::g" 
 
 -zf~H |::l::4:=t-:: 
 
 zh ^ ^ ** ^ _j* J* 
 
 t ^ ^ 
 
 t s 
 
 ± S 
 
 J i tZ^ 
 
 i ^M& 
 
 ' ^wx 
 
 W 
 
 > 
 
 S 
 
 " J£ 
 
 "t s 
 
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 :<? 
 
 to 
 
 20 
 
 30 40 
 
 /t/7fos. L/ne 
 
 50 
 
 60 
 
 20 
 
 
 
 
 
 7 I 
 
 
 
 
 
 _/ 
 
 
 
 
 
 A 
 
 
 
 
 
 ^ V 
 
 
 
 
 
 S § 
 
 
 
 
 
 „5§^'V Ni,_ 
 
 
 
 
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 20 
 
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 60 
 
 30 40 
 
 /Imps. Line 
 Fig. 90 
 EFFICIENCY AND LOSSES ON A 1070 H.P., 13,200 VOLT, 500 R.P.M. 
 25 CYCLE, 3-PHASE SYNCHRONOUS MOTOR 
 
 should be taken at rest on each of the taps of the compensator 
 in the starting position to determine the voltage ratio of the taps 
 of the compensator. All these tests should be made with the 
 field circuit of the motor open. During the test with the com- 
 pensator, enough time should be taken between the trials to allow 
 the compensator to cool, as it is designed for intermittent service 
 onlv. See Calculation Sheet 24. 
 
 INPUT- OUTPUT, OVER-SPEED and WAVE FORM have been 
 described. 
 
 187 
 
COMPLETE TEST consists of special tests together with normal 
 and overload heat runs at unity power-factor. 
 
 STANDARD EFFICIENCY TEST is made by the method of losses, 
 page 439 and Calculation Sheet 15 and Fig. 90 show the method 
 of calculating and plotting results. 
 
 Impedance-Position Curves 
 
 An impedance position curve is taken in the same manner 
 as given for Induction Motors on page 215. A curve should be 
 plotted using the average current per phase as ordinates and 
 position number as abscissae. 
 
 Torque Tests 
 
 Torque tests may be divided into stationary torque and 
 running torque tests. 
 
 Stationary Torque tests are made in a similar manner to that 
 given for Induction Motors on page 220, using a spring balance 
 and lever. The rotor is blocked in the position which gives an 
 average of the average current per phase as shown by the 
 impedance-position curve, which should always be taken on a 
 synchronous motor before stationary torque tests. Care must 
 be used to allow sufficient time between readings and to take 
 readings quickly enough so as not to overheat the windings. 
 
 Running Torque is taken by running the motor with no field 
 excitation and belted to a d-c. generator, the voltage and fre- 
 quency of the motor being held constant. The voltage is usually 
 held at one-half the rated voltage of the machine. The field 
 on the belted generator should be held constant at such a value 
 that approximately its normal voltage will be obtained with full 
 speed on the synchronous motor. The brushes used for reading 
 voltage on the d-c. machine should be insulated from the holders. 
 Readings should be taken of volts armature (held constant), 
 amperes armature, watts and speed of the motor under test; 
 and volts and amperes armature, amperes field and speed of the 
 d-c. generator. With no field on the d-c. generator the motor 
 should be started and brought up to as near synchronous speed as 
 it will come, and all readings then taken. Then with field on the 
 d-c. generator but with no load, the test is repeated. The d-c. 
 generator should then be lightly loaded and a new set of readings 
 taken. These tests should be repeated with small increments 
 in load to give about 5 per cent change in the final speed of the 
 motor and should be continued until a reading is obtained with at 
 least 200 per cent of the rated current of the motor. Watch 
 the motor and do not let it become overheated. The tachom- 
 eter should be checked at all speeds, and care should be taken 
 to use the proper signs for the wattmeters'. After the above 
 readings are completed the belt should be removed and running 
 light readings obtained at all speeds used in taking the torque 
 tests. The same field current should be held as in the original 
 test. Curves may then be plotted with speed as abscissae and 
 kw. output and torque as ordinates. 
 
 188 
 
Calculation Sheet No. 23 shows the form used in calculating 
 a running torque test, and Fig. 91 shows the method of plotting 
 the curve. 
 
 ^ 
 
 
 GOO — | 1 1 1 i 1 1 1 1 
 
 zjzzL 
 
 
 ^v 1 
 
 kjOl/ X 
 
 s ]__ 
 
 \ 
 
 i ^ 
 
 4*30 \ 
 
 
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 it V 
 
 1 \ 
 
 JOO-T ■* 
 
 ± I 
 
 4 "^ 
 
 L 
 
 <?£*? Y 
 
 Jj 
 
 ^ 
 
 
 /£fc7 V" 
 
 \ 
 
 n 
 
 /9 .— — -- . _ ^ -—J L— 1 1— 1 1 1— ■ 
 
 20 40 60 SO /OO /20 /40 /GO /SO 200 220 240 260 
 
 Fig. 91 
 
 RUNNING TORQUE CURVE ON A 75 KV-A., 2300 VOLT, 276 R.P.M. 
 
 3-PHASE, 60 CYCLE, SYNCHRONOUS MOTOR 
 
 189 
 
CHAPTER 11 
 
 SYNCHRONOUS CONVERTERS 
 
 Inasmuch as a synchronous converter is a combination of 
 a direct current generator and a synchronous motor the tests 
 taken are somewhat similar to those for the individual machines 
 with certain modifications. 
 
 Preliminary Tests consist of drop and polarity, cold resist- 
 ance measure, air gap, checking of equalizer and collector 
 ring taps, and other tests as specified in Chapters 4, 7 and 10. 
 
 It is very important that any error in the winding or assembly 
 of field coils be discovered at the time drop and polarity tests 
 are taken, as most converters do not have their series fields con- 
 nected in for test, and hence any reversed series field polarity 
 would not otherwise be discovered before shipment. Reliance 
 should not be placed on the compass, but the polarity of adjacent 
 poles should be tested out with two iron bars. 
 
 The machine should be examined to see that the bridges 
 on the pole pieces do not project beyond the end of the pole 
 face. The air gap measured between such projecting bridges 
 and the armature is not the effective gap of the machine and 
 any such projections should be reported as a defect if the gap is 
 less than the normal gap. 
 
 The cold resistance of the armature must be carefully 
 measured between the different collector rings. On a three- 
 phase armature, measure between rings 1-2, 1-3, 2-3; on a 
 quarter-phase armature, between rings 1-3, 2-4; on a six-phase 
 armature, between rings 1-4, 2-5, 3-6. The resistance of each 
 circuit for any particular style armature should be the same. 
 Ring No. 1 is always the one nearest the armature. 
 
 The cold resistance of each field circuit should be measured 
 and recorded. 
 
 If necessary the commutator should be baked and trued 
 as for a d-c. generator. 
 
 The spacing of the equalizer and collector ring taps should 
 be closely checked by counting the coils from each tap to the 
 next. Occasionally a wrong connection is made, and if not 
 corrected before the machine is run, one or more leads may be 
 burned off and considerable damage done to the armature. 
 
 Before any machine is started the wiring should be checked 
 by the Head or Assistant Head of Section and the machine 
 must operate correctly when connected according to the proper 
 diagram of connections. 
 
 Short Commercial Test 
 
 Short Commercial Test consists in operating the machine at 
 no load for certain definite tests to demonstrate that it is a 
 duplicate electrically of machines of the same type already 
 shipped, and that it is free from manufacturing defects. For 
 this test the machine should be run for one hour as an inverted 
 converter at 110 per cent normal volts across the rings. No- 
 
 190 
 
load voltage ratio, balance across rings and running light readings 
 from the d-c. end should be taken. Bearing temperatures should 
 be read. 
 
 Speed Limit and End Play Devices 
 
 As soon as the machine is running properly the speed limit 
 device should be adjusted to operate as described in Chapter 6. 
 
 The end play should then be tried out to see that the field 
 poles and armature are correctly aligned. The machine must 
 be set level and the end play should be equal in both directions. 
 The end plav device should then be adjusted as described in 
 Chapter 6. 
 
 Phase Rotation 
 
 Phase rotation should then be taken to see that the collector 
 rings are connected to the correct taps on the armature. This 
 test is made by running the machine from the d-c. end and 
 using the phase rotation indicator described in Chapter 2. 
 
 Brush Setting 
 
 Since very little armature reaction occurs in a converter the 
 brushes should be set on the mechanical neutral. It may be 
 found, however, that a slight shift from the neutral may give 
 better commutation under load. 
 
 Voltage Ratio 
 
 The measurement of the ratio of the alternating to the direct 
 voltage of a converter is one of the important tests and care 
 should be used to obtain accurate results. The machine may 
 be driven from either the a-c. or d-c. end, but a statement as to 
 which method was used must be entered on the Testing Record. 
 When running from the a-c. end, the field should be held at that 
 value which gives unity power-factor as found from the phase 
 characteristic. 
 
 In order to check the accuracy of the instruments, two a-c. 
 voltmeters, two potential transformers and two d-c. volt- 
 meters should always be used. During the tests the direct 
 voltage is held constant, and the alternating voltage read 
 between rings 1-2 on three-phase, 1-3 on two-phase, and 1-4 
 on six-phase machines. 
 
 The ratio is taken at no load and full load and should be as 
 follows when taken with the machine running from the a-c. end: 
 
 No Load Full Load 
 With direct current 
 Single-phase 
 
 Two-phase (measured on diam.) 
 Three-phase 
 
 Six-phase (measured on diam.) 
 Six-phase (measured on adj. rings) 
 Six-phase (measured on alternate rings) 
 
 Converters with commutating poles may give values \]/2 
 per cent greater than the above. 
 
 191 
 
 00 
 
 100 
 
 71.5 
 
 73 
 
 71.5 
 
 73 
 
 61 
 
 62.5 
 
 71.5 
 
 73 
 
 35.8 
 
 36.5 
 
 61 
 
 62.5 
 
The amount of pole face arc will change the ratio. Any 
 variation from these values greater than .2 per cent must be 
 referred to the Head of Section, so that it may be investigated 
 and brought to the attention of the Engineers. 
 
 The standard shunt wound converter gives a very nearly 
 constant ratio of alternating to direct volts at all loads, so any 
 fluctuation in the a-c. supply affects directly the direct voltage 
 delivered. Such machines are unsatisfactory when much varia- 
 tion in load occurs. 
 
 When it is required to vary the direct voltage on such stand- 
 ard, machines, the applied alternating voltage must be changed. 
 This may be done by using transformers with a dial switch, or by 
 an induction regulator, or a synchronous a-c. booster. 
 
 By adding a series field winding to the standard machine 
 if it is required to operate with sudden changes of load, a practi- 
 cally constant voltage can be obtained either by introducing 
 reactance into the a-c. circuit, or by making use of the inductance 
 inherent in its feeder circuit. This is possible since an alternating 
 current passing over an inductive circuit will decrease the 
 potential if lagging and increase it if leading. 
 
 A converter running as a synchronous motor requires a 
 certain field excitation to give the minimum input current to the 
 armature. Varying the excitation either way changes the 
 input current, so, by using sufficient reactance in the a-c. 
 circuit from which the converter receives its power, the alter- 
 nating voltage at the converter terminals may be increased or 
 decreased by increasing or decreasing the exciting current. By 
 adjusting the shunt excitation of the compound wound machine 
 so it gives a no-load lagging current of about 25 per cent of full 
 load current, and adjusting the series field to give a slightly 
 leading current at full load, the impressed voltage at no load 
 will be lowered and that of full load increased automatically. 
 Hence with proper adjustment of the series field and sufficient 
 reactance, the same direct voltage will be delivered at no load 
 and full load. 
 
 The ratio may be independently varied by making use of a 
 split field-pole, as in "Split Pole Converters." 
 
 HEATING TESTS 
 
 The heating tests taken on converters usually consist of 
 actual load test taken either by the "water box," "feeding 
 back" or "circulating current" method. 
 
 « 'Water Box" Method 
 
 When loading a converter on a water box see that all cables 
 from the transformers to dynamometer boards and to the 
 a-c. rings of the machine are of the same length and capacity. 
 All contacts must be cleaned and brightened before connection. 
 Equal resistance will thus be obtained per phase and unbalancing 
 in the a-c. circuits external to the armature prevented. In 
 wiring the d-c. circuit the series field and its shunt are discon- 
 nected. 
 
 192 
 
In wiring converters, as with all other high current d-c. 
 machines, both sides of the circuit should be laid close to one 
 another. No iron, such as a bearing pedestal or a section of the 
 frame, must lie within the loop of the circuit, since it will become 
 magnetized and materially affect the operation of the machine 
 and instruments. Always divide the shunt field into at least 
 four sections, by a "break-up switch." This switch must 
 always be open while starting from the a-c. end, since due to 
 transformer action and relative number of turns of the field 
 and armature, a high voltage is induced in the field at starting. 
 
 Always wire the positive brush ring of the machine through 
 a breaker to the blade of the water box, and the negative ring 
 to the box of the water box. Connect enough boxes in multiple 
 so that none will be overloaded. Make provisions for reading 
 amperes and volts armature (a-c. side) ; amperes and volts 
 armature, amperes and volts field (d-c. side) and the speed of 
 the alternator. 
 
 To start the machine close the a-c. line switches and the 
 field switch of the driving alternator. Increase the excitation 
 of the alternator, keeping close watch on the current in the a-c. 
 lines. If this current reaches 150 per cent normal before the 
 converter starts, check over the wiring and report to the Head of 
 Section. If the machine starts rotating in the wrong direction, 
 reverse two of the leads on the primary side of the transformers. 
 After starting, as soon as the alternating current drops to the 
 minimum value, showing the machine is in synchronism, and 
 the alternating volts are normal, close the field ' ' break-up switch. ' ' 
 If, after closing the shunt field switch, the brushes begin to spark, 
 the residual magnetism left in the poles by the induced voltage 
 at starting is of the wrong polarity. 
 
 Two methods can be used to correct this. First, reverse 
 the field with respect to the armature by flashing with the field 
 reversing switch. Second, reverse the residual polarity by open- 
 ing the alternator field switches. Then close this circuit and 
 bring the converter back into synchronism, repeating this oper- 
 ation if necessary until the field builds up in the right direction. 
 
 Before proceeding further read the current in each phase to 
 make sure there is no unbalancing. These currents should not 
 vary more than one per cent from the average; any greater 
 variation due to wiring must be remedied at once. 
 
 After balance is obtained the no-load phase characteristic 
 should be taken in a similar manner as for a synchronous motor, 
 and holding the direct voltage constant. The machine may 
 then be loaded and the full load phase characteristic similarly 
 taken holding the direct voltage and current the same for each 
 value of field current. (See Calculation Sheet 6.) At the point 
 of minimum input the ratio of alternating to direct current 
 should be as follows: 
 
 Three-phase, alternating and direct current practically the 
 same. 
 
 Two-phase, alternating current equal to % the direct current. 
 Six-phase, alternating current equal to Y2 the direct current. 
 
 193 
 
These operations having been completed, the full load heat 
 run may be started after the brushes have been set for the best 
 commutation. On the load run hold full load d-c. amperes and 
 direct volts constant, with minimum input field current. When 
 holding minimum input by means of wattmeters make sure that 
 they are connected to the proper rings, otherwise they may show 
 unity power-factor when in reality the actual amount being held 
 is about 60 per cent. The load should be kept on at least one 
 
 £ty/?a/7?o/j7e£er£0asz/ 
 
 tfeosterfo St/jOp/ySfo/fo/' I*/? losses 
 
 Fig. 92 
 
 CONNECTIONS FOR LOADING SYNCHRONOUS CONVERTERS 
 
 WITHOUT THE USE OF A REGULATOR 
 
 hour after all temperatures are constant, and at the end of the run 
 temperatures must be taken on all parts of the machine, and the 
 resistance measured on the armature (from the a-c. end) and 
 on all field circuits. 
 
 If an overload run is required an overload phase character- 
 istic should be taken similarly to the full load. The direct volt- 
 age should be held constant at the normal rating and the amperes 
 output constant at the required overload value. The field 
 excitation should be varied through as near the same range used 
 on the full load as possible. The heat run should then be applied 
 for the specified time and care should be taken that the time 
 does not run over the limit. 
 
 194 
 
With Boosters in the D-C. Side (Circulating Current Method) 
 
 Fig." 92 shows the connections for two three-phase con- 
 verters wired for a feed back heat run, without a potential 
 regulator to control the load. The core losses and PR losses 
 are supplied from the d-c. end. The diagram shows, also, 
 the standard starting panel which should always be used when 
 two converters are tested together. 
 
 To start the machine, choosing No. 1 for instance, close the 
 shunt field switch and switches K and K l which short-circuit the 
 armatures of the loss supply. Note that the shunt fields are wired 
 across the core loss supply, which is wired to busses B and C 
 of the starting panel, and that the series fields are left open. 
 Throw switch A to the left and slowly reduce the resistance of 
 the water box till it is practically short-circuited, when switch 
 5 may be closed. The blade of the water box should then be 
 drawn out of the water and the switch A thrown to the right. 
 Machine No. 2 is then started in a similar manner. 
 
 The strength of the field of each machine is then decreased 
 until they both run at normal speed. (See cautions on page 203 
 regarding inverted converters.) Now connect a number of 
 incandescent lamps in series, of which the rated voltage is 
 equal to the sum of the machine voltage across rings aa', viz., 
 across switches located on the dynamometer board. Two sets 
 of lamps should be provided, one being connected across one 
 of the switches while the other is used to step across each of the 
 other switches in turn. Should one set show a rise and fall in 
 voltage directly opposite to that of the other, the two phases are 
 reversed, and must be corrected. When all phases show a 
 simultaneous rise and fall, the machines may be phased together, 
 bringing their speeds to the same value by changing the field on 
 one of them. When the rise and fall of voltage shown by the 
 lamps decreases to a period of 5 seconds or longer, close all the 
 switches simultaneously, when the lamps are dark. 
 
 Never close a single switch on the a-c. end as this would make 
 a short-circuit on the armature. 
 
 During the period of starting and phasing the machines 
 together, the boosters should be short-circuited, with open 
 fields. When the machines are synchronized the short-cir- 
 cuits are removed. Apply a weak field on the booster and 
 watch the line ammeter on No. 1. The reading of this ammeter 
 should reverse from that given on motor load if No. 1 is taking 
 load as a converter. By reversing the booster field either 
 machine can be made to run as a converter. 
 
 After balancing the current in each phase, the full load phase 
 characteristic may be taken. The speed should be held constant 
 by varying the field of the inverted converter, and the load held 
 constant with the boosters while the shunt field of the converter 
 is varied throughout its range and readings of current input 
 carefully taken. Full load voltage ratio should then be taken 
 after which the heat runs may be made. 
 
 A line ammeter-shunt must be used in each side of the d-c. 
 circuits. The currents flowing through them must have equal 
 
 195 
 
values, otherwise one line has more resistance than the other, the 
 unbalanced current returning through the a-c. ends - of the 
 machines. The currents in these lines can be balanced by 
 decreasing the resistance of copper to the low reading line. 
 The direct currents should be balanced before attempting to 
 balance those in the a-c. side. Two boosters for supplying the 
 PR losses are necessary to eliminate unbalancing. 
 
 In running this test there will be a slight difference in the 
 direct voltages equal to the IR drop of the machines. The 
 field of the inverted machine will be less than that required 
 for minimum input. 
 
 Inisertecf 
 Converter- 
 
 roTob/e 
 
 ToTcrb/e 
 
 7brab/e 
 anc/Boxes. 
 
 Fig. 93 
 
 CONNECTIONS FOR FEEDING BACK SYNCHRONOUS CONVERTERS 
 
 WITH REGULATOR 
 
 This method of supplying the PR losses with boosters 
 requires such large low voltage boosters that it is not often used 
 except for small converters. 
 
 With a Regulator in the A-C. Side (Feeding Back Method) 
 Using D-C. Loss Supply 
 
 A second method of testing converters for actual load 
 heat runs, is to use a voltage regulator in the a-c. side of the 
 machines as shown in Figs. 93 and 94. The regulator is con- 
 nected with its secondaries in series with the a-c. lines and its 
 primaries excited from the inverted machine. It is always 
 preferable to connect the regulator between the inverted con- 
 verter and the dynamometer board so that the instruments 
 of the converter will not read the losses in the regulator. The 
 
 196 
 
regulator takes the place of the booster used in the previous 
 method, and is very satisfactory for supplying the PR losses. 
 
 Starting the machine, checking the phase rotation, phasing 
 in, and the other matters already described are repeated with 
 this method. Always see that the regulator is set at the neutral 
 point before phasing in, otherwise load will be thrown on when 
 the switches are closed. For the no-load phase characteristic 
 the regulator should be disconnected. 
 
 Load is increased by turning the core of the regulator in 
 the direction of boost, at the same time watching the ammeter 
 
 
 
 Fig. 94 
 TABLE CONNECTIONS FOR SYNCHRONOUS CONVERTER FEED BACK 
 
 of machine Xo. 1. If the reading reverses from motor load, 
 then No. 1 is running as a converter. If No. 1 does not reverse, 
 turn the regulator in the opposite direction. This shows that 
 the regulator is wrongly connected in reference to its markings. 
 There is no necessity, however, to change connections. 
 
 Using A-C. Loss Supply 
 
 If instead of supplying the losses from a d-c. source of power, 
 we connect an alternator across the a-c. lines (between the 
 inverted converter and the regulator to avoid reading the losses 
 in the regulator) in the preceding method the losses can be 
 supplied at the a-c. end. When the alternator is large enough 
 to start the converters, the wiring on the d-c. end is greatly 
 simplified. The starting panel is omitted, and the shunt fields 
 are connected according to the print of connections for the 
 machine. Load is obtained by means of the regulator as before 
 and the test carried out as already described. 
 
 197 
 
If the alternator is too small to start the machines, the 
 latter may be started from the d-c. side as before, and phased 
 together. The alternator is then synchronized on the pair. 
 If only one machine can be started by the alternator, bring it 
 up to speed, then open all its circuits, and let it run by its own 
 momentum, and quickly start the second machine. Take off 
 the excitation from the alternator field, and then close the 
 switches on the first machine. Excite the alternator field, and 
 bring both machines up to speed, together. After the machines 
 are once started they can be brought up to speed without 
 excessive current being required. 
 
 After the necessary heat runs have been taken and while 
 the machine is still warm, the wiring should be removed and the 
 high potential test applied. Hot drop on field spools, running 
 light from the d-c. end, etc., should be taken as for other direct 
 current machines. 
 
 SPECIAL TESTS 
 
 Special tests consist of d-c. and a-c. starting tests, core losses, 
 saturation, impedance, voltage ratio at no load and full load. 
 Voltage range curves at no load and full load will be taken on 
 split pole machines. 
 
 Saturation and impedance are taken in the same manner as 
 for d-c. and a-c. generators, previously described. 
 
 D-C. starting tests are taken with the machine running a*s 
 a d-c. motor and wired to a d-c. machine of ample capacity to 
 give satisfactory readings without an excessive fall in voltage. 
 The main field of the converter should be excited at that cur- 
 rent necessary for no load minimum input unless full field is 
 specified. The current through the armature should be increased 
 gradually until the armature begins to revolve and held constant 
 at that value until the machine reaches synchronous speed. 
 The elapsed time from start to synchronous speed should be 
 recorded. This test should be repeated with higher values 
 of armature current held and enough readings taken to plot a 
 curve with amperes armature, as ordinates against time as 
 abscissae so as to determine the current necessary to bring the 
 converter to synchronous speed in one minute. 
 
 A-C. starting tests are taken in the same manner as for a 
 synchronous motor. 
 
 The converter should be wired to an a-c. generator of suffi- 
 cient capacity to start it without overloading. If transformers 
 are needed, in order to get the correct voltage, they should be 
 placed between the dynamometer board and the generator. 
 
 Converters at starting from the a-c. end are similar to a 
 transformer. The armature corresponds to the primary, and 
 the field, having a large number of turns, corresponds to the 
 secondary. Hence the induced volts on the field may be very 
 high (often 3000 or 4000 volts). In all cases, therefore, the 
 field connection must be broken in two or more places to keep 
 this voltage within safe limits. A potential transformer and 
 voltmeter should be connected across one or two spools in series, 
 
 198 
 
for reading the induced volts field, and a note made on the 
 record sheet as to the number of poles included in the reading. 
 
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 Fig. 95 
 
 EFFICIENCY AND LOSSES ON A 300 KW, 600 VOLT, 750 R.P.M., 
 
 25 CYCLE, 3-PHASE SYNCHRONOUS CONVERTER 
 
 Starting tests should be made from several different positions 
 of the armature with respect to the field. A scale, corresponding 
 to the distance between collector ring taps, should be laid off 
 on the armature, divided into five equal parts. A point of 
 reference is marked on the field, opposite to which the marked 
 
 199 
 
positions of the armature are placed for the successive starts. 
 These positions should be numbered and a sketch showing the 
 numbering be made on the Record Sheet. 
 
 Having brought point No. 1 opposite the reference point, 
 the a-c. switches should be closed and a moderate field put 
 on the alternator, sending about one-half normal full load 
 current through the converter. Read volts and amperes in the 
 various phases. As it will be impracticable to read all phases 
 at once during the start, cut the ammeter into that phase which 
 shows the highest current and the voltmeter across the phase 
 which indicates the highest voltage, so as to get the maximum 
 readings at the instant of starting. Increase the field of the 
 generator until the armature begins to revolve, when volts 
 and amperes input and induced volts on the field should be 
 read. The voltage across the collector rings should then be 
 held constant, until the converter reaches synchronism, the time 
 required to reach this point from the start being noted. 
 
 There are several methods of determining whether the ma- 
 chine is in synchronism. One is, the induced volts field will fall 
 to zero; another, the voltmeter across the armature will read a 
 definite voltage, which would vary from a negative to a positive 
 reading if the machine were below synchronism. 
 
 Readings should be taken on all phases, of volts and amperes 
 after the machine has reached synchronism. The machine should 
 then be shut down, the armature brought to position No. 2 
 and the test repeated. In this manner all five points should be 
 taken. After these tests have been taken, the time required 
 to bring converter to synchronism should be taken by throwing 
 one-half voltage across the collector rings. 
 
 Core Losses are taken with the converter running as a gener- 
 ator and results recorded as given in previous chapters. A 
 reading should be taken of the volts across the collector rings 
 as a check on the no load ratio. Calculation Sheet 25 shows the 
 results of a core loss taken by the motor core loss method. 
 
 STANDARD EFFICIENCY TEST is made by the method of losses. 
 Page 435 and Calculation Sheet 13 shows the method used in 
 calculating the efficiency of a converter. See Fig. 95. 
 
 COMPLETE TESTS consist of normal and overload heat runs 
 and special tests. 
 
 Other tests which may be called for on synchronous con- 
 verters are: 
 
 Compounding Test with Reactance 
 
 When a converter is required automatically to deliver a con- 
 stant direct voltage, with a load subject to sudden changes, a 
 compound wound machine is used with a definite reactance 
 inserted between the converter and the line. Such reactances 
 must be tested with the machines for which they are designed. 
 A constant voltage is possible, since an alternating current pas- 
 sing through a reactance will increase the potential if leading, 
 and decrease it if lagging. By adjusting the shunt field so that 
 about 20 per cent lagging current flows at no load and the current 
 
 200 
 
at full load leads slightly, the strength of the series field can be 
 adjusted so as to give the same voltage at no load and full load. 
 A compound wound converter, running with reactance, must be 
 compounded like a direct current generator. Unless other specific 
 instructions are issued in reference to compounding, hold con- 
 stant the voltage of the alternator by which the converter 
 is driven. Adjust the shunt field to give the correct no-load 
 voltage, then, without touching the field rheostats, put on full 
 load and read the direct volts. If the machine over-compounds, 
 the series field is too great, and gives too much leading current. 
 In this case a shunt must be adjusted across the terminals of 
 the series winding to shunt a portion of the current. On this 
 compounding test, all readings are taken and adjustments made 
 as on a direct current generator without touching the field 
 rheostats after the no-load adjustment is made. 
 
 Pulsation Tests 
 
 Since the torque of a converter need only be great enough 
 to overcome that due to its own losses, it is very sensitive to 
 changes in line conditions, viz., excessive line drop or speed 
 changes of the driving unit. Line drop alone will start a machine 
 pulsating, in many cases. Once started the pulsation generally 
 increases rapidly, till the machine falls out of step or flashes 
 over. To prevent pulsation, copper or brass bridges are located 
 between the poles, which act as a short-circuited secondary 
 and oppose sudden changes of the input armature current. 
 Converters of new design are tested for pulsation by inserting a 
 resistance per phase, between them and the driving alternator. 
 The drop through this resistance corresponds to the line drop 
 which will probably occur in practice. Usually 15 per cent 
 drop is used. If two machines are tested together each machine 
 would have 15 per cent drop between it and the driving alternator 
 or there would be 30 per cent between the two machines as 
 shown in Fig. 96. 
 
 With the two machines running in synchronism self-excited 
 and with the fields adjusted to give minimum input, observe 
 the voltmeters on the d-c. end of the two machines. Any slight 
 pulsation will be shown by these instruments at once. Hold 
 the direct volts constant on one machine throughout the test. 
 With one field held at minimum input value, reduce the field 
 current in the other machine to about one-half minimum input 
 value. If no pulsation is noted, take a full set of readings on 
 both machines, then reduce the field current of the other machine 
 to one-half minimum input value, and watch for pulsation on 
 both machines which now take a heavy lagging current. Take 
 a full set of readings under these conditions. Next adjust 
 the field of the first machine again to the minimum input value, 
 watch for pulsation and take readings. With this field held at 
 minimum input, change the field of the other machine from 
 its value at one-half minimum input to twice the minimum 
 input value, observe and read. The other field is then brought 
 up to twice normal value, readings are taken and the effect of 
 
 201 
 
the heavy leading current in each machine noted. Leaving 
 one field over excited, weaken the other field so as to get half 
 minimum input, look for pulsation and take a full set of readings. 
 Next adjust both fields for minimum current and raise and lower 
 one field about once a second between the extreme values used 
 above and repeat this test for the other machine. If no pulsation 
 develops with the high line drop under these extreme conditions 
 the machines are satisfactory. 
 
 
 Dynamometer 
 Board 
 
 Alternator 
 
 A A 
 
 Resistance 
 
 Resistance. 
 
 Fig. 96 
 CONNECTIONS FOR PULSATION TEST 
 
 Input-Output Efficiency Test 
 
 Input-output tests on small machines are made with 
 the machine running as a converter, dead loaded on a 
 water box. Larger machines are tested in pairs, one 
 machine feeding back on the other with electrical loss supply. 
 The machines are wired exactly in a similar manner to that 
 used in a heat run (circulating current method) special atten- 
 tion being given the wiring to see that no unbalancing occurs 
 in either the a-c. or the d-c. circuits. On the machine running 
 as a converter, wattmeters are connected in the a-c. end, between 
 the converter and the transformers and preparation made for 
 reading d-c. armature and field current and volts. If current 
 transformers are used with the wattmeters, duplicate trans- 
 formers must be used in the other phases of the machine to 
 prevent unbalancing caused by the resistance and inductance 
 of the transformers. With the machine running in synchronism 
 at rated speed with zero load, and all meters connected, hold 
 constant the alternating volts impressed on the converter 
 and take careful readings of all instruments. Then read the 
 current and volts in each phase, as a check on the wiring and 
 balancing of all phases. Also carefully check all instruments 
 for stray fields. Any instruments so affected must be protected 
 by iron shields or their location changed. With full load, repeat 
 
 202 
 
the test for stray fields, since any instrument affected will give 
 misleading and erroneous results. With the no-load minimum 
 input field current held constant, carefully read the a-c. input, 
 as shown by the wattmeters, as a check on the no-load losses. 
 As efficiency is usually guaranteed at \i, 3^2, Z A, 1> M and 1^ 
 load, careful readings must be taken at these loads. Each time 
 the load is changed, the converter field excitation must be 
 changed to the minimum input value for that load. This is 
 shown when the sum of the wattmeter readings is exactly equal 
 to the kv-a. input. To obtain this condition every time usually 
 requires several trials and considerable time, so that an efficiency 
 test made in this way is more expensive than when made by 
 the separate loss method. The likelihood of error is also greater. 
 
 INVERTED CONVERTERS 
 
 The speed of a converter, running from the a-c. side, is deter- 
 mined by the line frequency. The same machine running as an 
 inverted converter and delivering alternating current operates 
 as a d-c. motor. Its speed depends upon the field excitation 
 and load, and it will deliver a variable frequency, particularly 
 if compound wound. When run inverted, a compound wound 
 machine should have its series field almost, if not entirely, 
 short-circuited when part of its load is inductive, since a lagging 
 alternating current will weaken the field and increase the speed, 
 sometimes causing a runaway. For this reason, care must 
 always be taken when running a converter inverted, to see that 
 sufficient field excitation has been obtained to prevent excessive 
 speed, particularly when another machine is operated as a 
 converter from the inverted machine. 
 
 SPLIT POLE CONVERTERS 
 
 The field poles of split pole converters consist of two or 
 more separate and independent parts each equipped with 
 its own field coil. The ratio of the converter is changed by 
 varying the relative strengths of the main and auxiliary wind- 
 ings. The transformers should never be connected delta primary 
 with diametral secondary because of the harmonic current 
 that may flow if this connection be used. The testing instruc- 
 tions will include, besides the regular tests to be made, the volts 
 to be held across the collector rings and the range through which 
 the direct volts are to be varied by means of the auxiliary field. 
 
 All preliminary tests are taken as for standard converters and 
 the following tests are modified according to instructions below. 
 
 Phase Characteristics 
 
 Phase characteristics should be taken under three different 
 conditions of excitation. 
 
 NO-LOAD PHASE CHARACTERISTICS 
 
 (a) Hold the direct volts constant and vary the main field 
 with the regulating and compensating fields unexcited. 
 
 (b) Hold the alternating volts specified in the testing 
 instructions and with the main field only, find the main field 
 
 203 
 
current for minimum input. (This may check with [a].) Set 
 the main field rheostat to give minimum input current as just 
 determined and vary the compensating field while using the 
 regulating field to maintain the direct volts constant at the 
 lowest limit. 
 
 (c) Same as (b) except it is taken at the highest limit of 
 direct volts. 
 
 NOTE. — In case there is no compensating winding take 
 curves corresponding to (b) and (c) by holding the direct volts 
 constant with the regulating field while varying the main field. 
 
 FULL LOAD PHASE CHARACTERISTICS 
 
 The full load phase characteristics should be taken in the 
 same manner as the no load, except that in all cases the current 
 in the d-c. end should be held at the value necessary to give the 
 rated output of the machine at the voltage on which the kilo- 
 watt rating is based. 
 
 Voltage Range Curves 
 
 Voltage range curves are taken by holding the impressed 
 volts constant and, with the main field rheostat set for minimum 
 input current as found in (a) of the phase characteristics varying 
 the current in the regulating field to obtain the specified range of 
 direct voltage. Minimum input current must at all times be 
 maintained by varying the compensating field. 
 
 NOTE. — In case there is no compensating winding two 
 curves should be taken. 
 
 (1) Holding the main field rheostat constant. (2) Holding 
 minimum input current by changing the main field rheostat. 
 
 Curves are plotted with direct volts line as ordinates and 
 amperes regulating field as abscissae. 
 
 Similar curves should be obtained for full load conditions. 
 
 Core Loss and Saturation 
 
 Two core loss tests are required to cover the various condi- 
 tions of operation. 
 
 (1) Vary the direct volts by means of the main field only 
 with the auxiliary field unexcited. This test is the same as for 
 a standard machine. 
 
 (2) Holding^ the alternating volts constant at the value 
 specified in the instructions and with the main field rheostats 
 in the position determined from (1) for obtaining the specified 
 alternating volts, vary the regulating and compensating wind- 
 ings to change the direct volts throughout the range. (It will 
 be found necessary to vary the compensating winding in order 
 to hold the specified alternating volts.) NOTE. — If there is no 
 compensating winding, change the main field rheostat to hold 
 the alternating volts constant. 
 
 Saturation curves should be taken under the same conditions 
 as core loss. 
 
 204 
 
Running Light Readings 
 
 Running light readings from the d-c. end should be taken 
 under three different conditions. 
 
 (a) Holding the specified alternating voltage using the 
 main field onlv, and allowing the direct volts to come what they 
 will. 
 
 (b) Holding the minimum direct volts and the specified 
 alternating volts by varying the regulating field, and varying 
 the compensating field to obtain correct speed. 
 
 (c) Taken in the same manner as (b) except at the maxi- 
 mum direct volts. 
 
 Heating Tests 
 
 The heat runs should be made by holding the specified 
 alternating voltage, varying the regulating field to obtain the 
 desired direct voltage and adjusting the compensating winding 
 to obtain minimum input. The main field rheostat should 
 remain in the position found in obtaining the specified alternating 
 voltage with normal current output and minimum current 
 input when the compensating and regulating fields are unexcited. 
 On those machines not equipped with compensating field, the 
 main field must be varied to obtain minimum input. 
 
 COMMUTATING POLE CONVERTERS 
 
 The brushes of the commutating pole converter should be 
 set on mechanical neutral for best commutation. This point is 
 located by placing the armature bars, which are painted red, 
 central with respect to a main pole, and then setting the brushes 
 so that the center of the brush comes over the center of the red 
 mark on the commutator as specified under "Commutating 
 Pole Generators" in Chapter 7. It sometimes may be necessary 
 to shift the brushes slightly forward to secure a falling voltage 
 characteristic under load. 
 
 When adjusting the commutating field on a converter, in 
 order to determine whether it has the proper field strength, 
 run the machine at full load or as near this value as possible, 
 and take the drop from the pigtail of one brush to various 
 points on the commutator under the brush. If the drop is 
 the same to all points under the brush the adjustment is cor- 
 rect, but if it is higher on the trailing side the commutating 
 field is weak and if higher on the leading side, the field is too 
 strong. 
 
 Most commutating pole machines have a brush raising device 
 to lift all except two pilot brushes from the commutator during 
 the period of starting from the a-c. end. This device should be 
 carefully examined to see that it operates satisfactorily, that 
 it does not bind, that it raises all the brushes (except the pilot 
 brushes) well off the commutator and that it allows all the 
 brushes to make proper contact on the commutator with plenty 
 of allowance for the wear of brushes. The pilot brushes are for 
 the purpose of getting field on the machine and correcting 
 reversed polarity if necessary. 
 
 205 
 
Converters with A-C. Boosters 
 
 Commutating pole converters which have an a-c. booster 
 are equipped with an auxiliary shunt winding on the commutat- 
 ing poles. The strength of this field is controlled by means 
 
 'echanica.Ho 
 Connected. 
 
 Fi e. /a /?h&osta.t 
 
 Fig. 97 
 
 CONNECTIONS OF A-C. BOOSTER FIELD AND AUXILIARY SHUNT 
 
 COMMUTATING FIELD WITH CONTROL FOR SYNCHRONOUS 
 
 CONVERTER HAVING COMMUTATING POLES AND 
 
 A-C. BOOSTER 
 
 of a double-dial rheostat, which is mechanically connected 
 and operated with the double-dial rheostat in the booster field, 
 and an auxiliary resistance which is divided into steps that are 
 
 206 
 
controlled by contactors. These contactors are set to operate 
 at various loads thus changing the resistance in the shunt 
 commutating field according to the load on the converter. 
 (See Fig. 97.) The double dial rheostat takes care of any change 
 in commutating field strength made necessary because of a 
 change of the direct voltage of the converter. 
 
 The contactor-controlled resistance is set for the maximum 
 value of auxiliary field which will give good commutation at 
 no load. The load is then increased to the maximum value which 
 can be carried with good commutation at this field strength. 
 The first contactor should be adjusted to close at this value 
 (which will be about 40 per cent normal load) and the auxiliary 
 field strength thus increased to the greatest value permissible 
 without sparking. The load should then be increased to the 
 maximum which will not cause sparking at this setting (which 
 will be about 85 per cent normal load) and the second contactor 
 adjusted to close at this point. The same operation should be 
 repeated for the other two contactors which should be set to 
 close at about 110 per cent and 130 per cent normal load. 
 
 The only phase characteristics which need be taken on this 
 type of machine are those with the booster field unexcited and 
 are the same as those described for standard converters. 
 
 The voltage range curves should be taken at no load and full 
 load with the alternating volts held constant and are similar 
 to those for split pole machines without compensating windings. 
 The booster field is used in place of the regulating field. 
 
 Core loss and saturation curves should be taken. 
 
 (a) With the main field of the converter excited (booster 
 not excited). 
 
 (b) With the booster field excited and the converter not 
 excited. 
 
 The alternating and direct voltage of the converter should 
 be read in each case. 
 
 Other tests should be taken as previouslv described. 
 MOTOR CONVERTERS 
 
 A motor converter consists of a standard synchronous con- 
 verter and an induction motor. The induction motor has a 
 wound rotor with taps brought out to a set of common rings 
 that take the place of the collector rings for both motor and 
 converter. The voltage of the induction motor rotor is the 
 alternating voltage of the converter. The advantage of the 
 motor converter is that high tension (up to 13,000 volts) may be 
 applied on the stator of the induction motor, the rotor delivering 
 low voltage to the converter. Hence the intervening bank of 
 transformers always necessary with a synchronous converter 
 are not required. No reduction of power-factor is caused by the 
 induction motor, since unity power-factor may be maintained 
 with the motor converter by proper adjustment of the field of 
 the synchronous converter. Caution should be observed when 
 when staiting a motor converter to see that it does not exceed 
 synchronous speed. This synchronous speed is always the syn- 
 chronous speed of a machine having a number of poles equal to 
 the sum of the number of poles on the synchronous converter 
 and induction motor forming the motor-converter. 
 
 207 
 
CHAPTER 12 
 
 INDUCTION MOTORS 
 
 The tests made on an Induction Motor either for Engineering 
 information, or for checking guarantees may be divided as 
 follows: Preliminary tests; commercial tests; heating tests; 
 special tests; input-output tests. 
 
 Preliminary test consists of air gap, resistance measure, and 
 inspection as contained in the instructions in Chapters 3 and 4 
 which should be carefully followed. Special measuring scales 
 are used in taking the air gap of Induction Motors, as noted 
 on page 83, Chapter 3. Great care should be used in taking 
 both the stationary and revolving gap measurements. Ordinarily 
 there should be as many points measured as there are openings 
 in the end shield. On machines equipped with pedestal bearings 
 at least eight equally spaced points should be taken. 
 
 Resistance measure is generally made between terminals. 
 On some machines the separate phases are each brought out to a 
 terminal block. Whenever the resistance is measured per phase 
 it should be clearly indicated on the record sheet. Quarter-phase 
 machines are usually measured between terminals 1-3 and 2-4. 
 Detailed descriptions of the apparatus and methods used in 
 resistance measurements are given in Chapter 2. When a motor 
 is delivered to test it bears a tag on which the resistance 
 between terminals as measured by the Armature Department, 
 is written. This value is generally accepted by the Testing 
 Department and the machine need not be re-measured except 
 when heat runs or special tests are to be made. All heat runs 
 and special tests should be preceded by a resistance measurement 
 taken when the machine is cold and a careful measurement by 
 thermometer of the machine windings. 
 
 Commercial Tests 
 
 Commercial tests consist of preliminary tests, excitation 
 readings, stationary impedance, and voltage ratio on Form M 
 and Form P motors. The excitation readings consist of taking 
 running light readings of volts and amperes with normal voltage 
 impressed on the stator. The windings of phase wound rotors 
 must be short circuited. Form L and Form P rotors should be 
 short-circuited by means of the short-circuiting switch provided 
 on the motor; Form M rotors should be short-circuited by con- 
 necting the brush-holders together with a short cable. The 
 brushes should be sanded to a good fit to reduce the -contact 
 resistance as much as possible. In starting, the voltage should 
 be applied gradually or in steps, the lowest being about one- 
 quarter of the normal voltage. The majority of motors should 
 start on one-fourth normal voltage with the rotor short-circuited. 
 The voltage necessary to start must be recorded. The bearings 
 must be watched carefully to detect any undue heating, especially 
 in the case of high speed machines. End play must be tried out, 
 both with and without voltage applied to the stator. A tachom- 
 eter reading of speed should be taken and recorded to show 
 
 208 
 
that the motor is running at the correct speed for the frequency 
 of the circuit used, and also as a rough check on the frequency of 
 the driving alternator. After the motor has been run for several 
 minutes to show up any defects the readings of volts and amperes 
 should be made and recorded. Care should be taken to detect 
 any unbalancing in the voltage or current in the different 
 phases. 
 
 Stationary Impedance consists of taking readings of volts 
 and amperes, at normal rated amperes, with the rotor short- 
 circuited and blocked with the clamping device furnished for 
 this purpose. On Form K motors, this value will be practically 
 the same for any position of the rotor. On motors having 
 phase wound rotors, it is necessary to vary the position of the 
 rotor, with respect to the stator, in order to obtain the max- 
 imum and minimum effects. Normal amperes is first obtained 
 with any convenient position of the rotor, and the corresponding 
 voltage is held constant during the shifting of the rotor position. 
 This voltage is generally found to be about one-fifth of the 
 rated voltage of the motor, a fact which will serve to detect 
 any gross error which might be made in testing. On Form L 
 motors, a reading must also be taken and recorded with the 
 resistance in. Close attention must be given to current and volt- 
 age balance on the different phases and much care must be used 
 to avoid applying excessive currents and damaging the winding. 
 
 Voltage ratio readings must be taken and recorded on all 
 Form M and Form P motors. This consists in applying normal 
 voltage to the stator winding, and measuring the voltage be- 
 tween rings on the rotor winding, the rotor being open-circuited 
 and held stationary. The primary exciting current must also 
 be read and recorded. 
 
 HEATING TESTS 
 
 Heating tests generally taken on Induction Motors may be 
 divided into actual load runs and equivalent load runs. 
 
 ACTUAL LOAD RUNS 
 
 The actual load runs may be sub-divided into normal load, 
 overload, crane motor, and intermittent heat runs. They are 
 usually made by belting or direct connecting the motor to a 
 d-c. shop generator and holding normal voltage and the speci- 
 fied current. The instructions in Chapter 4 relating to thermom- 
 eters should be followed carefully. Readings should be taken 
 every half hour on normal load runs, and every fifteen minutes 
 on overload and crane motor runs. 
 
 Crane motor heat runs are taken on motors designed for 
 intermittent service and are generally made holding normal 
 voltage and current for a half hour. In some cases the runs 
 extend over a period of one hour. Readings should be taken 
 every fifteen minutes. 
 
 Intermittent heat runs are usually made according to instruc- 
 tions from the Engineering Department. 
 
 The Induction Generator method is sometimes employed in 
 making load runs on Induction Motors. Two similar induction 
 
 209 
 
motors are belted together and run in parallel from the same 
 alternator which supplies the losses. See Fig. 98. In order to get 
 full load in both machines, the diameter of the pulleys must 
 differ by a percentage equal to double the full load per cent slip. 
 In starting, the switches A are closed and the motor allowed 
 to come up to speed, until the speed of the motor running as 
 a generator is above synchronism. The alternator field is 
 opened momentarily, while the switches B are closed. The 
 circuit in the alternator field is then closed again, and full 
 load current flows through the two machines. No changes in 
 
 Fig. 98 
 INDUCTION GENERATOR METHOD OF FEEDING BACK 
 
 load can be made without changing the pulley ratio and it is 
 absolutely necessary that this ratio be correct in order to obtain 
 full load. 
 
 Several modifications of this method are possible. The shafts 
 of the two machines may be direct connected or belted together 
 and one winding of the machine to act as the induction generator 
 be separately excited with either alternating or direct current 
 and the other winding connected to water boxes. In this 
 method the induction generator cannot be a Form K machine. 
 
 Another modification sometimes used is to wire the induction 
 generator to the synchronous motor of a motor-generator set 
 and load the set, the field of the synchronous motor being 
 adjusted to supply the exciting current for the induction gener- 
 ator. 
 
 Slip readings should be taken during all heat runs as des- 
 cribed on page 217. 
 
 EQUIVALENT LOAD RUNS 
 
 Equivalent load runs are generally made on large motors 
 which it would be difficult to load on account of the large 
 amount of power required. The heating due to iron losses is 
 obtained by running the motor light at normal voltage until 
 the temperatures of the various parts become constant, readings 
 being taken and recorded as in actual load heat runs. The heat- 
 
 210 
 
ing due to copper losses is obtained by running the motor under 
 partial load at a voltage less than normal, and holding normal 
 and overload currents. From the results obtained in these tests 
 the temperatures which would be obtained under actual load con- 
 ditions may be approximately determined. 
 
 SPECIAL TESTS 
 
 Special tests consist of excitation curves, impedance curves, 
 slip curve, stationary torque test and starting tests. The excita- 
 tion, impedance and slip curves are very important, since it is 
 from these curves that the data are taken for the calculation of 
 the characteristic curves of the induction motor. These curves 
 are generally accompanied by torque tests and occasionally 
 by starting tests. 
 
 Excitation Curves consist of a series of readings of volts, 
 amperes and watts, taken at different voltages when the motor 
 is running light, the frequency of the applied voltage remaining 
 constant. 
 
 The motor should be so located that all conditions affecting 
 its operation remain unchanged throughout the test. A solid 
 foundation is necessary to prevent vibration at full speed. The 
 driving alternator should be at least three-fourths of the kilo- 
 watt capacity of the motor. It should be driven by an endless 
 belt or by direct connection to its driving motor to avoid pulsa- 
 tions in the instrument readings. The transformers and other 
 apparatus must be connected so that the alternator is working 
 under normal conditions, since satisfactory wattmeter readings 
 cannot be obtained if the alternator is run too low on its satura- 
 tion curve. Transformers when used must be well balanced 
 and must not be forced beyond their voltage range. The alter- 
 nator used should have a sine waveform. 
 
 The testing table must be adapted for wattmeters. If the 
 voltage be too high for direct reading on the wattmeters and 
 voltmeters, multipliers or potential transformers must be con- 
 nected between the points measured and the instrument; similarly, 
 if the current be too high for direct reading, current transformers 
 must be used in the wattmeter and ammeter circuits. On 
 motors of less than 20 h.p., the potential lines must be attached 
 on the generator side of the testing table, since, if they are 
 attached to the motor side of the table or to the motor terminals, 
 the exciting current of the potential transformers passes through 
 the wattmeters. Although this current is small, it may be quite 
 an appreciable percentage of the exciting current of a small 
 motor, and the error involved may cause an abrupt break in 
 the curve whenever a potential transformer ratio is changed. 
 In the case of large motors, the exciting current of the potential 
 transformer is so small in comparison with that of the motor, 
 that the incidental errors are negligible. When multipliers are 
 used the above precautions may be disregarded since they are 
 non-inductive. On large motors the potential leads should be 
 connected to the motor terminals to eliminate the line drop in 
 switches and cables leading from the table to the motor. The 
 
 211 
 
current leads to the wattmeters and ammeters should be twisted 
 together throughout their length and should be free from sharp 
 bends or loops. All connections must be bright and clean. 
 The short-circuiting switches must always be closed when instru- 
 ments are changed. On circuits of more than 500 volts all 
 instruments must be discharged to eliminate static charge. 
 Do not ground the secondary circuits of the potential trans- 
 formers. The iron cases of oil-insulated potential transformers 
 should be connected together and grounded. Each man should 
 become thoroughly familiar with the characteristics and limi- 
 tations of instruments and transformers as explained in detail 
 in Chapter 2. 
 
 In starting up, the same precautions should be observed 
 as in commercial tests. After preliminary inspection of wiring, 
 bearings, etc., the line switches of the testing table should be 
 closed. Always see that the wattmeter short-circuiting switches 
 are closed in starting, or whenever a change is made in the 
 generator field excitation. The exciter field switch should be 
 closed, and the voltage brought up gradually until the motor 
 starts and reaches normal speed. The motor should then be 
 inspected to see that it is operating normally. The amperes 
 and volts in the different phases should be read, and any unbal- 
 ancing discovered and a few check readings made with a dif- 
 ferent set of instruments. The end play must be tried out, since 
 defective end play may cause friction losses, which would render 
 the excitation curves inaccurate. Small motors should be run 
 about 1^ hours and larger ones at least 2J^ hours, in order to 
 obtain constant friction, before beginning the curves. 
 
 In taking an excitation curve on a quarter-phase motor 
 both wattmeters read positive. However, in the case of a 
 three-phase motor, one wattmeter reads negatively through the 
 upper portion of the curve. It is, therefore, necessary to deter- 
 mine the algebraic signs of the readings of both wattmeters 
 before beginning the curve. Adjust the circuit so that both 
 wattmeters show a positive deflection on the scale, then open 
 one of the phases in which a wattmeter current coil is connected 
 and observe the other instrument. If the needle drops off the 
 scale below zero, the instrument reads negatively. If the needle 
 drops to some value above zero the reading is positive. This 
 process must then be repeated for determining the sign of the 
 other wattmeter. 
 
 In taking the data for the curves, the frequency of the 
 alternator must be held constant. A value of about 125 per cent 
 normal volts should be used for the first reading. Readings of 
 volts, amperes, watts, and frequency must be made and recorded. 
 The volts should then be decreased in steps to give 15 or 20 
 points on the curve, down to a value of 10 or 15 per cent normal 
 volts. At this point the motor becomes unstable. As readings 
 are taken on the descending curve, the instrument with the 
 negative sign will read less than the positive reading instrument, 
 and its readings fall off more rapidly, becoming less and less until 
 zero is reached and its sign changes. When it becomes positive 
 
 212 
 
its current leads must be interchanged. The two most important 
 points on the excitation curve are amperes and watts at normal 
 voltage, and friction watts. These readings determine the 
 core loss of the motor. Several readings only a few volts apart 
 
 §4000 
 75 
 
 3500 
 
 65 
 
 3000 
 
 55 
 
 2500 
 
 45 
 
 2000 
 
 35 
 
 1500 
 
 25 
 
 1000 
 
 15 
 
 500 
 
 
 -E t I 
 
 -Z tt 
 
 It 17 
 
 + t-r-t- 
 
 + 4 U 
 
 /Jr 
 
 MUhttsj 1/ 
 
 t-j 7 
 
 -E 4 1 t 
 
 t-f -t 
 
 / I/<t>Amps. J 
 
 
 // /aMmps. 
 
 # t 
 
 afHb^ V J 
 
 Jl f 
 
 -X 7 
 
 z y 
 
 A -J- 
 
 / Z 
 
 + y /- 
 
 T s t 
 
 a -^ 
 
 ■**- ^7 
 
 
 ==r y 
 
 S 
 
 
 ^ s> 
 
 ^=_->" 
 
 
 
 j 
 
 v 100 200 300 400 500 600 
 
 Vo/tS 
 
 Fig. 99 
 
 EXCITATION CURVES ON A 100 H.P., 6 POLE, 500 R.P.M., 440 VOLT, 
 FORM M, 3-PHASE INDUCTION MOTOR 
 
 should be taken on each side of normal voltage. The volts and 
 amperes in the different phases should be read at normal volts, 
 and at two or three other points in the curve as a check on the 
 phase balance of the motor. These readings should be recorded. 
 
 213 
 
As the lowest point on the curve is approached, a large number 
 of readings should be taken, since it is from these readings 
 that the friction watts of the motor are determined. In many 
 cases hunting begins at low voltage. This causes the wattmeter 
 needle to swing with a slow beat. Reliable readings can generally 
 be obtained between beats but care must be used to avoid 
 taking readings when the motor is accelerating or decelerating. 
 Bad cases of hunting are not numerous. 
 
 As a check on the three-phase curve, single- phase readings 
 of several points around normal volts should be taken on the 
 two phases in which the wattmeters are connected. Volts, 
 amperes and watts should be read as in the three-phase curve, 
 A few check readings should also be made with a different set 
 of instruments. Before shutting down, curves should be plotted 
 using volts as abscissae, and amperes and the algebraic sum of 
 the wattmeter readings, as ordinates. The single-phase 
 amperes are theoretically 1.73 times the three-phase or twice 
 the quarter-phase amperes. Practically, however, the single- 
 phase amperes have a value from 1.4 to 1.8 times the polyphase, 
 for either three-phase or quarter-phase motors. The single- 
 phase excitation watts generally come about 10 per cent higher 
 than the polyphase on account of higher PR losses, the iron 
 losses being practically the same whether the motor is running 
 single-phase or polyphase. The temperature of the laminations 
 should be recorded at the end of the test. 
 
 The calculation of the excitation curves is done in the Cal- 
 culating Room. The instrument readings are corrected by 
 means of the calibration curves furnished by the Calibrating 
 Laboratory. The data are then worked up, and the curves 
 plotted. The data of a calculated excitation test are shown on 
 Calculation Sheet No. 16. Fig. 99 shows a typical set of excita- 
 tion curves, plotted from this data. 
 
 Impedance Curves consist of a series of readings of volts, 
 amperes and watts, taken at different values of current, when 
 the rotor is blocked and short-circuited, the frequency of the 
 applied voltage being constant. The test table arrangement 
 is the same as that for the excitation curve. 
 
 The rotor of a squirrel cage (Form K) motor is a sym- 
 metrical bar winding; therefore, the impedance of the motor 
 is practically the same for any position of the rotor relative 
 to the stator. In Forms L, M, and P motors having 
 phase-wound rotors the impedance varies with different posi- 
 tions of the rotor relative to the stator. It is therefore neces- 
 sary to determine the rotor positions at which the impedance is 
 maximum and minimum so that the rotor may be blocked on 
 an average position for the impedance curves. For accomplish- 
 ing this, a position curve is taken. Before taking the position 
 and impedance curves, the rotor must be short-circuited. This 
 is accomplished in Forms L and P motors by means of 
 the short-circuiting switch and in the Form M motor either by a 
 short cable connected directly to the collector rings, or by short- 
 circuiting the brush-holders, using metallic brushes in order to 
 reduce the contact resistance to a minimum. 
 
 214 
 
Position Curve. In taking the position curve, an angular 
 distance should be marked off on the end shield, equivalent 
 to one-half of a pole pitch for quarter-phase motors, or two 
 thirds of a pole pitch for three-phase motors. This space should 
 then be pointed off into about ten equal parts. A pointer 
 should be attached to the motor shaft or pulley so that its 
 outer end will pass over the division marks. The pointer is first 
 set on position Xo. 1 and the rotor blocked so that it cannot 
 move from that position. The switches should then be closed 
 
 uv -■ 
 
 
 /34 J~ L 
 
 
 131 fY 
 
 
 -i 4 -^v 
 
 ,28 X -, h- 
 
 J 4^ t V 
 
 %m t v- f 4 
 
 I t t t 4 
 
 *\/?d -i I L — . 
 
 t /u 7 i t r 7 
 
 W t A 1 ± W 
 
 4 4 \4 
 
 mi 4 ^ t At 
 
 IZ0 Zt AT ^ 
 
 na h \t 
 
 118 eh 
 
 
 1 lb 
 
 1 M 
 
 I 2 3 4 5 6 7 8 9 
 /Position 
 Fig. 100 
 POSITION CURVE ON A 100 H.P., 500 R.P.M., 25 CYCLE, 
 440 VOLT, FORM M, 3-PHASE INDUCTION MOTOR 
 (Test Taken at 63 Volts) 
 and the impressed voltage increased gradually, until a value of 
 about normal amperes is obtained. Volts and amperes on all 
 three phases should be read and recorded to make certain that 
 there is no unbalancing on the different phases. Holding the 
 same volts as in position Xo. 1 the rotor should be turned until 
 the pointer is over position Xo. 2 where the amperes should 
 again be read. This is repeated on each of the succeeding posi- 
 tion?. A curve should then be plotted between position number 
 as abscissae, and amperes as ordinates (when this curve is 
 plotted for Engineering Data, the ordinates used are the 
 amperes at normal volts found by multiplying by the ratio 
 
 ,t \ ■ . ). The rotor is blocked for the Impedance 
 
 -oltage used in test/ * 
 
 Curve on the position which gives an average value of current. 
 
 See Fig. 100 and Calculation Sheet 17. 
 
 215 
 
 fe 
 
Impedance Curve 
 
 Having blocked the rotor in any convenient position, in the 
 case of a squirrel cage rotor, or on the average position as shown 
 
 S * r 
 
 1* 4 
 
 | | 7 
 
 ZdnS L- 
 
 340^ f- 
 
 8 3 
 
 7 
 
 7/7/7 1 
 
 i 
 
 7 7 
 
 t ■' *■ 
 
 7/T/7 ' / 
 
 Lk)U J y r 
 
 £ 7 / 
 
 f / 
 
 
 //C / .r 
 
 c \34>Watbs S34>JrnD y 
 
 J ' > 
 
 
 "' f- / 
 
 
 / J J //drfrnps 
 
 
 I4U f— ' Jr 
 
 ■x. i j X 
 
 tXXl 
 
 inn 1 / / /ft watts 
 
 IUU fry/ 
 
 2 ... J s n 
 
 
 £f) , J i 
 
 -XT 
 
 / -XT. 
 
 T \a 
 
 70 -XX 
 
 -XX 
 
 n n£*dL— 
 
 ' "0 10 ZO 50 4C 50 60 70 60 90 /00 //0 120 /30 
 
 Vo/ts 
 
 Fig. 101 
 
 IMPEDANCE CURVE ON A 100 H.P., 500 R.P.M., 25 CYCLE, 440 VOLT, 
 
 FORM M, 3-PHASE INDUCTION MOTOR 
 
 by the position curve in the case of a phase-wound rotor, the 
 impedance curve may now be taken. The readings of volts, 
 amperes and watts should be taken beginning at the lower part 
 
 216 
 
of the curve, the current readings increasing in steps until a 
 a value of 150 per cent normal amperes is reached. Up to this 
 point about 12 or 15 readings should be taken, special care being 
 used to get several good readings at and near normal amperes. 
 Above the 150 per cent normal ampere point the wattmeter read- 
 ings may be discontinued, the curve of volts and amperes alone 
 being extended with several points, to a value of 300 per cent 
 normal amperes. Great care must be used not to overheat the 
 motor windings. A set of phase-balance readings should be 
 taken at normal amperes. Single-phase check readings should 
 be made on the two phases in which the wattmeters are con- 
 nected, at a voltage equal to that necessary to obtain normal 
 amperes on the three-phase curve. The single-phase impedance 
 
 amperes should be times the three-phase at the same volt- 
 age. The single-phase impedance watts should be Y2 the three- 
 phase at the same voltage. In taking the curve data, the cur- 
 rent should not be held on the motor any longer than is neces- 
 sary to secure a reading. After each reading the exciter switch 
 should be opened until ready to take the next reading, thus 
 keeping the temperature of the motor more nearly uniform. 
 Final temperatures of the rotor conductors should be recorded. 
 
 Curves should be plotted using volts as abscissae, with 
 amperes and the algebraic sum of the watts as ordinates. The 
 volt-ampere curve is a straight line, curving slightly upward 
 on the higher values. Single-phase amperes are practically 
 equal to the polyphase, in the case of quarter-phase motors; or 
 about 86 per cent of the polyphase for three-phase motors. 
 Single-phase watts should be about one-half of the polyphase, 
 for either quarter-phase or three-phase motors. 
 
 The calculation of the impedance curves is done in the 
 Calculating Room. The data of a calculated impedance test 
 is shown on Calculation Sheet No. 19. Fig, 101 shows a typical 
 set of impedance curves, plotted from the data given there. 
 
 Slip Curve. There are several methods employed by the 
 Testing Department for measuring the slip of induction motors, 
 among which the following are the more important: First, by 
 means of a slip indicator; second, by means of an arc lamp 
 and revolving disk; third, by means of a voltmeter; and fourth, 
 by means of a revolution counter. 
 
 The method employing the slip indicator is the one most 
 commonly used. The construction and operation of this instru- 
 ment are described in detail in Chapter 2, page 27. 
 
 The arc light and revolving disk method is a good one but 
 it requires more time to set up the apparatus than does the slip 
 indicator method. A disk (see Fig. 102) having as many white 
 and as many black sectors as there are poles on the motor, is 
 attached to the shaft of the motor, so that it revolves with it. 
 This disk is illuminated by an alternating current arc lamp which 
 is operated from the same alternator as the motor. Assume 
 a six pole 60 cycle motor running at the synchronous speed 
 of 1200 r.p.m. or 20 revolutions per second. Then 20X6 or 120 
 
 217 
 
black sectors pass a stationary point on the circumference of the 
 disk, in one second. As the frequency is 60 cycles, the arc lamp 
 will give 120 maximum illuminations per second. The black 
 sectors, would therefore appear to be stationary. Practically, 
 the induction motor cannot run at synchronous speed, and the 
 slip, at each maximum illumination will cause each black sector 
 to lie a small angle behind that seen by the previous illumination. 
 These successive differences in position appear as sectors 
 rotating backwards, which can be followed by the eye. The 
 difference between the actual speed and the synchronous speed 
 of the motor can be counted. 
 
 Fig. 102 
 DISK FOR MEASURING SLIP OF SIX-POLE MOTOR 
 
 The voltmeter method affords a very accurate and con- 
 venient scheme for measuring the slip of motors having collector 
 rings. The alternating voltage drop across the brushes is read 
 by means of a low reading d-c. voltmeter. Every time the 
 rotor slips an angular distance of two poles behind the synchro- 
 nous revolving field of the stator, a complete voltage cycle is 
 generated in the rotor winding. The d-c. voltmeter will be 
 deflected in a positive direction every alternate half wave or 
 once everjr cycle. Therefore, by counting the number of positive 
 beats per minute of the voltmeter and dividing this value by 
 one half the number of poles, the slip of the motor is obtained 
 in revolutions per minute. 
 
 The method employing^ a revolution counter is generally 
 used in the case of high speed machines where it is not possible 
 to measure the slip by any of the methods above described. It 
 consists in reading the number of revolutions of the rotor for 
 a known interval of time by means of a revolution counter. The 
 difference between the speed thus measured, and the synchro- 
 nous speed, gives the slip of the motor in rev. per min. Several 
 readings should be taken and averaged, when this method is 
 employed. 
 
 In all of the foregoing methods for taking slip, it is very neces- 
 sary that the load and impressed voltage on the motor, and the 
 
 218 
 
frequency of the driving alternator, remain constant while the 
 readings are taken and in each case the speed must be checked with 
 a speed counter. 
 
 Slip readings must always accompany heat runs. When 
 special tests are made, a slip curve should always be taken. 
 This curve must have readings at no load, and at 50, 75, 100 
 
 
 
 > 
 
 
 
 t J 
 
 
 
 1 
 
 
 
 - T 7 
 
 " 
 
 
 y 
 
 
 
 ZaZ' 
 
 
 
 ti Z 
 
 
 
 - / 
 
 
 
 f 
 
 J 
 
 
 
 / 
 
 
 I 
 
 t 
 
 
 
 
 
 / 
 
 _ 
 
 
 ! / 
 
 
 
 y 
 
 
 
 / 
 
 
 
 / 
 
 
 
 T 
 
 
 
 / 
 
 
 
 I 
 
 
 
 f 
 
 
 
 / 
 
 
 
 ZL 
 
 
 
 z_ 
 
 
 y 
 
 
 
 ^t 
 
 
 
 7T_ 
 
 
 
 AO 
 
 m 120 160 
 
 » 200 220 
 
 Fig. 103 
 
 SLIP CURVE ON A 100 H.P., 500 R.P.M., 25 CYCLE, 440 VOLT, 
 
 FORM M, 3-PHASE INDUCTION MOTOR 
 
 and 125 per cent of normal load amperes. Sometimes it is not 
 possible to hold normal voltage on the motor on account of the 
 large amount of power necessary. In such cases the highest 
 obtainable voltage should be held and the voltage and current 
 should be reduced from normal in the same proportion. The 
 motor should always be heated to its normal running tempera- 
 ture at the time the slip readings are taken. All readings of 
 volts, amperes, and slip must be recorded. A typical calculation 
 
 219 
 
of a slip curve may be found on Calculation Sheet No. 18. 
 Fig. 103 shows a slip curve plotted from the data given. 
 
 Stationary Torque Tests. Two methods are employed for 
 measuring stationary torque, one in which a spring balance is used, 
 the other in which a special torque indicator is used, each in con- 
 nection with a lever arm attached to the shaft. The first method 
 applies to motors having squirrel cage rotors, in which the torque 
 is practically constant for varying positions of the rotor relative 
 to the stator. The second method is used on motors having 
 phase-wound rotors, in which the torque is not constant for all 
 positions of the rotor. 
 
 T S 
 
 Fig. 104 
 MEASUREMENT OF TORQUE BY MEANS OF SPRING BALANCE 
 
 In the first method the lever is clamped to the pulley or 
 shaft as shown in Fig. 104. The size and length of the lever 
 depends on the rating of the motor, the lever and spring balance 
 being chosen to give a maximum reading at about % of the 
 
 capacity of the balance used. Torque at 1 ft. radius = — 
 
 In estimating the length of lever needed, allowance should be 
 made for at least 175 per cent of full load torque. The balance and 
 length of lever L should be chosen to make ( W-\- F-\- T) (see below) 
 equal to at least twice (W+F). Let the point of attachment to 
 the lever be at X. Then XF = the length of the lever arm. On 
 the frame of the motor, a mark should be made at M, correspond- 
 ing to the position of the pointer P, when the distances TX and 
 SY are equal. If the weight of the lever is not sufficient to over- 
 come the friction of the bearings and allow it to turn downward 
 of its own weight, attach the additional weight, W. Open all 
 line switches, thus doing away with any torque effect resulting 
 from residual magnetism of the alternator field. By means of 
 a suitable windlass, raise the lever slowly, pulling vertically 
 on the spring balance H. As the pointer passes the mark M 
 read the tension as indicated by the balance. Call this reading 
 (W-{-F), W being the force due to the weight of the lever and F 
 
 220 
 
the force due to bearing friction of the motor. Raise the lever 
 until the pointer is some distance beyond M, then lower it slowly 
 allowing the force of gravity to pull it toward the floor. When 
 the pointer passes the mark M, the spring balance should again 
 be read. Call this reading (W — F). The lever should be moved 
 as steadily as possible, otherwise the tension indicated by the 
 spring balance will fluctuate. Several readings should be taken 
 as described above. 
 
 Now close the line switches and bring up the line current 
 gradually to a value of 200 per cent normal amperes. In so 
 doing, watch the motor carefully to see that it does not tend to 
 turn in the wrong direction. Take readings in the same manner 
 as that just described. Call the reading taken as the lever is 
 raised (W+F+T) t and that taken as it is lowered (W—F+T), 
 T being the force due to the stationary torque of the motor. 
 The readings should be recorded as follows: 
 
 Volts Amperes (W+F) (W-F) (W+F+T) (W-F+T) T. 
 Solving for the value of T, and knowing the length of the lever 
 arm in feet, L, the stationary torque is calculated from the formula 
 
 Stations To rqU e=(^L^y Xi xr 
 
 Care must be taken to see that the motor does not overheat. 
 To get reliable readings the frequencv of the alternator must 
 be held constant. If any variation of (W+F+T) and W-F+T) 
 should occur with change of rotor position, the maximum and 
 minimum values should be recorded. As a check on the readings 
 taken, the lever should be loosened and the rotor turned to a 
 different position relative to the stator. Here the lever should be 
 again clamped to the shaft or pulleys and readings of (W+F+T) 
 and (W—F+ T) taken. This should be repeated for several dif- 
 ferent positions. The temperature of the rotor conductors must 
 be taken and recorded at the end of the test. 
 
 The second method of taking torque applies to Forms L, M 
 and P motors having phase- wound rotors. The data is taken by 
 mean of a special torque indicator described in detail in Chapter 2, 
 page 29. The indicator must be fastened to the lever arm so 
 that the rope pulls vertically upward on the instrument. The 
 cord used should have no tendency to twist when decreasing 
 in length. In taking the torque cards, the diagram need cover 
 but one pole-phase, to represent a complete torque cycle of the 
 motor. The purpose of the indicator is to show the minimum 
 torque effect exerted by the motor. 
 
 On Form L motors two torque cards should be taken; one 
 with the secondary starting resistance in, the other with it all 
 cut out. A current of one-half normal amperes should be held 
 for the reading with resistance in. Normal amperes should 
 be held for the card taken with the resistance cut out. The 
 motor should be carefully watched to see that the secondary 
 resistance does not become too hot. Temperatures of the rotor 
 must be recorded. 
 
 On Form M and Form P motors, torque cards are generally 
 taken with different values of secondary resistance. Sometimes 
 
 221 
 
the secondary resistance is changed by changing the leads to 
 the grids, and often by means of a controller. Whenever the 
 test is made with a controller, a torque card should be taken 
 for each controller position. The current held for these cards 
 should be as near normal as the heating of the motor and grids 
 will permit. The grids must not be allowed to become too hot, 
 since this would lead to unreliable results, on account of the 
 
 600 
 
 
 
 
 
 
 
 _, 
 
 
 
 s 
 
 i 
 
 - 
 
 
 
 \ 
 
 
 
 
 ^ 
 
 
 
 
 \ 
 
 
 ^20 
 
 
 j 
 
 
 &,„ 1 -T~ 
 
 
 
 
 9//p 
 
 
 
 
 
 
 
 r 
 
 
 
 - Power Factor - 
 
 / 
 
 
 90 ?»- = -^- = - 
 
 
 ^, 
 
 
 CN / ^ 
 
 X- ^ 
 
 te s 
 
 
 §80 -f y 
 
 7 
 
 >? 
 
 
 ^7/7-T 7- 
 
 y \— = 
 
 "*\J 
 
 
 fl 4 
 
 S A 
 
 J 
 
 
 \nt t 
 
 -,* ~ 
 
 '* 
 
 
 it h 
 
 s 
 
 
 
 \wtl 
 
 ^ 
 
 
 
 \50 —t 
 
 ^ 
 
 
 
 % T 
 
 s^ 
 
 
 
 ^ - 
 
 3i^ 
 
 
 
 
 n 
 
 
 
 Z 30 ! MP 
 
 
 
 
 %mt ^ 
 
 
 
 
 \^w ^**~ 
 
 
 ' 
 
 
 % -<*^ 
 
 
 
 
 
 
 
 
 n 
 
 
 
 
 60 
 
 IZO 
 
 160 ZOO Z40 
 
 nroutput 
 
 Z80 
 
 500 
 
 400 \ 
 
 i 
 
 3Z0 360 ' 
 
 Fig. 105 
 
 CHARACTERISTIC CURVES OF A 100 H.P., 500 R.P.M., 25 CYCLE, 
 
 440 VOLT, FORM M, 3-PHASE INDUCTION MOTOR 
 
 rapid change in resistance with change of temperature. Tempera- 
 tures of the rotor and grids should be recorded for each card 
 taken. Calculation Sheet 22 shows the results of this test 
 
 Starting tests are closely associated with the torque tests 
 just described. They are generally taken according to instruc- 
 tions given by the Engineering Department. 
 
 Characteristic curves of the Induction Motor are calculated 
 from the data obtained from the special tests. The data of a 
 calculation are shown on pages 439 to 445 and Calculation 
 Sheets 20 and 21. The corresponding characteristic curves are 
 given in Fig. 105. 
 
 The data used in the calculation are taken from the excitation 
 curves (Fig. 99), the Impedance Curves (Fig. 101) and the slip 
 curve (Fig. 103). 
 
 222 
 
COMPLETE TESTS consist of normal and overload heat runs 
 and special tests. 
 
 SPECIAL OVERLOAD HEAT RUN consists of bringing the machine 
 to normal load temperatures, then applying 50% overload for 
 two hours and recording temperatures, then applying 25% over- 
 load until constant temperatures are reached and recording 
 temperatures. 
 
 LONG COMMERCIAL TEST consists of taking equivalent load 
 heat runs, readings of excitation and stationary impedance. 
 
 GENERAL TESTS consist of taking excitation and impedance 
 tests with wattmeters, single-phase, at points near normal volt- 
 age and normal current respectively. 
 
 Fig. 106 
 
 DIAGRAM OF APPARATUS USED IN TAKING INPUT-OUTPUT BY 
 
 THE STRING BRAKE METHOD 
 
 STANDARD EFFICIENCY AND POWER-FACTOR TESTS consist 
 of calculating from general or special tests the efficiency and 
 power-factor at any load. 
 
 INPUT-OUTPUT "EFFICIENCY AND POWER- FACTOR TESTS con- 
 sist of determining the efficiency and power-factor directly by the 
 input-output method with wattmeters. 
 
 They can be made either by the "String Brake" or "Electri- 
 cal Load" methods. Neither of these methods is particularly 
 accurate nor are they recommended. In certain cases, however, 
 these tests are made on Induction Motors. 
 
 String Brake Method 
 
 In Fig. 106 L is a lever or scale beam suspended at the point 
 ,Y. From T the small platform A is suspended, on which cali- 
 brated weights are placed. P is a flat faced pulley on the shaft 
 of the motor running in the direction shown by the arrow, 
 i.e., toward the lever L. One end of a small rope is attached 
 at B, which is wound one or more times around the pulley. 
 The other end is made fast to a spring balance G. A strip 
 bearing a mark is located at K so that when the point of the 
 lever L comes opposite to the mark, the lever is in a horizontal 
 position at an angle of 90 degrees to the force exerted by the 
 pulley. 
 
 223 
 
Since the stress along a rope is transmitted through its 
 center, adjust the brake until the points M and N are a distance 
 apart equal to the diameter of the pulley plus the diameter 
 of the rope, one-half the diameter of the rope being added to 
 each side of the pulley. This adjustment must be carefully 
 made and care taken to see that nothing moves to throw the 
 brake out of line or proper adjustment. When ready, slip one 
 turn of the rope off the pulley but leave it attached at B and G, 
 then balance the lever until the pointer on the end comes to rest 
 at the mark K. This balancing of L must be repeated each time 
 the rope is changed. 
 
 The motor should be run light for at least one hour before 
 the test proper is commenced, so that friction may become 
 constant. Since speed is one of the important factors in the 
 output of the motor it should be taken very carefully. 
 
 Running light readings should now be taken on the motor. 
 The voltage impressed on the motor should be held constant 
 as well as the impressed frequency. Attach a small weight 
 to the spring balance to give enough tension on the spring for 
 a reading on the balance of a quarter or half a pound. This 
 "no load" scale reading must be recorded and subtracted 
 from all subsequent readings taken. 
 
 Put a small weight on A and pull up on the spring balance 
 G until the pointer on lever L reaches K. Then when the motor 
 volts and speed of the generator are normal and all meters 
 are steady, read and record volts, amperes, watts, weights on 
 A, spring balance reading and speed given by the tachometer. 
 A reading should also be taken of the slip. Add more weight 
 to A and take another reading, continuing in this manner until 
 the breakdown load of the motor is reached. For an induc- 
 tion motor the readings should be recorded in the following 
 manner: 
 
 Volts Amps. 
 
 + Watts -Watts 
 
 Weight Tension 
 on A on balance 
 
 Speed 
 Slip of 
 Motor 
 
 A rope of small diameter gives better results than a larger 
 one, even though it may require more time to make the tests 
 on account of having to renew it more frequently. On motors 
 up to 20 h.p. a }/i in. oiled hemp rope is best and a Y2 in. rope 
 can be used up to 50 h.p. The rope will last longer, usually, 
 if doubled and two strands used in parallel. The rope turns 
 around the pulley should all lie closely and evenly together 
 on the face of the pulley. The tension read on the balance 
 G will vary with the temperature of the rope and may differ 
 widely with different loads. 
 
 The additional weight put on A each time should be such 
 as to give from fifteen to twenty readings between no load 
 and breakdown. 
 
 When the breakdown point has been reached and complete 
 readings taken and recorded the diameter of the pulley should 
 be carefully measured. 
 
 224 
 
(Weight on A ) — (tension on balance) -("no load ' ' reading on 
 
 balance) = actual load in pounds = P. 
 
 (Normal speed) —(slip) = actual speed of motor. 
 
 R = (Radius of pulley in inches) +(3^ diameter of rope.) 
 
 5 = Speed in revolutions per minute. 
 
 _, , . Watts 
 
 Power-iactor = 77- 
 
 Then H.P. 
 
 l-RXPXS 
 
 Volts Xamps. 
 
 12X33,000 
 
 _™ . H.P. output X746 
 
 Efficiency = =r— — : 
 
 \\ atts input 
 
 When making any special test, the tester should see that 
 
 the tests check among themselves before handing them in. 
 
 Efficiency by the "Electrical Load" Method 
 
 Consider Fig. 107; let if be the motor and L the load machine. 
 This should be of about an equal capacity and be belted to 
 
 rfies/stonce 
 
 To Measuring 
 Instruments 
 and l/'ne 
 
 To Water Box 
 orSu/tati/e Motor 
 
 Source of Current 
 
 Fig. 107 
 
 CONNECTIONS FOR MEASURING INPUT-OUTPUT BY 
 
 "ELECTRICAL LOAD" 
 
 the motor M. It should be a direct current machine, and 
 must be separately excited from a suitable source of energy. 
 
 To take the efficiency test, connect M so that the total 
 input can be obtained. Separately excite the field of L, con- 
 necting an ammeter and a variable resistance in circuit. Connect 
 the armature of L to a water-box or a motor the load of which 
 can be varied, placing an ammeter in the circuit and a voltmeter 
 across the brush terminals. If the test involves a considerable 
 range of speeds, run M over that range, and hold the field current 
 of L constant, its value being such that the speeds or loads 
 required for M can be obtained. 
 
 Having made the necessary connections, etc., keep the field 
 current of L constant at its predetermined values. Vary the 
 load on L by changing the water resistance or the load on the 
 
 225 
 
motor to which it is connected, to suit the testing conditions 
 required on M. The efficiency of M may be required for a 
 series of speeds or loads. Read the input and speed of M, 
 and the volts and amperes of L, keeping the field of L constant 
 and noting its value. The "counter torque" must now be 
 obtained to complete the calculations. 
 
 To obtain this, disconnect M, connect L to a source of 
 current which can be varied so as to give L different speeds, 
 keeping L separately excited. Run L as a motor driving M, 
 keeping the field current of L constant with the same value it 
 had when L was used as a generator. 
 
 Vary the speed of L so that the speed of M can be varied 
 slightly below its previous minimum speed to slightly above 
 its maximum speed. Take a number of readings at varying 
 speeds, reading volts and amperes input of L and speeds of L 
 and M. If the electrical efficiency alone is desired (case A), 
 sufficient readings have been taken. If the commercial efficiency 
 is desired (Case B), take off the belt from L, and run it light 
 as a motor. Vary its speed from slightly below to slightly 
 above the speeds used before when running as a motor, and 
 take a number of readings at different speeds, reading volts 
 and amperes input and speed, separately exciting L, with the 
 same current used in the two previous cases. The necessary 
 readings are now complete for calculating the efficiency. 
 
 Case A 
 
 Let Wm be the total input of M. 
 
 Let Wl be the product of volts and amperes read for L. 
 
 Let Fm be M's friction, windage, etc. 
 
 Let Fl be L's friction, windage, etc. 
 
 Divide the belt friction equally between L and M including 
 this in Fm and F/. 
 
 Let R be the hot resistance of Us armature, which must be 
 measured. 
 
 Let / be the current in L's armature. 
 
 Then electrical efficiency = ==. where CT is the 
 
 mechanical losses in L and M and the belt loss. 
 Case B 
 
 Commercial efficiency = == where CT is the 
 
 mechanical losses of L including belt loss. 
 
 In running the counter torque curves, the field of L must 
 be held constant throughout, and readings must not be taken 
 when accelerating. 
 
 HIGH POTENTIAL TESTS should be taken on all induction 
 motors as called for in the Engineering Instructions. 
 
 226 
 
CHAPTER 13 
 
 STEAM TURBINES 
 
 Since the horizontal type of turbine has almost entirely sup- 
 planted the vertical type, the following instructions and illustra- 
 tions will refer principally to the horizontal machines. How- 
 ever, the work of operating and testing is practically the same 
 for both types, except in certain features which will be dealt 
 with separately, and the instructions may, in general, be con- 
 sidered as applying to both types. 
 
 Nomenclature 
 
 Due to the radical differences in construction of the steam 
 turbine from that of any other prime mover, there are many 
 parts more or less unfamiliar to the average engineer. To 
 secure uniformity in the designation of parts, thus avoiding 
 any uncertainty and unnecessary cTelay, Figs. 108 and 109 should 
 be carefully studied until thoroughly familiar. 
 
 The number of stages of both vertical and horizontal machines 
 is indicated by the following form letters. 
 
 Xo. of 
 Stages 
 
 Vertical 
 
 Horizontal 
 
 Xo. of 
 Stages 
 
 Vertical 
 
 Horizontal 
 
 1 
 
 
 A 
 
 7 
 
 M 
 
 P 
 
 2 
 
 B 
 
 C 
 
 8 
 
 Q 
 
 R 
 
 3 
 
 D 
 
 E 
 
 9 
 
 S 
 
 T 
 
 4 
 
 F 
 
 G 
 
 10 
 
 u 
 
 W 
 
 5 
 
 H 
 
 J 
 
 11 
 
 
 AA 
 
 6 
 
 K 
 
 L 
 
 12 
 
 BB 
 
 CC 
 
 Generators are indicated thus: 
 
 Type 
 
 Form 
 
 ATB Vertical 
 ATB Horizontal 
 CC Horizontal 
 
 T 
 HT 
 
 T 
 
 Tests 
 
 Tests on a steam turbine may be divided into two classes, 
 Commercial Tests and Special Tests. 
 
 For commercial tests the turbine is assembled in Building 
 No. 60, and is operated non-condensing at practically no load, 
 and without regard to any definite steam pressure or super- 
 heat. The tests consist of dynamic balance, adjustment of 
 operating and emergency governors, and the inspection of the 
 
 227 
 
Fig. 108 
 VERTICAL TURBINE AND GENERATOR 
 
 228 
 
PARTS OF VERTICAL CURTIS TURBINE AND 
 GENERATOR (See Fig. 108) 
 
 1 Condenser base 
 
 2 Intermediate holder 
 
 3 Turbine head 
 
 4 Steam chest 
 
 5 First stage nozzle 
 
 6 Operating valve 
 
 7 Generator stool 
 
 8 Coupling 
 
 9 Ends of field coils 
 
 10 Field core 
 
 11 Armature core 
 
 12 Armature spider 
 
 13 Armature coils 
 
 14 Coil supporting rings 
 
 15 Ventilating fan 
 
 16 Top bearing bracket 
 
 17 Top bearing 
 
 18 Collector and brush-holder 
 
 19 Operating governor 
 
 20 Governor dome 
 
 21 Governor beam 
 
 21 Governor beam 
 
 22 Governor rod 
 
 23 Governor dome stool 
 
 24 Ventilating hood 
 
 25 Mid bearing cap 
 
 26 Mid bearing 
 
 27 Pilot valve chest 
 
 28 Hydraulic cylinder 
 
 29 Head end carbon packing rings 
 
 30 First stage wheel 
 
 31 Exhaust end carbon packing rings 
 
 32 Packing ring dome 
 
 33 Guide bearing 
 
 34 Step bearing 
 
 35 Intermediate buckets 
 
 36 Nozzle diaphragm 
 
 37 Cam shaft 
 
 38 Emergency governor 
 
 39 Shaft 
 
 40 Field spider 
 
 229 
 
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 231 
 
unit, complete with its generator, for proper assembly and 
 satisfactory mechanical and electrical operation. All machines 
 must be assembled complete in all details and pass inspection 
 before leaving the factory. 
 
 Special Tests include in addition to commercial tests, steam 
 consumption and efficiency tests. For this purpose machines 
 are set up and run in Building No. 61, where provision is made 
 for obtaining any desired steam pressure, superheat, and vacuum 
 and for loading on water boxes. 
 
 Steam, Exhaust and Oil Piping 
 
 For the commercial tests in Building No. 60, steam is pipe 
 from the Power Station in Building No. 61 through two 12 inch 
 mains. These mains enter Building No. 60 at the front of the 
 building and are carried overhead to the testing section. One 
 main runs along the test gallery and then enters a duct where it 
 connects with the other main which has been brought down on 
 posts nearer the side of the building. Through the duct the 
 main is brought around to the front of the test floor. Taps are 
 made to the main at each test stand. At the points where the 
 steam mains enter the test, are located in each main electrically 
 operated valves. The valves are provided with controlling 
 switches located at easily accessible points about the test floor 
 and gallery. These valves are for emergency use only. It must 
 be remembered that they control the steam for all pressure pumps 
 as well as steam for the turbines, hence must be used only as a 
 last resort. All men should become familiar with their location 
 and method of operation. Two main exhaust lines are provided. 
 They run under the gallery and across the test floor at the upper 
 end of the test. The upper main leads to the atmosphere, and 
 also to the factory heating system. This main may be connected 
 directly or through lateral sub-mains to any stand on the test 
 floor. 
 
 The lower main leads to a 6700 sq. ft. Worthington con- 
 denser located in a pit under the gallery, and is available for 
 use on about half of the test stands. Machines to be loaded 
 are connected to this main, but through a header provided with 
 valves by means of which the machine may also be connected to 
 the atmospheric main. The exhaust headers are also provided 
 with drains, and these may be connected with the condenser or 
 the atmosphere as occasion demands. 
 
 There are four pressure oil lines. One line known as the 
 "small accumulator" line, has connections at every stand on 
 the test floor. The small accumulator is located in the small 
 pump pit and maintains a pressure of about 125 lb. per sq. 
 in. The object of the accumulator is to reduce the pulsation 
 in the line due to the stroke of the pumps, and also to hold a 
 small reserve of oil under pressure long enough to allow a change 
 of pumps in case of a break down. This pressure line is used 
 on the oiling system and the governor valve hydraulic mecha- 
 nism of all vertical machines, and on the oiling system of hori- 
 zontal machines not provided with an auxiliary steam pump 
 
 232 
 
 . 
 
until such time as they may be ready to have their gear pumps 
 assembled. 
 
 The other three lines can be connected only to the testing 
 stands on that section of the floor used for vertical machines. 
 Of these lines, one is the "step" or "large accumulator" line, 
 and supplies oil at a pressure of 1150 lb. per sq. in. for use on 
 step bearings. The large accumulator is located in a separate 
 pit with the step pumps, and is used for the same purpose as 
 the small accumulator on the low pressure line. 
 
 The remaining two lines are known as the " variable pressure " 
 lines and are not connected to an accumulator, but by means 
 of adjustable relief valves may be operated at any pressure 
 desired. They may be used on water pressure if necessary to 
 supply a water step bearing. All oil is drained back into a 
 common supply tank located in one of the pump pits. All 
 steam piping is under the supervision of one man, not a test 
 man, who will take care of the opening and closing of all steam 
 valves, except the valve nearest the machines under test. This 
 last valve, that is, the valve controlling a single machine, will 
 be operated by the man in charge of the tests on the machine. 
 The test man will be responsible for the exhaust valves. 
 
 The oil system, pumps and condensers are in charge of a 
 pump man who will take care of all valves except those con- 
 necting directly with the machines under test. 
 
 Instruments 
 
 With the exception of electrical instruments, transformers, 
 and thermometers, all instruments used on turbine test, such as 
 gauges, tachometers, air-measuring devices, etc., are kept in the 
 turbine test supply cupboards in charge of the pumpman. They 
 are given out on receipt in the same way as instruments at the 
 Instrument Rooms. 
 
 Special Instructions 
 
 In addition to instructions given in this book, there will 
 be found further written instructions in a folder on the shelf 
 near the door of the turbine test office. These written instruc- 
 tions take up some matters more in detail than would be desir- 
 able here, and also give special instructions which are subject 
 to change at intervals. Hence this folder should be consulted 
 frequently. 
 
 Preparing Machines for Test 
 
 When a machine is first delivered to the Testing Depart- 
 ment the turbine only is assembled and made ready for wheel 
 balance. Considering a horizontal machine, the first step is to 
 test out the cooling coils in the bearings for water leaks. See 
 Fig.110. 
 
 Water should be turned on and the oil drains from the bear- 
 ings watched for indications of water which might leak through 
 inside the bearings. 
 
 233 
 
Fig. 110 
 
 BEARING (WATER COOLED, HORIZONTAL TURBINES) 
 
 1 Top half bearing 
 
 2 Bottom half bearing 
 
 3 Cooling coil 
 
 4 Retaining clip for (3) 
 
 5 Terminal block for (3) 
 
 6 Oil feed inlet 
 
 7 Oil guard for bearing shell 
 
 8 End packing ring for bearing standard 
 
 9 Oil deflector ring 
 
 234 
 
Fig. Ill 
 
 ADJUSTABLE REDUCING BAFFLER FOR REGULATING 
 BEARING PRESSURES (HORIZONTAL TURBINES) 
 
 1 Reducing baffler frame 
 
 2 Reducing baffler plug 
 
 3 Stuffing gland for (1) 
 
 4 Nut for (3) 
 
 5 Handwheel for (2) 
 
 6 Support for packing 
 
 7 Nut for (5) 
 
 8 Pipe plug for (1) 
 
 Any trace of water escaping into the oiling system should be 
 reported at once, and corrected before proceeding further. If, 
 however, there is no apparent leakage, the oil tank may be 
 filled, or oil turned on from the low pressure test system. It 
 is only on such machines as are not equipped with an auxiliary 
 steam pump that the department oil system is used, and then 
 only during balance work. The auxiliary steam pump, when 
 used, must be provided with a lubricator which must be in 
 operation whenever the pump is working. 
 
 With pressure on the oiling system, look over the machine 
 for leaks in the piping, and if all right, set the pressure at 15 
 to 20 pounds by means of the adjustable baffler shown in Fig. 
 111. 
 
 Before turning steam into a machine each bearing must be 
 inspected for oil flow. It is not enough to inspect the pressure 
 gauge only, as one bearing may have its flow entirely cut off 
 and still the gauge would read properly. The proper amount 
 of cooling water to be used on the bearings is better ascertained 
 after the machine has been run at normal speed a short time. 
 The quantity, which is adjustable at each bearing, should be 
 such that the water is lukewarm as it leaves the bearing. Using 
 a larger quantity is wasteful, and unnecessary. 
 
 The oiling system of the vertical machine differs from that 
 of the horizontal machine in several respects. Oil pressure is 
 always supplied from the shop system, and the flow to each 
 
 235 
 
S/yM '//o/6 » 
 £ear//?y 
 
 Fig. 112 
 STEP BEARING 
 
 236 
 
DETAILS OF STEP BEARING (Fig. 112) 
 
 1 Collar for supporting rotor when removing bearing 
 
 2 Step guide bearing with holding bolts and keepers 
 
 3 Guide pin 
 
 4 Key for driving (5), with screws 
 
 5 Revolving step plate 
 
 6 Plug for (5) 
 
 7 Bolts and keepers for fastening (5) to shaft 
 
 8 Stationary step plate 
 
 9 Bushing and pin for (8) 
 
 10 Key for driving (8), with screws 
 
 11 Step bearing head with bolts 
 
 12 Adjusting screw 
 
 13 Threaded bushing and pin for step bearing head 
 
 14 Hardened steel cap for (12) 
 
 15 Key for driving (17) by (12) 
 
 16 Supporting bracket for (17), with bolts 
 
 17 Worm wheel for adjusting device 
 
 18 Worm and worm shaft for adjusting device 
 
 19 Bearing cap for (18) and (11) 
 
 20 Ratchet handle for adjusting device 
 
 21 Drain for step bearing 
 
 237 
 
bearing is regulated by individual bafflers. Fig. 113 shows the 
 type of step baffler used in test. This is the old style of baffler, 
 and is not a part of the permanent equipment of the machine. 
 The new type will be shown later. The top and middle bear- 
 ings are supplied from a manifold, and the flow regulated 
 
 Out/et Qot/onaA 
 
 Baff/er Frame 
 
 Ba/T/er P/ug 
 
 %'f/pe, 
 
 Cap 
 Adjust fng Screw 
 
 Wire Gauze 
 
 8/otvOrT 
 
 Stra/ner 
 
 Fig. 113 
 STEP BEARING BAFFLER (OLD TYPE) 
 
 by bafflers similar to those used on horizontal machines. These 
 bearings are not water cooled. The step bearing (see Fig. 112) 
 is piped from the large accumulator line and special care must 
 be used in handling this high pressure. It should be remembered 
 that the valve stem on the hydraulic valve used in all high pres- 
 sure lines is free to turn entirely out of the body of the valve. 
 These valves should be opened six turns only. If opened further 
 than this the result may be disastrous. 
 
 238 
 
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 239 
 
SEALING STEAM 
 
 SEC TION A AA -A A -A A 
 GZZZZZ* \ 
 
 Fig. 114 
 
 CARBON PACKING (FLOATING RING TYPE) 
 
 1 Carbon packing casing (half) 
 
 2 Clamp bolt for (1) 
 
 3 Carbon ring segment 
 
 4 Retaining bolts for casing 
 
 5 Stop for carbon rings 
 
 6 Bracket for (5) 
 6 Garter spring 
 
 8 Alloy packing ring 
 
 9 Retaining ring 
 
 10 Drain to 2nd stage shell 
 
 11 Drain to 3rd stage shell 
 
 12 Drain to atmosphere 
 
 13 Supporting spring 
 
 240 
 
In turning oil on the step bearing proceed as follows: 
 
 Open the valve until the step is raised and note the gauge 
 pressure. Then close the valve, allowing the step blocks to 
 come together again. Now open the valve very slowly, and 
 watch the gauge. Hold the pressure between 90 and 95 per 
 cent of that required to raise the step, and watch for oil leakage 
 at the drain from the step. At this pressure the step will not be 
 raised, and if the blocks are parallel the leakage between them 
 will be practically nothing. However, if the blocks are not 
 quite parallel there will be an opening on one side which will 
 allow a considerable flow of oil. 
 
 Having ascertained that the step blocks are all right the 
 valve should then be opened to give about a quarter of the 
 required flow, and the step bearing and pipes allowed to become 
 warm. This must be done since the oil will not drain away from 
 the step rapidly enough to prevent flooding when cold. The oil 
 in the supply tank is kept at a temperature of 45 to 51 deg. cent, 
 and a short time should be sufficient to warm up the bearing 
 and drains. The valve may then be opened the full six turns. 
 
 A table of the flow and probable pressures for various machine 
 capacities is given on page 239. 
 
 This table is calculated for machines that are completely 
 assembled. 
 
 It is usually necessary to readjust the baffler between the 
 periods of adjusting wheel and field balance. 
 
 Oil leaks in the step bearing should be carefully watched 
 for, and remedied before starting the machine. 
 
 Carbon Packing Rings 
 
 The carbon packing rings (see Fig. 114) should have enough 
 steam to lubricate, and to seal in case vacuum is used. Too 
 much steam is injurious. The right amount will be indicated 
 by the escape of a little vapor from the drain leading from the 
 carbon ring casing. This drain should always be left open. 
 It sometimes happens that, through insufficient steam lubrica- 
 tion or other cause, the carbon rings tend to grip the shaft, 
 become very noisy and throw the machine into vibration. When 
 this occurs, which is more often on horizontal than on vertical 
 types, a very thin solution of graphite and water should be 
 introduced into the carbon casing. One or two applications will 
 effectually remove the trouble. The graphite must never be 
 mixed with oil, nor made into a thick solution with water, as 
 it then becomes gummy, and causes the rings to stick in the 
 casing and hold away from the shaft. When this happens the 
 rings cannot seal. 
 
 Trip Rigging 
 
 Before starting a machine, try the trip rigging on the emer- 
 gency throttle valve to see that it will trip the valve easily 
 See Fig 115. 
 
 241 
 
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 7urnintnis direction to 
 c/ose i/n/ve wnen /erer/'s 
 noo/redup, u/sotono/se 
 si/ding nut on a" /e yen /or 
 engaging ///to no o/r after 
 vo/re i?as /been trippe 
 
 Section "Z-£" 
 Loo/ring Down 
 
 Fig. 115 
 
 THROTTLE VALVE AND EMERGENCY GOVERNOR 
 TRIP RIGGING 
 
 1 
 
 Valve bonnet 
 
 11 
 
 Trip bell crank 
 
 2 
 
 Valve body 
 
 12 
 
 Large gland 
 
 3 
 
 By-pass nut 
 
 13 
 
 Small gland 
 
 4 
 
 By-pass valve cover 
 
 14 
 
 Sliding nut 
 
 5 
 
 By-pass valve 
 
 15 
 
 Yoke 
 
 6 
 
 Valve spool 
 
 16 
 
 Trip handle 
 
 7 
 
 Valve stem 
 
 17 
 
 Trip hook 
 
 8 
 
 Valve seat 
 
 18 
 
 Lever for sliding nut 
 
 9 
 
 
 Trip spring 
 
 Valve stem bushing 
 
 19 
 
 Handwheel 
 
 242 
 
Wheel Balance 
 
 Before the main valve is opened to admit steam into the 
 line to the emergency throttle, the exhaust valve should be 
 opened. This will obviate any danger of excessive steam pres- 
 sure on the turbine shell should the throttle valve leak. 
 
 Cold machines, in being started, should have enough steam 
 given them to start them revolving at once. Otherwise the 
 steam may distort the wheels, due to local heating. As soon 
 as a machine starts to revolve, place one end of a wrench or 
 bar against the intermediate holder, and rest the ear against 
 the other end, and listen for rubbing. If the wheels seem to be 
 running clear, bring the speed up to about 50 rev. per min., 
 and then shut steam off completely. Listen for rubbing as 
 before and at the same time notice whether the speed dimin- 
 ishes rapidly or not. The time that a machine should run 
 before stopping varies greatly with the size and type, hence 
 it is left largely to the judgment of the man in charge of the 
 machine as to whether it is operating as it should. It is not 
 necessary to let the machine come to a stop to see if it is run- 
 ning freely, as any marked diminution of speed can be noticed 
 in a minute or two. Heat the machine up thoroughly before 
 bringing it to normal speed by allowing it to run at about 
 one fourth normal speed for fifteen to thirty minutes, depending 
 on the size. When well heated, bring to normal speed (if the 
 balance permits) and note the balance, or amount of vibration, 
 on the bearings and on the intermediate holder. If the balance 
 is good enough at normal speed it should then be tried at 110 
 per cent normal speed. Balance at 110 per cent speed should be 
 as good, or nearly as good as at normal. 
 
 Some machines are in good balance when they come to 
 test, but more often they have to be balanced dynamically. 
 Before beginning wheel balance, the method of numbering the 
 balance weight holes should be understood. It is impracticable 
 to mark the wheel alongside the holes themselves, as the steam 
 would soon efface the marking, so the following method is used: 
 
 On horizontal machines, holes for introducing balance weights 
 into the wheels are provided in the turbine head and in the 
 exhaust chamber. The wheels are revolved until a hole in the 
 wheel is in line with the hole in the exhaust chamber. This 
 is considered hole No. 1. A definite point of reference is made on 
 the middle bearing in line with this hole, and a mark made on 
 the coupling also in line. This locates hole No. 1 and should be 
 permanently indicated by a prick punch mark on the coupling. 
 The wheels are now slowly revolved and the location of each 
 balance weight hole is marked on the coupling with chalk or 
 whiting. Beginning with No. 1 the holes are numbered, always 
 in the direction of rotation. 
 
 In vertical machines the holes are numbered in a slightly 
 different manner. The coupling is not assembled during wheel 
 balance, so a key- way is selected to locate hole No. 1, this 
 key-way being indicated by a prick punch mark. The balance 
 weight hole in the wheel nearest in line with the key- way is 
 
 243 
 
brought under the hole in the turbine head and No. 1 marked 
 on the bearing under the key-way. Revolve the wheels slowly 
 and mark under the key- way on the bearing the location of each 
 hole. Numbering on the bearing must be against rotation in 
 order that the numbering on the wheels themselves may be in 
 the direction of rotation. 
 
 All turbines revolve counter clockwise facing the steam inlet end. 
 
 Before beginning work on balance, the shaft should be painted 
 with whiting, at both ends when accessible. When the machine 
 is up to speed or at as high a speed as the vibration will permit 
 mark the shaft lightly with a pencil. The pencil line will 
 appear heavier in one place which is generally opposite or 
 nearly opposite the side that requires additional weight. Place 
 a weight in the side indicated, in either the first or last stage 
 wheel, depending on which showed the greater amount of 
 unbalancing as indicated by the pencil mark. Use a fair sized 
 weight, e.g., one two inches long. Bring the machine up to as 
 high a speed as the balance will permit and note the balance 
 of all parts. Then move the weight one-quarter way around the 
 wheel and try the balance again. Proceed thus until both first 
 and last wheels have been tried. Then continue trials in. the 
 holes in which the best balance was noted, using larger or smaller 
 weights as may seem necessary. No rigid rule can be set down 
 for the size and use of weights in balancing. It is a matter 
 which must be left entirely to the judgment of the test man. 
 A balance record similar to that given on page 245 should be 
 kept, and on this an accurate record of weights used and the 
 per cent balance should be noted. 
 
 From this record it is evident that weights in hole No. 7 
 gave the best results in "quartering," hence it was then only 
 necessary to try slight variations and changes in the neighbor- 
 hood of hole No. 7 to obtain a perfect balance. 
 
 A number of things may influence the balance of wheels 
 at the start which are not due to an actual unbalancing of the 
 wheels themselves. 
 
 (1) The carbon packing rings may be gripping the shaft. 
 This has already been discussed, and the proper remedy ex- 
 plained. 
 
 (2) The diaphragm packing rings may be rubbing on the 
 shaft or wheel hubs. That surface of the packing ring that bears 
 against the shaft consists of a series of V-shaped grooves. When 
 there are indications of rubbing at this point, the turbine should 
 be run continuously at a speed at which there is a slight vibra- 
 tion. This will in a short time wear a clearance between the 
 rings and shaft and remove the source of trouble. This method 
 should be followed in all cases in which a turbine vibrates 
 at low speeds, and for which no other cause can be found. 
 
 (3) The wheels may be rubbing at the circumference. When 
 this is the case it should be reported at once, and an investi- 
 gation made. 
 
 (4) There may be water in the turbine. See that all drains 
 are free. If, when opened, neither water nor steam escapes, it 
 
 244 * 
 

 BALANCE HOLE NUMBERS 
 
 PER CENT BALANCE 
 
 
 1 
 
 n 
 
 2' 
 
 2 
 Wl 
 
 3 
 
 light 
 
 4 
 
 2" 
 
 2" 
 
 5 
 
 6 
 
 
 
 1" 
 
 7 
 
 2" 
 
 
 
 2" 
 
 2" 
 2" 
 
 2" 
 
 2" 
 
 8 
 
 
 
 2" 
 2" 
 
 9 
 
 
 
 10 
 
 2" 
 
 11 
 
 12 
 
 v be 
 
 4u 
 
 i— iW 
 
 Is 
 
 
 
 I 
 
 93 
 
 95 
 
 54 
 
 
 
 I 
 
 90 
 
 94 
 
 55 
 
 
 
 I 
 
 92 
 
 95 
 
 93 
 
 
 
 I 
 
 97 
 
 97 
 
 95 
 
 
 
 I 
 
 93 
 
 95 
 
 94 
 
 
 
 I 
 
 93 
 
 94 
 
 93 
 
 
 
 I 
 
 95 
 
 97 
 
 96 
 
 
 
 I 
 
 92 
 
 95 
 
 92 
 
 
 
 I 
 
 98 
 
 99 
 
 98 
 
 
 
 I 
 
 99 
 
 100 
 
 98 
 
 
 
 I 
 
 100 100 
 
 100 
 
 " O "Indicates the outside, or first stage wheel. 
 "I" Indicates the last stage wheel. 
 
 Note — Italics indicate pencil notations by the one doing the 
 balancing. 
 
 245 
 
is evident there is a stoppage somewhere, and all valves and 
 piping should be carefully examined. 
 
 CA UTION. Do not run wheels with loose weights. Be sure 
 that all weights are tight, and that none project so far on either 
 side of the wheel as to strike any stationary parts. 
 
 Field Balance 
 
 The method employed in balancing the field is practically 
 identical with that used in balancing the wheels. In this case 
 the numbers may be painted directly alongside each balance 
 weight screw hole, beginning at the field leads and numbering 
 in the direction of rotation. When the field leads are brought out 
 on opposite sides of the shaft, hole No. 1 should be indicated by 
 a prick punch mark. 
 
 On a later type of field the balance weight screw holes are 
 replaced by a dove-tail groove in which are carried the heads of 
 the bolts securing the weights. It will be necessary on this type 
 to divide the groove into a number of equal sections, or "loca- 
 tions" which should be numbered as are the screw holes on the 
 older type of field. Twenty-four is the most convenient number 
 of "locations" to use. 
 
 On the older type of field the balance should be obtained by 
 the use of one weight only in each end of the field. If this is 
 impossible and more than one weight is necessary the weights 
 must be concentrated, not scattered or counter-balancing each 
 other. 
 
 On the later type with the groove, the procedure is some- 
 what different. Here the balance weights are always used in 
 pairs, i.e., a pair of weights in each end of the field. The weights 
 of any one pair must always be equal in size and similar in shape 
 and each weight must be secured by at least two bolts. When a 
 balance is finally obtained the size of the weights of a pair should 
 have been so selected that the weights are located approxi- 
 mately 60 deg. to 90 deg. apart. This method of balancing 
 allows of a very wide range of adjustment. By bringing the 
 weights together or moving them further apart along the groove 
 any effective value from zero to a maximum may be obtained, 
 and the resultant value may be placed in any position desired. 
 If the weights have been selected as directed there will be ample 
 latitude for further adjustment should it become necessary at 
 any time. 
 
 In all field balance work the shaft should be painted with 
 whiting at each end of the field, and indications of the direction 
 and amount of unbalancing made as described under the head 
 of "Wheel balance." These indications should be used as a 
 guide in the location of weights throughout all balance work, but 
 the knowledge of how to do this must be gained by experience 
 as the significance varies with every machine. 
 
 CAUTIONS 
 
 1. Balance weights must fit tightly, all bolts be inf place and 
 drawn up tightly. 
 
 246 
 
2. Weights must fit firmly for their full length against the 
 outer side of the slot. 
 
 3. Xo balance weight should be used whose thickness is 
 more than twice the depth of the balance weight slot. 
 
 4. Weights should never be superimposed. 
 
 In loading machines for shutting down, do not load them 
 single-phase. 
 
 The foregoing instructions on the balancing of alternator 
 fields will also apply, in a general way, to the balancing of direct 
 current armatures. The weights used in direct current arma- 
 tures are of different shapes, and are secured in various ways, 
 but the method employed in obtaining a balance is the same as 
 that used in balancing turbine fields and revolving fields. 
 
 Before beginning balance work on any generator, all wiring 
 should be completed and cold resistance measurements taken. 
 
 One condition to be watched in all balance work is the number 
 of operating valves that are held open. Only just so many 
 valves as are necessary to bring the machine up to speed should 
 be used. If a greater number of valves is opened a greater 
 amount of steam is required to do the same work. This is 
 wasteful, and in the case of large machines the steam pressure 
 in the mains may be so reduced by the excessive flow as to let 
 the step-accumulator down, causing considerable damage if 
 not stopped at once. This rule in regard to the number of valves 
 opened should, in fact, be observed in the starting of machines 
 at all times, especially those of larger sizes. The only case 
 in which it cannot apply is in the testing of operating governors 
 to be described later. 
 
 Too much importance cannot be attached to the main- 
 tenance of steam pressure. Low steam pressure may, through 
 the loss of pressure in the step-accumulator oil system as just 
 referred to, damage the wheels of a vertical turbine to such 
 an extent as to require an entirely new set of wheels. 
 
 Governor Tests 
 
 EMERGENCY GOVERNORS 
 
 After the wheels are balanced and before the field is assembled, 
 the emergency governor should be adjusted and tested. There- 
 after it should be tripped at least once every twenty-four hours, 
 and a record made in a folder provided for this purpose. Emer- 
 gency governors are known as Type E. There are two forms 
 now used. Form D, the eccentric ring type (Fig. 116) is used on 
 all machines of 2000 rev. per min. and under, and Form E, the 
 plunger type (Fig. 117) used on the higher speed machines. 
 
 The Form D governor is shown in Fig. 116 in its normal 
 concentric position before operating. In operating, the ring 
 (1) moves out eccentrically against the spring (13) coming in 
 contact with the trip finger (9) (Fig. 118) thereby releasing the 
 emergency throttle valve. The adjusting nut (8) (Fig. 116) over 
 the spring screws on to the spindle (4). The thread is right- 
 handed, so that by turning the nut to the right more tension is 
 
 247 
 
^^»5-^ 
 
 Fig. 116 
 
 EMERGENCY GOVERNOR (FORM D), (DOUBLE RING 
 TYPE, HORIZONTAL TURBINES) 
 
 Emergency governor ring 8 
 
 Emergency governor guide 9 
 
 block 10 
 
 Emergency governor spring 12 
 
 box 13 
 Emergency governor spindle 
 
 Emergency governor stop 14 
 
 Bushing for (2) 15 
 Collar for (3) 
 
 Adjusting nut for (4) 
 Guide pin for (1) 
 Cotter pin for (5) 
 Bushing for (3) 
 Emergency governor 
 
 spring 
 Support for (13) . 
 Rivet for (1), (2) and (3) 
 
 248 
 
Fig. 117 
 
 EMERGENCY GOVERNOR,*PLUNGER TYPE (FORM E) 
 
 1 Governor plunger 
 
 2 Tension adjusting bushing 
 
 3 Guide bushing 
 
 4 Retaining nut for spring 
 
 5 Adjusting nut for spring 
 
 6 Governor spring 
 
 7 Cotter pin for retaining nut 
 
 8 Pin for adjusting nut 
 
 9 Clamping collar for governor 
 
 10 Dowel pin for clamping collar 
 
 11 Holes for spanner wrench 
 
 12 Cap screw for clamping ring 
 
 240 
 
Fig. 1 
 EMERGENCY GOVERNOR AND THRUST BEARING 
 
 1 
 
 Pillow block or stand- 
 
 17 
 
 Stationary plate, front 
 
 
 ard 
 
 
 thrust 
 
 2 
 
 Gear casing 
 
 18 
 
 Adjusting shims, front 
 
 3 
 
 Shaft 
 
 
 thrust 
 
 4 
 
 Gauge board 
 
 19 
 
 Bearing cap bolt 
 
 5 
 
 Lock nut for gears 
 
 20 
 
 Bearing cap 
 
 6 
 
 Spiral gear 
 
 21 
 
 Bearing 
 
 7 
 
 Emergency governor 
 
 22 
 
 Babbitt lining 
 
 8 
 
 Deflector 
 
 23 
 
 Bearing packing ring 
 
 9 
 
 Emergency governor trip 
 
 24 
 
 Air deflector 
 
 
 finger 
 
 25 
 
 Oil guard 
 
 10 
 
 Emergency governor con- 
 
 26 
 
 Adjusting shims, back 
 
 
 necting rod to throttle 
 
 
 thrust 
 
 
 valve 
 
 27 
 
 Revolving plate, back 
 
 11 
 
 Emergency governor rig- 
 
 
 thrust 
 
 
 ging bell crank 
 
 28 
 
 Roller cage, back thrust 
 
 12 
 
 Cover plate 
 
 29 
 
 Stationary plate, back 
 
 13 
 
 Emergency trip finger rod 
 
 
 thrust 
 
 14 
 
 Thrust nut 
 
 30 
 
 Water drain sight cup 
 
 15 
 
 Revolving plate, front 
 
 31 
 
 Bearing standard dowel 
 
 
 thrust 
 
 
 pin 
 
 16 
 
 Roller cage, front 
 
 32 
 
 Dowel pin nut 
 
 
 thrust 
 
 33 
 
 Bearing standard bolt 
 
 
 250 
 
given to the spring and the speed at which the governor operates 
 is increased. The nut (8) is held in position by a lock-screw, 
 which goes through one of the holes in the nut and screws into 
 a stationary plate below. This screw must always be replaced 
 after it has been removed to make an adjustment of the governor. 
 
 The Form E governor is shown in Fig. 117. Here, instead 
 of an eccentric ring, we have a plunger (1) to strike the trip- 
 finger. The entire mechanism is contained in a bored out sec- 
 tion of the shaft, and held in place by the two clamping rings 
 (9,9). The adjusting nut (5) over the spring, does not turn, 
 but is moved in or out by turning the bushing (2). Since 
 the nut has a right-hand thread, turning the bushing to the 
 left, forces the nut in, puts more tension on the spring, and 
 increases the speed at which the governor will operate. The 
 bushing (2) is held in position and prevented from turning 
 by the clamp rings (9), hence these rings must be loosened 
 before any effort is made to move the bushing. The rings are 
 clamped by four cap screws in the holes (12). 
 
 All emergency governors must be adjusted to trip at 10 per 
 cent above the normal speed of the machine, with an allowable 
 variation of 3^2 per cent either high or low. The speed at which 
 they return to their normal position must be, on the Form D, 
 between 90 per cent and 100 per cent of normal speed, and on 
 the Form E, between 100 and 101 per cent. After the proper 
 adjustment has been obtained, the governor must be tripped 
 five or six times in succession, and the operation of all parts 
 of the trip rigging noted. There should be no lag to any of the 
 parts, and the valve should close quickly. Any defect must be 
 reported at once. 
 
 Fig. 118 shows the assembly of a Form D governor and the 
 arrangement of the trip rigging. 
 
 This illustration also gives a good idea of the arrangement of 
 the thrust bearing and adjusting shims of the roller type of 
 thrust. 
 
 Fig. 119 shows the arrangement of a later type of thrust 
 bearing known as the "Block" type. This is the type of thrust 
 also shown in the illustration of a general turbine assembly, 
 Fig. 109. A third arrangement of a thrust bearing, known as 
 the "Ring" type is shown in Fig. 120. The Ring type and the 
 Block type thrusts are interchangeable. Either may be as- 
 sembled in the outer housing (9) Fig. 119. 
 
 OPERATING GOVERNOR 
 
 The operating or main governor is known as Type M gover- 
 nor, Form C, and is shown in Fig. 121. 
 
 On vertical machines the governor is set directly on the top 
 of the main shaft, see Fig. 108, but on horizontal machines it 
 is driven from an auxiliary shaft connected to the main shaft 
 by a worm and gear. See Fig. 122 and Fig. 123. This auxiliary 
 shaft also drives the gear oil pump. After the gear pump is 
 assembled and operative the steam driven oil pump should not 
 be used except when starting and stopping the machine. 
 
 251 
 
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 253 
 
Fig. 120 
 
 RING TYPE THRUST BEARING 
 
 1 Alloy thrust rings 
 
 2 Thrust bearing shell 
 
 3 Thrust bearing 
 
 4 Bolts 
 
 5 Shims for adjusting clearance of wearing shoe 
 
 6 Wearing shoe 
 
 7 Set screw for shaft nut 
 
 8 Shaft nut 
 
 254 
 
Before beginning governor tests the machine should be run 
 for a short time with the governor holding speed to ascertain 
 that all parts of the governor and hydraulic rigging function 
 properly, that there is no sticking in any part, and that there is 
 no hunting in the governor itself. Any defects noted should be 
 reported at once and the necessary corrections made before 
 proceeding with the governor test. 
 
 OPERATING GOVERNOR TEST 
 
 Fasten a pointer on the machine in some convenient place 
 where it will be near the piston or connecting rod (No. 14, 
 Fig. 122). Paint the section of rod opposite the pointer with a 
 coat of whiting. Move the pilot valve by hand, opening all 
 the operating valves. As the last valve opens so that the roller 
 12 (Fig. 124) just rises over the point of the cam (14) make a 
 mark on the whiting opposite the pointer. Then lower the 
 pilot valve stem so that the valves close, and as the last valve 
 is just closed make a second mark on the whiting opposite the 
 pointer. The foregoing refers to high pressure machines only. 
 Machines designed to operate on both high and low pressure 
 steam are provided with a low pressure butterfly valve, Fig. 125, 
 whose operation precedes that of the high pressure valves. 
 Hence the two marks must include the total travel of the piston 
 rod (2), necessary to operate both the high pressure valves and 
 the butterfly valve. 
 
 The first mark is located as described above. The second 
 mark is made when the piston or connecting rod (2), Fig. 125, 
 has, by means of the cam (8) and connecting rod (10) brought 
 the butterfly valve to the "closed position" as indicated by 
 dotted lines. The length of the connecting rod (10) should be 
 so adjusted as to give a compression on the spring (5) of from 
 s5 to tV in. Having located the two limit marks, divide the 
 intervening space into five equal parts, thus obtaining six 
 marks. In order to bring the speed above the point at which 
 the governor would normally hold the speed, and so make each 
 mark on the scale pass the pointer, it is necessary to block open 
 one or more valves. Before any valves are blocked open, and 
 with the. governor holding speed, check the tachometer.' This 
 is done preferably by holding the speeder on the end of the gover- 
 nor spindle (8), "Fig. 121, rather than on the end of the main 
 shaft. Take a two minute reading. The proper governor speed 
 may be determined from the ratio of the worm and gear. The 
 tachometer, which is always belted, should be provided with a 
 pulley of such diameter as to give a reading well up on the scale. 
 
 All is now ready for the actual governor tests and adjust- 
 ments. Speed readings should be taken as the marks on the 
 scale pass the pointer, first as the machine is brought above 
 normal speed, and again as it falls below normal. 
 
 The first readings are taken with the synchronizing spring 
 (27), Fig. 121, set in mid-position; that is/ with the plug (26) 
 Fig. 121, set at the mid-position of its travel. All adjustments 
 
 255 
 
Fig. 121 
 
 OPERATING GOVERNOR 
 
 1 
 
 Governor dome 
 
 21 
 
 Thrust plate for (19) 
 
 2 
 
 Governor lever 
 
 22 
 
 Worm wheel 
 
 3 
 
 Governor bracket 
 
 23 
 
 Worm 
 
 4 
 
 Weights 
 
 24 
 
 Supporting plate for worm 
 
 5 
 
 Fulcrum block for (15) 
 
 
 wheel 
 
 6 
 
 Links 
 
 25 
 
 Handwheel 
 
 7 
 
 Yoke for (6) 
 
 26 
 
 Plug for synchronizing 
 
 8 
 
 Spindle or connection rod 
 
 
 spring 
 
 9 
 
 Spring for universal joint 
 
 27 
 
 Synchronizing spring 
 
 10 
 
 Lower spring plug 
 
 28 
 
 Limit switch base 
 
 11 
 
 Main spring 
 
 29 
 
 Limit switch details 
 
 12 
 
 Adjusting nut for (11) 
 
 30 
 
 Trunnion for lever 
 
 13 
 
 Adjusting plate 
 
 31 
 
 Nut for (30) 
 
 14 
 
 Key for (13) 
 
 32 
 
 Stop for weight 
 
 15 
 
 Knife edge for (4) 
 
 33 
 
 Studs for lever bracket 
 
 16 
 
 Transmission roller bear- 
 
 34 
 
 Nuts for (33) 
 
 
 ing 
 
 35 
 
 Lead screw for (26) 
 
 17 
 
 Lever bracket 
 
 36 
 
 Shaft for worm 
 
 18 
 
 Roller bearing for lever 
 
 37 
 
 Knife edge bearing block 
 
 19 
 
 Bracket for synchronizing 
 
 
 for (4) and (7) 
 
 
 gear 
 
 38 
 
 Knife edge for (6) 
 
 20 
 
 Bracket for worm gear 
 
 39 
 
 Upper spring plug 
 
 
 
 40 
 
 Stop blocks 
 
 256 
 
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Fig. 123 
 
 GEAR PUMP AND CASING (OUTSIDE TYPE PUMP) 
 
 (See page 259) 
 
 258 
 
PARTS OF GEAR PUMP AND CASING (Outside Type Pump) 
 (See Fig. 123) 
 
 1 Gear casing 
 
 2 Spiral gear driver 
 
 3 Turbine shaft and keys 
 
 4 Spiral gear driven 
 
 5 Lower bushing (governor end) 
 
 6 Governor and pump shaft 
 
 7 Bronze thrust plate for governor 
 
 8 Steel thrust plate for governor 
 
 9 Upper bushing (governor end) 
 
 10 Keys for (4) and (6) 
 
 11 Steel thrust plate for spiral gear 
 
 12 Upper bushing for (6) pump end 
 
 13 Upper bushing for (14) pump end 
 
 14 Idler shaft for pump gear 
 
 15 Bolt for (1) and (16) 
 
 16 Pump casing 
 
 17 Stuffing gland for pump suction 
 
 18 Stuffing box packing 
 
 19 Pump gear 
 
 20 Plug in bottom of casing 
 
 21 Bottom bushings for (6) and (14) pump end 
 
 22 Pump discharge 
 
 23 Pump suction 
 
 259 
 / 
 
Fig. 124 
 
 HIGH PRESSURE CONTROLLING VALVE 
 
 1 Adjusting screw for valve spring 
 
 2 Supporting plate for (1) 
 
 3 Spring supporting plate (adjustable) 
 
 4 Controlling valve spring 
 
 5 Stud for spring supporting plate, with nut 
 
 6 Frame for controlling valve, with bolts 
 
 7 Guide plate for valve stem 
 
 8 Upper cup for (7) 
 
 9 Thrust pin 
 
 10 Lower cup for (11) 
 
 1 1 Controlling valve lever 
 
 12 Cam roller for lever 
 
 13 Spindle for cam roller with nut 
 
 14 Cam with key 
 
 15 Cam shaft 
 
 16 Cam shaft bracket with bearing cups and bolts 
 
 17 Gland for packing 
 
 18 Nut for stuffing box 
 
 19 Gnide plate and stuffing box for valve stem 
 
 20 Valve stem 
 
 21 Valve (wing type) 
 
 22 Valve seat 
 
 23 Valve casing 
 
 24 Pin for (20 and (21) 
 
 260 
 
P OSIT ION OF 
 BUTTERFLY VALVE 
 WHEN FIRST HIGH 
 PRESSURE VALVE 
 STARTS TO OPE^ 
 
 FULL OPEN 
 POSITION 
 
 Fig. 125 
 
 ARRANGEMENT OF HYDRAULIC GEAR ON MIXED 
 PRESSURE TURBINE 
 
 1 Cam shaft for high pressure valves 
 
 2 Piston rod 
 
 3 Pilot valve chest 
 
 4 Hydraulic cylinder 
 
 5 Spring 
 
 6 Cam roller 
 
 7 Slot for cam roller (6) 
 
 8 Cam plate 
 
 9 Cam lever 
 
 10 Connecting rod for butterfly valve 
 
 261 
 
-2/ 
 
 ( gjio @ 
 
 /8 
 
 +-/Q 
 
 m& 
 
 Fig. 126 
 
 HYDRAULIC OPERATING CYLINDER AND PILOT VALVE 
 (HORIZONTAL TURBINES) 
 
 Pilot valve stem guide 
 
 Pilot valve pivot clamp 
 
 Pilot valve middle bushing 
 
 Pilot valve end bushing 
 
 Pilot valve seat bushing (hardened 
 
 steel) 
 Floating lever 
 Differential lever 
 Link for (18) 
 Rod end — adjustable 
 Connection to governor lever 
 
 1 
 
 Hydraulic cylinder 
 
 12 
 
 2 
 
 Cylinder head 
 
 13 
 
 3 
 
 Stuffing gland for (2) 
 
 14 
 
 4 
 
 Nut for stuffing box 
 
 15 
 
 5 
 
 Piston 
 
 16 
 
 6 
 
 Piston ring 
 
 
 7 
 
 Piston rod 
 
 17 
 
 8 
 
 Piston rod nut 
 
 18 
 
 9 
 
 Pilot valve 
 
 19 
 
 10 
 
 Pilot valve chest 
 
 20 
 
 11 
 
 Pilot valve stem 
 
 21 
 
 262 
 
of the governor must be made with the spring in this position. 
 On a properly adjusted governor a set of readings similar to the 
 following is obtained. 
 
 Marks 
 
 Accelerating 
 Decelerating 
 Lag 
 
 1728 
 
 1725 
 
 3 
 
 1740 
 1736 
 
 4 
 
 1748 
 
 1743 
 
 5 
 
 1757 
 
 1752 
 
 5 
 
 1770 
 
 1767 
 
 3 
 
 1790 
 
 1786 
 
 4 
 
 Tachometer reading = 1750 
 Speed of machine = 1800 
 
 The requirements to be met are as follows: 
 
 (1) Normal speed must be between readings No. 3 and No. 4. 
 
 (2) The total regulation, that is, the difference between 
 reading No. 6 accelerating and reading No. 1 decelerating, must 
 be between 3.6 and 4.0 per cent of normal speed. 
 
 (3) The "lag" is the difference in the readings accelerating 
 and decelerating for the same mark on the rod and must not 
 exceed an average of 0.4, or a maximum for any one reading of 
 0.5 per cent of normal speed. If the speed or regulation of the 
 
 :rnor is not correct, it can be adjusted by varying the tension 
 on the main governor spring (11), Fig. 121, or by changing 
 weights in the pockets of the governor weights (4), Fig. 121. 
 
 Increasing the tension on the main spring will raise the speed 
 and decrease the regulation. Decreasing the tension lowers the 
 speed and increases the regulation. 
 
 Increasing the weight in the pockets of the governor weights 
 lowers the speed without appreciably affecting the regulation. 
 
 If the lag is excessive take a set of readings on the governor 
 rod (17), Fig. 122, with the rod disconnected from the piiot 
 valve. This will indicate whether the excess lag is in the gover- 
 nor or in the hydraulic rigging. See Fig. 126. In either case 
 the lag should be corrected before proceeding. After the gover- 
 nor has been properly adjusted, take three sets of readings 
 using the scale or marks laid out on the piston rod, the synchro- 
 nizing spring being in mid-position. Then take two sets of 
 readings on each of the two limit positions of the synchronizing 
 spring: " Spring all in " (maximum compression) and "spring all 
 out " (minimum compression). 
 
 Bafflers 
 
 The step bearing baffler, Fig. 127, is furnished with all vertical 
 machines, having replaced the old style baffler (Fig. 113), now 
 used only as a part of the permanent testing equipment. 
 
 The baffler frame is first tested for sand holes and porous 
 places in the casting. It is carefully painted over the entire 
 surface with whiting, filled with oil, and kept under a pressure 
 of 2500 lb. per sq. in. for 24 hours. If at the end of this time 
 
 263 
 
Fig. 127 
 
 STEP BEARING BAFFLER (ADJUSTABLE) 
 
 1 Head (inlet end) 
 
 2 Plug for blowoff 
 
 3 Strainer (gauze mesh) 
 
 4 Barrier frame 
 
 5 # Adjusting screw 
 
 6 Head (outlet end) 
 
 7 Washer (inlet end) 
 
 8 Strainer frame 
 
 9 Baffler screw 
 
 10 Washer (outlet end) 
 
 264 
 
there is no indication of oil anywhere on the whiting, the baffler 
 is completely assembled with strainer and plug. 
 
 The plug^ or screw (9), Fig. 127, has a thread with a taper- 
 ing depth of groove which allows of a wide range of adjustment. 
 The deepest grooves should be assembled at the discharge end. 
 The following table shows the approximate flows for given 
 pressure drops across the baffler and various adjustments of the 
 adjusting screw (5), Fig. 127. The temperature of the oil is 
 •50 deg. cent. 
 
 FLOW IN GALLONS PER MINUTE 
 
 \^ Length 
 
 
 
 
 
 
 
 
 ^^^^ of 
 
 
 
 
 
 
 
 
 Drop ^^---^"A" 
 
 2 In. 
 
 3 In. 
 
 4 In. 
 
 5 In. 
 
 6 In. 
 
 7 In. 
 
 8 In. 
 
 lb. per sq-t n. ^^~~^~ 
 
 
 
 
 
 
 
 
 50 
 
 1.0 
 
 2.2 
 
 3.1 
 
 4.4 
 
 6.0 
 
 8.0 
 
 12.5 
 
 75 
 
 1.5 
 
 2.9 
 
 4.2 
 
 5.4 
 
 7.6 
 
 10.7 
 
 16.8 
 
 100 
 
 1.9 
 
 3.4 
 
 5.0 
 
 6.5 
 
 9.0 
 
 12.7 
 
 20.5 
 
 125 
 
 2.2 
 
 3.9 
 
 5.5 
 
 7.4 
 
 10.1 
 
 14.5 
 
 24.0 
 
 150 
 
 2.4 
 
 4.4 
 
 6.3 
 
 8.4 
 
 11.2 
 
 15.6 
 
 27.5 
 
 "A" is the distance between the end of the plug and the 
 baffler head. See Fig. 127. 
 
 Stage Valves 
 
 In most of our multi-stage vertical turbines, valves are pro- 
 vided which open additional second stage nozzles at times of 
 overload. 
 
 The usual arrangement of this valve is shown in Fig. 128. 
 The pipe (16) connects with the first overload valve on the 
 operating valve casing. When the operating valve is opened 
 steam is admitted to the upper side of the piston (14) and the 
 stage valve (2) is forced open against the spring (5). This 
 valve should open quickly and positively, and should close in 
 the same way. 
 
 The only test made on the assembled stage valve is to open 
 and close the controlling valve a few times, and note that the 
 stage valve acts properly and operates without sticking. Also 
 the travel of the stem or indicator rod (8) should be measured. 
 
 A modification of this valve carries the spring outside of the 
 casing, but the operation is essentially the same. 
 
 GENERATORS 
 
 Sectional views of vertical and horizontal turbo-generators 
 ai^ shown in Figs. 129 and 130. 
 
 The scheme of ventilation of the turbine generator is rad- 
 ically different from that of other types of generators. Referring 
 to Fig. 129, air is drawn in through an opening in the side of 
 the hood (9), forced by the fans (21), through the air gap and 
 out through the ducts in the armature laminations (1) to the 
 
 265 
 
Fig. 128 
 STAGE VALVE (See page 267) 
 
 266 
 
PARTS OF STAGE VALVE. (See Fig. 128) 
 
 1 Casing for stage valve 
 
 2 Valve and piston 
 
 3 Valve seat 
 
 4 Cylinder lining 
 
 5 Spring 
 
 6 Cylinder head 
 
 7 Adjusting screw 
 
 8 Indicator rod 
 
 9 Balance-cylinder head and stuffing-box 
 
 10 Gland for stuffing-box 
 
 11 Spring seat 
 
 12 1 
 
 12 r Rings for piston 
 
 13 Indicator 
 
 14 Balance piston 
 
 15 Packing ring for balance piston 
 
 16 Admission from overload operating valve 
 
 17 Drain for valve 
 
 2G7 
 
Fig. 129 
 
 VERTICAL GENERATOR SECTION 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 12 
 
 13 
 
 14 
 
 15 
 
 Armature punching section 16 
 
 Armature punching space block (outside) 17 
 Armature punching space block (inside) 18 
 
 Armature spider 19 
 
 Armature flange (top or lower) 20 
 
 Armature key 21 
 
 Armature coil 22 
 
 Bearing bracket (upper) 23 
 
 Ventilating hood 24 
 
 Floor plates 25 
 Generator base and middle bearing bracket 26 
 
 Pole piece revolving 27 
 
 Revolving field spider 28 
 
 Field spider rings 29 
 
 Shaft 30 
 
 Field coil support 
 
 End flange 
 
 Field coil retaining bolts 
 
 Retaining rings 
 
 Field coil 
 
 Fan 
 
 Air deflector (upper) 
 
 Air deflector (lower) 
 
 Collector lead supports 
 
 Brush-holder studs 
 
 Collector 
 
 Field lead 
 
 Brush-holder lead 
 
 Binding bands 
 
 Coupling 
 
 268 
 
space between the laminations and the armature shell (4) and 
 thence downward to be discharged through openings in the gen- 
 erator base (11). 
 
 The ventilation scheme on the horizontal generator, Fig. 130, 
 is similar to that on the vertical, except that air is drawn in 
 from below at both ends. The air is forced by the fans through 
 the air gap and out through the laminations, and may be dis- 
 charged at either the top or bottom of the armature as the 
 customer may require. 
 
 On small machines of 1000 kw. and less, the fans are usually 
 omitted from the field. On machines in test, where a bottom 
 discharge is called for, the opening at the bottom of the armature 
 is temporarily blocked off, and the air taken from the top. 
 Otherwise, a more or less elaborate arrangement of air ducts 
 would be necessary to prevent the hot discharged air from being 
 drawn in and circulated through the armature over and over 
 again. 
 
 Generator Tests 
 
 ALTERNATORS 
 
 Generator tests comprise the lesser part of the work on tur- 
 bine sets. On standard machines, and those for stock, the only 
 tests usually required are saturation and synchronous impedance 
 curves, phase rotation, current leakage from shaft to pillow 
 block, field and armature measurements, and high potential 
 tests. These tests are invariably made on every machine. 
 
 In addition to the above, heat runs, either open circuit and 
 short circuit, or a "zero power-factor" run may occasionally 
 be called for. Other tests much less frequently made are ven- 
 tilation tests, motor core loss, phase characteristic, armature 
 impedance with rotor removed, open-delta heat runs, zero- 
 excitation heat runs and full load heat runs. 
 
 As all the above mentioned tests except ventilation tests 
 and "zero-excitation runs" have been dealt with elsewhere 
 in this book no further mention is necessary except such details 
 as may need special attention due to slightly different condi- 
 tions that may be found on turbine generators. 
 
 Before beginning generator tests all pipe joints, and joints 
 about the gear casing, pump and bearings where there is a 
 possibility of oil leakage, should be carefully painted with 
 whiting so that any leaks existing may be located during the 
 progress of generator tests. 
 
 The limits to which saturation and synchronous impedance 
 curves are to be run, and the values of voltage and current held 
 on open- and short-circuit heat runs are varied from time to 
 time under instructions from the turbine generator Engineers, 
 hence, the book of "Special Instructions" previously referred to 
 should be consulted for this data. 
 
 Cold Measurements 
 
 Under the head of "field balance" reference was made to 
 taking cold measurements on the generator. This should be 
 
 269 
 
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 271 
 
done invariably before the field has been run. In addition to 
 galvanometer measurements of the armature and field, the field 
 is also measured by the voltmeter-ammeter method, as a basis 
 for the field temperature measurements to be made and recorded 
 with each half-hourly reading during the heat runs. When an 
 armature is equipped with temperature coils these must be 
 measured at the same time the other measurements are taken, 
 both before and during heat runs. The information obtained 
 from temperature coil measurements is the most important of 
 any obtained from heat runs on a turbine generator, for it is by 
 this means only that the actual internal temperatures of the 
 armature can be learned. Hence, it is of the utmost importance 
 that an absolutely accurate record of the cold resistance and 
 temperature of these coils be made. 
 
 Shutting Down After Heat Runs 
 
 Whenever possible an alternator should be so wired that it 
 may be quickly shut down after a heat run by loading it on 
 water-boxes. The load must be three- or quarter-phase, as 
 the case may be, never single-phase, and should be reducedas 
 the machine slows down in order not to increase the heating 
 due to decrease in ventilation. 
 
 In some instances it is impracticable to load on water-boxes, 
 and when such is the case the Head of the test, or an assistant, 
 should be consulted as to the best method to be used in shutting 
 down. 
 
 Direct current machines should always be arranged for 
 separate excitation for shutting down rapidly, and always 
 provided with a water-box load, even when the tests and heat 
 runs are being made by the "feeding-back" method. 
 
 Running Turbine Sets as Motors 
 
 When a turbine set is "motored" for a zero power-factor 
 heat run, or any other test, special attention should be given 
 to heating in the turbine. The friction of the air on the buckets 
 will raise the temperature of the wheels to a degree far above the 
 temperature of steam, and will cause serious trouble. To 
 obviate this, the exhaust should be left open and a slight amount 
 of steam passed through the turbine. This will hold the tem- 
 perature down to a safe value. It is also necessary to keep steam 
 turned on the carbon packing rings to prevent their cutting 
 and scoring the shaft. 
 
 "Zero Excitation" Heat Run 
 
 A certain amount of heating on a turbine-generator is caused 
 by the friction of the air which is forced through it at a high 
 velocity. To determine this heating a heat run is occasionally 
 made with no excitation on the field. Two hours are usually 
 required to bring temperatures constant, the field being measured 
 at intervals in the'usual manner, but with a very small current 
 
 272 
 
in order to prevent heating from this cause. The current should 
 be on only long enough for a quick reading. At the end of this 
 run the armature and field should both be measured and final 
 temperatures by thermometers taken as on any other heat run. 
 
 Ventilation Tests 
 
 When ventilation tests are to be made, a special pipe for 
 this purpose is erected on top of the armature. There are 
 two sizes of pipes in use at the present time, one, of 30 in. 
 diameter for use on smaller machines, and another of 40 in. 
 diameter for the large machines, both rising about 12 feet above 
 the generator. Reducing cones may be fitted to the upper end 
 for varying the diameter of the outlet, and a butterfly valve 
 is sometimes inserted between the lower end of the pipe and 
 the armature opening, for varying the volume of air from a 
 maximum to zero. The manometer used in measuring volume 
 is connected either to an impact tube located in the center of the 
 plane of the outlet opening, or to a special plug inserted radially 
 in the air pipe near the top, but below the base of the cone. 
 
 On machines of 1000 kw. and less, readings are taken with 
 the impact tube only. Above 1000 kw. both methods are used. 
 Simultaneously with every manometer reading, readings of 
 the pressure inside the inner shields of the armature (see Fig. 
 130) are taken at each end of the armature, a U-tube being used 
 for this purpose. The pressure in the shields is also taken 
 occasionally with the opening in the armature entirely closed, 
 that is, with no air circulating through the generator. 
 
 Testing Record Sheets 
 
 There are certain items and questions on turbine generator 
 sheets which do not appear on sheets for other forms of gen- 
 erators, hence, these sheets should be carefully looked over 
 and these items noted. It is important that they be checked 
 carefully and that questions be answered in every case. 
 
 DIRECT CURRENT MACHINES 
 
 The only tests made on direct current machines are saturation, 
 shunt adjustments and heat runs. 
 
 Compound is always adjusted for a rise in speed of 2 per cent 
 from full load to no load. As steam conditions in the Testing 
 Department are not the same as those under which a machine is 
 to operate when permanently installed, the governor cannot be 
 relied on to give the proper 2 per cent regulation, hence, it is 
 necessary to vary the speed as required by means of weights on 
 the governor arm. 
 
 DEFECTS 
 
 After tests are completed, the entire machine, both turbine 
 and generator, should receive a thorough inspection for any 
 defects which may not have been previously corrected during 
 the tests. 
 
 273 
 
All defects, large and small, should be carefully noted and 
 recorded on regular "defect sheets," special attention being 
 given to steam leaks and oil leaks, and oil throwing at bearings, 
 If any doubt exists as to whether or not some particular condi- 
 tion is to be regarded as a defect, enter the item on the sheet 
 as though it were a defect, and if on investigation it is found 
 not to be, it can easily be marked off. 
 
 STEAM CONSUMPTION TESTS 
 
 These tests are conducted in order to check guarantees 
 made to customers or to obtain engineering information on new 
 or experimental machines. 
 
 In either case it is essential that accurate and thoroughly 
 reliable data be obtained, and to this end every man concerned 
 with the test must be held responsible for his individual part of 
 the work. 
 
 Assembly of Machines 
 
 While the machine is being assembled the following record 
 should be made: 
 
 The number of the Drawing List. 
 
 What combination is assembled in the turbine. 
 
 Changes made since previous test. 
 
 Any special features of construction. 
 
 During the assembly of the turbine, all necessary drilling 
 and piping for gauges and thermometer wells should be done 
 and a calibrated orifice should be placed in the feed pipes to 
 the carbon packing rings in order that the amount of steam 
 necessary to seal the rings can be determined. Before the steam 
 piping is assembled a very accurate measurement of the pipe 
 diameter should be taken at the point where the nozzle plug for 
 the steam flow meter is to be installed. 
 
 If a water-brake is to be used for load, it is absolutely neces- 
 sary that the brake hang free on the knife edges for a very 
 little friction will give very erratic results in the scale reading. 
 
 Preparation for Test 
 
 The electric meters to be used in the test should be newly 
 calibrated. Where exceptionally accurate results are desired, 
 it is well to calibrate the meter transformers although as a 
 general rule their calibration changes very little. In case a 
 water-brake is used, the scale should be adjusted, using the 
 standard weights furnished for that purpose. 
 
 It is sometimes very difficult to obtain the required amount 
 of vacuum when the turbine is first started. Therefore, after 
 the turbine is assembled and before starting the test, the ma- 
 chine should be run under load to determine if the required 
 vacuum can be obtained. In case this is impossible, it is neces- 
 sary to find the air leaks and stop them up. Large leaks can be 
 
 274 
 
found by holding a lighted torch near the crack, the air current 
 drawing the flame in with it. Leaks can sometimes be found by 
 applying soapsuds to the leaky joint. Leaks that cannot be 
 closed by tightening the bolts should be subjected to a few inches 
 of vacuum and the leading joints then painted with thick black 
 japan. A serious leak may be closed by caulking with lead or 
 solder and afterward painting with japan. 
 
 Readings Taken During Test 
 
 The following readings should be taken during test: 
 
 Pressures (or vacuum), 
 
 Temperatures, 
 
 Flow, 
 
 Load. 
 
 Pressure 
 
 The pressures to be read are: 
 
 Steam pipe (above throttle and strainer), 
 
 1st valve bowl, 
 
 Operating valve bowl, 
 
 Shell pressures of all stages (when called for), 
 
 Exhaust chamber (near exhaust opening), 
 
 Carbon packing steam. 
 
 The steam pressure is read outside of the emergency throttle 
 valve and strainer, and is held constant during the test by 
 throttling down the steam, at boiler pressure, with a specially 
 equipped valve. The man holding this pressure should at once 
 notify the man in charge of the test if the pressure cannot be 
 held constant. 
 
 The bowl pressure is taken on the steam passage between 
 each of the controlling valves and the 1st stage nozzle. The 
 bowls are numbered in the order of their opening, the first 
 one to open being No. 1. The pressure on this bowl is read as 
 well as the pressure on the bowl on which the governor throttles, 
 both readings being recorded every two minutes. Knowing 
 the area of the nozzles open, the theoretical steam flow can be 
 calculated and used to check the flow recorded. 
 
 Stage shell pressures are read on each stage just below the 
 wheel and above the diaphragm for the next stage. The first 
 stage should be equipped with both a siphon and a quill, to 
 read either pressure or vacuum. If there are more than four 
 stages the second stage may need a similar equipment but 
 the lower stages only need a quill. The 1st stage pressure is 
 read at two minute and the lower stages at four or six minute 
 intervals. 
 
 The quill for the exhaust pressure should be tapped into the 
 connection between the turbine and condenser close to the 
 exhaust opening of the turbine. 
 
 Gauges are used to read all pressures above atmosphere, 
 and they should always be calibrated with a dead weight tester, 
 both before and after test. Before shutting down, except in 
 
 27.5 
 
case of an emergency, all gauges should be shut off to prevent 
 being subjected to a vacuum. If this occurs, the needle may 
 be drawn back against the stop pin so forcibly as to alter the 
 calibration. The calibration may also be changed by sudden 
 jars or by heating. To prevent the latter, all gauge piping 
 must be equipped with a siphon, which is kept cool by applying 
 wet waste. If a gauge is allowed to heat up, the solder in the 
 Bourdon spring will melt and ruin the gauge. 
 
 +W.C." 
 
 1 
 
 1 
 
 <0 
 
 *£>» 
 
 
 
 Fig. 131 
 WATER COLUMNS ON GAUGES 
 
 The water column on the gauges should be measured and 
 entered on the testing Record Sheet with the number of the 
 gauge. The water column is measured from the top of the 
 siphon coil to the center of the gauge and recorded as + or — WC 
 in inches. (See Fig. 131.) 
 
 U-tubes are used to read all vacuum and pressures of a 
 few inches. These consist of a thick glass tube with }/% in. 
 bore bent in the shape of a U, and mounted in a wooden case 
 carrying a brass scale. (See Fig. 132.) The scale is graduated 
 in inches with a zero at the center and numbered each way 
 to read at least 16 in. The tube is then rilled with mercury. 
 The U-tube is connected up through a heavy rubber tube. 
 The glass tube should be clean and free from water and the 
 connections should be free from air leaks. These may be detected 
 by turning the cock off, leading to the vacuum being measured, 
 and noting if any perceptible fall of the column occurs. Both 
 columns should be read and added together. Never read one 
 
 276 
 
and multiply by two. When the U-tube is disconnected both 
 columns should stand at the same level. When reading vacuum 
 the U-tube may be left connected to the machine, but it should 
 be disconnected after each pressure reading, or the tube will 
 gradually fill with water. 
 
 Fig. 133 
 ABSOLUTE PRESSURE GAUGE 
 
 Absolute pressure gauges are used only on the high vacuum 
 of the exhaust, to check the U-tube. These are made of a thin 
 glass tube bent in the shape, of a U with one end longer than 
 the other. The longer end is bent over and brought down 
 below the bottom of the U. (See Fig. 133.) The short leg of 
 the U and a couple of inches of the other leg is completely 
 filled with mercury, which is then boiled out and the top sealed. 
 The whole tube is then mounted in a wooden case carrying a 
 brass scale graduated in inches. The lower end is connected 
 to the vacuum to be measured by a heavy rubber tube. 
 Normally the difference in the heights of the two columns 
 will be six to eight inches, but with a high vacuum on the lower 
 end they will tend to equalize. The upper column has an 
 absolute vacuum on it so that the difference in the height of 
 the two columns represents the difference between the vacuum 
 
 277 
 
being read and an absolute vacuum, or the absolute back pres- 
 sure. The sum of the readings on the absolute gauge and the 
 U-tube should check the barometer reading within less than 
 0.1 in. 
 
 The mercury in the end ,open to the atmosphere slowly 
 oxidizes and when this takes place the absolute gauge will 
 record a smaller back pressure than is actually present. The 
 gauge should be placed above the opening into the vacuum 
 space and the rubber tube kept free from loops or water may 
 lodge in it and be carried over on the top of the mercury when 
 the vacuum is broken. If this occurs, the gauge must be sent 
 to the laboratory and cleaned and refilled. The gauge must 
 always be kept in a vertical position and never laid down or 
 carried horizontally, or air will get into the sealed end. Turn 
 on to vacuum very slowly and never take it off suddenly, or 
 the mercury may break the sealed end. 
 
 Temperatures 
 
 The temperatures to be read are: 
 
 Steam pipe (near pressure gauge), 
 
 All stage shells (when called for), 
 
 Air (near U-tubes and absolute gauges). 
 The temperature of the initial steam is read as nearly as 
 possible to the pressure gauge, the thermometer-well being 
 placed diametrically in the steam pipe. Steam is available at 
 any pressure up to 200 lb. gauge, and of varying quality. For 
 running tests, which require high pressure arid low superheat, 
 it is sometimes necessary to inject a spray of water into the 
 steam. This is done at a considerable distance from the turbine 
 in order to get a good mixture of water and steam. When dry 
 steam is specified, it is best to hold about 15 deg. superheat; 
 for, if a lower superheat be held, the temperature may drop to 
 the saturation point where the condition of the steam cannot be 
 determined without a calorimeter. " " ' 
 
 When the testis finished, always shut off injection water to 
 avoid filling the steam pipe with water, as this would cause a 
 water hammer when steam is again turned on. 
 
 In cases where it is necessary to read the temperature in 
 the various stages, the thermometer wells should be located 
 near the gauge and in the path of the steam; special precautions 
 being taken so that the revolving part of the turbine will not 
 strike the thermometer well. 
 
 The temperature of the air near all U-tubes and absolute 
 gauges is taken in order to correct the length of the mercury 
 column to the same temperature as that at which the barometer 
 reading is read. 
 
 The man reading temperatures should fill the thermometer 
 wells with mercury and be sure that there are no broken mercury 
 columns in the thermometers in use. A thermometer should be 
 placed as low in the well as possible with the readings to be 
 taken, but do not have the mercury column below the point of 
 immersion as vaporization of the mercury in the thermometer 
 may take place. 
 
 278 
 
Flow 
 
 There are two methods in common use of measuring the 
 quantity of steam to be consumed: The first is to weigh the water 
 after the steam has been condensed in a surface condenser. The 
 second is to measure the steam flow by means of a steam flow 
 meter. 
 
 The first method is the one most commonly used in the 
 Testing Department, although in nearly all cases a flow meter is 
 installed and readings recorded. 
 
 Flow Tanks 
 
 After the steam has been condensed in the surface condenser 
 it is pumped from the hot well to the flow tanks where it is 
 weighed. These tanks should be of sufficient capacity to hold 
 the amount of steam condensed during six minutes. They are 
 mounted one above the other. Both outlet pipes should be 
 equipped with quick closing valves which shut perfectly tight. 
 The upper tank is used as a reservoir, when taking weights 
 on the lower, which is mounted on a pair of platform scales. 
 
 To measure the amount of condensed steam, proceed as 
 follows: Close the upper tank outlet valve on an even six 
 minutes. Then close the lower tank outlet and balance the 
 scale. This reading is called "tare." The upper valve is then 
 opened, and closed after exactly six minutes have elapsed from 
 the first closing. After closing, the scale is again balanced, 
 and this reading is called "gross." The difference between the 
 "gross" and "tare" is the "net" reading which when multiplied 
 by 10 gives the flow per hour. After taking the "gross" reading, 
 the lower valve is opened and the water allowed to run to waste. 
 The valve is then closed and the "tare" again taken. This 
 cycle is repeated as long as the test continues, care being taken 
 to close the upper valve at exactly each six minute interval. 
 If the flow is extremely rapid, readings may be taken at four 
 or even three minute intervals. Slight variations will occur 
 due to irregular pump or condenser action, but the average 
 of a number of readings will give accurate results with constant 
 conditions. At least five readings should be obtained for each 
 load, or operating condition. 
 
 Before taking any readings, the scales should be carefully 
 inspected to see that the platform and the scale beam move 
 freely. The scales should be calibrated frequently. This can 
 be done by balancing the scales and then adding a 50 lb. standard 
 weight. These should be placed on each of the four corners of 
 the platform. The scales should be thoroughly overhauled 
 occasionally and all knife edges kept sharp. When not in use 
 the weight should be taken off the knife edges, by throwing 
 the lever to the off position. 
 
 Load 
 
 There are two methods of obtaining load; one with an electric 
 generator, and the other by the use of a water brake. 
 
 279 
 
When an electric generator is used, the load is measured 
 by means of wattmeters; ammeter and voltmeter readings 
 being taken as a check. 
 
 <T Cvrnrnt 7nm/&rmerj 
 
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 Ammeterj 
 
 Wattmeters 
 
 Vto/tmeterj 
 
 Fig. 134 
 WIRING CONNECTIONS FOR LOAD TEST 
 
 The meters required for reading the load on three-phase 
 a-c. generators are: Two wattmeters, three a-c. ammeters, 
 two a-c. voltmeters, one d-c. ammeter, and one d-c. voltmeter. 
 Each a-c. instrument is provided with a separate potential or 
 current transformer of sufficient ratio to bring the reading well 
 within the scale of the meter. Five current and four potential 
 transformers are required. (See Fig. 134.) 
 
 One side of the current transformer secondary is grounded 
 and each circuit is provided with a single-throw, single-pole, 
 short-circuiting switch, which must be used when the meter 
 is disconnected. The volts, amperes and watts are read, using 
 a separate transformer, to check the correctness of the load and 
 the power-factor, which should be greater than 0.99; otherwise, 
 the test cannot be accepted. The meters and transformers should 
 be calibrated frequently, and a copy of the calibrations kept at 
 hand for calibrating the load. A record of the number and date 
 of calibration of each meter and the number, ratio, and date of 
 calibration of each transformer should be entered on each sheet 
 of every test. 
 
 The man reading the wattmeters is responsible for the 
 load, and, assisted by the man reading the ammeters, must keep 
 the phases as nearly balanced as possible. Average readings 
 are taken at two-minute intervals; all readings being taken as 
 nearly simultaneously as conditions permit. The man reading 
 the voltmeters must hold the voltage constant by varying the 
 
 280 
 
field, when the governor is operating, and must read and record 
 volts field and amperes field at four-minute intervals. 
 
 Quarter-phase generators require one less current trans- 
 former and one less a-c. ammeter. On d-c. generators, two 
 sets of milli-voltmeters with shunts and two voltmeters are used 
 to check the load. Considerable trouble is often experienced 
 in getting shunts that will check within 1 per cent after they 
 have been heated. 
 
 In cases where a water-brake is used, the same precautions 
 concerning the care of the scales for the steam flow tanks apply- 
 to the water-brake scales. The knife-edges on the brake shell 
 should bear properly and the brake shell turn without friction. 
 Readings should be taken only when the scales remain balanced 
 for an appreciable length of time and when the speed is exactly 
 right. Care should be exercised to make sure that water is 
 continually flowing through the brake in order to prevent exces- 
 sive heating. The flow of water on each side of the brake disk 
 should be very nearly equal; otherwise, the brake may vibrate 
 severely, making it impossible to obtain accurate readings. 
 
 The following formula is used to calculate the kw. output: 
 
 Let R = Length of brake arm in inches. 
 P = The load on scales in pounds. 
 5 = Speed in revolutions per minute. 
 
 Then h.p. output = 12X33QQ0 
 
 Kw. output = h.p. output X 746 
 
 Tests 
 
 The tests generally required are "load curve" and "no load 
 flow with field excited" and vacuum and speed curves at various 
 loads. The following may also be required: Bowl pressure 
 curve, superheat curve, and shell pressure curve. 
 
 The readings to be taken and the time intervals are as 
 follows for all tests: 
 
 Pipe pressure 2 minutes 
 
 Valve casing 2 
 
 1st bowl 2 
 
 Throttling bowl 2 
 
 Superheat 2 " 
 
 1st stage shell 2 or 4 minutes 
 
 2nd " " 4 or 6 
 
 3rd " " 4 or 6 
 
 Additional shells 4 or 6 
 
 Exhaust-vac. and abs 2 minutes 
 
 Packing steam exhaust and head if used. . .6 to 10 minutes 
 
 Temperature of all U-tubes 10 minutes 
 
 Flow (water rate) 6 
 
 A-c. watts 
 
 A-c. amperes \ 2 
 
 A-c. volts J 
 
 Field amperes and volts 4 
 
 D-c. amperes 1 9 << 
 
 D-c. volts / z 
 
 281 
 
In taking a load curve (water rate with load) with the gover- 
 nor operating, the initial pressure, superheat and vacuum are 
 held constant, and at least three, and preferably five, loads are 
 used. These may be half-load, full-load, and 50 per cent over- 
 load, together with the quarter-load and 25 per cent overload. 
 
 "No-load flow" is taken by running the machine under 
 normal steam conditions; holding normal voltage on the generator. 
 
 A vacuum curve may be run with or without the governor. 
 When the governor operates, the initial pressure, superheat 
 and load are held constant and the vacuum varied. For a 
 short vacuum curve four or five points are taken at pressures 
 varying 1 in. If it is desired to carry the test to atmospheric 
 pressure, two or three of the higher vacuum readings are taken 
 close together and the pressure differences then gradually 
 increased to five or six inches at atmosphere. The same read- 
 ings are taken as on the load curve. 
 
 In running a vacuum curve without the governor, a number 
 of valves are blocked open to give approximately the desired 
 load at 28 in. vacuum. The speed is held constant by varying 
 the load and readings taken on the table, only when the speed, 
 initial pressure, superheat and vacuum are correct. They are 
 then taken at 1 minute intervals. All other readings are the 
 same. The field amperes are held at the constant value, which 
 gives normal voltage at normal speed. The water flow will 
 be constant at the different vacuums so that the vacuum can be 
 changed as soon as a sufficient number of steady readings 
 on the table are obtained. Usually not more than four points 
 are taken, at 1 in. pressure differences. 
 
 This test and the speed curve are the two most difficult 
 water rate tests to make. Every man must work together, 
 or the speed will continually vary and no results be obtained. 
 The load should be varied in small increments and sufficient 
 time allowed for a corresponding change in speed. The field 
 amperes should be held absolutely constant as but a small 
 change in excitation produces a large change in the load, espe- 
 cially on high voltage machines. 
 
 On a speed curve, the conditions are similar to that in a 
 vacuum curve without governor and the same precautions 
 apply. The speed is varied by varying the load, and field 
 amperes are held constant to give normal voltage at normal 
 speed. If, however, at the higher speeds the voltage is too 
 high either for the safety of the windings or for the meters, 
 the excitation may be reduced sufficiently to enable readings 
 to be taken. 
 
 Maximum load non-condensing may be taken from a point 
 on the normal load vacuum curve by a separate test. Occasion- 
 ally back pressure curves above atmosphere are required. 
 
 If the turbine has no atmospheric exhaust openings the 
 back pressure test can be obtained only by throttling down 
 the air pump until atmospheric pressure is obtained at the 
 exhaust opening of the turbine. This produces a high temper- 
 ature in the condenser and is likely to cause leaks. 
 
 282 
 
If, as is usual, the machine has atmospheric exhaust openings, 
 they can be piped to the condenser through a gate valve, the 
 condenser exhaust being blanked off. With this arrangement 
 any desired back pressure may be held on the turbine, while 
 the condenser is working under a high vacuum. The condenser 
 is kept cool and there is no danger of damaging it or the air 
 pump. The readings are the same as for the load curve. The 
 load should be gradually increased until the last valve is practi- 
 cally wide open. If too much load is applied, the speed will 
 fall off when the last valve is wide open. 
 
 A bowl pressure curve is generally taken at full load, with 
 the governor operating. The range of initial pressures should 
 be as large as possible, in order to neutralize the effect of throt- 
 tling on any of the valves. All readings are taken in the same 
 manner as for a load curve. 
 
 .4 superheat curve is generally taken at two points, though 
 more may be taken, one at low and the other at high superheat. 
 The conditions and readings are the same as for the load curve, 
 with which it may often be combined to advantage. 
 
 A shell pressure curve is taken on those turbines that are 
 equipped with stage valves, or with a movable diaphragm 
 between stages. 
 
 This can generally be combined with the load curve. The 
 group of nozzles controlled by the stage valve should always 
 be wide open or closed tightly. They should never be throttled, 
 as this will invariably increase the water rate. 
 
 Arrangement of Apparatus 
 
 In order to conduct the tests outlined on the previous pages, 
 the Testing Section in Building Xo. 61 is equipped with appara- 
 tus especially arranged for this work. 
 
 Steam Controlling Equipment 
 
 There are four stands equipped with connections to the 
 condensers and with a suitable switchboard for controlling 
 the generator load. The condensers and their auxiliary appa- 
 ratus are located under the switchboards in such a manner that 
 they are readily accessible for repairs. The cooling water pump 
 is located at the end of the Test Floor, the piping being so 
 arranged that it can supply cooling water to one or both con- 
 densers at the same time. There are two hot-well pumps and 
 the piping is so arranged that either or both pumps can be con- 
 nected to either of the condensers. Each pump has a separate 
 discharge line to the weigh-tanks. The air pumps are located 
 as close to the condensers as possible. 
 
 The condensers are equipped with relief valves set to operate 
 at slightly above atmospheric pressure. These valves should 
 be inspected frequently to make sure that they are in operating 
 condition, for it is a very dangerous practice to allow the pres- 
 sure on the condensers to become excessive. 
 
 283 
 
Electrical Equipment 
 
 Each of the four stands have switchboards so arranged 
 that any of the stands can be connected to the water-boxes and 
 to the exciters through a plug board. The switchboards are so 
 connected that the instruments and transformers can be installed 
 without any changes in the permanent winding: The exciters, 
 two in number, are turbine driven sets, the fields of both being 
 excited from the 125 volt shop circuit. Located directly back 
 of the Testing Section office are the water-boxes used for obtain- 
 ing load. The blades are remotely controlled, the controls being 
 wired to the plug-boards so that they can be connected to any 
 of the four stand switchboards. 
 
 Auxiliary Pumps 
 
 Injection water pumps for controlling the superheat, the step- 
 bearing oil pumps, oil tanks, and other auxiliary apparatus are 
 also located near the testing stands. When running a vertical 
 machine it is well to detail a man to watch the step-bearing 
 pump as there is no accumulator in the oiling system. 
 
 Caution 
 
 Although there is a regular attendant, whose duty it is 
 to operate the pumps, exciters, etc., the man running a machine 
 should know at all times what apparatus is in use and should be 
 certain that the water, vacuum, and oil pumps are running 
 before starting the turbine. When a turbine has been shut 
 down for any length of time, the attendant should be notified 
 so that he can shut down the auxiliary apparatus or make other 
 changes that are necessary. In general all instructions applying 
 to commercial testing of turbines apply and should be adhered to 
 when taking steam consumption tests. 
 
 284 
 
CHAPTER 14 
 
 MARINE ENGINE SETS 
 
 The Marine Engine Sets consist of vertical type double 
 acting steam engines direct connected to multipolar generators. 
 (See Fig. 136.) 
 
 Fig. 135 
 MARINE ENGINE 
 
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 287 
 
ENGINE 
 
 Single cylinder engines are used with generators from 2% 
 to 60 kw. capacity, and vertical tandem compound engines with 
 machines from 25 to 75 kw. capacity. The engines are standard 
 commercial machines. See Fig. 135. 
 
 Steam Pressures 
 
 The ratings of the standard single cylinder engines are based 
 on the steam pressures given in the following table and those 
 designed for 80 lb. steam pressure can be operated at pressures 
 up to 125 lb. either condensing or non-condensing. If higher 
 boiler pressures are used a suitable reducing valve must be 
 placed in the steam line to give the desired pressure. For steam 
 pressures of less than 80 lb., single cylinder engines are fitted 
 with large cylinders, to operate at pressures ranging from 35 to 
 60 lb. The tandem compound engines are designed to operate 
 economically at 125 lb. condensing or 140 lb. non-condensing. 
 
 Unless otherwise advised by Engineering instructions, all 
 engines must be tested at the pressures given in the tables on 
 pages 289 to 292 inclusive. These tables are a complete list of 
 all types of engines manufactured. 
 
 Lubrication 
 
 Two systems of lubrication are used, gravity and forced. 
 
 In the gravity system all the main bearings of the engine are 
 lubricated from an oil reservoir attached to the engine (refer to 
 Fig. 136) ; each bearing being provided with an adjustable sight 
 feed for regulating the flow of oil. The waste oil collects in a 
 bedplate reservoir, from which it can be drained, filtered and 
 used over again. The bearings of the governor and valve gear 
 are lubricated by compression grease cups. 
 
 In the forced system the lubricant is passed under pressure 
 to the various parts of the engines. The base of the engine forms 
 an oil tank to which is attached a small plunger pump driven by 
 an eccentric on the shaft. The oil is forced through grooves in 
 the main bearings, drilled holes in the shaft connecting these 
 grooves with the crank pin. The oil is also forced to the wrist 
 pin through the pipe on the side of the connecting rod. 
 
 The passages in the crosshead pass the oil from the wrist pin 
 to the guides. After passing through the bearings the oil is 
 collected in the base, where it settles and is used over again. 
 The bearing caps must be set up tight and the main bearing 
 liners must be close to the shaft; otherwise too much oil leakage 
 will occur before reaching the last bearing. To prevent the 
 entrance of foreign matter a strainer is attached to the suction 
 valve of the pump. When the crank chamber is inspected, no 
 waste, dirt or other matter must be allowed to enter and mix with 
 the oil. When cleaning the oil chamber, canvas and not waste 
 should be used, since the latter clogs the strainer. 
 
 Only mineral oil should be used for lubricating. Since the 
 oil passes through the bearings repeatedly, it gradually loses its 
 lubricating properties, becoming thick and gritty. It should, 
 
 288 
 
SINGLE VERTICAL CYLINDER ENGINE SETS, 
 GRAVITY LUBRICATION TYPE 
 
 
 DIMENSIONS IN INCHES 
 
 
 
 
 
 Dia. 
 
 
 Dia. 
 
 Dia. 
 Ex- 
 haust 
 Pipe 
 
 Volts 
 Full 
 
 Amp. 
 Full 
 
 Steam 
 Pres- 
 
 Classification 
 
 Cyl- 
 inder 
 
 Stroke 
 
 Steam 
 Pipe 
 
 Load 
 
 Load 
 
 Lb. 
 
 MP 4- 2 3^-700 
 
 3 Mi 
 
 3 
 
 % 
 
 1 
 
 110 
 
 23 
 
 80 
 
 MP 4- 3 -700 
 
 3K 
 
 3 
 
 % 
 
 1 
 
 110 
 
 27 
 
 100 
 
 MP 4- 4 -600 
 
 4^ 
 
 4 
 
 1 
 
 IV 
 
 110 
 
 36 
 
 80 
 
 MP 4- 5 -600 
 
 4K 
 
 4 
 
 1 
 
 Wa 
 
 110 
 
 45 
 
 100 
 
 MP 4- 7 -550 
 
 5 
 
 4H 
 
 Wa 
 
 m, 
 
 110 
 
 64 
 
 80 
 
 MP 4- 8^-550 
 
 5 
 
 4^ 
 
 Wa 
 
 IV?, 
 
 110 
 
 77 
 
 100 
 
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 QV?, 
 
 5 
 
 IV?, 
 
 2 
 
 110 
 
 91 
 
 80 
 
 MP 6-12^-450 
 
 W, 
 
 5 
 
 IV?, 
 
 2 
 
 110 
 
 114 
 
 100 
 
 MP 6-15 -400 
 
 8 
 
 6 
 
 2 
 
 2V? 
 
 110 
 
 136 
 
 80 
 
 MP 6-17K-400 
 
 8 
 
 6 
 
 2 
 
 2V?, 
 
 110 
 
 160 
 
 100 
 
 MP 6-20 -360 
 
 9 
 
 7 
 
 2 V?, 
 
 3 
 
 125 
 
 160 
 
 80 
 
 MP 6-25 -360 
 
 9 
 
 7 
 
 2 V? 
 
 3 
 
 125 
 
 200 
 
 100 
 
 MP 6-30 -305 
 
 11 
 
 8 
 
 3 
 
 m 
 
 125 
 
 240 
 
 80 
 
 MP 6-35 -305 
 
 11 
 
 8 
 
 3 
 
 3V?, 
 
 125 
 
 280 
 
 100 
 
 MP 6-40 -305 
 
 11 
 
 8 
 
 3 
 
 SV2 
 
 125 
 
 320 
 
 125 
 
 Generators can be wound for 110, 125 or 250 volts. 
 
 SINGLE VERTICAL CYLINDER ENGINE SETS, 
 FORCED LUBRICATION TYPE 
 
 
 DIMENSIONS IN INCHES 
 
 
 
 
 Classification 
 
 Dia. 
 
 
 Dia. 
 
 Dia. 
 
 Volts 
 Full 
 
 Amp. 
 Full 
 
 Steam 
 Pres- 
 
 
 Cyl- 
 
 inder 
 
 Stroke 
 
 Steam 
 Pipe 
 
 haust 
 Pipe 
 
 Load 
 
 Load 
 
 Lb. 
 
 MP 4 -7 -550 
 
 5 
 
 4^ 
 
 IV 
 
 IV? 
 
 110 
 
 64 
 
 80 
 
 MP 4- 8^-550 
 
 5 
 
 4H 
 
 IVa 
 
 IV?, 
 
 110 
 
 / i 
 
 100 
 
 MP 6-10 -475 
 
 sv?, 
 
 5 
 
 IV 
 
 2 
 
 110 
 
 91 
 
 80 
 
 MP 6-12^-475 
 
 QV?, 
 
 5 
 
 IV? 
 
 o 
 
 110 
 
 114 
 
 100 
 
 MP 6-15 -425 
 
 8 
 
 6 
 
 2 
 
 2V 
 
 110 
 
 136 
 
 80 
 
 MP 6-15 -425 
 
 6 
 
 6 
 
 2 ' 
 
 2Vo 
 
 110 
 
 136 
 
 150 
 
 MP 6-17V 2 -425 
 
 8 
 
 6 
 
 2 
 
 2V 
 
 110 
 
 160 
 
 100 
 
 MP 6-17^-425 
 
 6 
 
 6 
 
 2 
 
 2V 
 
 110 
 
 160 
 
 175 
 
 MP 6-20 -400 
 
 9 
 
 7 
 
 2V? 
 
 3 
 
 125 
 
 160 
 
 80 
 
 MP 6-25 -400 
 
 9 
 
 7 
 
 2 V? 
 
 3 
 
 125 
 
 200 
 
 100 
 
 MP 8-30 -315 
 
 11 
 
 8 
 
 3 
 
 33^ 
 
 125 
 
 240 
 
 80 
 
 MP 8-35 -315 
 
 11 
 
 8 
 
 3 
 
 3V 
 
 125 
 
 280 
 
 100 
 
 MP 6-40 -315 
 
 11 
 
 8 
 
 3 
 
 3 V 
 
 125 
 
 320 
 
 125 
 
 MP 8-50 -280 
 
 12 
 
 11 
 
 3H 
 
 4 
 
 125 
 
 400 
 
 100 
 
 MP 6-60 -280 
 
 12 
 
 11 
 
 sy 2 
 
 4 
 
 125 
 
 480 
 
 125 
 
 Generators can be wound for 110, 125 or 250 volts. 
 289 
 
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292 
 
therefore, be occasionally run through a filter and mixed with 
 new oil. The number of filterings required depends upon the oil 
 as well as the length of time the engine operates. 
 
 The oil should stand about % in. above the suction and dis- 
 charge valves, and no water should be allowed to mix with it. 
 An oil pressure of about 15 lb. should be maintained by regulating 
 the adjusting screw of the relief valve. 
 
 Valves 
 
 In all single cylinder engines, the plain plug piston valve is 
 employed without any expanding rings. These valves take steam 
 through the inner edges, and exhaust past the outer edges. (On 
 tandem compound engines the low pressure valves take steam 
 through the outer edges and exhaust past the inner edges.) The 
 travel of the valve is controlled by the automatic governor; 
 varying the cut-off from % to zero, depending upon the load. 
 Great care is used in grinding and fitting these valves to their 
 chambers, to obtain economical and satisfactory operation. 
 The fit of these parts is most important. 
 
 Starting the Engines 
 
 Before steam is admitted to the cylinder see that the valve 
 moves freely by turning the governor wheel by hand. As the 
 expansion of the valve is much more rapid than the cylinder, the 
 cylinder should be allowed to warm up before full pressure is 
 applied. By allowing the set to come to full speed gradually, 
 no trouble will be experienced due to the valve "seizing." The 
 engineer in charge of the section always prepares the engines for 
 test, including the adjustment of valves, governors, packing, 
 taking of indicator diagrams, care of indicators, piping, con- 
 densers and apparatus for weighing water when water consump- 
 tion tests are made. 
 
 Tests 
 
 Unless otherwise advised by the Engineering Notice covering 
 the particular requisition and engine, all single cylinder com- 
 mercial engines are tested for the following only: 
 
 (1) Speed Regulation. 
 
 (2) Steam Consumption. 
 
 (1) The steam and back pressures and electrical load are 
 held constant. Then the speed variation is tested by suddenly 
 putting on or throwing off load when the conditions are con- 
 stant. The total variation between full and no load should not 
 exceed 3 Y2 per cent. A speed regulation of 3 per cent is usually 
 obtained and at this value the stability of the governing 
 mechanism is satisfactory. When adjustments are being made 
 for speed regulation, duplicate readings on the generator must 
 be obtained, and the voltage must be carefully noted to see if 
 it is affected by fluctuation in engine speed. If any voltage 
 fluctuation occurs, it must be reported to the engineer and the 
 proper correction made. With the engine exhaust connected 
 to the condenser, the load must also be thrown on and off and 
 
 293 
 
the speed noted, especially at no load, to see that the valve 
 completely shuts off steam and that the engine does not "run 
 away" or "race." 
 
 (2) The performance of every engine must lie within the 
 limits given in the tables furnished the Testing Department 
 regarding steam consumption. The method of weighing the 
 condensed steam is exactly the same as employed on the turbine 
 test. The piping in the testing stand and valves is arranged 
 so that the exhaust steam from the engine can be passed either 
 to atmosphere or through a condenser. If the steam consump- 
 tion is excessive, the piston should be examined to see that the 
 rings are free in the grooves and that they have a good and even 
 bearing against the cylinder wall. If the rings are in good condi- 
 tion the valve is probably too small in diameter and allows steam 
 to blow directly into the exhaust. In bad cases there will gener- 
 ally be a considerable variation in speed as the governor can not 
 control the speed, with leaky valves. 
 
 Poor steam economy is generally due to the above causes, but 
 lack of lubrication in the steam spaces, excessive friction in the 
 stuffing boxes and bearings, or poor valve setting will increase 
 the amount of steam used. 
 
 Operation 
 
 During the operation of the set in test the following points 
 should be carefully noted: 
 
 (1) Balance of governor pulley. 
 
 (2) Concentricity of crank shaft with armature coupling 
 and commutator. 
 
 (3) Absence of oil and grease throwing. 
 
 (4) Operation of engine with reference to quiet running. 
 
 (5) Proper alignment of all parts, especially the crank and 
 wrist pin boxes, and central position of piston with reference to 
 the cylinder; clearance of oil deflector of armature shaft from 
 outboard bearing. 
 
 (6) Oil leakage around ends and at unions of Multiple 
 Oiler, and points where supply pipes pass through column on 
 gravity lubrication engines ; that the oil drips from supply pipes 
 into proper oil cups and channels, and in engines employing 
 the forced system of lubrication, the quiet operation of oil pump 
 check valves, and of the relief valves and pressure gauge in the 
 system. 
 
 (7) The operation and "hang" of throttle valve and align- 
 ment of handwheel in reference to the valve stem in engines 
 having the valve bolted to the cylinder. 
 
 (8) Absence of leakage in cylinder casting, due to porous 
 metal or other causes. 
 
 (9) Fit of oil shields. 
 
 (10) Tightness and adjustment of cylinder relief valves. 
 These should be allowed to open at the proper pressure, then 
 tighten the set screw in casing about one turn. 
 
 (11) Vibration. 
 
 (12) General appearance of entire set. 
 
 294 
 
Governor 
 
 The governor used in connection with the gravity lubrication 
 type of engines is shown in Fig. 137, and is simpler than the 
 various flywheel governors using shifting eccentrics. It consists 
 of a heavy flywheel A, keyed to the shaft, and carrying the 
 governor weight B, pivoted at C, and containing the eccentric 
 D, which operates the valve. 
 
 The governor connecting rod transmits motion from the 
 governor to the valve, and is connected to eccentric pin D. 
 The length of the valve stroke, therefore, depends upon the 
 
 Fig. 137 
 GOVERNOR 
 
 distance of D from the center E. The amount of steam admit- 
 ted to the cylinder varies directly as the distance between the 
 center of D and E. 
 
 If the engine speed increases, then the weight B is moved 
 by centrifugal force toward the perimeter A, decreasing the 
 distance of D from the center E and reducing the amount of 
 steam admitted to the cylinder. If the speed of the engine 
 becomes excessive, the distance of B from E is reduced to the 
 minimum and the steam is entirely cut off. 
 
 The motion of the fly weight B is opposed by the spring 
 F, which is attached to the pulley and fly weight. By increasing 
 or decreasing the tension of the spring, "the speed may be raised 
 or lowered. The same effect will be produced by moving the 
 spring in the slot of the weight, moving it away from the fulcrum 
 increases the speed, and vice versa. 
 
 Unstable regulation is due to too close an adjustment of 
 speed, and may be avoided by moving the spring attachment 
 away from the fulcrum. A leaking valve or insufficient 
 
 295 
 
lubrication of the fly weight fulcrum will also produce the same 
 effect. If the lubrication is not sufficient the governor should be 
 taken apart and cleaned. Only the best of soft grease should be 
 used in the cup, and the governor should occasionally be taken 
 apart and cleaned to obtain the best results. The governors of 
 some of the forced lubrication engines are enclosed by the engine 
 column and the bearing pin and eccentric are lubricated by oil 
 under pressure from the oiling system. 
 
 Indicator Diagrams 
 
 When indicator diagrams are required, a stud is screwed into 
 the wrist pin of the connecting rod for driving the motion, con- 
 necting through a link to a lever pivoted to the bracket on the 
 engine column. The motion for the indicator is taken from a 
 cord pin on this lever. 
 
 The indicator is a delicate instrument, and must be handled 
 with care and kept in good order. The piston springs should be 
 frequently calibrated. Before attaching the indicator to an 
 engine, blow steam freely through the pipes and three-way 
 cock to remove any particles of dust or grit that may have 
 accumulated in them. After being used, the indicator should be 
 carefully wiped and oiled. If any grit or other obstruction gets 
 into the cylinder of the indicator the diagrams will give wrong 
 results. This trouble is easily detected and should be remedied 
 at once by taking out the piston, detaching it and cleaning with 
 oil and replacing. The piston must move perfectly freely in its 
 cylinder. To test this, take out the piston and spring, detach 
 the latter and replace the piston and piston rod in their operating 
 position, then, holding the indicator in an upright position, 
 raise the pencil arm to its highest point and let it drop. It should 
 freely descend to its lowest point. 
 
 Before taking diagrams, steam should be admitted to the 
 indicator, and the cylinder allowed to become thoroughly heated. 
 Indicator springs are made in different sizes of steel wire, to 
 adapt them to different steam pressures. Springs are usually 
 made to the following scales: 8, 12, 16, 20, 30, 40, 60, 80 and 100 
 pounds per inch travel of the indicator pencil. This scale is 
 stamped on the spring. The spring used for indicating an 
 engine depends upon the maximum steam pressure used; a 
 spring should be chosen to give a diagram with maximum height 
 not exceeding 1% in. The diagram should not exceed 2 3^ in. to 
 3 in. in length. The less the vertical and horizontal motions 
 are, the slower will be the movement of the paper cylinder with 
 a correspondingly more delicate pencil tracing. The proper 
 spring required may be found as follows: Divide the boiler pres- 
 sure, expressed in pounds, by the desired height of the diagram, 
 expressed in inches, and the result will be the spring required. 
 For instance, with a boiler pressure of 140 lb. gauge and a 
 diagram height of 1 % in. then 140 ■*■ 1 % /± = 80, is the number of 
 the spring required. 
 
 If too weak an indicator spring is used it will vibrate inside 
 the indicator cylinder at admission and cause a wavy line on 
 
 296 
 
the card, hence the strength of the spring should be chosen with 
 due regard to this point. The indicator cord should have 
 sufficient tension on it to prevent any whipping action occurring 
 at the extreme point of the stroke. Hence sufficient tension 
 must be given to the rotary spring in the indicator to prevent this- 
 
 Cor-r-cj&cttec/ 
 Copper- GosHet, 
 
 g waste f=>/p>e &r>c/ Vo/ve 
 
 Fig. 138 
 PISTON ROD PACKING 
 
 action. If the tension on this spring is not sufficient, the length 
 of the indicator cards will vary; the higher the speed of the 
 engine the greater will the variation be. 
 
 The pressure of the pencil upon the paper can be adjusted 
 by screwing the handle in and out. The line should not be 
 heavy as this will cause unnecessary friction. After the diagram 
 has been taken, close the cock and take the atmospheric line; 
 then disconnect the cord to avoid excessive wear on the drum. 
 
 297 
 
The following notes should be made on the card and any- 
 other data which it is proper to add: 
 
 Date Time 
 
 Requisition No. Dia. of Rod 
 
 Kw. Capacity Cylinder 
 
 Card No. Boiler Pressure 
 
 Stroke Exhaust Pressure 
 
 Clearance Revolutions per min. 
 
 Scale of Spring Volts 
 
 Engine No. Amperes 
 
 Cylinder No. Pounds of water per kw-hr. 
 
 Dia. of Cylinder 
 
 A trifle more lead at the crank end of the valve should be 
 given at no load, as at % or full load the average pressure on 
 either side of the piston will be found to be. practically equal, 
 due to the angularity of the connecting rod. Various adjustments 
 will be necessary to obtain the best diagram and operation of the 
 engine. 
 
 Packing 
 
 In all single cylinder engines, up to and including the 30 kw. 
 size, the Garlock Spiral Packing is used in both piston rod and 
 valve stem stuffing boxes, and in the valve stem stuffing boxes 
 of all engines, the leakage being taken up by tightening the brass 
 nut on the box. 
 
 In the piston rod stuffing boxes of the tandem-compound, 
 cross-compound and of the single cylinder 50 kw. engine, 
 United States Metallic Packing is used. Fig. 138 shows the 
 "Double" type which is commonly used, but in some machines 
 the "Single Junior" packing is employed. The general con- 
 struction of the two packings is similar. 
 
 The packings consist of vibrating cups A and A , receiving the 
 packing rings 1, 2 and 3. These rings are in halves and, in assem- 
 bling the packing, the joints should be broken. The vibrating cups 
 rest upon rings B and B, which have a spherical bearing, so that 
 the packing will follow the rod in any position. The steam 
 pressure forces the packing down in the cups and against the 
 piston rod, thereby preventing steam leakage. The coil springs 
 C and C assist this pressure, at the same time holding the pack- 
 ing in place and preventing the rings from following the rod at 
 the moment of reversing. If the packing has been taken out for 
 examination, the ground surfaces should be cleaned and freed 
 from grit before reassembling. The box holding the packing 
 is drilled and tapped for a % i n - waste pipe and fitted with a 
 globe valve which should always be open. 
 
 General Instructions 
 
 An engine unit should not be considered mechanically nor 
 electrically perfect, until the tests have so proved. Testers 
 should familiarize themselves with every detail of design and 
 operation, thereby helping toward the production of the most 
 
 298 
 
reliable piece of apparatus. After the inspection in the Engine 
 and Testing Department the unit is dismantled and thoroughly 
 overhauled, touched up and re-inspected, preparatory to final 
 shipment. 
 
 GENERATOR 
 
 The tests taken on the generator are duplicates of those 
 described in preceding chapters. All standard d-c. generators 
 are given only compounding tests and adjustment of shunts. 
 On standard a-c. generators saturation and synchronous imped- 
 ance are taken. 
 
 If core losses are called for they are taken as previously 
 described, the generator being either disconnected from its engine 
 and assembled in shop bearings or the connecting rod, etc., 
 of the engine is dismantled and a driving belt slipped over the 
 engine flywheel. 
 
 299 
 
CHAPTER 15 
 
 GENERAL ELECTRIC TEST TRACKS 
 
 As the work on the General Electric Test Tracks is almost 
 entirely experimental a large number of the tests require special 
 instructions. The following rules, however, have been issued 
 relative to the operation of trains on these tracks, as well as 
 instructions for obtaining data, in testing apparatus. 
 
 No test should be started nor should changes be made in any 
 test without instructions from the office of the Supervisor of 
 Test Tracks. 
 
 All data should be recorded upon special record sheets and 
 supplementary column sheets, or upon the special form sheets 
 provided for that test. 
 
 All data sheets should contain the name of the man in charge 
 of the test, and date of test, while all supplementary column 
 sheets should also contain in the upper right hand corner the 
 number of the record sheet to which they belong. 
 
 ELECTRIC LOCOMOTIVES 
 
 Special form sheets are printed for testing locomotives, which 
 should be carefully filled out. The procedure of testing is as 
 follows : 
 
 1st. Inspect motors, contactor compartments, rheostat 
 compartments, controllers, etc., for loose material, scrap wire, 
 etc. Examine all bearings to see that they are properly lubri- 
 cated, including motors, air compressors, dynamotors and all 
 operating parts. 
 
 2nd. Ring out wiring to see that all connections are accord- 
 ing to the wiring diagram. Inspect the wiring to see that all 
 terminals are properly soldered and secured with lock washers; 
 also that all parts of both the main and auxiliary circuits are 
 properly insulated and that all wiring is so secured as to prevent 
 the insulation being cut by chafing. 
 
 3rd. Take clearance measurements to see that the locomo- 
 tive conforms to the clearance diagram. 
 
 4th. See that the current collecting devices are in proper 
 condition and satisfactory for operation. 
 
 Where third rail shoes are used this should include the 
 pressure on the rail in the running position as well as the measure- 
 ments showing the position of the shoe with respect to the third 
 rail. 
 
 On trolley poles and bases it should include the pressure of 
 the wheel on the wire at some given angle of the trolley pole. 
 This can be taken with a small spring balance attached to the 
 trolley rope. It is well to note what this pressure is, both going 
 up and coming down, to insure that the base does not have an 
 undue amount of friction. 
 
 On pantograph trolleys the pressures of the pans, or rollers, 
 against the wire should be taken as on trolley poles and wheels. 
 Where rollers are employed as collecting devices it should be 
 
 300 
 
carefully noted -whether the rollers are free to revolve and whether 
 they are in every way satisfactory to operate. 
 
 5th. Connect to the power circuit and try out the lighting 
 circuit, including headlights. Pump up the air pressure and 
 try out the air brakes, adjust all valves, gauges, etc., according 
 to the air brake diagram and inspect all air piping for leaks. 
 
 6th. Check with the wiring diagram the contactors that 
 are closed, both forward and reversed on each notch of one 
 controller and if there are two controllers check in one direction 
 of the second controller. For some typical connections see DS 
 prints No. 15466, 28765, 28234, 29302, 39188. These prints 
 are on file in the Testing Section office. 
 
 7th. Determine the rotation of the motors, each motor or 
 pair of motors separately and with all motors cut in. This 
 should be done in both directions on each combination. 
 
 8th. Measure the resistance of each step of the starting 
 resistance to see that it agrees with the specification. This 
 should be done by applying the air brakes so that the locomotive 
 does not move and having an ammeter wired in the motor 
 circuit. Put the controller on the first point with the main 
 switch closed so that the current will pass through the motor 
 circuit. Simultaneous readings should be taken of the current 
 flowing and the voltage drop across the various steps of resist- 
 ances. The voltmeter leads should be applied at the con- 
 tactors, or controller fingers to which the resistances are attached 
 in order to make an additional check on the wiring. Care should 
 be taken not to keep the current on longer than is absolutely 
 necessary to take each reading so as to avoid an increase in 
 resistance due to heating. 
 
 9th. Where a blower is used for forced ventilation of the 
 motors the distribution of air to the different motors should be 
 taken, holding constant the voltage of the trolley and reading 
 volts line, amperes input to the blower motor, speed of the 
 blower motor and the air pressure at some given point on the 
 motor so that the volume of air going through the motor can be 
 obtained by comparing these results with the result of tests 
 previously made on the test stand. Before starting this test an 
 inspection should be made to make sure that all motor covers 
 are on, air outlets from the motors open and that the air inlet 
 and outlet of the blower are free from any obstruction. 
 
 10th. Run for tests on bearings and note the operation 
 of all auxiliary parts. This test should be started at slow speed 
 and the speed increased as soon as the temperature of the 
 bearings will permit, to the maximum speed at which the 
 locomotive is to be run and continued at this speed for several 
 miles, or until the bearings and all operating parts are in satis- 
 factory operating condition. 
 
 11th. Make a wheel slipping test by bringing the controller 
 up, point by point, until the wheels slip and read volts line and 
 amperes to the motor on each step of the controller. This test 
 should be made in both directions with and without sand and 
 with all the various combinations of motor cutout switches. 
 
 301 
 
It is necessary to take readings on each point, beginning with 
 the first, only once for each combination and after this the 
 controller should be immediately brought to the point next 
 below the one at which the wheels slip and readings taken at this 
 point and continued as before until the wheels slip again. The 
 controller should be thrown off as soon as the wheels start to 
 slip so as to damage the track as little as possible. The wheels 
 should not be allowed to slip more than once in the same spot 
 otherwise a false indication of tractive coefficient might be ob- 
 tained. 
 
 12th. Remove all grounds and take insulation and high 
 potential test. These should include all the wiring and all 
 parts of the electrical equipment. 
 
 Mounting Motors on Trucks 
 
 Before mounting motors on trucks, the following measure- 
 ments should be taken: Compare bore of gears with size of 
 axle for gears ; compare bore of axle liners with size of axle for 
 liners ; compare the distance between wheel hubs with the length 
 of the motor; axle liner flanges and gear hub; compare the 
 distance between the center of axle and suspension bar face on- 
 truck with the distance between the axle box centers and face 
 of motor under nose suspension. 
 
 After these dimensions have been checked, and the motors 
 have been found to fit on the truck, the key for the gear should 
 be fitted in the key- way and the gear put on, care being taken 
 to get the right side of the gear next to the hub of the wheel, and 
 to see that all lock washers and cotter pins are in place. The 
 motor should then be hoisted by the two lugs opposite the axle 
 bearings with a two hook chain, and the motor placed on the axle 
 without axle linings. The motor can then be lowered in place, by 
 allowing it to revolve around the axle until the nose suspension 
 rests on the suspension bar. The chains can then be hooked 
 in the two lugs nearest the axle bearings and raised enough to 
 allow the axle linings to be put in place. The axle caps, gear 
 cover and strap fastening the motor to the suspension bar can 
 then be put on and the installation is complete. 
 
 Before the motors are put into service or the car run as a 
 trailer, the motor bearings and gears should be properly lubri- 
 cated. 
 
 Trolley Bases 
 
 Test sheets should contain the following data: 
 Number and size of spring (outside diameter, free length, 
 number of turns and size of wire). Position of tension adjusting 
 screw during test. Length of pole from pivot to center of 
 trolley wheel. Style of harp and wheel. Length and tension of 
 springs with pole, in horizontal and 45 degree positions. 
 
 Pull Curve 
 
 This curve is taken by measuring the vertical pull in pounds 
 at the center of the trolley wheel for different heights of the wheel. 
 
 302 
 
The "height" of the wheel is the vertical distance of the center 
 of the trolley wheel above its position when the pole is hori- 
 zontal. (For pantograph trolleys the height is the distance of 
 the top of the pan above its position when locked.) In taking 
 this test a rope should be fastened about the wheel and readings 
 of pounds pull taken, both going up and coming down. 
 
 Service Heat Runs on Motors 
 
 These heat runs are made on motors under as nearly as 
 possible the same conditions as will obtain in service. By 
 making a number of heat runs under various conditions data is 
 obtained from which the thermal characteristics of the motor 
 are determined. These curves show the relation between the 
 ratio of distribution of losses (ratio between watts loss in field 
 and in armature) to the degree (Centigrade) rise per watt loss 
 for the armature and for the field. 
 
 The instructions for the test include the following points: 
 
 (a) Weight of train. 
 
 (b) Line voltage to be held. 
 
 (c) Accelerating current required. 
 
 (d) Schedule (includes length of run, time power is on, 
 time of coasting, time of braking, and time of lay-over). 
 
 The following readings must be taken before starting the 
 test: Resistance of field, total and partial. resistance of armature. 
 
 In order to facilitate the measurement of armature resist- 
 ance during the run, resistance readings are taken between 
 commutator bars nearer to each other than the distance between 
 brushes. These bars should be marked or the resistance taken 
 with a templet, in order that all measurements can be made 
 between the same points or including the same number of bars. 
 The ratio between the partial resistance to the total resistance is 
 a constant from which the total resistance can be calculated. 
 
 The following must also be taken during the test: 
 
 Air temperature, velocity and direction of wind, readings 
 during test (taken every hour), field resistance, partial resistance 
 of armatures of alternate motors, temperature by thermometer 
 of field spools and frame, and air temperatures. 
 
 During the run a record is kept of the schedule, direction of 
 wind, weather conditions and all points of any interest in 
 connection with the runs. 
 
 Records of the line voltage and amperes motor are taken 
 with graphic recording meters for a couple of runs in each 
 direction during the hour. 
 
 When the temperatures of the motors have become constant, 
 the test is stopped. Besides the regular hourly readings the 
 following temperatures are taken: Armature core surface, and 
 conductors; commutator; field spools; frame. 
 
 These readings should be taken indoors in order to avoid 
 all draughts. 
 
 Train Friction 
 
 Train friction curves show the relation between the train 
 or car friction expressed in pounds per ton and speed in miles 
 per hour. 
 
 303 
 
There are two methods by which car friction may be obtained, 
 coasting tests and free running. 
 
 Friction from Coasting Curves 
 
 The. test should be made on a straight and preferably level 
 track. The car is accelerated to a speed slightly greater than 
 the highest speed called for on the friction curve and allowed 
 to coast. Speed should be measured with a speed recording 
 instrument. Runs should be made in both directions. 
 
 From the rate of retardation at any point the retarding 
 force is calculated which represents the total car friction at that 
 speed. 
 
 The weight of the car plus the flywheel effect of the revolving 
 parts is the weight that tends to keep the car moving. When 
 geared motors are used, a test should be made to obtain the rate 
 at which the armature will slow down due to the friction of its 
 own bearings in order that it may be known whether the flywheel 
 effect of the armature will be sufficient to overcome the friction 
 of its own bearings and furnish power to assist in keeping the 
 car moving, or whether the car will have to furnish power to keep 
 the armature revolving. The type of motor and the gear ratio 
 should be given, together with any information that can be 
 obtained, regarding the type of car, arrangements of wheels, 
 wheel base of truck, etc.; if possible a photograph, or a sketch 
 showing the cross section of the car, or locomotive should be 
 included. 
 
 Friction by Free Running 
 
 With the car running at constant speed, readings of speed, 
 volts line and amperes should be taken, preferably with graphic 
 recording meters. The input to the motors, minus their elec- 
 trical losses, gives the power absorbed in friction at a given 
 speed. 
 
 It is very difficult to get accurate results by this method on 
 account of the difficulty of keeping the car speed absolutely 
 constant. 
 
 The test sheets should contain the following data: 
 
 Weight of car or train. 
 
 Diameter of wheels and speed of car. The number, rating 
 and serial numbers of motors, and gear ratio, must be given. 
 
 Operating Rules 
 
 Each man, when starting work on the Test Tracks, is given 
 a copy of the "Operating Rules." These must be carefully 
 learned and implicitly followed at all times. 
 
 304 
 
CHAPTER 16 
 
 BLOWERS 
 
 Commercial Tests consist of the operation of the blower 
 for such a length of time as is necessary to demonstrate that no 
 electrical or mechanical faults exist. In case the motor is of 
 sufficient power to drive the fans with unrestricted inlet and 
 outlet it is so tested, but in most cases the motor is provided 
 for a certain specified pressure and volume delivered from the 
 fans and will not operate the fan with unrestricted inlet and 
 outlet without overloading the motor. In such cases the load 
 on the motor can be limited by partially obstructing the inlet to 
 the fan by means of a blower or other restriction so that the motor 
 will not be subjected to an excessive load. 
 
 Standard Heat Run consists of the operation of the 
 machine with air delivery restricted for a specified time or until 
 constant temperatures of the motor are reached. This restriction 
 may be for the purpose of bringing the load on the motor to a 
 specified amount or may be a restriction to give the required air 
 delivery for which the fan is to be supplied. 
 
 Minimum Speed Heat Run consists of a heat run at full 
 field with unrestricted inlet and outlet for a specified time or 
 until constant temperatures are reached. 
 
 Maximum Air Delivery Heat Run consists of operating 
 the blower at full speed with the inlet and outlet unrestricted 
 for a specified time or until constant temperatures of the motor 
 are reached. 
 
 Endurance Run consists of running the machine for 48 
 hours with the specified restriction of blower inlet and outlet. 
 
 In case of ventilating fans for the Government, this consists 
 of a 40 hr. run in addition to the 8 hr. " Normal Air Deliverv Heat 
 Run." 
 
 General Tests consist of the following: 
 
 (a) Running the machine with air delivery restricted for a 
 specified time, or until constant temperatures of the motor are 
 reached. 
 
 (b) 48 hr. endurance run (40 hr. in addition to the normal 
 air delivery heat run). 
 
 (c) Heat run at full field with unrestricted inlet and outlet 
 for a specified time, or until constant temperatures are reached. 
 
 (d) Air measurements to determine the delivery of the 
 blower. 
 
 Special Tests consist of general tests on the blower to 
 obtain air delivery under different conditions of opening and 
 under different speeds. 
 
 Complete Tests consist of the following: 
 
 (a) Running the machine with air delivery restricted for 
 a specified time, or until constant temperatures of the motor 
 are reached. 
 
 (b) 48 hr. endurance run. 
 
 305 
 
(c) Heat run at full field with unrestricted inlet and outlet 
 for a specified time, or until constant temperatures are reached. 
 
 (d) Tests on the blower to obtain air delivery under differ- 
 ent conditions of opening and under different speeds. 
 
 1. DOUBLE PITOT TUBE OR GOVERNMENT METHOD 
 
 This test is made in accordance with Government specifi- 
 cations issued by the Navy Department under the cognizance 
 of the Bureau of Construction and Repair. 
 
 For making air tests in accordance with this method using 
 double Pitot tubes, a testing pipe preferably of galvanized iron 
 having the same shape and size as the outlet of the fan and a 
 length equal to twenty times the diameter of the pipe, if round, 
 or twenty times the average of the width and depth, if rectangu- 
 lar, should be connected to the fan outlet. This pipe should be 
 smooth and carefully fitted to the fan in order to avoid any 
 unnecessary obstruction to the free passage of the air. 
 
 It is sometimes inconvenient to use a pipe of exactly the same 
 shape as the fan outlet, and in many cases it would be permissible 
 to use a pipe of nearly the same area connected to the fan outlet 
 by an adapter gradually changing from the size of the outlet 
 to the size of the pipe. 
 
 The double Pitot tubes should be supported in the middle 
 of the test pipe half way between the two ends and should 
 be parallel to the sides of the pipe and pointing toward the fan. 
 All connections between the Pitot tube and the Manometer or 
 U-tube should be carefully made to avoid any possible leakage, 
 as a very small leakage in the connections of these rubber tubes 
 might seriously affect the reading of the manometer. 
 
 In making the measurements the exact area of the pipe 
 where the Pitot tube is located should be carefully measured 
 allowing for curvature of the sides of the pipe which sometimes 
 takes place when the pipe is made of thin material and the pres- 
 sure in the pipe is considerable. When the area of this pipe differs 
 from the area of the outlet of the fan, the results should be 
 corrected accordingly, as the air velocity will be greater in a 
 smaller pipe and the static pressure less, but the total impact 
 pressure will not be affected except by the increased friction 
 of the smaller pipe. 
 
 A suitable damper or door should be placed at the end of the 
 testing pipe so that the size of the opening may be adjusted 
 to obtain the proper pressure and volume. Care should be taken 
 to run the fan at rated speed as nearly as possible, but where 
 this is impracticable, correction may be made for small varia- 
 tions in speed by correcting the volume in proportion to the 
 speed and the pressure in proportion to the square of the speed. 
 
 The most accurate results are obtained by using a nest of 
 Pitot tubes connected to floating manometers which consist of 
 metal cans floating in water, divided into as many air tight 
 compartments as there are Pitot tubes ; but it is more convenient 
 to use a single tube in the middle of the pipe, in which case, 
 according to the U.S. Navy rules, the velocity determined by 
 
 306 
 
the Pitot tube should be divided by 1.10 to obtain the assumed 
 average velocity through the whole pipe. 
 
 In calculating the horse power the total impact pressure 
 is used without any reduction, although to be strictly consistent 
 the velocity head due to the average velocity of the pipe added 
 to the static pressure should be used. 
 
 When the blower is provided with a straight inlet a con- 
 siderable loss is occasioned by vena contracta which will not take 
 place when the inlet piping is finally installed on the fan. If 
 the fan were tested with nothing added to the inlet, the efficiency 
 shown by the test would be too low and it is desirable to put 
 a short cone or bell on the inlet of the blower in making the 
 efficiency test unless the fan is built with a cone inlet. 
 
 Use of Air Table 
 
 When conducting a fan test the temperature of the air in 
 the testing room should be taken by two Fahrenheit thermom- 
 eters, placed near the fan. One should hang free in the air, and 
 the other, with its bulb wrapped in thin cloth, should be sus- 
 pended over a small receptacle filled with water so that the cloth 
 will be saturated. The temperature of the water must be the 
 maximum that it will naturally attain in the room, Corrected 
 barometer reading must also be recorded on the test sheet. 
 
 The method of finding the weight of air from the air tables 
 mentioned in the specifications, is as follows: On the page 
 containing the dry bulb reading as recorded on the test sheet, 
 note the barometer reading corresponding to the first three 
 figures of the corrected barometer reading recorded on the test 
 sheet. In the column under the dry bulb temperature and 
 opposite the barometer reading, the corresponding weight of 
 saturated air is given. The weight of air found in the table must 
 then be corrected to correspond with the corrected barometer 
 reading found in test. This correction will be found in the second 
 line from the top of the page. Correction must also be made for 
 the difference between the wet and dry bulb temperatures by 
 adding to the weight of air already obtained the number in the 
 third sub-division of the column under the dry bulb temperature 
 which corresponds to the difference between the wet and dry 
 bulb reading. This reading will be found in the second sub- 
 division of the column. 
 
 Example 
 
 Given barometer reading 30.15 in. 
 
 Dry bulb reading 67° F. 
 
 Wet bulb reading 59° F. 
 Under the column showing the dry bulb temperature of 67° 
 and opposite the barometer reading of 30.1, the weight of air 
 is given as 0.07517. The addition for each 0.01 of an inch of 
 barometer is given as 2.6 in the second line from the top of the 
 page. Multiply this by 5, i.e., by the excess of the corrected 
 barometer reading over that selected in the table; the result 
 is 13, which must be added to the weight of air previously found. 
 
 307 
 
The wet bulb depression is the difference between 67° and 59°, 
 or 8°. The number opposite 8 is 23. This must also be added, 
 making the total weight of air 0.07553. All pressure readings 
 should be corrected for standard air (see page 309) by multiplying 
 the actual pressure obtained by the ratio of the weight of standard 
 air to the weight of air at the time of test. The readings of horse, 
 power input to the fan should also be multiplied by this ratio. 
 Pressure and Horse Power Curves by Double Tube Method 
 
 A pressure curve may be taken by the double tube method 
 as follows: 
 
 The opening at the outer end of the discharge pipe should 
 be closed and pressure and power readings taken. Under this 
 condition the static and impact pressures should be exactly the 
 same since no air passes through the fan. Readings should then 
 be taken by increasing the opening by suitable increments from 
 closed to wide open, measuring the opening each time. The 
 speed of the fan should be held constant throughout the test. 
 The air readings and electrical input readings should be taken 
 simultaneously. 
 
 It will be noted that in a test which is made with a pipe 
 on the discharge side of the fan, the reading of the impact tube 
 is always greater than the static reading. If the pipe is on the 
 suction side the readings will be negative and the greater numeri- 
 cal value will be given by the static side of the tube. This 
 should be considered as the value for impact pressure of the fan. 
 The smaller value is given by the impact tube and should be 
 treated as static pressure when considering the capacity of the fan. 
 
 If readings are taken by means of a U-tube, the reading of 
 both sides of the tube should be given on the test sheet. The 
 test sheet should always specify whether the readings were 
 taken by the U-tube or by a manometer. If by a manometer, the 
 manometer constant should be recorded and must always be 
 used in working up the test. 
 
 CALCULATION OF FAN TESTS BY THE DOUBLE TUBE METHOD 
 
 A fan test of this kind should be recorded in the following form 
 of the standard column paper provided for this purpose. The same 
 abbreviations should always be used to avoid confusion. 
 
 TYPE OF FAN SERIAL NUMBER DATE... 
 
 Motor Rating 
 
 Double Tube Test, Taken at R.P.M. 
 
 No. 
 
 hi 
 
 hi 
 
 h 3 
 
 *S 
 
 V 
 
 Q 
 
 hl+hf 
 
 ht+h f 
 
 Air 
 H.P. 
 
 Fan 
 H.P. 
 
 EfL 
 
 1 
 2 
 3 
 4 
 
 
 
 
 
 
 
 
 I 
 
 
 
 Wet Bulb °F. Barometer... ....in. 
 
 Dry Bulb °F. Wt. of Air lb. 
 
 Effective area of Pipe = Sq. Ft. 
 
 308 
 
The first column gives the number of the reading. 
 
 The second and third show the impact and static readings 
 taken from the test sheet and corrected for standard air. 
 
 The fourth column shows the velocity head or the difference 
 between hi and h 2 . 
 
 The fifth column is friction which must be calculated from 
 
 the velocity head bv the formula H = ^- X 0.000 16 lv 2 . 
 
 ab 
 
 TT 
 
 hf= w?r-^, where h/ equals friction loss in inches of water, / is 
 
 oy./o \ 
 
 the length of pipe in feet between the fan and the Pitot tube. 
 
 a = length of long side of pipe in feet. 
 
 b = length of short side of pipe in feet. 
 
 i» = average velocity in feet per second. 
 
 The friction loss should be added to both the static and 
 impact readings before the curves are plotted, but it does not 
 affect the volume. 
 
 The sixth column showing the air velocity at the center of 
 the pipe may be obtained from the curves shown on prints 
 C-4487-A, B, C, and D. It may also be obtained from the 
 
 formula V=1097-*|— 
 
 Where to = weight of air per cu. ft. in pounds. 
 
 This gives the velocity at the center of the tube. For the 
 average velocity use 91 per cent of this value or use the same 
 formula with a constant of 997 instead of 1097. 
 
 The volume must be given in the seventh column. It is 
 obtained by multiplying the average velocities given in column 
 six by the area of the pipe. 
 
 The horse power in the air can be calculated from the formulas 
 
 .. , PXQ PXQ hXQ 
 
 Air h ' p - = 33000 ° r 3667 ° r 6345 . 
 
 The horse power input to the fan is the horse power output 
 of the motor. 
 
 Unless instructions are issued to the contrary, all fan tests 
 for Government work should be plotted with pounds per sq. ft., 
 horse power input to fan, and efficiency as ordinates; and volume 
 in cu. ft. per minute as abscissae. Both static and impact pres- 
 sure should be plotted. 
 
 The tester should carefully date and sign each test sheet, 
 and should include sufficient data to distinguish all sheets used 
 on the same test. For instance, electrical readings are usually 
 placed on one sheet and fan pressure readings on another, 
 therefore, each of these sheets should state the name and number 
 of the fan, the rating of the motor, the speed at which the test 
 was taken and the method used. The Calculating Room must 
 see that this data is placed on the Calculation Sheet. 
 
 The sheet on which the curves are plotted should give the 
 name, type and number of fan, rating of the motor, speed at 
 which the test was taken, and the method employed. Curves 
 should always be plotted across the width of the sheet. 
 
 309 
 
2. CONE METHOD OF TEST 
 
 The following method of conducting a fan test is used only 
 when a short convenient method is required for purposes of 
 comparison. In this method of test an adapter is used, where it 
 is necessary, to change the fan outlet from rectangular to cir- 
 cular, a cone being placed on the circular end. This cone is 
 made up of sections about two feet in length, the sides of which 
 slope about two inches to the foot. Readings are taken by a 
 single Pitot tube, the open end of which is held flush with the 
 opening in the outer end of the cone and pointed against the 
 stream of air. Pressure is registered as before, by a manometer 
 or U-tube. The readings are taken, one at the top, one at the 
 bottom, and one at each side of the cone at a distance from the 
 edge of the pipe of about % of the diameter of the opening. 
 A reading is also taken in the center of the cone opening. The 
 average of these five readings represents the impact pressure 
 produced by the fan, and is taken as the velocity head. The 
 velocity may be obtained from the curve or from the formula 
 given for the double tube test. 
 
 The static pressure may be obtained as follows: Divide the 
 volume of each opening by the area of the fan opening, which 
 gives the outlet velocity V\. The corresponding velocity head 
 can then be obtained from the curve. The velocity head sub- 
 tracted from the impact pressure gives the static pressure. 
 The static pressure should be plotted as well as the impact 
 pressure. 
 
 These tests should be plotted with pressures in inches of 
 water, h.p. inputs to the fan, and efficiencies, as ordinates; and 
 volumes as abscissae. 
 
 The following form should be used for tabulating the results 
 of calculations: 
 
 TYPE OF FAN SERIAL NUMBER DATE 
 
 Motor Rating 
 
 Cone Test Taken at R.P.M. 
 
 No. 
 
 hi 
 
 V 
 
 Ae 
 
 Q 
 
 Vi 
 
 h s 
 
 hi 
 
 Air 
 H.P. 
 
 Fan 
 H.P. 
 
 Eff. 
 
 1 
 2 
 3 
 
 
 
 
 
 
 
 
 
 
 
 Wet Bulb °F. Barometer in. 
 
 Dry Bulb °F. Wt. of Air. lb. 
 
 After the curves are plotted, the efficiency, as given by the 
 calculations, should be checked, with the efficiency obtained 
 from the curves. This will correct any discrepancy between 
 the efficiencies as obtained from the curve and as calculated. 
 
 310 
 
3. THE BOX METHOD 
 
 The box method of testing fans is as follows: 
 
 The fan is arranged to discharge directly into a large box 
 which has a sufficient capacity to reduce the air velocity to 
 a minimum. An opening is made in the side of the box at right 
 angles to the opening into which the fan discharges, and cones 
 are attached similar to those used in the cone test. Readings 
 are taken by the same method and readings should also be 
 taken of the box pressure by a U-tube connected to a pipe 
 inserted through a hole in the side of the box. The end of the 
 pipe should be flush with the inside of the box to avoid eddy 
 currents. The pressure shown by this pipe will be somewhat 
 higher than that registered at the end of the cone, and both 
 pressures should be corrected for standard air and plotted on the 
 final curve sheet. 
 
 The volume must be calculated as in the cone test, but the 
 pressure obtained in the box is taken as the static pressure 
 produced by the fan, since the velocity head is lost in the box. 
 To obtain the impact pressure the volume obtained should be 
 divided by the area of the opening of the fan, and the cor- 
 responding velocity head taken from the curve. This velocity 
 head should be added to the static pressure shown by the cone 
 readings. For transformer ventilation it is customary to calculate 
 the pressure in ounces, measured at the cone opening. 
 
 The following form should be used in tabulating the calcula- 
 tions: 
 
 TYPE OF FAN SERIAL NUMBER DATE 
 
 Motor Rating... 
 
 Box Test Taken at R.P.M. 
 
 NO. /J2 
 
 P v 
 
 Ae 
 
 Q 
 
 Vi 
 
 hz 
 
 hi 
 
 Air 
 H.P. 
 
 Fan ' -pa: 
 H.P. btt - 
 
 1 
 
 2 
 3 
 
 4 
 
 
 
 
 
 
 
 
 
 
 Wet Bulb °F. 
 
 Dry Bulb °F. 
 
 Barometer in. 
 
 Wt. of Air..... lb. 
 
 Fan h.p. should be calculated from the static pressure and 
 the efficiencv obtained will be the static efficiencv. 
 
 FORMULAE FOR BLOWER TESTS 
 
 h\ = Impact head in inches of water. 
 
 h 2 = Static head in inches of water. 
 
 h 3 = Velocity head in inches of water — hi — hi. 
 
 h= Total head in inches of water =/*i+ Ay 
 
 w = Weight of air in test in pounds per cu. ft. 
 
 311 
 
B = Barometer reading. 
 
 h f = Head lost in friction in the pipe from the Pitot tube to 
 the fan, in inches of water. 
 
 H/ = Head lost in friction in the pipe from the Pitot tube to 
 the fan, in feet of air. 
 
 Hz = Velocity head of the air in feet of air. . 
 
 a = Length of long side of pipe in feet. 
 
 b = Length of short side of pipe in feet. 
 
 / = Coefficient of friction =0.00008 for ordinary piping. 
 
 This value should be used in determining the friction loss 
 between the fan and Pitot tube, but for determining the amount 
 of pressure required to overcome the resistance of air piping, 
 it is usually safer to use a coefficient of 0.00010. 
 
 I = Length of pipe in feet from Pitot tube to fan. 
 
 v = Mean velocity of air in ft. per sec. 
 
 V = Velocity of air in ft. per min. 
 
 Q = Volume of air in cu. ft. per min. 
 
 P = Pressure of air in lb. per sq. ft. 
 
 . -p , . . . PX16 P 
 
 p = Pressure of air in ounces per sq. in. = . = -^. 
 
 A =Area of pipe in sq. ft. 
 
 A e = Effective area of pipe in sq. ft. =A XK 
 
 K = Constant for effective area of pipe =0.94 for the Cone 
 
 Method. 
 Eff = Efficiency. 
 
 w = Weight of air in test in pounds per cu. ft. 
 Weight of 1 cu. ft. of air at 30 in. Bar; 70 deg. F and 70 
 per cent humidity = 0.07465 lb. 
 This is taken as standard air. 
 Wefght of water = 62.36 lb. per cu. ft. at 62 deg. F. 
 
 Weight of a column of water 1 ft. sq. and 1 in. high = ' 
 
 = 5.2 lb. at 62 deg. F. 
 
 Weight of a column of standard air 1 ft. sq. and 1 ft. high 
 = 0.07465 lb. 
 
 Weight of a column of any other air 1 ft. sq. and 1 ft. high 
 
 = w. 
 
 xt 1 x- 1 .j-x 0.07465X5X530, ^ u 
 
 Neglecting humidity w = 30X ( 46 q +1 o j for Fahr - 
 
 at i ,■ i. ■/■, 0.07465X5X294, _ , 
 
 Neglecting humidity w = 30 x (273 +^ °)~ 
 
 Therefore, to change from feet of air to inches of water 
 
 5 2 
 divide by - _ ' Anr =69.73 for standard air. 
 0.0/465 
 
 5 2 
 
 or divide by — — for any other air. 
 w 
 
 H f 
 
 hf= 5.2 
 
 312 
 
ab 
 For round or square pipe JHy-=4/-j- o 2 
 
 where d = diameter in feet. 
 
 / / — Jo. 2 hz \hz 
 
 v =\/2 ^ 3 = 8.02 \ Hz= 8.02 J— ^~ = 18.28-J- 
 
 F =60 f=60v2 £# 3 =481.2\/#3 
 
 = 1097 —at the center of the pipe. 
 
 $"'« 
 
 = -i015\/liz for standard air. 
 P =9 p 
 
 = o.2Xh 
 Therefore 9 p=5.2Xh 
 
 P = IT32 = °- 577 * 
 
 <2 =rx.4,= Fxxi 
 
 av. vel. I . 
 = 0.94 J 
 
 Ihz =3654.0 A \/hz, using <x 
 
 = 1097 A -X^4 ___//_!' * _ ^torstd.air 
 \ -' = 3774.0 A \/hz for K 
 
 For a given opening, pressure varies as the square of the speed 
 of the blower. Volume varies as the square root of the pressure, 
 hence, directly as the speed, 
 
 Air h.p. varies as the cube of the speed. 
 
 Eff. = *£*& 
 
 Fan h.p. 
 
 313 
 
CHAPTER 17 
 
 AIR COMPRESSORS 
 
 Wearing in Running 
 
 The air compressor should be run unloaded,- that is, not hav- 
 ing the delivery end of the compressor connected to the tank 
 until the friction has reached a constant value. 
 
 Fig. 139 
 AIR COMPRESSOR 
 
 Commercial Test 
 
 Resistance measurement should be made. The compressor 
 (see Fig. 139) should be run light and the voltage, current and 
 speed noted and recorded. The friction value should be checked 
 with that given in the Standing Instructions (S. I.) 7884 and 
 if it is excessive the defect must be remedied before the test 
 is continued. 
 
 A full load run should be made for a half hour or an hour as 
 specified by the Standing Instructions during which three suc- 
 cessive capacity tests should be made in the following manner: 
 The compressor should be connected to tank No. 1, see Fig. 140. 
 The gauge .pressure in tank No. 1 should be brought to 90 lb. or 
 other standard working pressure as specified and the air then led 
 into tank No. 2 at such a rate that the specified working pressure 
 is maintained on tank No. 1. Note should be made of these 
 items; the time from the opening of the valve between tank No. 
 1 and tank No. 2 until the gauge of tank No. 2 shows that work- 
 ing pressure has been reached; the total armature revolutions 
 (on the testing record this should be reduced to compressor 
 revolutions); the current required; the temperature of the air 
 in tank No. 2 and the temperatures on the compressor cylinders. 
 
 The high potential test should be made at the end of the run 
 with the motor hot. The oil leakage indicated by the glass gauge 
 
 314 
 
should be noted and also the air leakage of the compressor 
 valves after the end of the test. 
 
 All compressors should be carefully observed for unnecessary 
 noise or vibration in operation due to gears, connecting rods, 
 valves or unbalanced armature. They should be observed for 
 air leaks due to porous cylinder heads and defective gaskets and 
 valve plugs; for oil leaks due to defective crank chamber 
 gaskets or porous castings, for oil leaks entering the inner end of 
 the motor frame from the compressor frame, and for vapor 
 escaping from the crank chamber vent. If defects are found they 
 must be reported at once. 
 
 Complete Tests 
 
 Complete tests consist of special tests, special heat runs, 
 starting tests, and oil leakage tests. 
 
 Thermometer 
 
 Exhaustin 
 8hop Line 
 
 \Safty 
 waive 
 
 Gauge 
 
 Gauge 
 Exhaust under ... JLL (F^ 
 
 Compressor ~~W 
 
 Fig. 140 
 TANK CONNECTIONS FOR AIR COMPRESSOR TEST 
 
 Special Tests 
 
 A speed curve should be taken in the operating direction of 
 the compressor only, at 600 volts unless otherwise specified, on 
 compressor loads in which the tank pressure varies from zero to 
 140 lb. During this test, or by making an independent test, the 
 capacities of the compressor should be taken while pumping 
 against pressures varying from zero to 140 lb. From these tests 
 one curve should be plotted of tank pressure and compressor 
 speed against amperes as abscissae. Another should be plotted of 
 watthours per cu. ft. of free air and cu. ft. per minute of free air 
 against tank pressure. 
 
 315 
 
The field of the motor should now be separately excited, 
 the gears removed and the friction and motor core loss test 
 taken. 
 
 The armature should be run on a voltage which will give. a 
 speed corresponding to the speed curve and the field should be 
 separately excited with the same current values as used when 
 the speed curve was taken. A curve is then plotted of watts 
 against rev. per. min. showing the friction and core loss com- 
 bined. 
 
 The preceding results should be consolidated into a curve 
 showing the speed, torque and efficiency of the motor at the 
 pinion. 
 
 Special Heat Runs 
 
 These consist of several heat runs made with the compressor 
 operating at different time cycles and different pressures. 
 Usually three successive tests should be made at the rated work- 
 ing pressure, 90 lb. or otherwise as specified. 
 
 No. 1. 5 min. on and 5 min. off repeated to the end of the 
 test. 
 
 No. 2. 7 min. on and 3 min. off repeated to the end of the 
 test. 
 
 No. 3. Continuously. 
 
 Heat runs at other pressures and cycles of time operation 
 should be made as specified for the given machine. 
 
 The machine should be allowed to stand idle not less than 
 eight hours between each test and in each case the test should be 
 continued until either the temperatures of the armature and 
 field become constant or until the temperature rise amounts to 
 125 deg. cent, by resistance measurement. The commutator door 
 and all covers should be kept closed during the test and unless 
 otherwise specified, the machine should operate at 600 volts and 
 pump against 90 lb. gauge pressure. Temperatures and resist- 
 ances should be taken at regular intervals throughout the run, 
 and final temperatures and resistances at the end. 
 
 From the results of the test, curves should be drawn on one 
 sheet, of the temperature rise by thermometer of the field coil 
 against time as abscissae. Over these, curves of temperature 
 rise by resistance measurement should be drawn. 
 
 On another sheet a similar set of curves should be made for 
 the armature. 
 
 On the third sheet should be plotted a series of curves of 
 thermometer rise at the end of each hour against the percentage 
 of operating time. 
 
 In connection with run No. 3 the compressor capacity should 
 be taken as nearly cold as possible and at frequent intervals 
 throughout the test. Temperatures should be taken every five 
 minutes on the cylinder and exhaust chamber. The temperature 
 rise of the cylinder and exhaust chambers, watthours per cu. ft. 
 of free air, and cu. ft. of free air per minute should be plotted 
 against time. The volume and temperature of the air in the 
 measuring tank must be known to determine the watthours per 
 
 316 
 
cu. ft. A curve should be plotted showing the relation of capac- 
 ity to cylinder temperature. 
 
 Starting Tests 
 
 The starting tests for direct current air compressors should 
 consist of tests made at various reduced voltages making note 
 of the current, voltage and rev. per min. of the motor expressed 
 on the testing record as r.p.m. of the compressor. The manner 
 of starting of the compressor should be observed and noted, that 
 is, whether it starts properly from rest or whether it hesitates 
 and starts with an irregular rotation of the motor, or finally 
 whether it fails to slart at all. 
 
 In taking starting tests for alternating current motors 
 special attention should be paid to the equipment serving the 
 motors with current; that is, it should be sufficiently large so 
 that the momentary conditions existing when the compressor 
 is starting from rest against full load pressure do not cause any 
 material drop in voltage. These tests should be repeated step 
 by step at various voltages to determine the conditions under 
 which the compressor starts irregularly, and finally fails to start. 
 
 Oil Leakage Tests 
 
 These tests commonly consist of a 20 hour half time cycle 
 of compressor operation under the control of the governor. 
 An oil separator is installed between the compressor and the 
 tank for the purpose of taking these tests. After the com- 
 pletion of the run the separator and tank should be allowed to 
 stand at least an hour to allow the oil to collect at the draw off 
 valves. It should then be drawn off, measured and the quantity 
 noted, both separately as collected from the separator and the 
 tank and the total quantity. Any water found in the graduated 
 glass with which the measurement is made should be deducted. 
 
 317 
 
CHAPTER 18 
 
 VOLTAGE REGULATORS 
 
 General Principle of Operation 
 
 Voltage regulators are used to control the voltage of a 
 circuit within narrow limits by rapidly opening and closing 
 a shunt circuit connected across the field rheostat of the exciting 
 circuit of the generator. Those for use for a-c. generators are 
 known as Type TA, and those for use on d-c. circuits are Tvpe 
 TD. 
 
 TYPE TA REGULATORS 
 
 TYPE TA FORM A2 
 
 These regulators operate by rapidly opening and closing 
 a shunt circuit connected across the exciter field rheostat. 
 Actual electrical connections vary, but a schematic diagram is 
 shown in Fig. 141. 
 
 Ma/'r? Contacts 
 
 Corpper7s<2t/ngr 
 
 Current 
 Transformer 
 
 AC Fi eld. ^AC Generator 
 ftheostat 
 Fig. 141 
 ELEMENTARY DIAGRAM OF TA, FORM A REGULATOR 
 
 The regulator has a d-c. control magnet, an a-c. control 
 magnet and a relay. The d-c. control magnet is connected to the 
 exciter busbars and has a fixed stop core in the bottom and a 
 movable core in the top which is attached to a pivoted lever 
 having at the opposite end a flexible contact pulled downward 
 by four spiral springs. The a-c. control magnet has a potential 
 winding and also an adjustable compensating winding connected 
 through a current transformer to the principal feeder. This 
 compensating winding raises the voltage of the a-c. busbars 
 as the load increases, and thus compensates for line drop. 
 The a-c. control magnet has a movable core and a lever and 
 contacts similar to those of the d-c. control magnet, and the 
 two combined produce the "floating main contacts." The relay 
 coil has a differential winding and a pivoted armature controlling 
 
 318 
 
the contacts which open and close a shunt circuit across- the 
 exciter field rheostat. One of the differential windings is per- 
 manently connected across the exciter busbars and tends to 
 keep the contacts open; the other is connected to the exciter 
 busbars through the floating main contacts, and when the 
 latter are closed, neutralizes the effect of the first winding and 
 allows the relay contacts to short-circuit the exciter field rheostat. 
 Condensers are connected across the contacts to prevent arcing 
 and possible injury. 
 
 CYCLE OF OPERATION 
 
 The circuit shunting the exciter field rheostat through the 
 relay contacts is opened by means of a single-pole switch at the 
 bottom of the regulator panel and the rheostat turned in until 
 the alternating voltage is reduced 65 per cent below normal. 
 
 Fig. 142 
 
 ELEMENTARY DIAGRAM OF TYPE TA, FORM F3 REGULATOR 
 
 CONNECTIONS 
 
 This weakens both of the control magnets and the floating main 
 contacts are closed. This closes the relay circuit and demag- 
 netizes the relay magnet, releasing the relay armature, and the 
 spring closes the relay contacts. The single-pole switch is then 
 closed and as the exciter field rheostat is short-circuited the 
 exciter voltage will at once rise and bring up the voltage of the 
 alternator. This will strengthen the alternating current and 
 direct current control magnets and at the voltage for which 
 the counterweight has been adjusted the main contacts will 
 open. The relay magnet will then attract its armature and by 
 opening the shunt circuit at the relay contacts will throw the full 
 resistance into the exciter field circuit tending to lower the 
 exciter and alternator voltage. The main contacts will then 
 
 319 
 
again be closed, the exciter field rheostat short-circuited through 
 the relay contacts and the cycle repeated. This operation is 
 continued at a high rate of vibration due to the sensitiveness 
 of the control magnets and maintains a steady exciter voltage. 
 
 TYPE TA FORM F 
 
 The TA Form F Regulator has several relays according to 
 the size and number of exciters used. The principle of operation 
 is the same as for the Form A2. An elementary diagram is 
 given in Fig. 142. 
 
 TYPE TD REGULATORS 
 
 The Type TD Regulator consists essentially of a main control 
 magnet with two independent windings, and a series wound relay 
 magnet. The elementary connections are shown in Fig. 143. 
 
 Comp ens a t mg 
 Resistance Shunt 
 
 ^^M 
 
 Sfide\ 
 
 Potentia/ 
 I Winding 
 
 To Line I . — 
 
 Compensating 
 Winding 
 
 Main Control 
 Magnet- 
 
 Generator 
 maybe Shunt or 
 compound wound 
 
 \ 
 
 fie/ay \ 
 
 Contacts\ Condenser j» ( . 
 
 ^p g Generator Field 
 
 ffe/ay 
 Magnet 
 
 rotor j 
 Rheostat 
 
 %Extema//teSistonce% 
 
 Fig. 143 
 
 DIAGRAM SHOWING ELEMENTARY CONNECTIONS OF 
 
 TYPE TD REGULATOR 
 
 The potential winding of the main control magnet is con- 
 nected across the generator terminals, and the compensating 
 winding across a shunt in one of the load mains, and opposes 
 the action of the potential winding, so that as the load increases 
 a higher potential at the generator is necessary to overcome the 
 line drop. The control magnet has an adjustable stop core at 
 the bottom with a movable core above. The movable core is 
 attached to a lever operating the main contacts, the pull of the 
 magnet being opposed by a spiral spring which tends to keep 
 the main contacts closed. 
 
 The armature of the relay magnet operates the contacts that 
 open and close the shunt circuit across the field rheostat. The 
 relay magnet winding is permanently connected, through resist- 
 ance, to the busbars, and this winding is short-circuited by the 
 
 320 
 
main contacts of the control magnet. When the main contacts 
 are open the relay contacts are open. 
 
 CYCLE OF OPERATION 
 
 The shunt circuit across the generator field rheostat is first 
 opened by means of a switch on the base of the regulator and the 
 rheostat turned to a point that will reduce the generator voltage 
 35 per cent below normal. The main control magnet is at once 
 weakened and allows the spring to pull out the movable core 
 until the main contacts are closed. This short circuits the relay 
 winding, which demagnetizes the relay magnet core. The 
 relay spring then lifts the armature and closes the relay con- 
 tacts. The switch in the shunt circuit across the generator 
 field rheostat is now closed, practically short-circuiting the field 
 rheostat, and the generator voltage at once rises. As soon as it 
 reaches the point for which the regulator has been adjusted the 
 main control magnet causes its movable core to open the main 
 contacts, which in turn open the relay contacts across the 
 rheostat. The rheostat is thus connected in the field circuit, the 
 voltage at once falls off, the main contacts are closed, the relay 
 armature is released and the shunt circuit across the rheostat 
 again completed. The voltage then starts to rise and this cycle 
 of operation is continued at a high rate of vibration maintaining 
 a steady voltage at the busbars. 
 
 TYPE TD FORM G 
 
 The Form G Regulator is designed to control the voltage of 
 generators of small capacity, and is provided with both potential 
 and compensating winding on the main control magnet. It may 
 be connected to several small compound wound machines 
 operating in parallel. It is then used on only one of the gener- 
 ators at a time, the others being allowed to "trail" by means of 
 their compound winding and equalizers. 
 
 TYPE TD FORM R 
 
 The Form R Regulator operates as the Form G, but contains 
 two, three or four separate relays, and is designed to control 
 the voltage of two or more generators operating in parallel. 
 
 TYPE TD FORM L 
 
 The Form L Regulator is designed for use with two or more 
 separately excited d-c. generators and operates the same as the 
 Type TA, Form A2 regulator described above. 
 
 ADJUSTMENT 
 
 Before setting any voltage regulator upon the testing table 
 the following defects should be looked for: Improper stamping 
 of name plate, wrong stamping of resistance box, loose coils, loose 
 magnet frames, loose or inclined dashpot, bent switches and 
 studs, wrong a-c. cores. - Check the air gap on the relay, the 
 
 321 
 
friction of the relay armature, alignment of the relay contacts, 
 relay numbering, loose screws, and loose terminals. See that 
 different kinds of nuts and washers are not used on the same 
 stud, that compensating switches on the a-c. regulators are not 
 stamped for the wrong direction. Care should be taken to see 
 that the regulator hangs true after it is installed, as any variation 
 may cause trouble in operation. Each regulator should be 
 wired according to its print and no testing should be done if 
 the terminals are stamped incorrectly or if connectors are on 
 the wrong studs. The internal connections on the regulator 
 should be inspected for loose joints, improper connections, or 
 poorly soldered terminals. After the regulator has been wired 
 properly the cores should be made to hang in the center of the 
 magnet spools and the levers should not fit too loosely nor too 
 tightly. 
 
 HIGH POTENTIAL 
 
 High potential should be applied to all parts of the regulator 
 to ground and between coils. The potential between coils should 
 not be instantaneously applied nor must the circuit be suddenly 
 broken but the high potential terminals should be placed on the 
 coil under test and the voltage gradually raised on the alternator 
 to the desired amount and then reduced in the same manner 
 until zero voltage is reached before removing the high potential 
 leads. 
 
 RESISTANCE MEASUREMENTS 
 
 All relay coils, d-c. magnets, a-c. magnets and resistance 
 boxes should have their resistance measurements carefully 
 taken and the variations should not exceed those specified in the 
 Engineering Brief which will be found in the files of the Testing 
 Section. 
 
 HEAT RUNS 
 
 Heat runs are made on all regulators to determine the maxi- 
 mum heating on the different coils and the external resistance. 
 The run on the a-c. regulator is made at 115 volts, and at normal 
 rated voltage on the d-c. coil. The run on the d-c. regulator is 
 made at the standard rated voltage, the value of which will be 
 found on the name plate of each regulator. The length of run 
 in each case is three hours. 
 
 ADJUSTMENT OF RELAY CONTACTS 
 
 The manner of adjusting the relay contacts is the same on 
 all regulators. Press the armature firmly against its stop 
 stud and set the contacts, one directly over the other and ^ in. 
 apart. 
 
 322 
 
TYPE TA FORM A2 REGULATOR 
 
 This type of regulator is built for the following standard 
 voltages : 
 
 Fig. 144 
 
 DASHPOT FOR TYPES TA-60 AND TA-125, FORM A2 VOLTAGE 
 
 REGULATOR FOR GENERATORS 
 
 Type 
 
 Form 
 
 Exciter 
 Volts 
 
 Range of 
 Exciter 
 Volts 
 
 A-C. Volts 
 
 TA-60 
 
 TA-90 
 
 TA-125 
 
 TA-250 
 
 TA-550 
 
 A2 
 A2 
 A2 
 A2 
 A2 
 
 90 
 125 
 
 250 
 550 
 
 33/67 
 
 50/100 
 
 70/140 
 
 140/280 
 
 308/616 
 
 100 to 125 
 100 to 125 
 100 to 125 
 100 to 125 
 100 to 125 
 
 ADJUSTMENT OF DASHPOT 
 
 The dashpot is shown in section in Fig. 144. The piston fits 
 closely, but should move freely, as friction will result in unstable 
 voltage. The piston (1) is attached to the lower end of the 
 alternating current magnet core stem (2) and its normal position 
 is about midway between the two port holes (3) and (4). Piston 
 
 323 
 
(5) may be raised by turning thumbscrew (6). This results in 
 closing port hole (4) thus retarding the movement of piston (1). 
 When the port hole is entirely closed and the dashpot full of oil, 
 the piston moves very slowly. The dashpot should never be filled 
 with anything but light dynamo oil. This can best be done as 
 follows : 
 
 Remove screws (10) and (11), give the dashpot a quarter 
 turn, then it can readily be taken off. See that it is free from all 
 dirt, then fill it to within about z /% in. of the top, replace it and 
 securely tighten screws (10) and (11); the oil should then stand 
 
 Fig. 145 
 
 MAIN CONTROL MAGNETS AND LEVERS FOR TYPES TA-60 
 
 AND TA-125 FORM A2 VOLTAGE REGULATORS 
 
 FOR GENERATORS 
 
 about }/$ in. from the top of the cup. By raising and lowering 
 core (8) by hand and at the same time varying the height of 
 thumbscrew (6), the position of piston (5) can be readily deter- 
 mined, as a slight change in the height of piston (5), when at the 
 position shown varies greatly the free action of core (8). The 
 dashpot should be adjusted until core (8) moves with very little 
 retarding. The retarding effect of the dashpot necessarily 
 depends entirely upon the time constants of the exciters and 
 generators but ordinarily the piston should move freely. 
 
 ADJUSTMENT OF SPRINGS NOS. 1, 2, 3 AND 4 FOR 
 TA-125 REGULATORS 
 Before adjusting lever (5) Fig. 145, core (11) should be raised 
 to its highest position and blocked, thus bringing main contact 
 
 324 
 
(30) to its lowest position, to prevent contact being made be- 
 tween (19) and (30) while lever (5) is being adjusted. This is 
 necessary since if contacts (19) and (30) were to come together, 
 the proper adjustment of lever (5) could not be made. Springs 
 (1), (2) and (3) should be loosened to their extent or taken out 
 while spring (4) is being adjusted. A gauge for use in adjusting 
 lever (5) is always furnished with the regulator. To adjust 
 spring (4) first see that the voltage on the exciter to which the 
 direct current control magnet (6) is connected, is maintained 
 at 65 volts. Then by taking the gauge between the thumb and 
 index finger at "A" place it firmly against the brackets "B" and 
 "C" and against the under side of pivot sockets (7) and (8) as 
 illustrated. Then adjust spring (4) by means of the small nut 
 at the top of its adjusting screw, until the under side of lever 
 (5) comes even with the top of the gauge at (9). After this 
 adjustment has been made, the exciter voltage should be 
 increased to 122, and at exactly this point spring (4) should be 
 overpowered by the magnet, and the cores (12) and (13) will 
 come together. Should it require more or less voltage to over- 
 power the spring and bring these cores together, core (13) 
 should be either raised or lowered, and spring (4) readjusted 
 until the under side of lever (5) comes to the gauge as before. 
 The adjustment of spring (4), lever (5), and core (13) must be 
 repeated several times to insure correctness as this adjustment is 
 of the utmost importance. After the proper adjustment has been 
 obtained, the lock nut beneath the lever on spring (4) should be 
 securely tightened after which the exciter voltage should again 
 be varied over its range, and the adjustments checked. 
 Then screw (14), which holds stop core (13) in position, should 
 be securely tightened. This screw should, however, be kept well 
 tightened while the adjustments are being made. After these 
 adjustments have been made, spring (1) should be adjusted by 
 raising the exciter voltage to 90, and at exactly this point this 
 spring should begin to come under tension, and the small head 
 (15) on the spring stem will be brought in contact with the spring 
 support (16). After this adjustment has been carefully made, 
 the lock nut below the lever on spring (1) should be securely 
 tightened and the adjustment of spring (1) checked to see if 
 it is correct. Then spring (2) should be adjusted by increasing 
 the exciter voltage to 115, when it will come into action as does 
 spring (1). After adjusting this spring, the lock nut beneath the 
 lever on spring (2) should also be securely tightened and the 
 adjustment checked. Spring (3) should then be adjusted by 
 raising the exciter voltage to 138, at which point this spring will 
 come into action as did springs (1) and (2). Following this 
 adjustment, the lock nut underneath the lever on spring (3) 
 should be securely tightened and the adjustment of spring (3) 
 checked. 
 
 Springs for Standard Regulators are adjusted as in the fol- 
 lowing table: 
 
 325 
 
TYPE TA-60 VOLTAGE REGULATORS 
 
 Spring No. 4 adjusted with gauge at 31 volts. 
 Spring No. 1 adjusted to pick up at 43 volts. 
 Spring No. 2 adjusted to pick up at 55 volts. 
 Spring No. 3 adjusted to pick up at 66 volts. 
 
 TYPE TA-90 VOLTAGE REGULATORS 
 
 Spring No. 4 adjusted with gauge at 47 volts. 
 Spring No. 1 adjusted to pick up at 65 volts. 
 Spring No. 2 adjusted to pick up at 83 volts. 
 Spring No. 3 adjusted to pick up at 99 volts. 
 
 TYPE TA-125 VOLTAGE REGULATORS 
 
 Spring No. 4 adjusted with gauge at 65 volts. 
 Spring No. 1 adjusted to pick up at 90 volts. 
 Spring No. 2 adjusted to pick up at 115 volts. 
 Spring No. 3 adjusted to pick up at 138 volts. 
 
 TYPE TA-250 VOLTAGE REGULATORS 
 
 Spring No. 4 adjusted with gauge at 130 volts. 
 Spring No. 1 adjusted to pick up at 180 volts. 
 Spring No. 2 adjusted to pick up at 230 volts. 
 Spring No. 3 adjusted to pick up at 275 volts. 
 
 TYPE TA-550 VOLTAGE REGULATORS 
 
 Spring No. 4 adjusted with gauge at 286 volts. 
 Spring No. 1 adjusted to pick up at 396 volts. 
 Spring No. 2 adjusted to pick up at 506 volts. 
 Spring No. 3 adjusted to pick up at 607 volts. 
 
 ADJUSTMENT OF THE FLOATING MAIN CONTACTS 
 
 Main contacts (19) and (30) are specially constructed, and no 
 contacts other than those supplied by the General Electric 
 Company should be used. Care should be taken in grinding 
 them not to cut away any more of the metal than is necessary. 
 
 For the proper adjustment of these points, maintain 65 volts 
 on the exciter and with levers (5) and (17) in position according 
 to gauge, the contacts should be set squarely one above the 
 other after which screws (31) and (32) should be securely tight- 
 ened. 
 
 With levers (5) and (17) in this position, the upper contact 
 (19) should be raised or lowered until it will just touch contact 
 (30), after which the set screw (20) should be securely tightened. 
 Screw (21) should be adjusted to within ^ in. of screw (19) 
 and lock nut (22) securely tightened. With lever (17) still in its 
 proper position, screw (33) should be adjusted to within ^ in. 
 of lever (17) and nut (34) securely tightened. 
 
 The screw (33) is for the purpose of limiting the excessive 
 upward travel of lever (17) ; and immediately back of this screw, 
 passing through the same post is a threaded stud extending down 
 
 326 
 
and bent at right angles to extend underneath lever (17). This 
 stud should be so adjusted as to limit the downward travel of 
 lever (17) at 20 per cent above normal exciter voltage or 150 volts 
 on a 125 volt exciter. 
 
 ADJUSTMENT OF THE A-C. MAGNET CORE 
 
 If the alternator voltage varies through the range of exciter 
 voltage as specified, it would indicate an improper adjustment 
 of the a-c. magnet core (11) and to correct this, proceed in the 
 following manner: 
 
 The exciter voltage should be varied from 70 to 140 volts by 
 means of the a-c. generator field rheostat, and if the alternating 
 voltage rises or falls, core (11) should be raised or lowered on 
 stem (24) until at a point that will give neither rise nor fall in 
 the alternating voltage on varying the exciter voltage from 70 
 to 140. If the alternating voltage falls on increasing the exciter 
 voltage from 70 to 140, core (11) should be lowered or vice versa. 
 After this adjustment has been determined, lock nuts (26) and 
 (27) should be securely tightened, and the previous adjustment 
 checked. 
 
 The values given for the adjustment of the a-c. magnet core 
 (11) of 70 volts to 140 volts are for 125 volt regulators and 
 exciters. Other standard regulator and exciter voltages are as 
 follows: 
 
 Minimum 
 
 Normal Standard 
 
 Maximum 
 
 Excitation Voltage 
 
 Exciter Voltage 
 
 Exciter Voltage 
 
 33 
 
 60 
 
 «7 
 
 6/ 
 
 50 
 
 90 
 
 100 
 
 70 
 
 125 
 
 140 
 
 140 
 
 250 
 
 280 
 
 308 
 
 550 
 
 616 
 
 For the proper adjustment of core (11) see also "Error in 
 Voltage" under the heading "Locating Trouble" on page 332. 
 
 ADJUSTMENT OF RELAY 
 
 A complete side view showing the connections of the relay, 
 etc., is shown in Fig. 146. As this relay is differentially wound 
 with two windings on each spool, there are four leads extending 
 from the side of each magnet spool. The two outer terminals 
 represent one winding and the other corresponding two inner 
 leads are connected to the other winding. These leads are 
 connected to binding posts A, B and C as follows: 
 
 (3) and (5) to "A." 
 
 (2), (4), (6) and (8) to "B." 
 
 (1) and (7) to "C." 
 
 Xo two of the various holes in the three binding posts are at 
 the same distance from the panel, and each lead from the spools 
 
 327 
 
is brought out opposite the binding post hole in which it should 
 be inserted, thus rendering the connections very simple. Inas- 
 much as the relays are differentially wound, they will work to 
 some extent whether the windings are in service or not. There- 
 fore, if the relays operate unsatisfactorily they should be tested 
 to ascertain whether the coils are all working properly. Should 
 trouble be experienced which is apparently due to improper 
 connection of the relay magnets or a possible open circuit, the 
 
 iOw — 
 
 EGaZter" ^^Ca^S^ i 
 
 2 
 
 33 
 
 a 
 
 <?e 
 
 WQ, 
 
 fcsc 
 
 ^n 
 
 LrA- 
 
 y 
 
 ^^ 
 
 Fig. 146 
 
 RELAY FOR TYPES TA-60 AND TA-125 FORM A2 VOLTAGE 
 
 REGULATOR FOR GENERATORS 
 
 fault may be easily located by ringing out the different coils 
 with a magneto or other circuit-testing device; when this is 
 done all leads should be disconnected from their respective bind- 
 ing posts. It is also important to ascertain that all the leads 
 are properly connected to posts (A), (B) and (C) and that the 
 set screws holding them are securely tightened. See that the 
 expanded core tips (11) and (12) are flush with the ends of the 
 wire cores; then securely tighten set screws (22) and (23). 
 
 Pivot holder (16) should be adjusted on the pivot until 
 contact stud (17) clears stop stud (14) by j$ in. The set screws 
 holding the pivot sockets should be tightly secured, leaving no 
 end play in the pivots. 
 
 328 
 
With contact holder (13) resting upon stop stud (14), core tips 
 (11) and (12) should be only ^ in. from armature (9). This 
 distance is very important and should be measured by gauge. 
 After these have been adjusted the four set screws on the 
 opposite side of the spools holding the iron cores in position 
 should be securely tightened. 
 
 Setting of Relay Adjusting Springs 
 
 With the relay contacts (18) and (19), Fig. 146, properly 
 adjusted (see adjustment of relay contacts, page 322) and 
 insulating material placed between the floating main contacts 
 (19) and (30), Fig. 145, the relay armature should be so adjusted 
 by means of spring (10), Fig. 146, that with 45 volts on the exciter, 
 the contact (19) just floats midway between the upper relay 
 contact (18) and the stop stud (14). 
 
 After the movable relay contact which is attached to the 
 armature has been adjusted in accordance with the above 
 instructions, the lock nut (21) should be securely tightened. 
 
 The above value of 45 volts applies to 125 volt exciters and 
 for the other standard voltages this adjustment figure is directly 
 proportional, as is indicated by the following table: 
 
 
 Values for Relav 
 
 Exciter Volts 
 
 Spring Adjustments 
 
 60 
 
 22 
 
 90 
 
 32 
 
 125 
 
 45 
 
 250 
 
 90 
 
 550 
 
 197 
 
 CONNECTIONS FOR LINE DROP COMPENSATION 
 
 The compensation may be accomplished by a single current 
 transformer which has its secondary connected to an adjustable 
 compensating winding on the a-c. control magnet as shown in the 
 standard diagrams. This transformer is preferably connected to 
 the main feeders and care should be taken that it be inserted in 
 one of the mains to which the potential transformer is connected; 
 for with three-phase as well as with two-phase currents, if the 
 current transformer is not connected to one of the same leads 
 with the potential transformer it is obvious that at unity power- 
 factor the current in the potential winding will be displaced by 
 an angle of 90 deg. from that in the current winding; therefore, 
 no compensating effect whatever will be obtained, although in 
 cases where the power-factor is below unity there would be a 
 slight compensation due to the lagging current. 
 
 In all cases, the current transformer should be placed beyond 
 the point where any load is taken off at the station, such as 
 motor load, constant current transformers, etc., as the draught 
 
 329 
 
of current through the current transformer for such loads would 
 increase the busbar voltage as though the load were out on the 
 line, which would be undesirable. A current transformer that 
 will give 33^ amperes secondary will compensate for about 15 
 per cent line drop. 
 
 Fig. 147 
 
 CONNECTIONS OF POTENTIAL AND COMPENSATING WINDING 
 
 OF TYPES TA-60 AND TA-125 FORM A2 VOLTAGE 
 
 REGULATORS FOR GENERATORS 
 
 The compensating winding (see Fig. 147) consists of three 
 layers of wire, the two inner layers of which are connected as 
 follows: The terminals of the first winding are connected to 
 buttons (1) and (2) while the second winding is connected to but- 
 tons (2) and (3). The third layer is divided into sections of 
 (5) turns each, which have taps brought out to buttons (4) to 
 (11) inclusive. Over these buttons, levers (A) and (B) are 
 arranged to swing. 
 
 In order to increase the busbar voltage the current in these 
 windings should oppose the current in the potential winding. 
 
 330 
 
Therefore, if it is found that with a load on the generator and the 
 levers (A) and (B) swung to the right, the busbar voltage falls, 
 it would indicate that the current in the compensating windings 
 is assisting the current in the potential windings in which case 
 the leads from the secondary of the current transformer to the 
 regulator should be reversed. 
 
 LOCATING TROUBLE 
 
 Should the regulator fail to build up the voltage 
 
 (1) See that the reversing switches at the bottom of the 
 regulator base are thrown to the extreme position either up or 
 down. 
 
 (2) See if the single pole switches at the bottom of the 
 regulator base are closed on the proper exciters. 
 
 (3) Look for improper connections. 
 
 Should the voltage fall 
 
 Examine the rheostat shunt circuit connections to see if 
 they are not so connected as to short-circuit the exciter field 
 instead of its field rheostat. 
 
 Fluctuating Voltage 
 
 If, after placing the regulator in service the potential fluctu- 
 ates to the extent of several volts, proceed as follows: 
 
 First — See that screw (21), Fig. 145, is properly adjusted as 
 contact between screws (19) and (21) will cause unsteady voltage 
 to the extent of from 5 to 10 volts on the secondary. (See 
 "Adjustment of Main Contacts," page 326.) 
 
 Second — See if contact screw (19) is loose. If so it should be 
 properly adjusted and set screw (20) securely tightened. 
 
 Third — Observe both levers (5) and (17) at the points where 
 the core stems (23) and (24) are attached, to see that there is no 
 friction at these points. 
 
 Fourth — The regulator should not be subjected to excessive 
 vibration such as might be the case when it is mounted on iron 
 brackets. Should such vibration exist, some rigid support 
 should be provided to overcome it. 
 
 Fifth — The dashpot should be carefully inspected to see that 
 it is actually full of oil within ^g i n - of the top. 
 
 Sixth — The dashpot should be examined to see that it is 
 securely attached to the supporting posts. 
 
 Seventh — The dashpot may be adjusted for too free a move- 
 ment. This adjustment should be made as free as possible 
 without causing "pumping" of the voltage at no load. (See 
 "Adjustment of Dashpot," page 323.) 
 
 Eighth — Examine cores (11) and (12) to see that they do not 
 touch the inside of the magnet spools. 
 
 Ninth — Carefully inspect all wiring, looking for such mistakes 
 as using the same lead for binding posts (1) and (14) (on standard 
 diagrams filed in the section), flat spots on the exciter commu- 
 tators, loose brushes, or any other poor contacts that might 
 cause an unsteady voltage. 
 
 331 
 
Tenth — Observe pin (35), Fig. 145, to see that it does not make 
 contact with spring (29), and that set screw (36) is securely- 
 tightened. 
 
 Error in Voltage 
 
 If there is an error in voltage from no load to full load without 
 the compensating winding in circuit, it must be due to improper 
 adjustment of the alternating current magnet core. 
 
 If after the core has become steady in going from no load 
 to full load, the main alternating voltage has fallen off, it would 
 indicate that the a-c. magnet core should be lowered slightly 
 until the voltage is the same at full load as at no load. If on the 
 other hand, the main alternating voltage is too high, it would 
 indicate that the a-c. core should be raised slightly to overcome 
 the error. 
 
 With ordinary exciters, if the a-c. magnet core is adjusted 
 while the lever is in a horizontal position so that the core extends 
 from the bottom of the spool to the end of the cap 1% in. there 
 is usually no error from no load to full load on the a-c. generators 
 or with the exciter voltage varied from 70 to 140 volts. (For 
 further adjustments see " Adjustment of the A-C. Magnet Core. ' ') 
 
 If this adjustment is checked and found correct, the error 
 may be caused by friction in the core stems on the magnet levers. 
 
 Error Due to Compensating Winding 
 
 If there is an error in voltage when using the compensating 
 winding, such as too high voltage at no load and corresponding 
 low voltage at full load at the center of distribution, thus requir- 
 ing daily adjustment of levers (A) and (B) (see Fig. 147), it would 
 indicate that the ratio of levers (A) and (B) is incorrect and that 
 they should be swung further to the right and the alternating 
 voltage lowered by means of counterweight (25) and spring 
 (29). See Fig. 145. After the setting of these levers is once 
 obtained, they should require no further adjustment, as it is 
 evident that they will automatically compensate for voltage at 
 all loads. (See "Connections for Line Drop Compensation," 
 page 329.) 
 
 Arcing at the Relay Contacts 
 
 If there is excessive arcing at the relay contacts: 
 First — Check the connections of the rheostat shunt circuit 
 to binding posts (7), (8), (12), (13) and (14) on standard diagrams 
 to see that they are properly made, and that the rheostat only 
 is being short-circuited. Also see that separate leads are run 
 from the exciter busses to binding posts (1) and (14) on the 
 regulator. 
 
 Second — The connections of the condensers should be 
 checked. 
 
 CONDENSERS 
 
 The condensers furnished with the regulator should be con- 
 nected in multiple if more than one is required, and connected 
 
 332 
 
to binding posts (6) and (11) (on standard diagrams). The 
 number of condensers required should, roughly speaking, be one 
 section for each 15 kw. or fraction thereof for exciters having 
 laminated poles, and for each 22 kw. for exciters having solid 
 poles. 
 
 TA FORM "L" REGULATORS 
 
 The Form L voltage regulator is the same as the A2 with the 
 exception that it is for mounting directly upon the switchboard 
 panel while the Form A2 regulator is mounted upon its own base. 
 The instructions given for the Form A2 also apply for the 
 Form L. 
 
 TA FORM "F" REGULATORS 
 
 The Type TA Form F regulators have the following standard 
 voltages. 
 
 Type 
 
 Form 
 
 Exciter 
 Volts 
 
 Range of 
 Exciter Volts 
 
 Alternating 
 Voltage 
 
 TA-90 
 
 TA-125 
 
 TA-250 
 
 F 
 
 F 
 F 
 
 90 
 125 
 250 
 
 50/100 
 
 70/140 
 140/280 
 
 100 to 125 
 100 to 125 
 100 to 125 
 
 ADJUSTMENT OF DASHPOT 
 
 See instructions under Form A2 regulators. 
 
 ADJUSTMENT OF LEVERS AND SPRINGS 
 
 Levers 
 
 First — See that the center of the slot in which core stems 
 
 (23) and (24), Fig. 148, are attached to the levers, is 1& inch from 
 the marble base. After the levers and pivots have been set to 
 give this distance, see that the set screws securing the levers to 
 the pivots, and those holding the pivot sockets, are securely 
 tightened. The pivots should be adjusted until they have but a 
 slight amount of end play. Be sure that the core stems (23) and 
 
 (24) do not bind in the slots in the levers; they should always 
 have sufficient clearance to prevent binding, as friction at this 
 point would be a serious defect. 
 
 Springs 
 
 Before adjusting lever (5) core (11) should be raised to its 
 highest position and blocked by some means, thus bringing 
 main contact (30) to its lowest possible position, to prevent 
 contact being made between contacts (19) and (30) while 
 adjusting lever (5). Springs (1), (2) and (3) should be loosened 
 to their full extent, or taken out while spring (4) is being adjusted. 
 
 333 
 
To adjust spring (4), first see that the voltage on the exciter, to 
 which the direct current control magnet (6) is connected, is 
 maintained at 60, assuming that a 125 volt regulator is being 
 adjusted. Then adjust spring (4) by means of the small nut at 
 the top of its adjusting screw, until the under side of lever (5) 
 comes even with the white mark on gauge (37). After this 
 adjustment has been made the exciter voltage should be increased 
 to 112 and at exactly this point, spring (4) should be over- 
 powered by the magnet, and the cores (12) and (13) will come 
 together. Should it require more or less voltage to overpower 
 
 se as 2a 
 
 Fig. 148 
 TYPE TA, FORM F VOLTAGE REGULATOR 
 MAIN CONTROL MAGNETS AND LEVERS 
 
 the spring and bring these cores together, core (13) should be 
 either raised or lowered, and spring (4) readjusted until the 
 under side of lever (5) comes to the gauge as before. The adjust- 
 ment of spring (4), lever (5) and core (13) must be repeated 
 several times to insure their being correct, as they are of the 
 utmost importance. After the proper adjustment has been 
 obtained, the lock nut beneath the lever on spring (4) should be 
 securely tightened, after which the exciter voltage should be 
 varied over its range again, and the adjustments checked. 
 Then screw (14) which holds the stop core (13) in position, 
 should be securely tightened. This screw should, however, be 
 kept well tightened while the above adjustments are being made. 
 Spring (1) should be adjusted by raising the exciter voltage to 
 80 and at exactly this point this spring should begin to come 
 
 334 
 
under tension, and the small head (15) on the spring stem will 
 be brought in contact with the spring support (16). After this 
 adjustment has been carefully made the lock nut below the lever 
 on springi(l) should be securely tightened and the adjustment 
 of spring (1) checked to see if it is correct. Then spring (2) 
 should be adjusted by increasing the exciter voltage to 110, 
 when it will come into action as does spring (1). After adjusting 
 this spring, the lock nut beneath the lever on spring (2) should 
 also be securely tightened and the adjustment checked. Spring 
 (3) should then be adjusted by raising the exciter voltage to 
 123 at which point this spring will come into action as did 
 springs (1) and (2). Following this adjustment the lock nut 
 underneath the lever on spring (3) should be securely tightened 
 and the adjustment of spring (3) checked. The values of the 
 different adjustment voltages in accordance with the standard 
 exciter voltages for which the regulators are designed are 
 tabulated as follows: 
 
 TYPE TA-60 VOLTAGE REGULATORS 
 
 Spring No. 4 adjusted to gauge mark at 29 volts. 
 Spring Xo. 1 adjusted to pick up at 38 volts. 
 Spring Xo. 2 adjusted to pick up at 53 volts. 
 Spring Xo. 3 adjusted to pick up at 59 volts. 
 
 TYPE TA-90 VOLTAGE REGULATORS 
 
 Spring Xo. 4 adjusted to gauge mark at 43 volts. 
 Spring Xo. 1 adjusted to pick up at 58 volts. 
 Spring Xo. 2 adjusted to pick up at 79 volts. 
 Spring Xo. 3 adjusted to pick up at 89 volts. 
 
 TYPE TA-125 VOLTAGE REGULATORS 
 
 Spring Xo. 4 adjusted to gauge mark at 60 volts. 
 Spring Xo. 1 adjusted to pick up at 80 volts. 
 Spring Xo. 2 adjusted to pick up at 110 volts. 
 Spring Xo. 3 adjusted to pick up at 123 volts. 
 
 TYPE TA-250 VOLTAGE REGULATORS 
 
 Spring Xo. 4 adjusted to gauge mark at 120 volts. 
 Spring Xo. 1 adjusted to pick up at 160 volts. 
 Spring Xo. 2 adjusted to pick up at 220 volts. 
 Spring Xo. 3 adjusted to pick up at 246 volts. 
 
 TYPE TA-550 VOLTAGE REGULATORS 
 
 Spring Xo. 4 adjusted to gauge mark at 264 volts. 
 Spring Xo. 1 adjusted to pick up at 352 volts. 
 Spring Xo. 2 adjusted to pick up at 484 volts. 
 Spring Xo. 3 adjusted to pick up at 541 volts. 
 
 335 
 
Fig. 149 
 
 SECTION OF RELAY MAGNET FOR TYPE TA FORM F 
 
 VOLTAGE REGULATOR 
 
 1 
 
 Connection strip 
 
 14 1 Adjustment screws for 
 
 2 
 
 Armature 
 
 15 j 
 
 spring contact 
 
 3 
 
 Pivot bearing 
 
 16 
 
 Spring contact 
 
 4 
 
 Relay armature lever 
 
 17 
 
 Contact in armature head 
 
 ,T 
 
 
 18 
 
 Armature head 
 
 6 
 
 ► Set screws 
 
 19 
 
 Relay spring for adjust- 
 
 7 
 
 
 
 ment screw 
 
 8 
 
 
 20 
 
 Core plate 
 
 9 
 
 [ Expanded core tips 
 
 21 
 
 Adjustment spring 
 
 10 
 
 
 22 
 
 Set screw 
 
 11 
 
 Stop stud for spring relay 
 
 23 
 
 Lock nut 
 
 
 contacts 
 
 24 
 
 Adjusting nut 
 
 12 
 
 1 Set screws for spring 
 
 25 
 
 Contact stud 
 
 13 
 
 J contact 
 
 
 
 336 
 
ADJUSTMENT OF THE FLOATING MAIN CONTACTS 
 
 For the proper adjustment of the main contacts (19) and 
 (30) swing block (37) underneath lever (5) and tighten screw (39) 
 then swing block (38) underneath lever (17), and with levers 
 (5) and (17) both resting upon blocks (37) and (38), first, see 
 that contact screw (30) is securely tightened and that the con- 
 tact screw (19) is centrally placed above contact screw (30), then 
 securely tighten screws (31) and (32), after which contact screw 
 
 (19) should be adjusted to just touch contact (30) and set-screw 
 
 (20) securely tightened. Then blocks (37) and (38) should be 
 swung out from under levers (5) and (17) so that engagement 
 with them is impossible, and they should be securely tightened 
 in this position. 
 
 ADJUSTMENT OF THE A-C. MAGNET CORE 
 
 If the alternating voltage varies through the regulator range 
 of exciter voltage as specified, it indicates an improper adjust- 
 ment of the alternating current magnet core and to correct this 
 error, proceed as for the Form A2 regulator. 
 
 ADJUSTMENT OF RELAY 
 
 A complete sectional side view of the relay is shown in Fig. 149. 
 As this relay is differentially wound with two windings in each 
 coil, there are four leads extending from the side of each coil. 
 These leads (not shown in Fig. 149) are connected to binding 
 posts A, B and C (on the regulator base) in the following manner: 
 
 1 and 6 to "A." 
 
 2, 3, 5 and 8 to "B." 
 
 4 and 7 to "C." 
 
 The above leads are all provided with stamped metal tags, 
 thus rendering their connection very simple, which should 
 therefore obviate any possibility of a mistake. Inasmuch as the 
 relays are differentially wound, they will work to some extent 
 whether the windings are in service or not. Therefore, if the 
 relays operate unsatisfactorily, they should be tested to ascertain 
 whether the coils are all working properly. If trouble is expe- 
 rienced which is apparently due to improper connections of the 
 relay magnets or a possible open circuit, the fault may be easily 
 located by ringing out the different coils with a magneto or other 
 circuit-testing device. Each coil is wound with two well insu- 
 lated parallel conductors, therefore, when testing the coils care 
 should be taken to see that there is no breakdown of insulation 
 between the two windings. It is also important to ascertain 
 that all leads are properly connected to posts A, B and C, and 
 that the set screws holding them are securely tightened. See 
 that the expanded core tips (8), (9) and (10) (Fig. 149) are flush 
 with the ends of the cores; then securely tighten set screws 
 (5), (6) and (7). 
 
 The pivot holder on the end of armature (2) should be adjusted 
 on the pivot until armature (2) stands centrally over the core 
 tips (8), (9) and (10). The set screws holding pivot and sockets 
 
 337 
 
should then be securely tightened, leaving no end play in the 
 pivots. 
 
 With armature (2) resting upon stop cap (10), the core and 
 tips (8) and (9) should be only 0.05 in. from armature (2). This 
 distance is very important and should be measured by gauge. 
 
 Setting of Relay Adjusting Spring 
 
 With the relay contacts (16) and (17) properly adjusted (see 
 "Adjustment of Relay Contacts") and insulating material 
 placed between the floating main contacts (19) and (30) (Fig. 
 148) the relay armature should be so adjusted by means of 
 spring (21) that with 45 volts on the exciter the armature (2) 
 just floats midway between the upper relay contact (16) and 
 the stop cap (10). 
 
 The above value of 45 volts applies to 125 volt exciters and 
 for the other standard voltages this adjustment figure is directly 
 proportional, as indicated by the table below: 
 
 Exciter Volts 
 
 Values for Relay- 
 Spring Adjustments 
 
 60 
 
 22 
 
 90 
 
 32 
 
 125 
 
 45 
 
 250 
 
 90 
 
 550 
 
 197 
 
 LOCATING TROUBLE 
 
 See instructions under the Form A2 regulators. 
 
 CONDENSERS 
 
 With each regulator there should be furnished one con- 
 denser section for each pair of relay contacts. 
 
 TA FORM K REGULATORS 
 
 There is the same difference between the Forms F and K 
 as there is between the A2 and the L, that is, the Form F is 
 mounted upon its own base while the Form K has the regulator 
 parts mounted directly upon the switchboard panel. The same 
 instructions given for the Form F also apply for the Form K. 
 
 TYPE TD FORM G VOLTAGE REGULATORS 
 
 ADJUSTMENT OF MAIN CONTROL MAGNET 
 
 Should the voltage be unstable or fluctuating, the adjust- 
 ments of the main control magnet should be gone over as follows: 
 With normal voltage on the generator, contacts (4) and (5) (Fig. 
 150) will be nearly closed and the lever (6) should be in a horizon- 
 
 338 
 
 
tal position. Then with an increase in voltage of 12 per cent, 
 core (9) should jump back and strike core (10). Should this 
 fail to occur at 12 per cent above normal voltage, core (10) 
 should be turned in one direction or the other and spring (8) 
 should be adjusted until the lever is again in a horizontal position. 
 The voltage should then again be raised to 12 per cent above 
 normal. The adjustment of these cores is very important and 
 
 Fig. 150 
 
 MAIN CONTROL MAGNET FOR TYPE TD, FORMS G AND R 
 
 VOLTAGE REGULATOR FOR DIRECT CURRENT 
 
 GENERATORS 
 
 should be checked carefully. Make sure that pivots (15) are 
 free and do not stick. A drop of oil on these pivots occasionally 
 will prevent their rusting. 
 
 ADJUSTMENT OF RELAY MAGNET 
 
 The adjustment of the relay magnet is not the same on all 
 TD regulators. A side view of the Forms S and G relay is shown 
 in Fig. 151. The easiest way to adjust the relay contacts is to bring 
 the voltage on 125 volt regulators to 88 volts or 30 per cent below 
 normal. At this voltage the contacts should not open or close 
 but should just come to a balance. If these contacts are open 
 at this voltage lock nut (12) should be loosened and spring (10) 
 should be tightened until the contacts merely come to a balance, 
 then lock nut (12) should be securely tightened. In adjusting 
 
 339 
 
the relay magnet, before attempting to adjust the contacts the 
 relay cores (3) and (4) should be t& in. from the armature with 
 the armature resting on stop stud (6). 
 
 TYPE TD FORM S REGULATORS 
 
 The only difference between the Form G and the Form S 
 regulator is that the latter has no compound winding. The 
 adjustments are the same as for the Form G regulator. 
 
 Fig. 151 
 
 RELAY MAGNET FOR TYPE TD, FORMS G AND S VOLTAGE 
 
 REGULATOR FOR DIRECT CURRENT GENERATORS 
 
 TYPE TD FORM L REGULATORS 
 
 The Type TD Form L regulator is an exact duplicate of the 
 Type TA Form A2 regulator with the exception that the TD 
 Form L is intended for a direct current generator separately 
 excited by an exciter, while the Form A2 is for an a-c. generator 
 separately excited from an exciter and therefore the instructions 
 for the TA-A2 apply for the TD Form L regulator. 
 
 TYPE TD FORM T REGULATORS 
 
 The TD Form T regulator is the same as the TD Form L 
 with the exception that the former is intended for mounting 
 directly upon the switchboard panel while the latter is mounted 
 directly upon its own base. The instructions given for the TA 
 Form A2 also apply for the TD Form T regulators. 
 
 340 
 
TYPE TD FORM R REGULATORS 
 ADJUSTMENT OF MAIN CONTROL MAGNET 
 See instructions for Type TD Form G regulators. 
 
 ADJUSTMENT OF RELAY MAGNET 
 
 Fig. 152 shows the side view of the relay magnet of the Form 
 R regulator. This relay is differentially wound with parallel 
 conductors having four windings on the two coils. Two windings 
 are connected permanently in multiple to the busbar through an 
 external resistance. The second two windings which are con- 
 nected in multiple are opened and closed by the main contacts. 
 
 uTTy—. — . 
 
 /5 /6 9 dJ-i 
 
 ^^c-B^g^ 
 
 Fig. 152 
 
 RELAY FOR TYPE TD, FORM R VOLTAGE REGULATOR 
 
 FOR DIRECT CURRENT GENERATORS 
 
 The adjustment of this relay is exactly the same as that 
 given under the adjustment of relay for the Type TA Form A2 
 regulator with the exception of the spring setting. The tension 
 of spring (10), Fig. 152, should be such that when the main con- 
 tacts on the regulator are opened the relay armature (9) will 
 just float midway between stop stud (14) and contact (18) with 
 88 volts impressed on the generator. This value, 88, is for the 
 125 volt regulator; for the 250 volt regulator this setting should 
 be made at 176 volts. 
 
 341 
 
The switch on the back of the relay is used for cutting out 
 the relays which are not always in use and by opening this switch 
 the main contacts have less work to do and consequently will 
 last considerably longer. 
 
 TYPE TD FORM W SPEED REGULATOR 
 
 This regulator is intended to control the speed of d-c. motors 
 and the adjusting spring (see Fig. 153) should be so adjusted 
 
 Raise Speed By 
 Increasing Tension 
 on Spring \ 
 
 Arrow Shows 
 Direction of 
 Rotation 
 
 Contact Screw A 
 an<^ Stop Screw 
 ° Interchanges 
 
 g4 Clearance 
 Bet ween 
 Contacts with 
 Motor 
 Stationary 
 
 For Clockwise Rotation 
 
 r~/yyve/aht C Should 
 
 Be Assembled in 
 
 Dotted Position with 
 
 Contact Screw A and 
 
 "top Screw B Inter channel 
 
 Brushes Should Bear 
 Evenly on Collector 
 Ririas Without Interference 
 Due to End Play 
 
 Fig. 153 
 
 ADJUSTMENT OF SPEED CONTROLLER FOR 
 
 DIRECT CURRENT MOTORS 
 
 that the vibrating contacts just close at the desired speed. The 
 regulating spring upon the back of this control device should be 
 so adjusted that the contacts which this spring controls should 
 open at about 15 to 20 per cent below normal speed. 
 
 The function of these contacts is to short-circuit the motor 
 field rheostat in starting to prevent the motor starting with a 
 weak field. 
 
 When relay magnets are furnished with this regulator their 
 adjustment should be the same as that given under TD Form R 
 regulators. 
 
 342 
 
CHAPTER 19 
 
 INDUSTRIAL CONTROL APPARATUS 
 
 GENERAL 
 
 Under this heading are included resistances, field, starting 
 and regulating rheostats, and controllers. The Testing Dept. 
 is responsible for detecting all mechanical and electrical defects 
 on apparatus which passes through the Department. A me- 
 chanical inspection should be given each piece of apparatus 
 before the electrical test is begun. Particular care should be 
 used in handling apparatus. Sliding contacts should move 
 freely, contact brushes should make good contact on the seg- 
 ments and have a uniform pressure throughout the arc of 
 movement. See that no loose bolts, nuts, terminals, or name- 
 plates are passed. Where bead insulation is employed, the 
 leads should be provided with a sufficient number of beads to 
 prevent a short-circuit in case two leads should touch one 
 another. Terminals should be spaced a sufficient distance 
 apart to insure safety for the voltage employed and should be 
 stamped according to the DS sketch or drawing list, as the case 
 may be. Xo apparatus except supply parts should be sent out 
 without a nameplate stamped with the drawing list or catalogue 
 number and rating of the apparatus, which will be given on the 
 Engineering Notice, drawing list, or DS sketch. 
 
 Owing to the fact that the resistance of materials is subject 
 to considerable variation, a standard list of the allowances 
 which are approved by the Engineering Dept. is posted in the 
 Section. Devices whose resistance measures above or below 
 these allowable percentages of variation from the specification 
 should be rejected. All rheostats which have reversed, open, 
 or short-circuited steps should be returned to the manufacturing 
 department for repairs. The tester must assure himself, before 
 approving any pieces of apparatus, that all circuits are wired 
 according to the wiring diagrams. 
 
 After all tests are complete, the nameplate should be marked 
 by the tester to indicate that the test is complete, and the 
 wiring sketch should be securely fastened to the apparatus 
 for delivery to the Shipping Dept. 
 
 Field Rheostats 
 
 All field rheostats should receive an insulation test, as given 
 in the Engineering Brief, and the total resistance and the 
 resistance of each step should be read and checked up with 
 the specifications, which will be called for on the drawing list. 
 Hand operated or chain operated rheostats should have the 
 contact arm moved through the complete arc and should make 
 full and even contact for the entire distance. Remote control 
 rheostats are operated by a ratchet and pawl actuated by a 
 solenoid. This should work satisfactorily on 80 per cent of the 
 voltage for which it is designed and should not jam on 120 
 per cent. Motor-operated field rheostats should have a resist- 
 
 343 
 
tance in multiple with the motor armature and another in series 
 with the motor. The value of both of these resistances is 
 determined by the Testing Department and after adjustment 
 to give the travel in a specified time on normal voltage they 
 should be tried on 80 per cent voltage, and with the above 
 adjustment must give satisfactory and positive operation. 
 
 Rheostats for Split Pole Synchronous Converters 
 
 These are for use in the auxiliary field of synchronous 
 converters and should have a load test as follows: Connect a 
 suitable resistance in the circuit marked "field" and in series 
 with this connect an ammeter of proper capacity. Turn the 
 contact arm to the neutral position and apply voltage to the 
 line terminals. The ammeter should read correctly when the 
 arm is turned in one direction and should read backward for 
 the other direction. This point must be checked for all rheostats 
 of this type. 
 
 Hand Operated, Starting and Regulating Rheostats 
 
 In addition to the regular mechanical inspection, the arm 
 should be brought to the first point and released to see if it 
 returns promptly to the "off" position. This should also be 
 tried from the running position. Regulating rheostats should 
 be tried for holding and releasing in each position of the arm. 
 
 All starting and regulating rheostats should be tried starting 
 a motor several times and the release voltage noted. The arm 
 must hold securely on half voltage. After this has been tried, 
 full voltage should be applied. Then with the arm in the 
 running position the line switch should be opened and the 
 voltage at which the arm opens the circuit should be read. 
 This must not exceed 35 per cent of the line voltage, but must 
 operate before the motor has stopped. The retaining coil 
 specification number should be checked and where an overload 
 release is provided, the overload should be tripped and should 
 release the arm immediately. The overload spool should after- 
 wards be calibrated. See the drawing list for values. In the 
 larger sizes which employ a contactor instead of a retaining 
 magnet the contactor should be tested. (See instructions on 
 "Contactor Testing" pages 345-6.) 
 
 Automatic Starters 
 
 These devices should receive a mechanical inspection; the 
 contactor coil specification should be checked against the 
 drawing list or Engineering Notice; all resistances should be 
 measured and checked, and contactors tested (see instructions 
 on "Contactor Testing" pages 345-6). Interlocks should be 
 checked to see that they close in proper sequence with reference 
 to the closing of the main contact tips of the contactor. All 
 interlocks which are open should close, and those which are 
 closed should open when the contactor closes. 
 
 All sliding levers which are attached to dashpots should be 
 moved by hand to see if they move smoothly and easily. There 
 
 344 
 
should be no burred or pitted spots on the contact buttons 
 or segments across which the contact arm moves. See also 
 that the lever is properly retarded by its dashpot. Series con- 
 tactors should be adjusted for the current values, as given in 
 the Engineering Brief. Counter e.m.f. starters must be adjusted 
 to pick up at the voltages specified, and after adjustment must 
 be given an operating test with a motor of suitable rating. 
 
 Alternating Current Panels 
 
 Each panel should be given a test which represents the 
 operating conditions as nearly as possible, and should be tried 
 under different conditions, such as low voltage and high voltage. 
 Where reversing features are provided, they should be tried 
 thoroughly, and other special features should be given careful 
 attention. For these tests the alternator should be held at 
 normal voltage and frequency, except for the high and low volt- 
 age tests. Automatic compensator panels should have the 
 taps on the compensator read at the motor terminals. The 
 magnetizing current should also be read at normal voltage and 
 frequency, as this will furnish an additional check on the com- 
 pensator coil. The XR number of the coil is stamped on a small 
 piece of fiber and is imbedded in the coil surface. This number 
 should be checked against the rating of the panel. If dashpots 
 are employed, they should be adjusted for time as specified on 
 the drawing list or Engineering Notice. This adjustment 
 should be such that a greater time limit cannot be obtained 
 in case the customer attempts to make readjustments. If this 
 is not done, a burned coil may be the result. After this adjust- 
 ment, the dashpot should be operated several times and the 
 time checked to see that the adjustment is constant. A rough 
 check on the temperature of the coils should be made by feeling 
 each one after the voltage has been applied for a considerable 
 time. 
 
 Direct Current Panels 
 
 As with alternating current panels, the operating conditions 
 should be approximated or equaled where possible. All over- 
 load, underload, field, and other relays should be calibrated 
 and adjusted. Current limit relays should be adjusted and tried 
 in all positions to see that they do not bind. Magnetic clutches 
 should be adjusted by the factory and checked by the Testing 
 Dept., and the operation on low voltage tried. Contactors 
 should be adjusted (see below). The control circuits should 
 be tried for normal operation, dashpots adjusted, and inter- 
 locks checked as given previously. All panels, after having 
 the circuits and resistances checked, should be connected to 
 the motor and given a complete operating test. High potential 
 tests should be applied after all other tests are completed. 
 The terminal stamping should be checked. 
 
 Contactors — Direct Current 
 
 Contactors should have the resistance of the coil measured 
 and recorded, the "pick-up" and "wipe" current checked, 
 
 345 
 
also the amount of "wipe." If the wipe current is higher than 
 the pick-up, this should be recorded separately. This current 
 must not be greater than that specified in the Engineering 
 Brief for the coil specification in use. Finger pressure, both initial 
 and final, should be taken. The high potential test should be given 
 after all other tests are completed and should be according to the 
 Engineering Brief for both a-c. and d-c. contactors. 
 
 Contactors — Alternating Current 
 
 The resistance of the coils should be measured and recorded 
 on the record of the panel. The coil specification, the "pick- 
 up" and "wipe current," and the amount of wipe should be 
 checked. Finger pressure, both initial and final, should be taken 
 and the watts consumed by the contactor should be recorded 
 and checked against the Engineering Brief. If an adjustable 
 shading coil is used, it should be adjusted to give a watt value 
 equal to, or lower than that specified in the Engineering Brief. 
 The voltage and frequency should be held at normal for this 
 test. The contactor must not hum at the minimum operating 
 voltage given in the Engineering Brief, or at normal voltage. 
 High potential tests should be applied after completion of 
 the above test. 
 
 Where a series resistance is used with contactors as a holding 
 resistance, the contactor must pick up and wipe on 80 per cent 
 of line voltage and remain sealed on this voltage with the series 
 resistance in the circuit. When the contactor is open and the 
 series resistance is in the circuit, the contactor must not pick 
 up on 120 per cent of the line voltage, even with considerable 
 vibration. The above does not apply where a series resistance 
 is used other than as a holding resistance. 
 
 Printing Press Controllers 
 
 Each resistance should be measured and recorded. The 
 circuits should be checked up and the contactors tested (see 
 instructions on contactor testing). On two-motor equipments, 
 the resistance should be checked as above and the pilot motor 
 connected up. The time for a complete movement of the arm 
 should be obtained at normal voltage with the variable pilot 
 motor armature shunt resistance both all in and all out. See 
 that the tripping of the overload opens the "stop" circuit of 
 the control and immediately stops the equipment. Try the 
 "safe" and "run " features of the push button stations. The small 
 motor reversing switch should open the large motor control 
 circuit when the small motor is reversed. All interlocks should 
 be checked. On current limit controllers the master dial 
 switch should be connected up and care should be taken to 
 see that proper sequence of contactors is obtained. Try the 
 current limit interlocks to see that they do not bind. Adjust 
 the field relays according to the Engineering Notice. Calibrate 
 the overload relay and check the wiring. The dynamic brake 
 contactor should wipe with the motor running at minimum 
 speed. 
 
 346 
 
High Potential Tests 
 
 All apparatus should receive a high potential test, as specified 
 in the Engineering Brief. This varies with the class of apparatus. 
 
 Shipment 
 
 After the completion of the test, the name plates should 
 be marked with the Testing Department's stamp and the 
 wiring diagrams should be securely attached. 
 
 There are occasionally special cases in which the diagram 
 is to be mailed, in such cases the Head of the Section should 
 obtain written permission from the Engineering Dept. to ship 
 the apparatus without diagrams, and should attach a card 
 marked "No connection diagram necessary." 
 
 STARTING COMPENSATORS 
 
 Compensators for starting Form K induction motors, 
 synchronous motors, and synchronous converters are built 
 for voltages from 110 to 13,200 volts. The switching mechanism 
 and connections constitute the chief difference between the 
 various forms. Forms A and B have double-throw oil 
 switches which are so connected that the fuses, or overload 
 relays, as the case may be, are in the circuit only when the motor 
 is thrown on the line. (See Figs. 154 to 159 inc.) The figures 
 show the connections for the Forms A and B two-phase and 
 three-phase compensators with the necessary overload and 
 no-voltage relays. The tests required are ratio, magnetizing 
 current, heat runs when specified, double potential and high 
 potential. The no-voltage release coil should, in addition 
 to the double potential and high potential tests, receive pick-up 
 and releasing tests and have its resistance measured. The 
 oil boxes should be removed and the switches carefully examined 
 before making any tests. 
 
 On compensators above 550 volts the oil switch must not 
 be used to break the magnetizing current unless the oil box is 
 filled with oil as the switch will arc across and not open the circuit. 
 
 Complete tests on compensators consist of commercial tests, 
 heat runs, impedance, and insulation tests. 
 
 Commercial tests consist of ratio of taps, exciting current 
 at normal voltage and frequency, and insulation tests. 
 
 Insulation tests consist of applying high potential between 
 the windings and ground for one minute, operating the com- 
 pensator at double potential for one minute and also at one 
 and one-half times normal potential for five minutes. 
 
 Ratio 
 
 Connect the line leads to the terminals on the testing stand. 
 These terminals are connected in multiple by busbars at the 
 back of the terminal board. Apply 100 volts to the lines; 
 throw the switch on the compensator under test to the "starting " 
 position, leaving all others in the "off" position. On the three- 
 phase compensator read the voltage between the taps (the 
 
 347 
 
6 A A' A' A B 
 
 Phased 
 
 Phase* Phases 
 
 Fig. 154 
 CONNECTIONS OF QUARTER-PHASE, TYPE IQ, INDUCTION MOTOR 
 AND TYPE NR, FORM A2 STARTING COMPENSATOR 
 WITH NO-VOLTAGE RELEASE ONLY 
 
 P/?aseA « 
 
 Generator 
 
 Over/ood 
 /?e/ays 
 
 /?e/ay 
 
 rff 
 
 Connect ie/ow tens/on c/rcu/t 
 w/j/c/> t*ot//d£>e aVfecteaf /n 
 case or^oz/ure or^o/tape 
 
 on motor or- tnroupn 
 tran&for/ner to motor /cads 
 
 Cat>/e 
 C/a/np 
 
 SacAr 
 f/nper B/oc/c 
 
 CyZ/rtcfer 
 
 front 
 /7/?aerfi/oc# 
 
 Fig. 155 
 CONNECTIONS OF QUARTER-PHASE HIGH VOLTAGE TYPE NR 
 STARTING COMPENSATOR WITH NO-VOLTAGE AND 
 OVERLOAD RELAY 
 
 348 
 
Fig. 156 
 CONNECTIONS OF THREE-PHASE, TYPE I, INDUCTION MOTOR 
 AND TYPE NR, FORM A2 STARTING COMPENSATOR WITH 
 NO-VOLTAGE RELEASE ONLY 
 
 Generator 
 
 Fig. 157 
 CONNECTIONS OF THREE-PHASE TYPE I, INDUCTION MOTOR 
 AND TYPE NR, FORM A3 STARTING COMPENSATOR, WITH 
 NO-VOLTAGE AND OVERLOAD RELEASE 
 
 349 
 
Connect to a /otv tens/on circuit lyh/ch 
 wot/A* be affected /n case of faik//e 
 of yo/tage on the motor or through 
 transformer to motor /eads 
 
 Fig. 158 
 CONNECTIONS OF CR HIGH VOLTAGE THREE-PHASE STARTING 
 COMPENSATOR WITH NO-VOLTAGE AND 
 OVERLOAD RELEASE 
 
 
 Fig. 159 
 CONNECTIONS OF QUARTER-PHASE, TYPE IQ, INDUCTION MOTOR 
 AND TYPE NR, FORM A3 STARTING COMPENSATOR WITH 
 NO-VOLTAGE AND OVERLOAD RELEASE 
 
 350 
 
lowest voltage tap is next to the core). Standard compensators 
 for motors up to and including 17 h.p. have 50, 65, and 80 per 
 cent taps; those for motors above 17 h.p. have 40, 58, 70 and 
 85 per cent taps. The ratios obtained should agree to within 
 3 per cent of the above. 
 
 In determining ratios see that both the primary and 
 secondary instruments are on the same phase. In checking the 
 ratio of quarter-phase compensators, join leads A' and A' 
 (see Fig. 154), apply 100 volts to the lines A and A, and read 
 the voltage on the taps between the motor leads B, B and each 
 tap. These compensators are tested "open delta." 
 
 Magnetizing Current 
 
 Magnetizing current is measured at normal primary voltage 
 and frequency. The alternator used should operate at normal 
 voltage. The exciting current at normal voltage and frequency 
 should, on 60 cycle compensators, not exceed 25 per cent, and, 
 for 40 and 25 cycle compensators, it should not exceed 30 per 
 cent of the full load current of the motor, assuming in the 
 smaller sizes, the motor to operate at 75 per cent efficiency 
 and in the larger sizes at 80 per cent. 
 
 On special compensators, covered by Engineering Notices, 
 the magnetizing current should be taken at 20 per cent above 
 normal potential as well as at normal. In making this test 
 hold the voltage constant across one phase and read the current 
 in all three legs, then hold the current constant in one leg and 
 read the three-phase voltage, or instead of holding current in 
 one leg, two voltmeters may be used, one to hold the voltage 
 constant, and the other to read the three-phase voltage. Owing 
 to the fact that these machines are used for starting duty only, 
 a high current and magnetic density is employed. Therefore, 
 a very small change in frequency or potential makes a con- 
 siderable difference in the exciting current, and care must be 
 exercised to see that the voltage and frequency are normal. 
 Quarter-phase compensators are tested "open delta." 
 
 It will be noted that on three-phase compensators one leg 
 will read slightly lower than the other two, which should be 
 balanced. This is due to leakage caused by the high magnetic 
 density and the close proximity of the iron case and supporting 
 straps. 
 
 Heat Runs 
 
 Short-circuit the motor leads and apply sufficient voltage 
 to the line leads to force the required current through the 
 coils. This current should be held constant for one minute 
 and the impedance volts read in each phase during this period 
 and on each set of taps. The value of the current will be given 
 in the standard Engineering Brief, or in Engineering Notices 
 covering special cases. Thirty minutes should elapse between 
 successive heat runs on the same compensator up to and in- 
 cluding 200 h.p. ; above this size one hour should be allowed. 
 A thermometer should be placed on each coil and the temper- 
 
 351 
 
atures watched until they attain a maximum after each run 
 and this value should be recorded. Directly after the close 
 of each run the tap leads should be changed to the next tap. 
 Heat runs should always be started on the tap next to the core. 
 
 On large compensators it sometimes happens that there is 
 not sufficient power available to make the heat run as called 
 for. In this case upon permission from the Engineering Dept. 
 the following alternative may be used: 
 
 Hold half the current called for, and hold it four times as 
 long. This will give an equivalent heating. 
 
 After the completion of the heat run the taps should be taped 
 up after placing the tap leads on the second set of taps. All 
 compensators should be sent out with the tap leads on this 
 tap. 
 
 Insulation Tests 
 
 The double potential and the high potential tests should be 
 applied after all other tests are completed and the compensator 
 is assembled with the taps taped up. The frequency should be 
 high in order to keep the magnetizing current below the normal 
 current for which the compensator is designed. In case the 
 normal voltage of the compensator is so high that it is impossible 
 to secure double potential, one set of taps may be connected 
 to the line and voltage applied, which shall be double the voltage 
 for which the tap is designed. 
 
 All compensators up to and including 550 volts normal rating 
 should receive 2500 volts insulation tests from windings to core 
 and frame for one minute; those from 550 to 4000 volts should 
 receive 7500 volts; those for 4000 volts should receive 10,000 
 volts; those above 4000 volts, double normal potential. In 
 applying the high potential tests all leads should be connected 
 together. 
 
 352 
 
CHAPTER 20 
 
 MINE AND INDUSTRIAL LOCOMOTIVES 
 
 MINING LOCOMOTIVES 
 
 Mining locomotives (LM type) are built for various gauges 
 in sizes of 3 to 20 tons. With, the exception of an occasional 
 3-motor, 6-wheel type they are all 2-motor, 4-wheel locomotives 
 and are equipped with either 250 or 500 volt series wound, totally 
 enclosed motors mounted directly on the axles and driving 
 through double reduction gearing. The controllers are of the 
 "R" type, which have a separate cylinder for forward and 
 reverse in which is incorporated a commutating switch that 
 permits starting the locomotive with motors either in series 
 or in parallel. 
 
 Before being sent to the Locomotive Department the various 
 parts of the equipment are tested separately; the motors being 
 subjected to the standard test for railway motors and the con- 
 trollers, circuit breaker, etc. being subjected to the regular 
 tests in force in their respective departments. The test of the 
 locomotive proper is, therefore, principally a bearing run, a 
 check of the wiring connections and a general inspection to see 
 that all parts operate properly, that clearances are sufficient 
 and that the apparatus is properly located. 
 
 Unless otherwise specified, tests should be conducted as 
 follows: 
 
 1. Anchor the locomotive securely on the testing stand 
 that is provided in the Locomotive Section and operate it on 
 all points of the controller, forward and reverse, both series and 
 parallel, to assure that connections have been properly made. 
 
 Caution: As these are series motors running practically 
 without load, power should be thrown off as quickly as possible 
 when checking with the controller in the "parallel" position. 
 
 2. Make a bearing run of 15 minutes duration in each 
 direction at full "series" position of the controller. 
 
 3. Measure and record the resistances of the several 
 rheostat steps. A 20 per cent variation from the values given 
 in the DS print is allowable. 
 
 4. Make a careful general inspection to see that the brakes, 
 sand rigging, headlights and circuit breaker operate properly; 
 that the wiring cables are clamped securely and that they do 
 not interfere with the access to the motor bearings or other 
 parts; see that the rheostat terminals have good clearances to 
 "ground" on the locomotive frame and check up carefully all 
 questions on the testing record. 
 
 Cable Reels 
 
 Many locomotives, particularly the 5 and 6 ton sizes are 
 equipped with motor-driven cable reels. The purpose of the 
 reel is to permit operation over those portions of the mine 
 roads that are not provided with trolley wires. The reel 
 
 353 
 
rotates with its axis vertical and is driven by a four pole, series 
 wound, vertical motor which is wired directly across the line 
 in series with a permanent resistance to protect it from an 
 injurious rush of current when the motor is stalled. The outer 
 end of the cable is hooked over the trolley wire and as the 
 locomotive moves forward the reel motor is overhauled and 
 acts as a series generator, its counter torque producing sufficient 
 tension in the cable to pay it out evenly. As soon as the loco- 
 motive starts back and slackens up on the cable, the motor 
 action comes into play and winds up the cable; the action is 
 analogous to that of a spring having infinite length. 
 Test as follows: 
 
 1. Measure and record the cold resistance of the armature, 
 field and permanent rheostat. 
 
 2. Check the polarity. 
 
 3. Check for satisfactory operation by mounting the reel 
 equipment on the shop locomotive that is provided for this 
 purpose and run it out on the test track. At least five trials 
 should be made running the full length of the cable. The 
 reel should pick up and wind the cable compactly when the 
 locomotive is running on the full series point of the controller. 
 
 4. When the reel equipment is mounted on its own loco- 
 motive, check the rotation (looking at the top of the reel) as 
 follows: If the motorman's seat is on the left hand side of the 
 locomotive the rotation should be counter-clockwise. If the 
 seat is on the right hand side of the locomotive the rotation 
 should be clockwise. 
 
 Winding Devices 
 
 For hauling cars out of mine slopes where the grade is too 
 steep for locomotive operation some locomotives are equipped 
 with winding devices. These consist of a vertical axis cable 
 drum fitted with 400 to 600 ft. of flexible steel cable and driven 
 by a series wound, totally enclosed motor. 
 
 Test as follows: 
 
 1. Give the drum and motor a 15 minute bearing run, 
 holding them down to moderate speed by applying the band 
 brake on the drum. 
 
 2. See that the brake and clutch levers operate readily 
 and that the clutch engages properly. 
 
 3. With the clutch disengaged, see that the cable can be 
 hauled out by hand easily. Use a spring balance and record 
 the pull required; this must not exceed 45 lb. 
 
 4. Measure and record the resistance of the starting 
 rheostat. 
 
 INDUSTRIAL LOCOMOTIVES 
 
 Industrial locomotives (LS type) are built for various 
 gauges and in sizes from 3 to 25 tons. They are practically 
 all of the single truck, 4-wheel, 2-motor type. The electrical 
 equipment in general is the same as for the mine locomotives 
 and they differ only in the mechanical arrangement of the 
 
 354 
 
frames. With the exception of the larger sizes (15 to 25 tons) 
 the test should be conducted in the same manner as for the 
 mining locomotives. Those of 15 tons and above are, as a rule, 
 built for the standard gauge (56 3^2 in.) and are equipped with 
 cabs, air brakes and MCB couplers. Instead of using the 
 testing stand in the Locomotive Section, these should be tested 
 on the General Electric Company test tracks and the general 
 instructions in force there will apply. 
 
 STORAGE BATTERY LOCOMOTIVES 
 
 Storage battery locomotives (C.S.B. and L.S.B. types) are 
 at present built in various sizes, from 2^ to 8 tons. These 
 as a rule will be single truck, 4 wheels, with either one or two 
 motors, and for various gauges from 24 in. to 563^ in. 
 
 The equipment differs from the standard mine (L.M.), and 
 industrial (L.S.) types, in having low voltage automobile type 
 motors, driving the wheels by double reduction gearing in 
 place of the regular 250-500 volt motors. The storage battery 
 will usually consist of 44 "lead acid" cells or 70 to 80 Edison 
 cells, all connected in series for an average discharge potential 
 of 85 volts. 
 
 After the battery is in proper condition of charge as herein- 
 after described, the locomotive should be placed on the testing 
 stand and test conducted in the same manner as before described 
 for mining (L.M.) and industrial (L.S.) type, i.e., operate on 
 all points of the controller forward and reverse to see that all 
 connections are properly made, make 15 minute bearing runs 
 in each direction; measure the resistance of the rheostat; and 
 make a general mechanical inspection of brakes, sand rigging, 
 headlights, wiring, etc. 
 
 When a locomotive has been delivered to test, each and 
 every cell should be carefully inspected to see that the electro- 
 lyte is at the proper level. This level varies for the different 
 types and makes. For the "Lead Acid" battery (distinguished 
 by a rubber jar) the level of the liquid should be Y2 in. above 
 the plate, for the Edison (distinguished by metal jars) the 
 level of the liquid should be Y2 in. above the plates for the 
 A-4 and A-6 types, and y % in. for the A-8, A-10 and A-12 types. 
 
 Caution: Gas may be present in the cells. Do not use a 
 match, candle or other open flame to inspect. 
 
 The lead cell batteries may be easily inspected by removing 
 the cover or the soft rubber plug. For determining the height 
 of liquid in Edison cells the method illustrated in Fig. 160 will 
 be found convenient. 
 
 If the liquid is low, sufficient pure distilled, water should be 
 added; never use water suspected of containing the slightest 
 impurities as very great damage to the battery may result. 
 
 After ascertaining if the liquid is at the proper height see 
 that the several battery trays or crates are properly connected 
 in series, as otherwise a portion of the battery might easily be 
 ruined. 
 
 355 
 
Since it is impossible here completely to describe the various 
 methods of charging the several types of batteries, due to the 
 fact that the several manufacturers recommend slightly different 
 procedure, the following brief summary must suffice for the 
 first charge while the battery is temporarily in our care: The 
 battery should be placed on charge at the normal rate as given 
 with the instructions that accompany each battery. For lead 
 
 Fig. 160 
 
 QUICK METHOD OF DETERMINING PROPER LEVEL OF 
 
 ELECTROLYTE ABOVE PLATES 
 
 batteries when the voltage has reached a value of 2.55 volts 
 per cell (112 volts for 44 cells) the charging should be discon- 
 tinued. For Edison batteries, charge at the normal rate as given 
 on the name plate for 7 hours or until the voltage has reached 
 a value corresponding to 1.85 volts per cell. 
 
 When all tests have been completed, the locomotive may be 
 shipped without recharging, as the running light test will as a 
 rule use but little of the battery charge. 
 
 Fig. 161 shows the proper method of connecting a battery 
 to the line for charging. 
 
 356 
 
Vo/t meter Ammeter 
 
 
 Fig. 161 
 DIAGRAM SHOWING GENERAL METHOD OF CHARGING BATTERIES 
 
 The trays are first connected in series, i.e., the. negative of one tray to the 
 positive of the adjoining tray. The current flows from the positive wire of the 
 current supply, into the positive terminal of the first tray (in this case on the 
 right) ; through the positive and out of the negative of each cell and each tray 
 in turn and returns to the current supply from the negative of the last cell. 
 
 The voltmeter is connected inside the resistance or rheostat, to show the 
 battery voltage only. 
 
 357 
 
CHAPTER 21 
 
 PORCELAIN INSULATORS 
 
 Insulators are of two distinct types; link insulators and 
 bushings. 
 
 The Link Insulators are those used for either strain or 
 suspension work and have holes, called cableways, for fastening 
 the cables. 
 
 Bushings comprise all other kinds of porcelain insulators 
 which are cylindrical in form, and serve as conduits. 
 
 Inspection 
 
 Before testing, all insulators should be given a rigid inspec- 
 tion for mechanical defects, such as cracks, flaws, warping, 
 chipping and non-uniformity in color of glaze. 
 
 Methods Used in Applying High Potential 
 
 In applying high potential to porcelain insulators, they 
 are placed on a rack which holds twelve, and these are tested 
 together. 
 
 In the larger type requiring a special test, it will be found 
 advantageous to use two racks at once. 
 
 The Link Insulators have cableways on either side between 
 which the potential is applied. 
 
 This can be done by using two spiral springs which can be 
 pushed through the cableways and hooked upon themselves, 
 thus making the insulator take the same position as it does 
 in service. 
 
 In testing bushings, a pipe or spring is laid through the 
 center of approximately the same size as the hole. A piece 
 of metal foil or spring is then wound around the outside at the 
 middle point. The potential test is then applied between the 
 metal parts. 
 
 Routine Potential Tests on Insulators for Switchboard Depart- 
 ment 
 
 Potential values, where called for, should be determined by 
 the needle gap and striking distance curve C-845. (See Fig. 186.) 
 This determination should be made under testing conditions 
 with the insulators connected to the transformer. (The capacity 
 currents taken by some insulators and the oscillating discharge 
 passing over their surface sometimes seriously affect the trans- 
 formation ratio.) Where arc-over values only are specified, 
 the tester must see that the testing outfit and conditions will 
 not facilitate arc-overs. 
 
 Insulators in production and not listed in Eng. Brief 10761A 
 should be called to the attention of the Engineering Department. 
 
 Any insulators listed showing serious discrepancies from 
 the results of specified tests, without defects being apparent, 
 should be referred to the Engineering Department before 
 proceeding further. 
 
 358 
 
Tests are called for by letters having the following signifi- 
 cance: 
 
 11 A" Apply potential between central stud filling the 
 insulator bore, and the foil band around the outside of insulator. 
 Foil should be so located as to bring the maximum tax (stress) 
 through that section of the insulator which is under maximum 
 stress in service. If the outer surface is not completely glazed 
 foil should be placed on the unglazed surface. 
 
 " B " Includes ' ' Blind ' ' Insulators. Apply potential between 
 the stud and foil around the opposite end of insulator, the foil 
 being located to give approximately service conditions. 
 
 " C" Apply potential between foil located inside and 
 outside the insulator on the unglazed parts. 
 
 "D" Apply potential between spiral springs coiled in 
 cableways. 
 
 ".4," "B," " C" and "D" tests consist of a flash-over 
 voltage applied instantaneously and a 90 per cent flash-over 
 voltage applied for 30 seconds. 
 
 TUBES 
 
 Wet process porcelain tubes must be tested at 20,000 volts 
 per each y% in. thickness applied for 30 seconds between central 
 stud and foil covering the outside completely except at ends 
 where the foil is omitted to obtain the necessary striking dis- 
 tance. 
 
 359 
 
CHAPTER 22 
 
 TRAIN CONTROL APPARATUS 
 
 Inspection and High Potential Tests 
 
 Before testing any apparatus, a careful inspection must be 
 made for any mechanical defects. Any part of apparatus that 
 will be subjected to a difference of potential must be given a 
 high potential test, corresponding to that specified in the 
 Engineering Briefs. 
 
 AIR BRAKE APPARATUS 
 
 This includes valves, governors, strainers, cylinders, and 
 all other parts that make up the braking system of a car or 
 train. 
 
 VALVES 
 
 Air valves are manufactured under the following type 
 letters: A, S, VL, E, and TE. 
 
 The A and S are motorman's valves, different forms of 
 which are used for straight air and emergency brake systems. 
 
 The VL is a pressure reducing valve used for automatic 
 air brake systems, and reduces the main air reservoir pressure 
 to a lower and constant pressure. 
 
 Type E includes all emergency valves. One of the most 
 important is the Form E, used with automatic air brake systems 
 in connection with the pilot valve located in the controller. 
 It exhausts the train pipe whenever the pilot valve is opened, 
 thus applying the brakes to the car or train. 
 
 Magnet valves are included under the Type TE. They are 
 used for remote control. The Form B is used for operating 
 pantograph trolleys. 
 
 Mechanical Inspection 
 
 Each valve is given a careful inspection to see that all the 
 pipe connections have good threads. In the Types A and S, 
 the fit of the handle should not be too loose. There should be 
 only enough clearance to allow it to be easily removed. The 
 handle should move over the different positions with compara- 
 tive ease and be removable only in the lap position. 
 
 Air Valve Tests 
 
 Every casting, which will be subjected to air pressure in 
 service, should be tested for porosity. This is done by immersing 
 the casting under pressure in water. Where this cannot be 
 done, cover the casting, under air pressure, with soap suds. 
 Water must be used in every case to determine the amount of 
 leakage, and all castings showing a continuous leakage must 
 be rejected. 
 
 After assembly, each valve should be subjected to an air 
 pressure and operated as near as possible at the service pressure. 
 All parts should then be again tested for leaks by immersing 
 
 360 
 
in water or by covering the part with soap suds, while under 
 pressure. 
 
 Valves with metal stem seats are provided with ground 
 stems. The stem and hood are inspected before being assembled 
 on the valve body. 
 
 GOVERNORS 
 
 Governors automatically keep the air pressure of the braking 
 system within a certain range by opening and closing the com- 
 pressor motor circuit. 
 
 Operating Test 
 
 Each governor is stamped with the type letters and numbers; 
 the letters represent the style of the governor, and the numbers 
 represent the capacity and range at which it will operate. The 
 first number indicates the minimum opening pressure in pounds 
 per square inch. The second number denotes the maximum 
 opening pressure. The third denotes the variation in the opening 
 and closing pressures. The tests are similar in all governors 
 and consist of connecting them to a source of compressed air, 
 the compressor motor circuit being wired through the governor 
 tested. The governor should then be adjusted to open the 
 circuit at the minimum opening pressure and close it as soon as 
 the pressure is reduced by an amount equal to the given pressure 
 range. It must then be tested for maximum opening pressure 
 and should again close when the pressure is varied through the 
 amount equal to the normal range. 
 
 All parts under pressure should be examined for leaks. 
 
 Type ME 65-100-10 Form A Governor 
 
 This governor is designed for use with a large compressor, 
 the circuit of which is made or broken by a contactor or con- 
 tactors controlled by the governor. The test is similar to 
 that given above, except that the main circuit of the com- 
 pressor is broken by the contactors controlled by the governor 
 instead of by the governor direct. 
 
 STRAINERS 
 
 Strainers are used in air brake systems to catch scale and 
 small particles that would interfere with the operation of any 
 of the apparatus. They are tested with air pressure and exam- 
 ined for leaks. 
 
 CONTROLLERS 
 
 The R, K, C and T controllers comprise the principal types, 
 All others are modifications of the above. 
 
 • The R and K types make and break the main motor circuit 
 within the controller. 
 
 The Type C controller makes and breaks a circuit which 
 operates contactors that open and close the motor circuits. 
 With a contactor box on each car and the control circuits 
 connected in parallel, the motor circuits for a whole train can be 
 controlled with one controller. 
 
 Type T is used with induction motors, generally being used 
 to cut out resistance in the rotor circuit of Type M motors. 
 
 361 
 
Inspection 
 
 The development of each cylinder and its fingers should be 
 examined to see that they check with the DS diagram. The 
 fingers should make good contact on the segments of the cylinder 
 and in the order shown. Controllers having several auxiliary 
 fingers in series should be tested to see that these fingers make 
 and break contact simultaneously. All auxiliary release knobs 
 should open the auxiliary contact fingers when released at any 
 position of the handle. -The main cylinder and reversing cylinder 
 should interlock, so that the reversing handle cannot be thrown 
 when the controller is in any but the "off" position. When the 
 reversing handle is in the removable position, the main cylinder 
 should be locked in the "off" position. All controllers should 
 receive a careful inspection for mechanical defects. All cables 
 passing through the frame of the controller should pass through 
 an insulating bushing, except in the case of Type R controllers 
 for mining locomotives. 
 
 There should be sufficient clearance between points at 
 different potentials and between all current-carrying parts and 
 frame. 
 
 Operating Test 
 
 All controllers should be connected and operated under 
 service conditions as nearly as possible. Those controllers 
 which operate the main motor circuit should be connected 
 and operated with a motor or motors with the proper resistance 
 in circuit, to check the wiring and the blow-outs on the different 
 fingers. Carefully note whether the arc blows in the proper 
 direction and ruptures satisfactorily when turning the con- 
 troller to the "off" position. When the controller is not adapted 
 to motors used in the testing department, the complete develop- 
 ment and wiring of the controller should be carefully checked 
 with the DS diagram. Those built to operate contactors should 
 be connected to the latter and operated, noting the direction 
 the arc blows as in other controllers. When turning the con- 
 troller to the "on" position the auxiliary finger or fingers should 
 make contact first, and should break last when turning to the 
 "off" position, unless otherwise stated on the Engineering Brief 
 for that particular type or form of controller. 
 
 Where a separate blow-out is used for the auxiliary fingers, 
 it should be carefully tested. The auxiliary fingers, whether 
 fitted with a blow-out coil or not, should break the total current 
 of the controller in any position, when the auxiliary release 
 knob is released. 
 
 Automatic and Semi-Automatic Controllers 
 
 Several types of the C controllers have their cylinders 
 fitted with a spring and governor so that when the handle of 
 the controller is turned to the "full on" position, the spring is 
 wound up sufficiently to rotate the cylinder. The governor 
 should be adjusted so that the cylinder will rotate in the specified 
 time. The governor is fitted with a small magnet coil which 
 
 362 
 
should lock and hold the cylinder in any position when the 
 specified current is passed through the coil. 
 
 Pilot Valves 
 
 Many C controllers are fitted with pilot valves operated 
 by the auxiliary release knob. This pilot operates a valve for 
 an emergency operation of the brakes. They should be con- 
 nected to an emergency valve which should trip whenever the 
 auxiliary release knob is released. The reversing handle should 
 interlock with the valve in the "off" position, and should prevent 
 tripping of the emergency valve. The valve should operate 
 quickly without leakage when closed. 
 
 REVERSERS 
 
 Reversers used in Type M control are operated by solenoids 
 energized through the reversing cylinder to the controller. 
 The segments on the rocker arm are so arranged that a move- 
 ment from one extreme position to the other changes connections 
 and reverses the armature or field circuits of the motors. 
 
 Operating Test 
 
 The operating test consists of connecting the inductive 
 resistance specified between the first and third fingers, one side 
 of the shop to the third finger, with the other side connected 
 alternately to the two solenoid coils. Under these conditions 
 the reverser should operate quickly and throw completely over, 
 without rebounding. It should be operated on the different 
 voltages specified. The arc formed on the control fingers must 
 be blown outward from the fingers and should rupture immedi- 
 ately. This should be noted. The coil resistances should be 
 measured and should check within 10 per cent of that specified 
 in the Engineering Briefs. 
 
 Spools for Supply Shipments 
 
 After the high potential test, the resistance of each spool 
 should be measured and should check within 8 per cent either 
 way, from that specified in the Engineering Briefs. 
 
 MS SWITCHES 
 
 MS switches are made up for the control of various car or 
 train circuits, and are in most instances equipped with magnetic 
 blowouts. Quick-break operation on some types is also employed. 
 
 Each switch should be examined for mechanical defects 
 such as broken or loose parts. The switch should work freely 
 and should not stick or bind in any position. It should make 
 good contact when closed. 
 
 Switches designed to open the main current should be 
 given a blow-out test, consisting of breaking a specified current 
 in order to see that the arc is blown outward, and ruptures 
 satisfactorily. All switches should be given a high potential 
 test between parts of opposite polarity when a blade or blades 
 are open. 
 
 363 
 
CUT-OUTS 
 
 Cut-outs for train control service are used to cut out the 
 control circuits of individual cars from the rest of the train, one 
 cut-out being placed on each car. 
 
 Besides seeing that the fingers make good- contact on the 
 contact segments, all fuses should be "rung out" to see that 
 they are in good condition. 
 
 CONNECTION BOXES 
 
 Connection boxes are used as splicing junctions where the 
 wiring of the car is run through conduit. They consist of a 
 metal box containing connection terminals to which wires 
 may be easily connected or disconnected. They receive a 
 high potential test only. 
 
 MU TRIPPING SWITCHES 
 
 These switches have a series coil through which the motor 
 circuit is wired, and a small control switch through which the 
 control circuit for the line contactors is wired. 
 
 The series coil operates an armature fitted with a calibrated 
 spring similar to a circuit breaker, so that if an excess of current 
 is taken by the motors, the armature trips out the control circuit 
 switch, opening the contactors in the motor circuit. Examine 
 the compound box to see that it is not cracked or broken, and 
 that all flat headed screws are center punched other than the 
 removable screws used in fastening the cables. 
 
 The control switch should work freely and make good 
 contact when closed. 
 
 The switch should open when the lever is thrown to the 
 "off" position. 
 
 All MU switches are calibrated for various tripping points. 
 (See Engineering Briefs.) They are sent to the Test Dept. for 
 calibration without the cover. The armature should be held 
 in the operating position by means of a block of fiber or other 
 non-magnetic substance, as though it rested against the cover. 
 Marks are made to determine the relative positions of the cap 
 of the calibrating springs for the different currents. The switches 
 are then returned to the shop for stamping and assembly of 
 cover, after which they are given a blow-out test, which consists 
 of breaking a small inductive circuit with the switch to deter- 
 mine the direction of the blow-out. 
 
 A high potential test should be made between the series 
 coil and the control switch, also between the switch blade and 
 upper left-hand terminal when the switch is open. 
 
 CONTACTORS 
 
 Contactors are used for making and breaking the motor 
 circuits on a car. They are operated by a solenoid which 
 actuates a lever carrying one contact tip, the other tip is 
 stationary, and iitted with a blow-out coil which helps to break 
 the arc between the tips. 
 
 364 
 
There are two distinct types of contactors: DB contactors 
 which are used for direct current work, and DBA contactors 
 which are used for alternating current work. 
 
 The DBA contactors have a laminated armature and an E- 
 or U-shaped laminated field with copper shading coils in the face 
 of the outside leg, to prevent humming when the contactor is 
 closed. 
 
 An arbitrary number is assigned to each contactor, and form 
 letters are used to indicate minor mechanical differences. A 
 numeral follows the form letter to indicate the operating coil 
 used, viz. DB-260-A-1. 
 
 Inspection 
 
 Each contactor should be examined carefully for mechanical 
 defects, such as broken arc chutes, cotter pins, loose screws or 
 bolts. Also note whether it bears the Mechanical Inspection 
 Department's stamp. The contact tips when closed should 
 make good contact over their full width. The copper shunt 
 should be free from sharp kinks or bends and should not rub 
 on any metal part having sharp or rough edges. All contac- 
 tors must operate freely, and must not stick or bind in any 
 position. 
 
 TYPE DB CONTACTOR 
 
 Commercial Tests 
 
 From the tables given in the Engineering Briefs, see that 
 specification on the spool corresponds with the stamping on 
 the name plate. 
 
 When hung in the proper position, the contactor should 
 pick up and wipe contact at or below the current values given 
 for the respective spools, care being taken that the contactor 
 wipes full contact, as sometimes the pick up current is taken 
 to be the same as that required for the wipe contact. To avoid 
 this error, note that the first upward movement of the plunger 
 only brings the contact tips together. This is called the pick 
 up. The next movement wipes the contacts over one another, 
 and also increases the pressure between them. The amount of 
 this movement should equal or exceed that given in the Engi- 
 neering Brief. 
 
 Measurement of Spring Pressure 
 
 Insert a strip of paper or cloth between the tips, and put 
 enough current through the operating coil to close the contactor 
 completely. 
 
 Hang a spring balance from the screw heads holding the 
 tip on the finger, and note the pull required on the spring 
 balance to loosen the paper between the tips. 
 
 Resistance Measurement of Spools 
 
 The resistance of each coil should be measured and be 
 within 8 per cent above or below the specified resistance at 25 
 deg. cent. 
 
 365 
 
TYPE DBA CONTACTOR 
 
 The pick up and wipe is similar to that in the DB contactors. 
 As each DBA contactor, however, is connected directly across 
 the line, it is tested for the operating voltage instead of the 
 current. The voltage should be obtained by gradually raising 
 the field on the alternator. 
 
 The magnetizing current is measured at the proper frequency, 
 and should be taken with the armature fully closed. 
 
 The finger pressure should be taken as in the DB type. See 
 that the contactor wipes on the same voltage at which it picks 
 up. It should do so to protect the tips from freezing (welding 
 together) due to insufficient contact area. The operating coil 
 would also burn out, since with a-c. contactors the current is 
 high until the contactor is closed. After the contactor has 
 wiped, it should be perfectly noiseless. 
 
 SPECIAL TESTS 
 
 The test sheet should contain the following data: 
 Coil specification (No. of turns and size of wire). Cold 
 resistance and temperature of coil at which the cold resistance 
 is taken. Number of coils in series or multiple during test. 
 
 Finger Pressure 
 
 This test is made by holding the contact fingers at full 
 wipe position, attaching a spring balance to the screw which 
 holds the finger to the jaw by means of a small loop of wire. 
 A pull is then exerted through the spring balance until the 
 fingers separate sufficiently to allow a thin strip of paper, 
 placed between them, to be drawn out. The pull as recorded 
 by the spring balance is taken as the finger pressure. The 
 pressure of each finger should be measured separately. 
 
 "Minimum Pick Up" and "Wipe" 
 
 A contactor is at "pick up" position, when the armature 
 is raised so that the fingers just make contact. At "wipe" 
 position the contactor is fully closed. 
 
 On a-c. contactors, two additional tests, regulation of alter- 
 nator, and chattering and drop-out voltage are made in connection 
 with the minimum pick up test. 
 
 Regulation of Alternator 
 
 With the armature blocked open, read the speed and voltage 
 of the alternator both with and without the contactor in circuit. 
 Repeat with the contactor blocked shut. 
 
 Chattering and Drop-Out Voltage 
 
 With the contactor picked up and fully wiped, note the 
 minimum to which the voltage can be reduced before the con- 
 tactor becomes noisy, and also note the voltage at which the 
 contactor opens. 
 
 366 
 
Saturation Curve 
 
 This curve is taken at different voltages reading amperes 
 and watts, readings being made both with the contactor closed 
 and opened, or at such air-gaps as special instructions may 
 require. 
 
 Pull Curves on D-C. Contactors 
 
 This curve is taken by holding a constant current and 
 reading the pounds pull for different air gaps. The curve is 
 taken in either of the following ways: 
 
 First: By carefully adjusting the air gap, weighting down 
 the plunger, and holding the amperes constant while weights 
 are subtracted from the plunger until it picks up. 
 
 Second: By weighting down the plunger and holding the 
 amperes constant, while the air gap is gradually decreased 
 until the plunger picks up. The air gap is then measured. 
 A variation of this curve is sometimes made by holding a con- 
 stant air gap and varying the amperes and weights. In connec- 
 tion with the data for these curves, the length, diameter and 
 weight on plunger should be given; the length of plunger being 
 taken as the length from the butt end to the center of the hole 
 in the lower end. The weight given in the table should be 
 exclusive of the plunger and should be so stated on the Test 
 Sheet. 
 
 Pull Curves on A-C. Contactors 
 
 The method of taking a pull curve on an a-c. contactor 
 is more complex than on a d-c. contactor. In either case the 
 pounds pull is dependent upon the ampere turns. In a d-c. 
 contactor, however, the amperes at any voltage varies directly 
 with the resistance of the coil and is independent of the plunger 
 air gap, whereas in an a-c. contactor the amperes at any voltage 
 does not vary with the resistance, but with the impedance. 
 The reactance varies with the armature air gap. For this 
 reason it is not desirable to hold the amperes constant. If, 
 however, the voltage is held constant, an error will be caused 
 due to the resistance of the coil being increased by heating. 
 
 In tests where great accuracy is required, this error can be 
 eliminated and all contactors can be compared upon a common 
 basis by the following method: 
 
 First: Measure the resistance of the coil cold. 
 
 Second: Holding the voltage constant at that value at 
 which the pull curve is desired, take an ampere air gap curve; 
 i.e., read amperes at various air gaps. This curve should be 
 taken as rapidly as possible to avoid undue heating of the coil. 
 
 Third: Take a check reading of the resistance to see if 
 the coil has been much heated. If the heating is slight, an 
 average of the two readings should be taken as the resistance 
 of the coil. 
 
 Fourth: The ampere air gap curve thus obtained should be 
 corrected for a temperature of 25 deg. cent, and replotted. 
 
 367 
 
Fifth: Take a pull curve as given by the first method for 
 d-c. contactors, holding the amperes constant corresponding 
 to the different air gaps as obtained from the corrected ampere- 
 air gap curve. 
 
 In cases where the cold temperature of the coil happens to be 
 within a few degrees of 25 deg. cent, the pull curve can be taken 
 directly, holding the voltage at the value at which the curve is 
 desired. Great care should be taken to prevent undue heating 
 of the coil. The current must be on only for a sufficient time 
 to obtain readings. At the completion of the test take another 
 check reading of the resistance to determine the heating. 
 
 Work Curve 
 
 This curve is taken by measuring the pounds pull necessary 
 to lift the plunger or armature at different air gaps, having 
 the complete operating mechanism of the contactor and spring 
 adjusted to give the finger pressure required. 
 
 Speed Curve 
 
 Speed curves are taken on contactors and relays to deter- 
 mine the time a contactor takes to close or to open. 
 
 For taking this curve, a special mechanism has been made 
 which operates as follows: The contactor is set on a special 
 stand and a mechanism is then fitted to the plunger of the 
 contactor so that a pencil attachment operates along a vertical 
 line. The pencil bears upon a sheet of sensitive paper which 
 is secured to a cylindrical drum, revolving about a vertical 
 axis. The drum is rotated by a small shunt motor operating 
 at constant speed. Upon the periphery of the drum, contact 
 fingers are fastened, which make and break the circuit through 
 the contactor coil. The contactor is then operated through a 
 number of cycles, and the mean curve is drawn. In this test 
 the required voltage must be held across the coil without resist- 
 ance in series, on account of the inductance of the circuit. 
 
 Heat Runs 
 
 This test is very similar to the heat runs made on other 
 apparatus and consists in measuring the temperature of the 
 coil or other part at frequent intervals, both by thermometer 
 and resistance. It should be noted that, as the operating coils 
 are well wrapped with twine or other binding, thermometers 
 placed on the outside of the coils do not give a fair indication 
 of the temperature of the interior of the coil. For this reason 
 the temperature must be calculated from the rise of resistance. 
 To get these readings as accurate as possible, care should be 
 taken in measuring the cold resistance. All heat runs on coils 
 should be made with coils assembled in the contactor frame, 
 unless otherwise specified. All heat runs should be made holding 
 the voltage constant. 
 
 Life Tests 
 
 Life tests on contactors are made generally to determine the 
 effect of service on the wearing qualities of the various parts. 
 
 368 
 
Before starting the test, the diameter of the hinge pins and 
 hinge pin bearings, the maximum air gap, finger pressure, and 
 all other parts of the contactor that will be affected by service, 
 should be carefully measured. During the test a daily record 
 should be kept of the number of operations, and of the operating 
 failures of any of the parts. At the completion of the test, 
 the parts measured at the beginning must be again measured 
 to determine the amount of wear. 
 
 FUSE BOXES 
 Commercial Tests 
 
 Fuse boxes are made of fiber or compound, and are fitted 
 with terminal blocks, in which ribbon fuses may be readily 
 placed. 
 
 The principal test is high potential, for the value of which 
 see Engineering Briefs. 
 
 Fuse Boxes with Magnetic Blowout 
 
 After the high potential test, a small fuse is placed across 
 the terminal of these boxes. A current is then passed of suffi- 
 cient capacity, and at sufficient voltage, to blow the fuse immed- 
 iately. This is done to determine the direction of the blow- 
 out. 
 
 FUSES 
 
 The test sheet should contain the catalogue number, ampere 
 rating and dimensions of the fuse, also the style of box or holder 
 in which the tests were made. 
 
 Before starting the test, carefully inspect the fuses for defects, 
 such as sharp bends, dents, burred holes, etc., discarding those 
 that are not perfect, unless the test is being made to get an 
 average curve on fuses from stock. 
 
 Test to Determine Rating 
 
 Connect a switch to the fuse box or holder, using a short- 
 circuiting switch in multiple with both. If run off the shop 
 circuit connect a water box in series. If run from the "booster," 
 the current can be controlled from the booster field with a low 
 resistance grid in series with the booster armature. 
 
 With the series switch open, and the short-circuiting switch 
 closed, adjust the current to the desired value, and hold as 
 near constant as possible. Then close the series switch quickly 
 and open the short-circuiting switch, and note the time by a stop 
 watch it takes before the fuse blows. Fuses are rated at one- 
 half the current at which they blow in thirty seconds. 
 
 When a number of fuses are blown, the holder is likely to get 
 very hot unless care is taken to cool it between tests. Ther- 
 mometers should generally be placed on the fuse holder and the 
 temperature kept below 75 deg. cent. 
 
 Time-Current Curve 
 
 To obtain time-current curves, fuses should be blown at 
 current values which will blow the ribbons at periods varying 
 from ten seconds to three minutes. 
 
 369 
 
COUPLERS 
 
 In train-control work, couplers are used to make temporary 
 connections for the bus line, and control circuits between the 
 cars of a train. Two parts are included in the complete coupling; 
 the socket coupler, Type DA, and plug coupler, Type DC, which 
 fits into the socket coupler. 
 
 The contact terminals should be well fastened in the com- 
 pound base, and the cover on the DA coupler should be held 
 firmly closed by the spring. 
 
 Couplers without cables are simply given a high-potential 
 test, from the frame to each terminal, and between each terminal 
 and the adjacent terminal. 
 
 Sockets are placed at the ends of the car and cables run 
 from them to the connection boxes in the car. When the socket 
 is assembled with a cable, it is given the usual high potential 
 test, and then each terminal is rung out with a lamp circuit to 
 see that it is connected to the proper cable wire. 
 
 CONTACTOR BOXES 
 
 In the Type M or C control, instead of breaking the motor 
 circuits in the controller, as is done in the K control, the con- 
 troller operates a set of contactors assembled in a contactor 
 box, which open and close the motor circuits. One contactor 
 box is placed on each car, and the control circuits, besides 
 being brought to the controllers of the car, are taken to couplers 
 at either end of the car, from whence they can be connected by 
 jumpers to other cars, and operated in multiple with them. 
 The whole train is thus controlled from one controller. This 
 control is manufactured either automatic or non-automatic. 
 
 In non-automatic equipments, the motorman has full 
 control of the acceleration of the car. In the automatic equip- 
 ments, however, he does not control the resistance (accelera- 
 tion) points. The automatic feature can readily be connected. 
 One end of the cable is left open which can be afterwards con- 
 nected to the connection boxes. The different wires are desig- 
 nated by various colors. For the colors and numbers correspond- 
 ing see the DS diagram. 
 
 Inspection 
 
 Each interlock should be carefully inspected to see that the 
 rod is properly stamped, and that the disks agree with the 
 Engineering Brief in regard to wipe and break. 
 
 The terminal board and the terminals on all wires should be 
 clearly and properly stamped and all wiring neatly done. The 
 interlock rods should clear the back frame of the box by at least 
 Y /i in. The name plate on each contactor and on the contactor 
 box itself should be checked. 
 
 Operation Test 
 
 Each contactor box is connected to a controller and reverser, 
 and operated so as to test all the control circuits. The main 
 or motor circuits are rung out according to the DS diagram. 
 
 370 
 
The operating voltage for each set of equipments should be 
 obtained from Engineering instructions. The contactors should 
 pick up and fully wipe on the minimum voltage, in the order 
 specified. See that the arc is promptly ruptured on the inter- 
 locks having magnetic blowouts. 
 
 Potential Relay 
 
 All automatic equipments having a potential relay should 
 operate at a voltage higher than that at which the relay picks 
 up. 
 
 JUMPERS 
 
 A jumper consists of two coupler plugs connected by a 
 cable. It completes the circuits between cars. 
 
 After the high-potential test, jumpers are "rung out" to 
 see that the correct connections exist between the plugs as called 
 for on the Engineering Notice. 
 
 CIRCUIT BREAKERS 
 
 There are several types of railway circuit breakers, the DB 
 and MR representing the present standard. Most of the forms 
 are fitted with a brush contact, auxiliary to the breaking finger 
 contact, the latter being protected from the arc when opening by 
 the contact fingers, which always open last. 
 
 The AIR circuit breaker is closed manually by throwing 
 the handle to the "on" position and can be tripped by throwing 
 the handle to the "off" position, which gives a quick break open- 
 ing. It is also arranged to trip out automatically on overloads. 
 
 The DB circuit breakers are used for Type M control and 
 are provided with solenoids for opening and closing. The coils 
 are energized through a switch in the motorman's cab, the 
 breakers themselves usually being under the car. 
 
 Inspection 
 
 All the cable terminal thimbles should be well fastened in the 
 terminal blocks to prevent being lost in transportation. The 
 arcing or secondary fingers should remain in contact when open- 
 ing the circuit breaker, after the brush has opened contact by at 
 least \i in. Both brushes and secondary fingers should make 
 contact over their full width. All auxiliary switches on the cir- 
 cuit breaker should be examined to see that they make good 
 contact at the proper time. The copper shunts should be free 
 from kinks or sharp bends. 
 
 Calibration 
 
 Each circuit breaker is calibrated for three tripping points. 
 It is first tested for low tripping point, then for high point 
 and finally for the intermediate point. It is left at the latter 
 point, and the check nut is then set. Marks must be made 
 designating the relative position of the cap of the calibrating 
 spring for the different currents. 
 
 Blow-Out Test 
 
 Each circuit breaker is given a blow-out test in order to 
 determine the direction of the arc. 
 
 371 
 
RELAYS 
 
 Railway relays can generally be classed under three heads: 
 Current, potential and accelerating relays. 
 
 Current Relays 
 
 Current relays comprise all those which have their tripping 
 coil in series with the circuit in which the current is to be con- 
 trolled; the controlling circuits being wired through its disks 
 or relays. 
 
 Potential Relays 
 
 Potential relays comprise all those having their operating 
 coil shunt connected. These relays are used where a certain 
 value of voltage is required for proper operation. Their func- 
 tion is either to cut out resistance in control circuits, thus per- 
 mitting lower voltage operation, or to transfer, or change control 
 circuits. 
 
 Accelerating Relays 
 
 Accelerating relays are used with automatic control, their 
 function being automatically to advance control connections. 
 
 OPERATING TEST 
 
 The relay should be able to break the specified amount of 
 current on the contact studs, and if provided with a blow-out 
 the arc should blow in the proper direction. 
 
 The operating coil should operate the relay under the con- 
 ditions specified in the Engineering instructions. The disks 
 or arms should make good contact on the studs, and the wiring 
 should be arranged in workmanlike fashion to prevent electrical 
 or mechanical breakdowns in operation. 
 
 372 
 
CHAPTER 23 
 
 PROJECTORS 
 
 Projectors are designed for operation from direct current 
 circuits and it is necessary to provide motor-generator sets or 
 mercury arc rectifiers where only alternating current supply is 
 available. 
 
 Fig. 162 
 HAND CONTROL PROJECTOR 
 
 The standard line of rheostats is designed with adjustments 
 for line volts varying between 110 and 125 volts. When pro- 
 jectors are operated in series or when one projector is operated 
 from a line of greater than 125 volts potential, it is necessary to 
 provide automatic cutouts with resistances equal to the resistance 
 of the arc under normal conditions and rheostat capacity suffi- 
 cient to take up the difference between the sum of the arc volt- 
 ages and the line voltage. 
 
 Inspection 
 
 All projectors are inspected before the final test to see that the 
 drum is balanced, that no bolts, screws, nuts, or cotter pins are 
 missing, and that the rating on the name plate is correct. 
 
 373 
 
Types of Control 
 
 Hand — The hand control projector shown in Fig. 162 is 
 controlled by handles on the rear of the drum and is provided 
 with clamping devices for the horizontal and vertical planes. 
 
 Fig. 163 
 PILOT HOUSE CONTROL PROJECTOR 
 
 Pilot House — The pilot house control shown in Fig. 163 
 is operated from the inside of the pilot house by a controlling 
 gear extending through the roof, the movement in both the hori- 
 zontal and vertical planes being controlled by one handle. 
 
 Rope Control — The rope control projector shown in Fig. 
 164 is operated by means of cables connected to the controlling 
 gear of the projector. As the movements in both the hori- 
 
 374 
 
zontal and vertical planes are controlled by a single handle the 
 controlling gear may be placed in the pilot house, on the bridge, 
 or at any other convenient place. 
 
 Electric Control — -The electric control is of three types. 
 First, the direct armature control in which the entire current 
 for the motors is carried through the controller cable, the con- 
 tacts in the controller being arranged to start, stop and reverse 
 both the elevating and training motors, and so connected that 
 the beam follows the movement of the controller handle. This 
 control is employed in the 13 and 18 inch sizes. 
 
 Fig. 164 
 ROPE CONTROL PROJECTOR 
 
 Second, the rheostatic control in which the training and 
 elevating motors are controlled from a distance through the con- 
 troller cable, the controller being provided with resistances 
 which give one or more speeds of training and elevating motors. 
 
 Third, the synchronous control in which only the current 
 required by the pilot motors is carried through the controller 
 cable, the controller operating the pilot motors which in turn 
 control the elevating and training motors. 
 
 Adjustment 
 
 A great deal of testing and adjusting of the electric control 
 is done during the construction of the operating mechanism. 
 For the synchronous control projectors, the pilot motors are 
 connected and tested for polarity in accordance with Fig. 165, 
 after which they are returned to the assembler for final connec- 
 tion. The motor is then wired to a controller and if connected 
 correctly the rotating field will take up 12 equidistant positions 
 per revolution. After this test the pilot and training motors 
 are assembled and wired, and thoroughly tested to insure the 
 wiring being correct. When the projector is assembled the 
 electric control is operated for some time to make sure that 
 
 375 
 

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the connections are correct and that there are no mechanical 
 faults in the training and elevating mechanism. Lamps are 
 wired, adjusted and operated at the proper current and arc 
 voltage, care being taken that the gap at the circuit breaker 
 in the feeding magnet circuit is of the proper length, also that 
 the screws limiting the motion of the pawls are properly set after 
 which the feeding magnet armature spring may be adjusted so 
 that the lamp will operate at its rated arc voltage. At the end 
 of this test the lock nuts should be tightened and a general 
 inspection of the mechanism made to see that everything is 
 properly secured. 
 
 With the lamp in position in the projector and in operation 
 the position of the lamp should be adjusted by means of the 
 
 Fig. 166 
 MEASUREMENT OF FOCAL DISTANCE 
 
 focusing screw so that the beam will appear to be composed of 
 parallel rays. 
 
 Mirrors 
 
 Referring to Fig. 166, the mirror A is held facing an object 
 B approximately 100 feet from the mirror and a piece of ground 
 glass or white card C is then moved backward and forward in 
 the focus. When the focus is reached the image of the object is 
 very distinct. The distance from the card to the center of the 
 reflecting surface of the mirror is the focal length. Mirrors are 
 tested for regularity of curvature and grinding by placing 
 them in front of a large white screen on which horizontal black 
 lines are drawn. The lens of the camera is placed back of the 
 screen and through a hole in the center and the reflection of the 
 right lines is photographed. Fig. 167 shows a mirror in which 
 the curvature of the reflecting surface and the grinding is correct. 
 Fig. 168 shows a mirror with irregularities in the reflecting sur- 
 face which can be distinctly seen in the photographic test. 
 
 Rheostats 
 
 A rheostat or ballast is connected in series with the arc when 
 it is operated from a constant potential circuit. The object of 
 this resistance is to prevent fluctuations of the arc current. 
 
 377 
 
Fig. 167 
 SHOWING CORRECT CURVATURE OF MIRROR 
 
 378 
 
Fig. 168 
 SHOWING IRREGULARITIES IN CURVATURE 
 
 379 
 
Carbons 
 
 One per cent of all projector carbons are tested. The points 
 to be observed are as follows: 
 
 The kind of arc obtained, whether quiet or noisy, steady or 
 wandering; the amount of refuse left in the lamp after the car- 
 bons have been consumed, and the amount which the carbons 
 burn out of focus. 
 
 The table on page 381 gives the sizes of carbons, etc., for 
 standard apparatus. 
 
 SIGNAL APPARATUS 
 Keyboards 
 
 Keyboards must be wired and every combination tried, care 
 being taken to see that the proper lamps light and that the con- 
 tact switch makes contact so that the lamps light simultaneously. 
 
 An insulation test is made at 500 volts. The cables are 
 connected to the keyboard and every combination gone through 
 to see that the connections are correct. The connections 
 to the receptacles should be inspected to see that there are no 
 loose ends of wire to short-circuit or ground the receptacle. 
 
 Trucklight Controllers 
 
 Trucklight controllers are wired and tested to see that the 
 proper lamps light and that the pulsator works correctly. 
 
 Diving Lamps 
 
 Diving lamps are tested under water, as specified in the 
 Government specifications for the apparatus, to see that leakage 
 does not occur. 
 
 380 
 
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Instructions contained in the following 
 chapter must be followed by all men 
 while working in the Transformer 
 Testing Department at Pittsfield. 
 
 383 
 
CHAPTER 24 
 
 TRANSFORMER TESTS 
 
 CONSTANT POTENTIAL TRANSFORMERS 
 
 Tests 
 
 Complete Tests consist of commercial tests and of normal 
 and overload heat runs. 
 
 Commercial Tests consist of cold resistance, polarity, 
 ratio and checking taps, impedance, core loss, exciting current 
 and insulation tests. These are applied to all transformers, 
 except for the resistance test which is often omitted on duplicate 
 transformers of small capacity. 
 
 Normal Load Heat Run consists of operating the trans- 
 former at normal load until it shows constant temperature. 
 
 Overload Heat Run consists of operating the transformer 
 until it has reached normal load temperature and then applying 
 the required overload for the specified time. 
 
 Efficiency is calculated from the core loss and the resistance 
 at 25 deg. cent. 
 
 Regulation is calculated from the impedance and the resist- 
 ance at 25 deg. cent. 
 
 Insulation Tests are: (1) the high potential test, which 
 consists of applying high voltage between windings and from 
 windings to ground; (2) the induced voltage test, which consists 
 of operating the transformer at considerably more than normal 
 voltage for a short time. 
 
 Types of Transformers 
 
 For purposes of test, constant potential transformers may 
 be conveniently divided into four classes, depending upon the 
 method of cooling as follows: 
 
 Natural draft 
 
 Air blast 
 
 Oil immersed self cooled 
 
 Oil immersed water cooled. 
 
 Natural draft transformers have the core and coils exposed 
 directly to the air, and depend entirely upon the natural cir- 
 culation of the air for their cooling. They are built only in small 
 sizes and low voltages, seldom over 25 kv-a. or 1000 volts. 
 
 Air blast transformers depend upon a forced circulation of 
 air over the surface of core and coils to carry away the heat. 
 They may be built for large capacities, but the voltage rarely 
 exceeds 30,000 because of the difficulty of insulating them prop- 
 erly. 
 
 Self cooled oil immersed transformers have the core and coils 
 immersed in a tank of oil. This tank is usually made of cast or 
 
 384 
 
sheet iron, and is quite often corrugated so as to increase the 
 surface available for dissipating the heat generated in the core 
 and coils. Sometimes external tubes or radiators through which 
 the oil circulates are used for this same purpose. 
 
 "Water cooled oil immersed transformers depend on the cir- 
 culation of water through a coil of iron, brass or copper, placed 
 in the top of the tank to carry away the heat from the oil. The 
 tank, which is usually made of steel plate dissipates only a small 
 portion of the heat. This type is used for the largest capacities 
 and is suitable for any voltage. 
 
 The method of cooling affects principally the insulation test 
 and the heat run, since oil immersed transformers depend on 
 the oil for insulation, as well as for cooling. It is necessary 
 that they be filled with oil of the proper quality when more than 
 a small percentage of their normal voltage is applied to or 
 induced in them. During the heat run, transformers must be 
 filled with oil if they are of the oil immersed type, and must be 
 subjected to the cooling conditions for which they are designed. 
 
 Order of Tests 
 
 The order of tests is to a great extent left to the discretion 
 of the man making them. The cold resistance must be measured 
 before the transformer has been heated up by any other tests, 
 care being exercised to obtain the correct temperature of the 
 windings. The heat run, high potential and induced voltage 
 tests should be made last and in the order named, except that 
 for transformers of 100 kv-a. or less the induced voltage may be 
 placed before the high potential test. 
 
 Preparation for Tests 
 
 Information from the Engineering Department, regarding 
 guarantees, rating, operating conditions, etc., is furnished to the 
 testing department by means of test data cards, Engineering 
 Notices, DS sketches, and specifications. On power trans- 
 formers, which include all sizes of over 100 kv-a. the test 
 records are prepared in advance by the calculators in the Test- 
 ing Department so that it is not necessary for the man making 
 the tests to refer to any instructions from the Engineering 
 Department. The test record then shows the guarantees, the 
 special requirements and sketches of windings. On standard 
 lighting transformers full information is given on the test data 
 card. On special transformers of small sizes the test data card 
 is sometimes supplemented by an Engineering Notice and 
 always by the DS sketch. Reference should be made to all these 
 before starting the tests. 
 
 The transformers must be properly placed in position for 
 test, especially if there is to be a heat run. Great care must be 
 exercised to see that air blast transformers are properly sup- 
 ported above the pit, as otherwise they may fall and injure 
 persons stationed under them. No opening should be left 
 through which air can escape and influence the readings of the 
 
 385 
 
thermometers on the iron. Large transformers, especially 
 those of self cooled types, should be so located as to allow free 
 air circulation between units during the heat run. The distance 
 between self cooled transformers of over 100 kv-a. capacity 
 should be at least 2 ft. and if possible, a greater distance. Such 
 transformers should always be placed not less than 12 in. from 
 the walls of the testing pit. Idle units used in checking heat run 
 temperatures should be located at least 4 ft. from the hot units 
 or other sources of heat. 
 
 Cold Resistance 
 
 The cold resistance measurements are used for two pur- 
 poses; first — for calculation of copper loss and consequently for 
 efficiencies; and second — for the determination of the tempera- 
 ture rise of the windings. 
 
 The drop of potential method should be employed unless the 
 rated current of the windings is less than 1 ampere, in which 
 case the Wheatstone bridge may be used. The current used 
 should not be more than 15 per cent of the rated current of the 
 winding, as a larger value is liable to cause heating, making it 
 impossible to obtain accurate values of the temperature of the 
 windings. The voltmeter leads should be attached to the ter- 
 minals of the transformer separately from the leads carrying the 
 current, so as to avoid including the drop in voltage due to the 
 temporary connections. In measuring cold resistance, a spot 
 on which to hold the voltmeter leads should be cleaned with 
 sandpaper. 
 
 Resistance of the full series winding should always be 
 measured. In case the heat run is to be made on a tap or on a 
 multiple connection the cold resistance of such connection should 
 also be measured. 
 
 It is important that the temperature of the windings at the 
 time the cold resistance is measured be determined accurately, 
 especially where this resistance is to be used for the calculation 
 of temperature rise. It is advisable therefore to take several 
 readings of resistance and temperature at half hourly intervals, 
 the thermometer being placed on or very near the coils. 
 
 The resistance of each winding at 25 deg cent, should be 
 calculated and noted on the test sheet. The method of calculat- 
 ing the rise in temperature by increase of resistance is 
 explained under the subject of heat runs on page 399. 
 
 Polarity 
 
 The polarity test gives the only means of readily determining 
 the connections required for transformers in banks, for instance, 
 several transformers in parallel. General Electric Company 
 transformers always have the same polarity, except in some 
 special cases where the customer requests that it be reversed. 
 There are three methods of making the test, the most convenient 
 one being used in each case. 
 
 (1) When a standard transformer of the same ratio as the 
 one under test is available, the polarity and ratio tests may be 
 combined. 
 
 386 
 
The high voltage winding of the transformer under test should 
 be connected in multiple with the high voltage winding of the 
 standard transformer and the low voltage winding of the 
 transformer under test should be connected in multiple with the 
 low voltage winding of the standard transformer. One winding 
 (usually the high voltage) should be excited while a voltmeter 
 is placed between the two low voltage windings to indicate 
 the difference in voltage. If there is no difference in voltage, 
 the polarity and ratio are both correct. If there is a small 
 difference the polarity is correct, but the ratio is not. If the 
 difference in voltage is great the polarity is probably reversed. 
 Further tests should be made to determine whether this is true. 
 
 (2) The polarity may be determined at the same time as the 
 resistance by making use of direct current as follows: 
 
 With direct current passing through one winding, usually 
 the high voltage, connect a high voltage voltmeter across the 
 terminals so as to obtain a positive deflection. Then transfer 
 the two voltmeter leads directly across the transformer, the 
 lead from the right-hand high voltage being placed on the right- 
 hand low voltage (facing the high voltage side), while the lead 
 from the left-hand high voltage is placed on the left-hand low 
 voltage terminal. Then break the current in the first winding, 
 thus inducing momentarily a voltage in the other. If a positive 
 kick of the voltmeter needle is produced the polarity is correct 
 according to the standard General Electric Company practice. 
 In case the polarity is indicated on the DS sketch by means of 
 positive and negative signs, it should be checked in the manner 
 explained above, except that the voltmeter lead resting on the 
 high voltage terminal bearing a given sign (positive or nega- 
 tive) should be moved to the low voltage terminal bearing the 
 same sign. 
 
 (3) If neither a standard transformer nor a source of direct 
 current is available, the polarity may be determined by ratio as 
 follows : 
 
 While facing the high voltage side connect the right-hand 
 high voltage to the right-hand low voltage terminal. Excite 
 the high voltage winding and read the voltage induced between 
 the left-hand high voltage and the left-hand low voltage ter- 
 minals. If this is greater than the voltage impressed on the high 
 voltage winding the polarity is correct according to standard 
 General Electric Company practice. In case the DS sketch 
 indicates the polarity the test should be made in the same way, 
 except that the positive high voltage terminal should be con- 
 nected to the positive low voltage terminal and the voltage read 
 between the two negatively marked terminals. 
 
 Determination of polarity on three-phase transformers 
 requires much care. The accompanying diagrams allow a 
 comparison to be made of the various standard connections. 
 
 Figs. 169 to 174 show standard connections for three-phase 
 shell type transformers and Figs. 175 to 180 for three-phase core 
 type transformers. It is understood that the leads are brought 
 out as shown in these standard sketches, unless distinctly specified 
 
 387 
 
otherwise by the DS sketch or by special instructions. It is 
 best to use direct current for such tests, each phase being checked 
 separately. 
 
 In checking polarity of delta-delta, delta- Y, Y- Y or F-delta 
 connections, impress direct current from X to Y on the high 
 
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 Figs. 169 to 174 
 STANDARD THREE-PHASE CONNECTIONS, THREE- 
 PHASE SHELL TYPE TRANSFORMER 
 
 Notes. — In effect, high voltage and low voltage windings are wound in 
 opposite directions. 
 
 Diagrams should be read facing low voltage side of transformer. 
 
 voltage, place the voltmeter across X to Y so as to obtain a 
 positive deflection; then move the voltmeter lead on X high 
 voltage over to X low voltage and the one on Y high voltage to 
 Y low voltage. Break the circuit and note the deflection of the 
 voltmeter. If it is positive the polarity is correct. The other 
 two phases must then be checked in the same way. 
 
 In checking F-diametrical connections (Figs. 173 and 179) 
 excite X to Y for checking phase 1 ; also for phase 2. For phase 
 
 388 
 
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 Fig. 179 
 
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 Figs. 175 to 180 
 STANDARD THREE-PHASE CONNECTIONS, THREE- 
 PHASE CORE TYPE TRANSFORMERS 
 
 Notes. — High voltage and low voltage winding wound in opposite direc- 
 
 Xumbers 1, 2, 3 on diagrams refer to corresponding phases. 
 
 Fig. 177a is for transformers having high voltage winding 5300 volts or less. 
 
 Fig. 177b is for transformers having high voltage winding over 5300 volts. 
 
 389 
 
1 transfer the lead from X high voltage to X low voltage and 
 from Y high voltage to X' low voltage. For phase 2 transfer 
 from Y high voltage to Y low voltage and from X high voltage 
 to Y' low voltage. For phase 3 excite Z to X, then transfer 
 from Z high voltage to Z low voltage and from X high voltage 
 to Z' low voltage. 
 
 In shell type delta-diametrical (Fig. 174), proceed as follows: 
 For the left-hand phase excite X to Y high voltage and transfer 
 from Y high voltage to X low voltage, and from X high voltage 
 to X' low voltage. For the middle phase excite X to Z and 
 transfer from X high voltage to Y low voltage and from Z high 
 voltage to Y' low voltage. For right-hand phase excite Y to Z, 
 transfer from Z high voltage to Z low voltage and from Y to Z' 
 low voltage. 
 
 For core type delta-diametrical (Fig. 180) proceed as follows: 
 For phase 1, excite X to Z, transferring X high voltage to X low 
 voltage and from Z high voltage to X' low voltage. For phase 
 
 2 excite X to Y, transfer from Y high voltage to Y low voltage 
 and from X to Y' low voltage. For phase 3 excite Z to Y, 
 transferring from Z high voltage to Z low voltage and from Y 
 high voltage to Z' low voltage. 
 
 Phase Rotation 
 
 In addition to the polarity test it is necessary to check the 
 phase rotation on all three-phase and six-phase transformers 
 except on such as are run in parallel with one on which the test 
 has already been made. 
 
 The phase rotation meter should be connected to the high 
 voltage side of the transformer and a relatively small voltage 
 applied. This voltage should be sufficient to cause rotation of 
 the meter but should not exceed 550 volts. The direction of 
 rotation should be noted. Then the leads from the meter should 
 be transferred straight across the transformer to the low voltage 
 terminals. The transformer should again be excited with voltage 
 sufficient to cause the meter to rotate end the direction of rota- 
 tion should be noted. When the direction is the same on the low 
 voltage as on the high voltage side, the result should be marked 
 on the test sheet as "Standard." When it is opposite on the two 
 sides, attention should be called to that fact on the test sheet. 
 
 Six-phase transformers having double delta connections 
 must have the rotation checked on each delta. 
 
 Transformers having diametrical connection with the middle 
 points of each phase brought out should have these points joined 
 after which phase rotation should be checked by selecting ter- 
 minals which will give two Y-connections. In addition to the 
 test with the meter these transformers should have the neutrals 
 connected together while the six voltages are read between each 
 pair of consecutively numbered leads. These should all be of 
 equal value and also should be equal to the voltage from any 
 one of them to the neutral point. When the neutral points are 
 not brought out a temporary delta connection should be made 
 for the phase rotation test. 
 
 390 
 
Ratio 
 
 The ratio of a transformer is the ratio of voltage of the high 
 voltage winding to the low voltage winding. The required 
 voltages are given in the rating and are shown on the DS sketch. 
 The ratio should be measured on at least one of each group of 
 similar transformers and compared with the ratio shown by the 
 DS sketch. The ratio of all other transformers in the group 
 should be checked by running each in parallel with the one on 
 which the ratio has been measured. 
 
 The transformer should be operated at normal frequency or 
 higher and at normal voltage or lower during the ratio test. An 
 exception to this rule is made for transformers having capacities 
 of 500 watts or less and with exciting current of more than 10 
 per cent. These should be tested at normal voltage and fre- 
 quency. 
 
 Where possible, it is best to make a ratio test by comparing 
 the transformer with a standard of exactly the same ratio. The 
 two should be connected in parallel on both sides and the high 
 voltage winding excited while a voltmeter is used to read the 
 difference in voltage between the two low voltage windings. 
 
 When the above method is not applicable, two voltmeters 
 should be used, one to read the low and the other to read the 
 high voltage, the latter being stepped down through a potential 
 transformer when necessary. Where voltages and scales will 
 permit, the instruments should be interchanged between read- 
 ings so as to eliminate errors. It is best to take at least two 
 sets of readings, calculating the ratio from each and considering 
 the average as the correct value. 
 
 The parallel run should be made at normal frequency and 
 normal voltage, the voltage being applied usually to the low 
 voltage winding. A test for circulating current between the 
 two high voltage windings should be made by closing and opening 
 the circuit. If a spark is observed a further test should be made 
 by measuring the amperes circulating through the high tension 
 winding and by measuring the difference in voltage on open 
 circuit. If no spark appears on the first test, it is best to make 
 sure of the presence of voltage in the winding by touching the 
 free high voltage terminal to the case (at reduced voltage). 
 If the circulating current is more than 5 per cent of the rated 
 current of the winding, attention should be called to the fact 
 on the test sheet. 
 
 On three-phase transformers it is preferable to use single- 
 phase power and to measure the ratio of each phase separately. 
 This is not possible when the neutral point of a Y-connection is 
 not brought out. In such cases three-phase power must be used. 
 
 On Y- diametrical transformers where the neutral point is 
 not brought out, three-phase excitation must be used. Any 
 inequality in the magnetizing characteristics of the three phases 
 will result in distortion of the neutral, thereby causing unequal 
 phase voltages. When such an inequality is found the diametric 
 connection should be changed to a Y-connection and the phase 
 voltages measured. If these are equal and of the proper value, 
 
 391 
 
i.e., V3 times the diametric voltage, the ratio may be con- 
 sidered as being correct. If the voltages are still unbalanced, 
 however, the transformer should be returned to the Assembly 
 Department so that the neutral point can be brought out. 
 It should then be tested single-phase and if -the phase ratios 
 are correct the transformer may be passed. The Y-connection 
 may be made from the diametrical by referring to the standard 
 connection diagrams previously referred to under polarity test. 
 A variation of more than Y% of 1 per cent above or below 
 the value shown on the DS sketch or connection label on stand- 
 ard lighting transformers should be called to the attention of the 
 Engineering Department. On other transformers the allowable 
 variation is 1 per cent. 
 
 Wattmeter Ammeter 
 
 Primary Secondary 
 
 Fig. 181 
 CONNECTIONS FOR IMPEDANCE TEST 
 
 Checking Taps 
 
 Nearly all transformers are provided with taps in one or both 
 windings, so that a slight change in ratio or a low voltage for 
 starting may be obtained. These tap voltages should be checked 
 to determine whether they agree in voltage and in position with 
 the DS sketch. This test may be made either by means of the 
 "two voltmeter method" or by running the transformer in 
 parallel with a standard transformer or with one on which the 
 test has already been made. When two voltmeters are used, it 
 is best to apply a low voltage to the full winding, then read the 
 voltage from the terminals to the first tap, then between succes- 
 sive taps of the same winding. Care should be taken in handling 
 the voltmeter connected to the tap, because, although the voltage 
 reading is low, the circuit to which it is connected may be 
 several thousand volts above ground. If the opposite end of 
 the circuit be grounded a severe shock may be obtained from 
 the meter. 
 
 On windings having low voltage taps at the ends it is some- 
 times necessary to check their location by checking the polarity 
 of each section of the winding. If the polarity of each is correct 
 the taps are properly brought out. 
 
 392 
 
Impedance 
 
 The impedance of a transformer is measured by short- 
 circuiting one of the windings and impressing an alternating 
 e.m.f. on the other windings and taking simultaneous readings 
 of amperes, volts, watts, and frequency. The impedance of 
 transformers should be carefully measured for the following 
 reasons: Transformers operating in multiple divide the load 
 inversely as their impedance voltages; i.e., the one having the 
 higher impedance will take the smaller part of the load and vice 
 versa. When transformers of different types are operated in 
 multiple, the impedance of one transformer must sometimes be 
 increased by putting a reactive coil in the secondary circuit, and 
 adjusting until the desired impedance is obtained. 
 
 Impedance tests show whether a given arrangement of 
 coils is satisfactory or not. If the arrangement is not satis- 
 factory, excessive magnetic leakage will take place and high 
 impedance voltage result. The impedance watts will also be 
 high, due to excessive eddy current loss in the copper. Since 
 regulation depends upon impedance to a great extent, a low 
 impedance is very necessary for close regulation. 
 
 The impedance voltage of lighting transformers varies from 
 about 1 to 4 per cent while that of power transformers is usually 
 from about 4 to 8 per cent. Transformers for operating syn- 
 chronous converters are often provided with magnetic shunts in 
 order to obtain high impedance, that is from 12 to 20 per cent. 
 The impedance watts do not as a rule exceed 1 to 1 Y2 per cent 
 of the total capacity of the transformer, although they are 
 higher than the calculated I 2 R on account of the eddy current 
 losses in the copper. 
 
 The following method should be used in making the test: 
 Place a thermometer on or very near the coil so as to obtain the 
 exact temperature. Make a good short-circuit on one winding, 
 using as short a cable as possible and one of ample cross section 
 so that no appreciable losses will occur. Make the connections 
 shown in Fig. 181. Adjust the current with the pressure circuits 
 of the voltmeter and wattmeter open, then close the pressure 
 circuits and take the reading of volts and watts. See Fig. 181. 
 The watts should be corrected for the losses in the voltmeter, 
 wattmeter and instrument transformers (if any are used). 
 
 In measuring the impedance of three-phase transformers, 
 the two wattmeter method should be used, a single set of instru- 
 ments being transferred from one phase to the other by switches. 
 The current should be adjusted so that the average value in the 
 three lines is equal to the normal rated current. 
 
 If the measured impedance watts exceed the calculated PR 
 watts by more than 15 per cent, attention should be called to 
 that fact on the test sheet. 
 
 Core Loss and Exciting Current 
 
 When the transformer is connected to a source of alternating 
 e.m.f. a loss of energy takes place in the iron due to the cyclic 
 reversals of the magnetic flux. This loss of energy is known as 
 
 393 
 
core loss. Its value depends on the wave form of the impressed 
 voltage as well as upon the value of that voltage. A peaked 
 wave gives lower losses and a flat wave gives higher losses than 
 a true sine wave. The core loss energy should therefore pref- 
 erably be taken from a sine wave alternator operated at about 
 its normal excitation. 
 
 The core loss test is similar to the impedance test except 
 that the voltage is applied to one winding, all others being open- 
 circuited. It is usually preferable to apply voltage to the low 
 voltage winding so as to avoid reading meters in high potential 
 circuits. Care should be taken to see that the high tension 
 cables are located so that no one can come in contact with them 
 
 r^AAAAAAA/VW 
 
 Pn 
 
 Normal 
 Secondary 
 Vo/tage. 
 
 ^AMA/WWS^ 
 
 SMAAAMMH 
 
 Fig. 182 
 CONNECTIONS FOR HEAT RUN 
 
 and so that there is no danger of a short-circuit. During the 
 test it is best to have the windings connected according to some 
 one of the connections shown on the DS sketch. It is par- 
 ticularly necessary to avoid leaving windings open at points 
 where they would not be left open under operating conditions 
 as it is sometimes possible to obtain excessive stresses between 
 points of the same winding by leaving such connections open. 
 
 The connection of instruments in measuring core loss should 
 be the same as in the impedance test and the reading should be 
 taken in the same way. In measuring the loss of three-phase 
 transformers it is advisable to take three entirely separate sets 
 of readings by the two wattmeter method, each of the three 
 lines being used in succession as the neutral. The average 
 value of the three sets of readings should be recorded as the 
 true core loss. 
 
 As alternators with perfect sine waves are very difficult to 
 obtain, it is customary to correct the measured loss to a sine 
 wave basis, by means of the core loss correction outfit. This 
 outfit consists of a single winding on a small core, the sine wave 
 loss of which has been carefully determined over a wide range of 
 voltage. The outfit should be connected to the same source of 
 power as the transformer under test, after which normal voltage 
 should be applied to the latter. The loss in the standard core 
 and the voltage across its terminals should be measured at the 
 
 394 
 
same time as that of the transformer under test. The sine 
 wave loss of the standard core at the same voltage should then 
 be determined from the calibration curve. The ratio of the 
 measured loss of the standard core to the reading taken from the 
 calibration curve should be used to reduce the measured loss 
 of the transformer under test to a sine wave basis. 
 
 The exciting current may be corrected for wave shape by- 
 carrying the test a little further. After the core loss correction 
 has been determined, the voltage should be raised until the 
 measured loss is equal to the corrected loss. The exciting cur- 
 rent read at this voltage is approximately the true sine wave 
 value. 
 
 To Alternator 
 Supplying Copper 
 Losses 
 
 wv*avvvvwiwwwivvw-^ 
 
 To Tnree phase Alternator 
 Supplying Core Loss 
 
 Pr/mary 
 
 Fig. 183 
 CONNECTIONS FOR HEAT RUN 
 
 Heat Run 
 
 The heat test may be conducted in several ways, all of which 
 are intended to approximate as nearly as possible the actual 
 operating conditions. The run with actual load may be made 
 by using lamps, water rheostats or choke coils, but as this is 
 very expensive except for small devices, some form of motor- 
 generator method is usually employed. 
 
 Fig. 182 shows the connections for testing two transformers 
 by the motor-generator method. The secondaries of the two 
 are connected in multiple and are then connected to an alter- 
 nator which supplies the core loss and exciting current. The 
 primaries are connected in series and opposing each other. If 
 the transformers have the same ratio, the voltage from A to B 
 will be zero. 
 
 The secondary of an auxiliary transformer D is connected 
 in series with the primaries and an alternator E is used to 
 
 395 
 
supply the copper losses through this transformer D. The 
 same method may be used for any even number of transformers, 
 but it is not advisable to connect more than two high voltage 
 units in this way, or more than six or eight units of any volt- 
 age. The arrows show the direction of the load currents. 
 
 Fig. 183 shows the connections for a heat run on three single- 
 phase transformers. This method may also be used for one 
 three-phase transformer when the windings can be connected 
 in delta on each side. The three-phase alternator is used to 
 
 Primary WWW\r^/VWV\r-> UvWV- 1 
 Secondary ^M^^^^^M^ 
 
 WWW\r-^/WwJ S/WWV-J 
 
 rWVWS 
 
 Primary 
 Secondary 
 
 UT 
 
 "LvvyvJ 
 
 L^/d Lv\/\/\J 
 
 A' A" 
 , x^^a l^^t n/WW-nMAr-WWVn 
 
 To Three-phase Alternator 8 
 
 To Three phase 
 AILernatorA 
 
 Fig. 184 
 CONNECTIONS FOR HEAT RUN, THREE-PHASE 
 
 supply the core loss and exciting current. One of the deltas is 
 opened and sufficient single-phase voltage is impressed to cause 
 full load current to flow. The current circulates within the 
 deltas and is entirely independent of the three-phase voltage 
 impressed by the core loss alternator. 
 
 Fig. 184 shows the connections for a heat run on two three- 
 phase transformers in which three-phase current is used to 
 supply the copper losses and three-phase voltage for the core 
 loss. The auxiliary transformers A, A', A" may or may not be 
 used depending on whether the voltage of the alternator B 
 supplying the core loss is of the proper value or not. Auxiliary 
 
 396 
 
transformers, B, B' and B" are used as series transformers to 
 supply the impedance voltage. 
 
 Fig. 185 shows connections for the heat run on two inter- 
 changeable single-phase units designed for operation on "T" 
 connected two-phase-three-phase circuits. It is the common 
 practice to make such units interchangeable, each having the 
 50 per cent and 86.6 per cent taps so that either may be used 
 as the main or the teaser. In actual operation the one used as 
 the main has a somewhat heavier load than the teaser. How- 
 ever, since either may be used as a main, the heat run should 
 be made with the heavier load. The connections shown in Fig. 
 182 should not be used as with such a connection and with normal 
 current in the winding for use on the two-phase circuit, the cur- 
 rent in the three-phase side will be only 86.6 per cent of that 
 
 
 --jgAVWvWMVWVVv 
 
 3 
 
 jYo/-/no/ 
 Ko/toge. 
 
 ¥¥ShamgL 
 
 isyVW^WvHVWWvVV^ 
 
 o 
 
 
 
 Fig. 185 
 CONNECTIONS FOR HEAT RUN ON SINGLE-PHASE UNITS 
 FOR OPERATION ON T-CONNECTED TWO-PHASE- 
 THREE-PHASE CIRCUITS 
 
 flowing under operating conditions. It is necessary to use con- 
 nections shown in Fig. 185. The core loss is supplied in the 
 regular manner and the normal current of the two-phase winding 
 is supplied from alternator E through transformer D. An 
 additional current is supplied from alternator / through trans- 
 former H to the middle points F and G of the two three-phase 
 windings. Since F and G are the middle points, no voltage is 
 induced between them by the core loss alternator, and further- 
 more, the current supplied by alternator / flowing in opposite 
 directions in the two halves has no resultant effect upon the 
 two-phase windings. The current from alternator J must 
 be of such value as to produce a resultant current in the three- 
 phase winding 15.5 per cent greater than that produced by 
 alternator E alone. The frequency of alternator / must be 
 different from that of alternator E so that the effect of the two 
 currents in the three-phase winding will be equivalent to that 
 obtained by adding them in quadrature. 
 
 The methods described above are the ones most commonly 
 used, but it is often necessary to modify them so as to fit special 
 conditions. 
 
 It will be noted that no provision has been made for making 
 a heat run on a single transformer, except for such three-phase 
 
 397 
 
units as can be connected delta on each side. As a rule such 
 units cannot be given a normal load run without the use of 
 actual load. However, there are other methods which may be 
 used in special cases. Sometimes, it is possible to use a set 
 consisting of two alternators on the same shaft, the transformer 
 being connected between the two and the load current being 
 adjusted by varying the alternator fields. Another method 
 is applicable in case each winding is divided into two equal 
 parts. The run may then be made by paralleling each winding 
 separately and supplying core loss to one side and forcing the 
 load current through each winding separately. In addition to 
 the above, there are some compromise runs which approximate 
 the load condition. One method of making a compromise run 
 is by supplying double the normal core loss over a short period 
 and then supplying double copper loss for an equal length of 
 time, this cycle of operation being repeated until constant 
 temperature conditions are reached. 
 
 In connecting the transformers under test for the heat run, 
 it is best to use the series connection of each winding, as this 
 connection is preferable for resistance measurements. Care 
 should be taken to see that the alternators and auxiliary trans- 
 formers are of sufficient capacity to carry the normal load and 
 the overload. In calculating the current necessary to supply 
 the core losses, take the sum of the exciting currents of the trans- 
 formers. To calculate the voltage required to supply the load 
 current add together the impedance voltages of the transformers. 
 Shop transformers should always be interposed between the 
 loading alternator and the transformers under test, so as to 
 avoid having high potentials on the switchboard and prevent 
 breaking down the insulation of the alternator. 
 
 Thermometers should be placed on air blast transformers, so 
 as to obtain the temperatures of the air at intake of blower, 
 air from primary coils, air from secondary coils, air from core 
 at top and bottom and temperature of core at top and bot- 
 tom. In placing thermometers on three-phase units, each phase 
 should have as many thermometers as are ordinarily used on a 
 single-phase transformer. On water cooled transformers, the 
 temperature of the ingoing water, outgoing water, top oil, top 
 of tank near oil level and bottom of tank should be determined. 
 On self cooled oil immersed units, the temperature of top oil, 
 top of tank near oil level and bottom of tank should be deter- 
 mined. It is best to avoid changing the position of thermometers 
 when taking readings. At the end of the run, especially in the 
 case of air blast transformers, the thermometers on the core and 
 coils should be carefully watched until the temperatures begin 
 to fall. The maximum values should be recorded. 
 
 When three or more transformers are available for the heat 
 run, it is advisable to use one of them as a base for determining 
 temperature rise. The resistance and temperature of this 
 transformer should be carefully measured in comparison with 
 that of the other units before the heat run is started. During 
 the run, it should be screened from the heat given out by the 
 
 398 
 
other units but should be subjected to the same cooling medium. 
 That is, if it is an air blast unit, air should be forced through it; if 
 a water cooled unit, water should be forced through its cooling 
 coil; and if a self cooled type, it should be subjected to the same 
 surrounding air conditions as the ones on the heat test. During 
 the run, its temperature should be noted at the same time as 
 that of the hot units, these values being used as base or reference 
 temperatures. At the end of the run, the resistance of the hot 
 and the "idle" units should be measured. The temperature rise 
 is calculated from these final readings, a correction being made 
 for any difference in the two initial resistances by multiplying 
 the final resistance of the idle unit by the ratio of the initial 
 resistance of the loaded unit to the idle unit. If an "idle" unit is 
 not available, the reference temperatures should be as follows: 
 On air blast transformers it should be the ingoing air; on water 
 cooled units, the ingoing water temperature should' be used, and 
 on self cooled transformers, the surrounding air temperature 
 should be considered as the base. 
 
 It is customary to overload self cooled transformers at the 
 start of the heat run, so as to bring them up to operating tem- 
 perature quickly. Air blast transformers are usually brought 
 up to temperature on normal load, but without the use of the 
 cooling agent. Water cooled units may be brought up on normal 
 load, or slight overload without having water passing through the 
 coils. 
 
 As soon as approximately normal operating temperatures 
 have been reached, the load is reduced to normal and the water 
 started on the water cooled units or the air on the air blast. On 
 water cooled transformers, the temperature of ingoing water 
 should be adjusted to be approximately the same value as the 
 room temperature at the start of the run. This value, when 
 once decided upon should, however, be held throughout the 
 run. The quantity of water should be adjusted so as to give a 
 rise of exactly 10 deg. cent, in passing through the transformers. 
 On air blast transformers, the air should be adjusted to the 
 required pressure and both dampers should be left wide open. 
 The quantity of air should be measured at the start of the run, 
 and the quantity of water each hour during the run. 
 
 The heat run should be continued until the rise of temperature 
 is constant within one degree in three hours, this rise being deter- 
 mined by means of thermometers. The load should then . be 
 removed and resistances of hot and "idle" units measured. 
 If the results do not seem to be consistent, the load should be 
 replaced and the run continued until rises are again constant, 
 after which a second set of resistance readings should be taken. 
 
 The rise by resistance is calculated as follows: 
 
 R h-Ro 
 0.0042 Ro 
 
 where Rh =h.ot resistance. 
 
 Ro = resistance at 0° cent. «, 
 
 /#=hot temperature of winding. 
 399 
 
The following variation of the formula is found to be service- 
 able for slide rule calculations: 
 
 Rh 238 +tH 
 
 Rc~238+tc 
 where Re = the cold resistance of the winding.. 
 
 tc = temperature corresponding to this cold resistance. 
 
 During the heat run the temperature of the hottest part of 
 a transformer should not be allowed to exceed 100 deg. cent, 
 unless specific instructions to the contrary have been received 
 from the Engineering Department. Where terminals carrying 
 more than 1000 amperes are used, the temperature of each should 
 be measured at the end of the heat run. 
 
 High Potential 
 
 The application of a high potential to the insulation of a 
 transformer is the only method of determining whether the 
 dielectric strength is sufficient for continuous operation. Me- 
 chanical examination amounts to little and measurement of insu- 
 lation resistance is equally valueless, since insulation may show 
 high resistance when measured by voltmeter with low voltage, 
 but offer comparatively little resistance to the passage of high 
 tension current. The voltage of the insulation test depends 
 upon the voltage for which the windings are designed, and upon 
 the conditions under which the transformer is to operate. This 
 voltage is always specified on the Standing Instructions or 
 test data card. As a general rule, the voltage is double the 
 operating voltage of the winding with a minimum test voltage 
 of 10,000 for the high voltage and 4000 for the low voltage wind- 
 ing. The duration of the tests is always one minute, unless 
 otherwise specified. 
 
 In testing from the high voltage winding to core or to low 
 voltage winding, the low voltage winding should always be 
 grounded to the core for the following reasons: In testing 
 between one winding and the core, a potential stress is induced 
 between the core and the other winding, which may be much 
 greater than the stress to which the insulation is subjected under 
 normal operation and greater, therefore, than it is designed to 
 withstand. In testing between the high voltage winding and 
 the core the induced potential between the low voltage winding 
 and core may be several thousand volts, and the low voltage 
 winding may thus be broken down by an insulation test applied 
 to the high voltage winding under conditions which would 
 not exist in normal operation. During the test all leads on the 
 same winding must be connected together. If only one terminal 
 of a winding is connected to the testing transformer, the strain 
 may vary throughout the winding and at some point 
 may even be greater than at the terminal at which the voltage 
 is applied. 
 
 The charging current of a transformer varies with its size 
 and design. This current may be measured by means of an 
 ammeter placed in the low voltage circuit of the testing trans- 
 
 400 
 
former. It will increase as the voltage applied to the insulation 
 is increased. Inability to obtain the desired potential across the 
 insulation may be due to large electrostatic capacity, or to the 
 inability of the testing transformer to supply large capacity 
 current at the voltage desired. 
 
 In making the insulation test, it is essential that the voltage 
 be brought up gradually. 
 
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 Fig. 186 
 SPARK GAP CURVE 
 
 The usual ways of controlling the voltage are as follows: 
 
 1st. By means of a resistance in series with the low voltage 
 side of the testing transformer. Another resistance of such 
 magnitude as to allow a flow of current at least five times the 
 exciting current should be connected in multiple with the low 
 voltage side, so as to maintain a smooth wave shape under all 
 conditions. 
 
 2nd. By means of an induction regulator on the low volt- 
 age side of the testing transformer. 
 
 3rd. By variation of the strength of the generator field. 
 
 401 
 
The first method is not well suited to very high potential 
 tests on account of the large amount of resistance required. 
 The second and third methods are, however, suitable for any 
 voltage. 
 
 In applying the test voltage, it should be started at less than 
 one quarter of the final value, should then be brought up during 
 30 seconds to the full value and after having been held the 
 specified length of time should be reduced during about 15 
 seconds to less than one-quarter of its maximum value, after 
 which the circuit may be opened. 
 
 The spark gap should be as near as possible to the trans- 
 former under test and on tests of more than 15,000 volts it 
 should never be more than 20 feet away. Resistances should 
 always be placed in series with this gap, but never between the 
 testing transformer and the one under test. The value of the 
 resistances placed in series with the gap should be such as to 
 limit the current from }/i to 2 amperes in case of a discharge 
 across the gap. This will require from 4 ohms to 3^2 ohm per 
 volt, 
 
 For tests of 10,000 volts or less, it is usually the practice 
 to depend upon the ratio of the testing transformer in determin- 
 ing the voltage that is to measure the voltage on the low voltage 
 side, a spark gap being placed across to the high voltage side 
 and being set at 10 per cent above the required voltage as a 
 safety valve. For tests from about 10,000 to 50,000 volts, 
 the gap should be set in accordance with the curve of arcing 
 distance shown. (See Fig. 186.) The voltage should be raised 
 slowly until the gap breaks, at which time the voltmeter reading 
 should be noted. The voltage should then be reduced to zero, 
 and the spark gap setting increased to 10 per cent above its 
 former value. The voltage should then be brought up until 
 the voltmeter reads the same value, this voltage being held 
 for the specified length of time. For tests above 50,000 volts, 
 it is not advisable to cause the spark gap to break with the 
 full voltage on the transformer under test. For such tests, 
 therefore, the gap is first set for the desired voltage, while 
 the transformer under test is entirely disconnected. The 
 gap is then broken and the voltmeter reading noted. Then the 
 gap is set for % of the required voltage and the voltmeter read- 
 ing obtained for the breaking of this gap. The transformer under 
 test is then connected and the gap broken at the setting for % 
 voltage. The voltmeter reading obtained with this last setting 
 is then multiplied by the ratio of the readings for full and for % 
 voltage with the transformer disconnected and this calculated 
 voltage is held by voltmeter for the actual test, the spark gap 
 being set at 15 per cent above this voltage during the test. 
 
 The presence of moisture in the coils and insulation lowers 
 the dielectric strength to such an extent that it is general practice 
 to dry carefully all high voltage transformers before they are 
 filled with oil. The drying-out run should ordinarily be made 
 on all transformers having test voltages above 100,000 volts, 
 and upon any transformer having test above 15,000 volts if it 
 
 402 
 
has been standing in the factory for more than two or three 
 weeks before test. The drying is ordinarily done by forcing 
 a blast of air at about 80 deg. cent, through the transformer 
 and this continued until the insulation resistance measured by 
 the megger shows practically constant values. 
 
 Transformers having high potential test voltages above 
 13,200 volts are filled with oil for the test. Care should be 
 taken to see that the oil itself is of sufficient dielectric strength. 
 Xo oil having strength of less than 20,000 volts between half 
 inch disks 0.2 in. apart, should be used during the high potential 
 tests. When the test voltage is higher, the strength of the oil 
 should be correspondingly greater. For tests above 100,000 
 volts, the oil should show a dielectric strength of at least 40,000 
 volts. 
 
 As the high potential test is made after the heat run, the oil 
 has had an opportunity to free itself from air bubbles and to 
 penetrate to every part of the transformer. In some cases, 
 however, especially when the oil does not meet the requirements 
 of dielectric strength, it is necessary to replace it before the high 
 potential test. In such cases the transformer should be allowed 
 to stand for some time before the test is applied. This period 
 should be at least one hour for voltages of 50,000 and less, and 
 at least 6 hours when the voltage is above 50,000. 
 
 Induced Voltage 
 
 Induced voltage is applied to transformers in order to test 
 the insulation between turns and between sections of the wind- 
 ings. The usual value of this test is twice normal voltage 
 induced for a period of one mimvte, followed by one and one- 
 half times normal voltage for five minutes. Low voltage trans- 
 formers (5000 volts or less), usually have three times normal 
 voltage applied for one minute. 
 
 The source of power should have an approximate sine wave 
 and a frequency such that the exciting current will not exceed 
 150 per cent of the rated load current of the excited winding. 
 It is common practice to use a frequency of 200 cycles for 25 
 and 60 cycle transformers. The voltage may be controlled by 
 any of the methods described for the high potential test. The 
 voltage should be started at less than 34 oi the final value and 
 should be brought up gradually to its full value. It should then 
 be held for the specified length of time, after which it should be 
 reduced slowly to less than l /i of the full value before the circuit 
 is opened. 
 
 During this test, windings designed for a voltage of over 
 1000 volts must be so arranged that all portions are connected 
 together using one of the connections shown on the DS sketch. 
 This precaution is necessary as otherwise excessive stresses might 
 be induced between parts of the windings, which under normal 
 operation would be subjected only to small voltages. 
 
 If the winding has a rated voltage of more than 20,000 volts, 
 it is best to use the full series connection during this test. 
 Three-phase transformers designed for Y-connection having 
 
 403 
 
voltage over 20,000 should ordinarily be connected for the 
 highest Y-voltage during this test, although exception is made 
 in the case of three-phase shell types for operation on Y-Y or 
 Y- diametrical systems. 
 
 Failures in Test 
 
 When transformers fail between turns, between coils, 
 between windings or from windings to other parts in such a 
 manner that it becomes necessary to dismantle them, careful 
 examination and tests should be made to determine whether 
 failures in other parts have also occurred. 
 
 Transformers failing under high potential should be given 
 an induced voltage test before they are dismantled. This test 
 should be made in the manner specified for the regular induced 
 voltage test. 
 
 Three-phase transformers failing in one phase should be 
 given the full high potential test on the other two phases, one 
 at a time, both windings of the two phases not under test being 
 grounded. If the transformer is of shell type construction, 
 induced voltage tests should also be made on each phase sepa- 
 rately (whether or not they fail on high potential), with both of 
 the other phases short-circuited. 
 
 Three-phase shell type transformers failing between turns 
 or between coils so that dismantling is necessary, should have 
 the broken phase short-circuited on both high and low voltage 
 windings, after which further induced voltage tests should be 
 made on the other two phases. Single-phase voltage should be 
 impressed on each phase separately while the other phase is 
 short-circuited. 
 
 Calculation of Efficiency 
 
 The efficiency of a transformer is the ratio of its net power 
 output to its gross power input, the output being at non-induc- 
 tive load. The efficiency is to be based on the maximum volt- 
 age and kv-a. rating, unless otherwise specified. It may be 
 determined by either of two methods: 
 
 1. By the input-output method, or 
 
 2. By the loss method. 
 
 The first method which requires the measurement of the 
 input and output on normal load is not accurate on account of 
 the small difference between the input and output, and is very 
 seldom practicable because of the difficulty of obtaining full 
 load. The loss method is, therefore, used exclusively for com- 
 mercial work. 
 
 The input includes the output together with the losses which 
 are as follows: 
 
 1. The core loss which is determined by the core loss test. 
 
 2. The PR loss of the windings calculated from their 
 resistances. 
 
 The core loss may be measured either on the high voltage 
 winding or on the low voltage winding. Rated voltage and 
 frequency should be used. If the generator does not have a 
 
 404 
 
sine wave, the loss should be corrected by means of the core 
 loss correction outfit. The measurement of loss should be made 
 at or near normal room temperature. The PR loss should be 
 calculated from the measured resistance reduced to a room 
 temperature of 25 deg. cent, unless otherwise specified. The 
 rated current of each winding should be squared and multiplied 
 by the resistance of that winding, the sum of these losses being 
 added together to obtain the total I 2 R loss. See Calculation 
 Sheets 29 and 30. 
 
 The rated kv-a. of a transformer is to be considered the 
 output and the losses are to be added to this value in order to 
 obtain the input. 
 
 For auto-transformers the core loss should be measured in 
 the same way as on a transformer, and the PR loss of each sec- 
 tion of the winding should be calculated from the rated current 
 and resistance at 25 deg. cent. The total loss should be added to 
 the rated output to obtain the input. The rated kv-a. of the 
 auto-transformer is not the same as the output, but the output 
 is always specified by the Engineers. 
 
 Calculation of Regulation 
 
 In constant potential transformers the regulation is the 
 ratio of the rise of secondary terminal voltage from full load to 
 no load (at constant primary impressed terminal voltage) to 
 the secondary full load voltage. Regulation may be determined 
 by loading the transformer and observing the rise in secondary 
 voltage when the load is thrown off. This method is not satis- 
 factory on account of the expense of making the test, and the 
 small difference between no load and full load secondary volt- 
 ages. Much greater reliance can be placed on results calculated 
 from separate measurements of reactance drop and resistance, 
 than on actual measurements of regulation. For non-inductive 
 load, we have the following formula : 
 
 (per cent IX) 2 
 Per cent regulation = per cent IR-\ — — — ^- — - — 
 
 where per cent IR= total resistance drop expressed in per cent 
 of rated voltage. 
 
 Per cent IX = total reactance drop expressed in per cent 
 of rated voltage. 
 
 For lagging currents, we have the following: 
 Per cent regulation = (per cent IR) P + (per cent IX) W+ 
 [(per cent IX) P - (per cent IR) W] 2 
 200 
 where per cent IR= total resistance drop due to load currents 
 expressed in per cent of rated voltage, 
 per cent IX = total reactance drop due to load currents 
 expressed in per cent of rated voltage. 
 P = power-factor (cos 6) 
 W = wattless factor (sin 0) 
 405 
 
The following table gives the values of W, the wattless 
 factor for various values of P, the power-factor: 
 
 p 
 
 w 
 
 1.00 
 
 
 
 0.95 
 
 0.312 
 
 0.90 
 
 0.436 
 
 0.85 
 
 0.526 
 
 0.80 
 
 0.60 
 
 0.75 
 
 0.66 
 
 0.70 
 
 0.714 
 
 0.60 
 
 0.80 
 
 The per cent IR is calculated from the rated current and the 
 resistance at 25 deg. cent. It may be obtained conveniently by 
 dividing the PR loss by ten times the rated kv-a. The per cent 
 IX is calculated by taking the square of the per cent impedance 
 volts, subtracting the square of the per cent IR and determining 
 the square root. See Calculation Sheets 29 and 30. 
 
 In auto-transformers the per cent IR drop should be cal- 
 culated in the same way as for a transformer, and may be 
 conveniently obtained by dividing the PR loss in watts by ten 
 times the equivalent transformer capacity in kv-a. The per- 
 cent IX drop should be calculated from the per cent impedance 
 in the same way as for a transformer. The auto transformer 
 should be connected as a transformer during the impedance 
 test. These values of per cent IR and the per cent IX should 
 then be multiplied bythe ratio 
 rated voltage (h.v. winding) —rated voltage (l.v. voltage winding) 
 
 rated voltage (high voltage winding) 
 after which they should be used in the formulae given above 
 for transformers. 
 
 INDUCTION REGULATORS 
 SINGLE-PHASE INDUCTION REGULATORS 
 
 The IRS, or single-phase Induction Regulator, may be 
 cooled by an air blast — it may be placed in a tank and be oil 
 cooled — or it may be oil and water cooled. Regulators of this 
 type are usually made for the control of single-phase lighting 
 circuits. The primary winding is placed in slots on a movable 
 core or armature, while the secondary winding is placed in slots 
 on a stationary core. The regulator may be wound with any 
 even number v of coils. 
 
 The voltage induced in the secondary winding depends upon 
 the relative position of the secondary with reference to the 
 primary winding, the primary being in shunt and the secondary 
 in series with the circuit to be controlled, the voltage of the 
 circuit thus being increased or decreased accordingly. Single- 
 
 406 
 
phase, as well as polyphase regulators have a distributed winding 
 for both primary and secondary, but the maximum pole face 
 which can be covered by an active winding in a single-phase 
 regulator so as to produce the best results, is approximately 
 60 per cent. In the neutral position the secondary winding, 
 therefore, encloses an area on the primary core not enclosed by 
 an active primary winding and the impedance would be extremely 
 high if no windings were provided. The slots of the primary 
 not used for an active winding are, therefore, filled with a 
 short-circuited winding, so that in the neutral position of the 
 regulator the current forced through the secondary induces a 
 current through the short-circuited winding which reacts upon 
 the primary and reduces the impedance. 
 
 Tests Required 
 
 The following tests are made on single-phase regulators: 
 
 Cold resistance. 
 
 Ratio. 
 
 Polarity. 
 
 Core loss. 
 
 Impedance. 
 
 Heat run. 
 
 High potential. 
 
 Induced voltage. 
 
 Xoise tests. 
 
 Tests of auxiliaries. 
 
 These tests are usually made in the order mentioned above. 
 The order may be changed, however, if desired. It is considered 
 desirable to have the high potential and induced voltage tests 
 made last and in the order named. 
 
 Cold Resistance 
 
 Cold resistance should be measured by the methods described 
 for transformers, care being observed to obtain accurate measure- 
 ments if the rise by resistance is to be calculated at the end of 
 the heat run. The resistance measurements should be reduced 
 to a room temperature of 25 deg. cent., and entered on the 
 test sheet. 
 
 Ratio 
 
 The ratio should be taken with normal voltage on the pri- 
 mary, by reading the volts across the secondary with the armature 
 in the limiting, maximum boosting, maximum lowering, and 
 neutral positions. The feeder volts should be read in each 
 position. The number of turns of the handwheel should be 
 noted for each position, starting at a limiting position. 
 
 Polarity 
 
 Polarity should be checked against the DS sketch with the 
 armature in the maximum boosting position. The regulator 
 should boost the line voltage when the handwheel is revolving 
 counter-clockwise. 
 
 407 
 
Core Loss 
 
 On this type of regulator with the permanent short-circuit 
 on the armature, the core loss must be taken from the primary- 
 winding. The power-factor will be low due to the air gap — - 
 hence, considerable care must be taken in making the test. 
 The core loss watts and the exciting current should be measured 
 at normal voltage and frequency with the armature in both the 
 maximum boosting and the neutral position. 
 
 Impedance 
 
 Impedance is always measured on the secondary winding 
 as it is impossible to force full load current through the primary 
 winding in the neutral position. With the primary short- 
 circuited, full load current should be f orced.through the secondary 
 and the voltage recorded with the armature in the neutral 
 position, maximum boosting position, and position of maximum 
 impedance. The positions should be recorded by giving the 
 number of turns of the handwheel from a limiting position. 
 
 Heat Run 
 
 The ordinary commercial regulators are given a short- 
 circuited heat run without oil. One of the windings is short- 
 circuited, and the rotor placed in the maximum boosting or 
 maximum lowering position. Currents of sufficient magnitude 
 to produce a temperature rise of from 50 to 60 deg. cent, in 20 
 minutes, are held in the secondary. The values of currents for 
 standard regulators are specified by the Engineers. 
 
 In case a load run is required, the regulator is either con- 
 nected as a transformer and placed on a non-inductive load, or 
 in case two are available they are given a bucking run with the 
 losses supplied from two sources of power. An idle unit is used 
 as a basis for calculating temperature rises, if one is available. 
 
 Oil immersed regulators should be filled with oil to the gauge 
 line at room temperature. Thermometers should be placed in 
 the tank between the second and third ribs — one at the bottom 
 and one 2 in. below the gauge line. One thermometer should 
 be placed in the top oil, the bulb being immersed about 1 3^ in. 
 Room temperature should be recorded at three or four positions 
 around the regulator. 
 
 Normal voltage and frequency should be held on the pri- 
 mary, and normal current in the secondary. Thermometer read- 
 ings should be taken at hourly intervals, and resistance readings 
 every two hours, primary and secondary being measured 
 alternately. The normal load run should be followed by a 125 
 per cent load for 2 hours, unless otherwise specified. 
 
 High Potential 
 
 High potential test is made in the same way as on a trans- 
 former. All leads must be connected to one or the other elec- 
 trode of the high potential testing set. Standard 1100 to 2500 
 volt primary regulators are given a test of 7500 volts for one 
 minute between windings, and from windings to frame. 
 
 408" 
 
Induced Voltage 
 
 The induced voltage test consists of the application of three 
 times normal voltage for 10 seconds to the primary winding, 
 followed by double normal voltage for 5 minutes. The fre- 
 quency should be sufficiently high to keep the exciting current 
 within the full load current of the regulator. The armature 
 should be placed in the maximum boosting or maximum lower- 
 ing position. 
 
 Noise Test 
 
 Every regulator must be carefully tested for noise with 
 normal excitation, frequency and load, while the armature is 
 moved through its complete range. When the noise exceeds the 
 standard which will be set from time to time, the regulator 
 should not be passed without the approval of the Engineering 
 Department. 
 
 Tests of Auxiliary Apparatus 
 
 The motor and limit switch should be connected in accord- 
 ance with the DS sketch, after which they should be operated 
 throughout the entire range without load or excitation on the 
 regulator. A record should be made of the minimum volts re- 
 quired to operate the motor, the amperes at normal voltage and 
 the time required to operate it through the entire range. The 
 tripping lugs should be adjusted during the test, so as to open 
 the limit switch in such a way that the regulator will stop in 
 the maximum boosting or maximum lowering position with 
 allowance made for standard hunting. There must be suffi- 
 cient allowance made to prevent the segment from coming against 
 the stop pin when operating. When the tests have been com- 
 pleted the bearings should be drained, washed out with kerosene 
 oil, and the oil plugs screwed in tight. 
 
 The brake shoes should be oiled, and the brake adjusted for 
 hunting of approximately 1 per cent of the total range. The 
 hunting should be recorded in turns of the hand wheel. 
 
 The relay switch should be supplied with normal voltage 
 at normal frequency, and the amperes measured with the 
 armature in the middle position and in the normal operating 
 position. A record should also be made of the resistance, and 
 the minimum volts required to operate. The minimum volts 
 should not exceed 80 per cent of normal. The connections should 
 be checked against the DS sketch. The stationary contacts 
 should be adjusted so that there is Y%vn. spring at the end of 
 the face of the moving element when the armature is against 
 the magnet coil. The stationary contacts must bottom in the 
 holders which should be placed tight in the support. The 
 switch should be given a double voltage test through the magnet 
 winding for five minutes at approximately double frequency, 
 with the magnet armature closed. 
 
 A high potential test of 1000 volts should be applied for one 
 miniate from windings to core, from contacts to frame, and 
 between the contacts of the switches. 
 
 409 
 
Special tests on motors will be called for by the Engineers 
 when required. These include starting torque, impedance, 
 heat run, minimum volts and amperes and watts with regulator 
 loaded. The heat run is made by operating the. regulator at no 
 load, reversing at limits during one hour. Normal voltage and 
 frequency should be applied to the motor. The brakes should 
 be set so as to allow a hunting of about 1 per cent of the total 
 range of the regulator, and should be oiled to maintain this 
 hunting throughout the run. The room temperature, rise in 
 bearings, windings, laminations, rotor, commutator, and brake 
 pulley, should be measured by thermometer, and the rise of 
 windings by resistance. 
 
 POLYPHASE INDUCTION REGULATORS 
 
 Induction regulators of the IRQ, IRT and IRH types are 
 used principally with synchronous converters, but are well 
 adapted to control polyphase transmission circuits. As in the 
 IRS type, they may be either air blast, oil cooled, or oil and 
 water cooled. The primary winding is connected in shunt and 
 the secondary in series with the circuit. In the polyphase 
 induction regulator, the voltage induced in each phase of the 
 secondary is constant, but by varying the relative positions of 
 the primary and secondary, the effective voltage of any phase of 
 the secondary on its circuit is varied from maximum boost to 
 zero, and to maximum lower. 
 
 Referring to Fig. 187 which represents "graphically the volt- 
 age of the three phases of a three-phase or IRT regulator, AAA 
 equals the line voltage or the e.m.f. impressed on the primary. 
 This is shown by the large circle. Let BA, BA and BA equal 
 the e.m.f. generated in the secondary coils and constant with the 
 impressed e.m.f. This is shown by the three small circles on the 
 circumference of the large circle. BBB shows the e.m.f. induced 
 in the secondary coils directly in phase with the primary im- 
 pressed e.m.f. This is the position of maximum boost. Posi- 
 tions CCC represent the neutral position, and DDD the maximum 
 lower position. EEE represents a position between neutral and 
 maximum lower. 
 
 By changing the position of the armature with respect to 
 the field, the secondary voltage may be made to assume any 
 phase relation with respect to the primary e.m.f.; it can be in 
 series with it or directly opposed to it. This movement of the 
 armature is obtained by means of a segment on the shaft which 
 meshes with a worm on the small operating shaft. The regulator 
 may be arranged for hand operation only, or can be motor- 
 operated. Either a direct current or an induction motor may 
 be used. The motor is controlled by a small double-pole double- 
 throw switch, on the switchboard, to allow the voltage to be 
 raised or lowered as desired. 
 
 To stop the regulator on reaching the limits of regulation 
 when moving in either direction, a limiting switch is provided, 
 which opens automatically. If properly connected, this auto- 
 matic cut off, however, does not interfere with movement in the 
 
 410 
 
opposite direction, which can be obtained by the double-pole 
 double-throw switch. 
 
 Tests Required 
 
 The following tests are required on all polyphase regulators: 
 
 Cold resistance. 
 
 Ratio. 
 
 Polarity. 
 
 Core loss. 
 
 Impedance. 
 
 Heat run. 
 
 High potential. 
 
 Induced voltage. 
 
 Xoise test. 
 
 a 
 
 Fig. 187 
 REGULATOR DIAGRAM— THREE-PHASE 
 
 The order of tests is immaterial, except that it is best to 
 have the induced voltage test follow the high potential test, both 
 of them being made after the other tests have been 'completed. 
 It is also advisable to check the connection with the DS sketch 
 after the tests are made, particularly where permanent con- 
 nections are made by the Assembly Dept. after tests. 
 
 Cold Resistance 
 
 The resistance in each phase should be measured and the 
 values at 25 deg. cent, calculated and reported on the test sheet. 
 
 Ratio and Polarity 
 
 Two separate tests are required in order to obtain the ratio 
 and polarity; (1) ratio of secondary to primary turns, and (2) 
 boost and lower and polarity. 
 
 The ratio of turns must be checked by applying normal 
 voltage at normal frequency to the primary and measuring the 
 induced secondary voltages. 
 
 The primary and secondary should then be connected to 
 a source of supply as shown on the DS sketch, normal voltage 
 being applied at normal frequency. The feeder voltage of each 
 
 411 
 
phase should be measured with the armature in the extreme 
 maximum boosting, neutral, maximum lowering and other 
 intermediate positions. The position of the armature in each 
 ease should be recorded in turns of the handwheel from one 
 extreme position. The direction of rotation of the handwheel 
 for boosting should be recorded. Standard regulators are 
 designed for counter-clockwise rotation to boost the voltage. 
 If the primary is incorrectly connected to the secondary, 
 either an unbalancing of the feeder voltages will be noted, or 
 with the feeder voltage balanced, the maximum boost, maximum- 
 lowering, etc., will be found at wrong positions of the armature. 
 It is possible, although very improbable, that such unbalancing 
 may be due to reversed secondary leads. In any event, the 
 proper connection must be determined and the leads plainly 
 marked so that the necessary changes can be made by the 
 Assembly Department. 
 
 Core Loss 
 
 The readings of core loss should be taken on the primary 
 side with normal voltage applied at normal frequency. As the 
 core loss is not the same in all positions of the armature, the 
 maximum and minimum should be found and the readings 
 taken at these points. The position of the armature should be 
 recorded in turns of the handwheel from one extreme position. 
 
 On IRH regulators having diametrical or double delta pri- 
 mary connections, it will be more convenient to make the test 
 with three-phase single delta temporary connections. The 
 connection used should be noted on the test record. 
 
 Impedance 
 
 The impedance is usually measured by short-circuiting the 
 secondary and applying sufficient voltage to the primary wind- 
 ing to give full load current. As the impedance is not the same 
 in all positions, the maximum and minimum readings should be 
 obtained, and the position of the armature noted in each case. 
 The impedance of an IRH regulator may be conveniently 
 measured by connecting the primary, secondary, or both as 
 three-phase. 
 
 Heat Run 
 
 It is customary to give standard regulators a compromise 
 run with 150 per cent normal current and 125 per cent normal 
 voltage for two hours, the proper cooling medium being used 
 throughout. Hot resistances should be measured and the 
 temperature rise calculated. Usually the secondary current is 
 held at a specified value, but in case it is too large to measure 
 it is considered satisfactory to hold the corresponding primary 
 current calculated from ratio of turns. 
 
 The ultimate heat runs are usually made with two regulators 
 connected according to the motor-generator method, with the 
 primaries in parallel and the secondaries in series so connected 
 that the primary fields will rotate in the same direction. Normal 
 
 412 
 
voltage is applied to the primary at the rated frequency. The 
 armature of one regulator, called the generator, should be held 
 in the maximum boosting position, while that of the other, 
 the motor, should be adjusted until the proper secondary current 
 is obtained. It is necessary to see that the currents in the pri- 
 mary and secondary windings are balanced, particularly when 
 the secondary current is large. The primary current will not 
 be the same in both regulators. 
 
 If the secondary current is too large to measure, the primary 
 current of the one running as a generator should be calculated 
 as follows: The theoretical primary current calculated from 
 the ratio of turns should be added at an angle of 90 deg. to the 
 magnetizing current measured at normal voltage. 
 
 Under such a test, the heating of the regulator running as a 
 generator will be equivalent to that under normal load con- 
 ditions, whereas the heating of the other will be somewhat 
 higher. 
 
 Water cooled regulators should be run with the specified 
 amount of water, which should be put in at about average room 
 temperature, and the same temperature held throughout the 
 run. Air-blast regulators should be furnished with air at the 
 specified pressure. The quantity should be measured at the 
 start of the run. 
 
 The temperatures should be observed at oil level on the 
 outside of the tank, at the bottom of the tank; also the tem- 
 perature of the top oil inside the tank. On air-blast regulators, 
 the temperature at the top of the tank and at a number of places 
 on the windings should be observed. Care should be taken to 
 avoid obstructing the passage of air. In case there are likely 
 to be hot spots in the windings or connections, thermometers 
 should be placed on them. Resistance of one primary and one 
 secondary phase should be taken alternately every hour, unless 
 the secondary resistance is too large. In that event, the primary 
 should be taken every hour. The resistance of each phase should 
 be measured at the end of the run, and the rise of temperature 
 calculated from the increase in resistance. 
 
 The proper number of single-phase regulators may be used 
 instead of a polyphase regulator as the motor on a motor- 
 generator run, provided they do not materially change the 
 conditions of the polyphase unit under test. The heat run may 
 also be made by putting dead load on the regulator, if necessary. 
 
 High Potential 
 
 The high potential test is usually made with the regulator 
 hot. On standard 1100 or 2200 volt machines, 7500 volts is 
 applied for one minute from primary to secondary and core, and 
 from secondary to primary and core. On other regulators, the 
 test voltage is specified. The same test voltage is applied 
 between secondary phases and between primary phases if they 
 can be separated. The test between phases should be made 
 from phase 1 to phase 2, from phase 2 to phase 3, and from phase 
 1 to phase 3 independently — not from phases 1 and 2 to phase 3, 
 
 413 
 
etc. The phase not connected during test should be short- 
 circuited on itself. 
 
 Induced Voltage 
 
 Triple normal voltage should be applied for 10 seconds to 
 the primary winding, followed by double normal voltage for 
 5 minutes. The frequency should be sufficiently high to keep 
 the magnetizing current within full load current limits. 
 
 The armature should preferably be placed in the maximum 
 boosting position. If three-phase connections are used on an 
 IRH regulator, care should be taken to see that the proper 
 voltage is applied, viz. double volts per turn. 
 
 Noise Test 
 
 The noise test consists of operating the regulator with normal 
 voltage and frequency, while the armature is rotated through all 
 positions. If a short-circuited heat run is made, the armature 
 should be moved over the full range during the run. If it is 
 suspected that it may operate in a noisy manner under full load, 
 a test should be made under as nearly full load conditions as can 
 be obtained. 
 
 Tests of Auxiliary Apparatus 
 
 The operating motor and limiting switch should be connected 
 in accordance with the DS sketch and normal voltage applied. 
 The current and the time necessary to operate from maximum 
 boost to maximum lowering position without load or excitation 
 on the regulator should be noted. The minimum voltage 
 required to operate the motor under such conditions should also 
 be ascertained. 
 
 The brake magnet, which is always designed for the same 
 voltage and frequency as the operating motor, should have 
 normal frequency voltage applied, and the current measured 
 with the armature up. The maximum volts required to operate 
 this device should also be determined, and the cold resistance 
 should be measured. If the minimum voltage is more than 80 
 per cent of normal, the brake should not be passed for shipment. 
 
 All auxiliary parts should be given a high potential test of 
 1000 volts for one minute from windings to frame and from 
 active switch parts to iron supports. 
 
 BR REGULATORS 
 
 Modern central stations employ alternating current gen- 
 erators of large capacity, each generator usually supplying two 
 or more districts through independent feeders. One feeder 
 may serve a business district, while another from the same 
 generator may feed a residential district. As the compounding 
 required on any of the feeders depends on the amount of load 
 carried by the feeder, and as the load peak occurs at different 
 times in different feeders, a device to regulate the feeder voltages 
 independently is necessary. 
 
 414 
 
Type IRS may be used, but the automatic BR feeder 
 regulator has been expressly designed for this work. Fig. 188 
 shows the circuits. 
 
 The automatic BR feeder regulators can change the line 
 voltage quicker and with a smaller power consumption than 
 other automatic types. The only moving part is a small and 
 light switch arm. The friction of a number of small switch 
 contacts constitutes the only turning resistance. 
 
 The moving part of the switch carries a series of fingers, 
 the majority of which are always in contact. See Fig. 189. 
 Each finger is connected to a corresponding stationary collector 
 ring by a brush, and the collector ring is connected to the line 
 through a preventive resistance. The resistances connecting 
 the fingers to the line prevent excessive exchange currents as 
 the fingers pass from contact to contact, and vary the line volt- 
 age uniformly. The regulator transformer is oil cooled. 
 Tests Required 
 
 The following tests are required: 
 
 Cold resistance. Heat run. 
 
 Ratio High potential. 
 
 Core loss. Induced voltage. 
 
 Impedance. Test of auxiliaries. 
 
 Cold Resistance 
 
 The cold resistance of the primary winding and of each 
 half of the secondary winding should be measured exclusive 
 of the preventive resistance. The resistance of each of the 
 preventive resistances should be measured cold. The spring 
 contacts should be insulated from the contact blocks by means 
 of a thin sheet of fiber, and the resistance measured between 
 the collector rings and the common connection. 
 Ratio 
 
 Ratio is taken at no load with full voltage on the primary, 
 by reading the voltage across the secondary with the switch 
 arm in maximum boosting and maximum lowering positions. 
 The voltage should be read between the middle point of the 
 secondary winding and each contact block. The polarity should 
 also be checked against the standard sketches provided by the 
 Engineering Department. 
 Core Loss 
 
 The magnetizing current and core loss readings should be 
 taken at normal voltage and frequency with the switch contacts 
 so arranged that each spring contact will cover one block only, 
 or the contacts may be insulated from the blocks by means of a 
 thin sheet of fiber. This arrangement is necessary as otherwise 
 part of the secondary windings would be short-circuited through 
 the preventive resistance and this loss would be included in the 
 core loss reading. 
 Impedance 
 
 With the primary short-circuited and the switch arm in one 
 extreme position, full load current should be forced through the 
 secondary and the voltage and watts measured between the 
 
 415 
 
middle point of the secondary winding and the contact block 
 covered by the spring contacts, after which the readings should 
 be repeated with the switch arm in the extreme position. The 
 same readings should be repeated with the drop, and loss in the 
 preventive resistances included. 
 
 Heat Run 
 
 The compromise heat run is made without oil, the primary 
 being open-circuited and one-half of the secondary short- 
 circuited, while current of sufficient magnitude is forced through 
 the other half of the secondary to produce a rise of from 50 to 
 60 deg. cent, in 20 to 30 minutes. Resistance should be measured 
 
 416 
 
at the end of the run and the rise by resistance calculated. The 
 two halves of the secondary should be measured separately so 
 as not to include the preventive resistance. 
 
 The voltmeter leads should, therefore, be attached to the 
 middle point of the two secondary coils and to the extreme 
 contact blocks. 
 
 15^^/^ww^Swvww^W^ Tbfeec/er 
 
 i 
 
 0/q/Sw/£c/) 
 
 I I I I II I 
 
 ^444- 
 
 ■H* 
 
 D/a/ Sw/ich 
 flevefoped 
 
 u 
 
 \* 4 4 <4 
 
 Co//ector R/ngs 
 
 Pnevent/ve 
 /?es/s6o/7ce 
 
 Fig. 189 
 BR REGULATOR 
 
 An ultimate heat run may be made by the motor-generator 
 method if two regulators are available at the same time. If 
 only one is in test, it may be pumped back on a suitably arranged 
 bank of transformers or it may be loaded on a water rheostat. 
 In the latter case, apply voltage to the primary, connecting the 
 secondary to a water box, adjusting until full load current is 
 obtained. The switch must be in one of the extreme positions. 
 
 417 
 
High Potential 
 
 On 2200 volt regulators, a 7500 volt test for one minute 
 should be applied from windings to ground. The test voltage 
 will be specified on other regulators. 
 
 Induced Voltage 
 
 Three times normal voltage should be applied for one 
 minute, followed by twice. normal voltage for five minutes. 
 
 Tests of Auxiliaries 
 
 The motor should be tested to determine the minimum volts 
 required to operate it, and the current consumed when operating 
 at normal voltage. 
 
 The clutch coils should have tests to determine the resistance 
 of each coil, minimum volts required to operate, and current 
 consumed at normal voltage. With the motor and clutch coils 
 connected to a line of rated voltage, the switch arm should be 
 turned back and forth for one-half hour from one extreme 
 position to the other. Operation should be watched closely and 
 the time required for turning the switch arm from maximum 
 boost to maximum lower should be measured. 
 
 High potential tests should be made before assembly with 
 the transformer parts as follows: 
 
 A test of 1000 volts for one minute from clutch coils to frame, 
 from active parts of limit switch to frame, from contact blocks 
 to switch pot, from collector rings to support, from contact 
 fingers to support, and between contact blocks. 
 
 A test of 500 volts for one minute between collector rings 
 and also between contact fingers. 
 
 High potential test of 1000 volts should be applied for one 
 minute between motor leads and frame, clutch coils and frame, 
 and between active parts of limit switch and cover, when the 
 final high potential test is made on the assembled regulator. 
 
 REACTANCES 
 
 At the present time reactances are built in several different 
 types, the design depending principally upon the use to which 
 the reactance is to be put. The largest sizes, called current 
 limiting reactances, consist of a winding of bare copper cable 
 on a cylindrical concrete core, the turns of this winding being 
 insulated from each other by strips of wood, and the whole 
 device being cooled by natural air circulation. Reactances of 
 large size are also used in connection with the operation of 
 synchronous converters, the design in this case being that of a 
 polyphase unit wound on a laminated iron core and cooled by 
 air blast or by oil circulation. The smaller reactances are used 
 mostly in connection with the operation of mercury arc recti- 
 fiers. These are wound on iron cores and are cooled by natural 
 circulation of the air. 
 
 418 
 
Tests Required 
 
 The following tests are usually made on reactances: 
 Cold resistance. 
 Impedance. 
 Heat run. 
 High potential. 
 Double or triple voltage. 
 
 Where there are taps, it is necessary to check the tap ratio 
 in the same way as on transformers. 
 
 Cold Resistance 
 
 No special instructions are needed for this other than those 
 given for transformers. 
 
 Impedance 
 
 The impedance test consists of forcing normal current 
 through the winding and reading the volts and watts. Care 
 must be taken to have magnetic material removed at least 
 3 ft. from current limiting reactances during this test. 
 
 Heat Run 
 
 The heat run on current limiting reactances is made by 
 forcing normal current at normal frequency through the wind- 
 ings and continuing the run until temperatures become constant. 
 Spirit thermometers only should be used to measure temperature. 
 
 The heat run on reactances for use with mercury arc rectifiers 
 usually consist of a 5-hour normal load run with a complete set 
 of auxiliary apparatus connected to the mercury arc rectifier 
 tube. 
 
 A stability test is usually made at the same time as the heat 
 run on reactances for rectifiers. This test consists in the deter- 
 mination of the lowest value of direct current necessary to 
 maintain the arc in the rectifier tube. 
 
 High Potential 
 
 The high potential test from windings to core is made accord- 
 ing to the rules given for transformers. No special instructions 
 are needed for reactances. 
 
 Double or Triple Voltage 
 
 This test is made in the same way as on transformers. The 
 frequency is increased in order to keep the current within 
 reasonable limits. 
 
 SERIES LIGHTING TRANSFORMERS 
 
 Series lighting transformers are used to insulate lamps from 
 a high voltage series circuit. They range in capacity from 40 
 watts to 2000 watts and the standard ampere ratings are 4, 
 5.5, 6.6 and 7.5. As a rule, they are air cooled because the small 
 capacity and low losses make it unnecessary to use oil as a 
 
 419 
 
cooling medium. The primary winding is connected in series 
 with a series arc or series incandescent circuit so that under all 
 conditions of load on the secondary, the primary carries the full 
 current of the circuit. For satisfactory operation of the incan- 
 descent lamps connected to the secondary, it is desirable to 
 obtain as near constant current in the secondary as possible. 
 
 The tests required are: 
 
 High potential. 
 
 Resistance. 
 
 Core loss and exciting current. 
 
 Open circuit voltage. 
 
 Impedance. 
 
 Regulation. 
 
 Heat run. 
 
 Induced voltage. 
 
 The high potential, resistance and impedance tests are made 
 in the manner specified for constant potential transformers. 
 
 Core loss should be measured at normal primary voltage 
 and at normal primary current, the secondary being open- 
 circuited in each case. The normal voltage is calculated by 
 dividing the rated kv-a. by the rated current. 
 
 The open-circuit voltage test is made by reading the voltage 
 across the open-circuited secondary with normal current passing 
 through the primary. 
 
 Regulation test is made by putting various loads on the 
 secondary with rated current passing through the primary and 
 measuring the secondary voltage corresponding to each load. 
 Readings should be taken at 34, H, Z A an d full voltage. Incan- 
 descent lamps should be used for the load. 
 
 The heat run is made with incandescent lamp load. 
 
 The induced voltage test is made by applying three times 
 normal voltage to the primary with the secondary open-cir- 
 cuited. 
 
 420 
 
CHAPTER 25 
 
 CALCULATION SHEETS 
 
 The following calculations, which have been made with the 
 slide rule, are intended to illustrate the method used in connec- 
 tion with testing work. Every effort is made to avoid error 
 but this Company does not guarantee their correctness nor does 
 it hold itself responsible for any errors or omissions in these 
 sheets. 
 
 SATURATION ON A 500 KW., 600 V., 360 R.P.M., 
 60 CYCLE, 3-PHASE GENERATOR 
 
 Volts 
 
 Volts 
 
 Amp. 
 
 Speed 
 
 Arm. 
 
 Field 
 
 Field 
 
 R.P.M. 
 
 192 
 
 25 
 
 18.0 ' 
 
 360 
 
 228 
 
 29 
 
 21.0 
 
 360 
 
 253 
 
 32 
 
 23.2 
 
 360 
 
 304 
 
 38 
 
 29.0 
 
 360 
 
 416 
 
 52 
 
 40.0 
 
 360 
 
 495 
 
 62 
 
 48.9 
 
 360 
 
 542 
 
 70 
 
 55.1 
 
 360 
 
 579 
 
 75 
 
 59.8 
 
 360 
 
 597 597 \ 
 597 J 
 614 
 
 79 
 
 62.0 
 
 360 
 
 83 
 
 65.4 
 
 360 
 
 707 
 
 110 
 
 87.5 
 
 360 
 
 785 
 
 146 
 
 117.0 
 
 360 
 
 755 
 
 130 
 
 102.0 
 
 360 
 
 555 
 
 74 
 
 55.5 
 
 360 
 
 453 
 
 5/ 
 
 43.6 
 
 360 
 
 287 
 
 35 
 
 26.3 
 
 360 
 
 178 
 
 26 
 
 16.1 
 
 360 
 
 CALCULATION SHEET NO. 1 
 
 421 
 
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 CALCULATION SHEET NO. 2 
 
 422 
 
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 CALCULATION SHEET NO. 3 
 
 423 
 
CALCULATIONS OF DECELERATION CORE LOSS ON A 
 
 3000 KW., 2300 V., 10-POLE, 60 CYCLE, 3-PHASE 
 
 GENERATOR 
 
 Moment of inertia is equal to 705,000 = Wr 2 . 
 
 The normal speed of the turbine being 720, Si is taken equal 
 to 730 and S 2 equal to 710. 
 
 Consider curve taken with no field on the machine. (See 
 Fig. 59.) 
 
 r 3 or time corresponding to Si =61.6 seconds. 
 
 T4 or time corresponding to 52=82.4 seconds. 
 
 Ta-T z =82.4 -61.6 =20.8. 
 
 (Si -St) 
 
 Kw. loss 
 
 2308 Tr; , 9 W-S 2 *) 
 
 10 10 
 2308 
 
 X 
 
 T A -T 3 
 705000 X 28800 
 
 2308 (Si+S.) 
 10 10 Ta 
 
 4700 
 
 10 10 Ta-T 3 Ta-Tz 
 
 Substituting the value of Ta — Tz in the formula 
 4700 
 
 Kw. loss 
 
 = 226 = Friction and Windage 
 
 20.8 
 
 For the curve taken with 77.4 amperes field current 
 Ti-Ti =70.6 -52.1 =18.5 
 
 Kw. =-r5-^ = 254 = Core loss + Friction + Windage. 
 18.5 
 
 Curves taken with 103, 129 and 142 amperes field are calcu- 
 lated similarly, and together with that taken at 77.4 amperes 
 field include the constant friction loss and core loss. The two 
 losses can be separated. 
 
 Amp. 
 Field 
 Held 
 
 Tz 
 or 
 Ti 
 
 r 4 
 
 or 
 
 T, - Tz 
 
 or 
 T 2 - Ti 
 
 Si 
 
 5 2 Si 2 -S 2 2 
 
 Fric- 
 tion 
 
 Core 
 Loss 
 and 
 Fric- 
 tion 
 
 Core 
 Loss 
 
 Volts 
 from 
 Satu- 
 ration 
 
 
 
 61.6 
 
 82.4 
 
 20.8 
 
 730 
 
 710 28800 
 
 226 
 
 226 
 
 
 
 
 
 77.4 
 
 52.1 
 
 70.6 
 
 18.5 
 
 730 
 
 710 28800 
 
 226 
 
 254 
 
 28 
 
 1570 
 
 103 
 
 48.2 
 
 66.1 
 
 17.9 1 730 
 
 710 28800 
 
 226 
 
 266 
 
 40 
 
 1990 
 
 129 
 
 44.4 
 
 60.5 
 
 16.1 
 
 730 
 
 710 28800 
 
 226 
 
 292 
 
 66 
 
 2350 
 
 142 
 
 42.8 
 
 58.2 
 
 15.4 
 
 730 
 
 710 28800 
 
 226 
 
 306 
 
 80 
 
 2500 
 
 From the saturation curve the volts armature corresponding 
 to the various field currents used can be obtained and a core 
 loss curve plotted between volts armature as abscissae and core 
 loss as ordinates. 
 
 Si and S 2 are usually assumed at 2 per cent above and 2 
 per cent below normal speed. 
 
 CALCULATION SHEET NO. 4 
 
 424 
 
FIELD COMPOUNDING ON A 150 KW., 250 V. 
 225 R.P.M., D-C. GENERATOR 
 
 6 BARS BRUSH SHIFT 
 
 6-POLE, 
 
 Volts 
 
 Amp. 
 
 Volts 
 
 Amp. 
 
 R.P.M. 
 
 Arm. 
 
 Arm. 
 
 Field 
 
 Field 
 
 250 
 
 
 
 226 
 
 10.8 
 
 225 
 
 250 
 
 150 
 
 240 
 
 11.65 
 
 225 
 
 250 
 
 300 
 
 270 
 
 12.90 
 
 225 
 
 250 
 
 450 
 
 300 
 
 14.3 
 
 225 
 
 250 
 
 600 
 
 334 
 
 15.9 
 
 225 
 
 250 
 
 750 
 
 370 
 
 17.6 
 
 225 
 
 CALCULATION SHEET NO. 5 
 
 PHASE CHARACTERISTICS ON A 300 KW., 600 V., 750 
 
 R.P.M. , 25 CYCLE 3-PHASE SYNCHRONOUS 
 
 CONVERTER 
 
 
 NO LOAD 
 
 
 
 FULL LOAD 500 AMPS. D-C. 
 
 Volts 
 
 Volts 
 
 Amp. 
 
 Amp. 
 
 Volts 
 
 Volts 
 
 Volts 
 
 Amp. 
 
 Amp. 
 
 Volts 
 
 D-C. 
 
 A-C. 
 
 A-C. 
 
 Field 
 
 Field 
 
 D-C. 
 
 A-C. 
 
 A-C. 
 
 Field 
 
 Field 
 
 600 
 
 378 
 
 315 
 
 0.75 
 
 91 
 
 600 
 
 384 
 
 601 
 
 1.05 
 
 125 
 
 600 
 
 377 
 
 255 
 
 1.25 
 
 150 
 
 600 
 
 383.5 
 
 570 1.25 
 
 150 
 
 600 
 
 376 
 
 210 
 
 1.50 
 
 180 
 
 600 
 
 381 
 
 543 
 
 1.50 
 
 180 
 
 600 
 
 375 
 
 156 
 
 1.75 
 
 210 
 
 600 
 
 380 
 
 520 
 
 2.00 
 
 240 
 
 600 
 
 374 
 
 120 
 
 2.00 
 
 240 
 
 600 
 
 379 
 
 512 
 
 2.25 
 
 270 
 
 600 
 
 373 
 
 85 
 
 2.20 
 
 265 
 
 600 
 
 378 
 
 507 
 
 2.50 
 
 300 
 
 600 
 
 373 
 
 65 
 
 2.30 
 
 275 
 
 600 
 
 378 
 
 505 
 
 2.65 
 
 320 
 
 600 
 
 372 
 
 41 
 
 2.40 
 
 290 
 
 600 
 
 378 
 
 510 2.75 
 
 330 
 
 600 
 
 371 
 
 23 
 
 2.50 
 
 300 
 
 600 
 
 376 
 
 525 3.00 
 
 360 
 
 600 
 
 370 
 
 14 
 
 2.55 
 
 305 
 
 600 
 
 375 
 
 547 3.50 
 
 420 
 
 600 
 
 370 
 
 17 
 
 2.60 
 
 315 
 
 600 
 
 374 
 
 585 4.00 
 
 485 
 
 600 
 
 369 
 
 21 
 
 2.65 
 
 320 
 
 600 
 
 373 
 
 627 4.50 
 
 540 
 
 600 
 
 369 
 
 35 
 
 2.75 
 
 332 
 
 600 
 
 370 
 
 685 5.00 
 
 600 
 
 600 
 
 369 
 
 75 
 
 3.00 
 
 360 
 
 
 
 
 
 
 600 
 
 368 
 
 116 
 
 3.25 
 
 395 
 
 
 
 
 
 
 600 
 
 367 
 
 170 
 
 3.50 
 
 420 
 
 
 
 
 
 
 600 
 
 366 
 
 205 
 
 3.75 
 
 450 
 
 
 
 
 
 
 CALCULATION SHEET NO. 6 
 
 425 
 
SYNCHRONOUS IMPEDANCE ON A 500 KW., 600 V., 
 20-POLE, 60 CYCLE, 3-PHASE GENERATOR 
 
 Amp. 
 
 Volts 
 
 Amp. 
 
 Speed 
 
 Arm. 
 
 Field 
 
 Field 
 
 R.P.M. 
 
 224 
 
 15.0 
 
 11.9 
 
 360 
 
 260 
 
 17.8 
 
 13.7 
 
 360 
 
 300 
 
 20.6 
 
 15.8 
 
 360 
 
 352 
 
 23.8 
 
 18.3 
 
 360 
 
 398 
 
 26.9 
 
 20.7 
 
 360 
 
 474 
 
 31.5 
 
 24.5 
 
 360 
 
 480 480 1 
 480 J 
 
 32.2 
 
 24.8 
 
 360 
 
 518 
 
 34.8 
 
 26.7 
 
 360 
 
 557 
 
 37.5 
 
 28.2 
 
 360 
 
 704 
 
 47.0 
 
 36.1 
 
 360 
 
 796 
 
 52.8 
 
 40.6 
 
 360 
 
 896 
 
 59.5 
 
 45.7 
 
 360 
 
 1000 
 
 66.5 
 
 51.1 
 
 360 
 
 CALCULATION SHEET NO. 7 
 
 426 
 

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 CALCULATION SHEET NO. 8 
 
 427 
 
SPEED, TRACTIVE EFFORT AND EFFICIENCY OF A 
 100 H.P. 600 V. RAILWAY MOTOR 
 
 INPUT 
 
 PR 
 
 % 
 
 Core 
 Loss 
 
 % 
 
 Gear + 
 
 Friction 
 
 % 
 
 Effici- 
 ency 
 
 % 
 
 Miles per 
 
 Hour on 
 
 33 In. 
 
 Wheels 
 
 Gear Ratio 
 
 3.35 
 
 
 Volts 
 
 Amp. 
 
 Tractive 
 Effort 
 
 600 
 600 
 600 
 600 
 600 
 600 
 600 
 600 
 600 
 600 
 
 40 
 60 
 80 
 100 
 120 
 140 
 160 
 200 
 240 
 280 
 
 1.7 
 2.5 
 
 3.3 
 4.2 
 5.0 
 5.9 
 6.7 
 8.4 
 10.0 
 11.7 
 
 5.3 
 4.1 
 3.4 
 3.0 
 2.6 
 2.3 
 2.1 
 1.8 
 1.5 
 1.3 
 
 30.0 
 14.0 
 9.0 
 7.5 
 6.5 
 5.7 
 5.0 
 5.0 
 5.0 
 5.0 
 
 63.0 
 
 79.4 
 84.3 
 85.3 
 85.9 
 86.1 
 86.2 
 84.8 
 83.5 
 82.0 
 
 45.0 
 35.4 
 29.6 
 26.2 
 23.8 
 22.5 
 21.3 
 19.5 
 18.1 
 17.2 
 
 170 
 
 407 
 
 687 
 
 984 
 
 1310 
 
 1615 
 
 1960 
 
 2630 
 
 3350 
 
 4040 
 
 Resistances at . . . 75° cent. 
 
 Armature . . 0.107 ohm 
 
 Exciting Field 0.076 " 
 
 Commutating Field 0.050 " 
 
 Brush Contact 0.017 " 
 
 Total 0.250 " 
 
 CALCULATION SHEET NO. 9 
 
 428 
 
PHASE CHARACTERISTICS OF A 187 KV-A., 2300 V., 
 
 10-POLE, 720 R.P.M., 3-PHASE SYNCHRONOUS 
 
 MOTOR 
 
 Volt Arm. 
 
 Amp. Arm. 
 
 Volts Field 
 
 Amp. Field 
 
 Cycles 
 
 
 NO LOAD ] 
 
 PHASE CHARACTERISTIC 
 
 
 2300 
 
 63 
 
 15 
 
 5.5 
 
 60 
 
 2300 
 
 50.76 
 
 24 
 
 10.2 
 
 60 
 
 2300 
 
 33.12 
 
 34.5 
 
 15.6 
 
 60 
 
 2300 
 
 18.6 
 
 44 
 
 19.5 
 
 60 
 
 2300 
 
 8.44 
 
 54 
 
 23 
 
 60 
 
 2300 
 
 1.4-4 
 
 58 
 
 26 
 
 60 
 
 2300 
 
 9.72 
 
 66 
 
 30 
 
 60 
 
 2300 
 
 19.56 
 
 73 
 
 33 
 
 60 
 
 2300 
 
 25.8 
 
 82 
 
 36.5 
 
 60 
 
 2300 
 
 32.52 
 
 85 
 
 39 
 
 60 
 
 2300 
 
 45 
 
 99 
 
 43.5 
 
 60 
 
 
 FULL LOAD 
 
 PHASE CHARACTERISTIC 
 
 
 2300 
 
 74.4 
 
 26.5 
 
 11.5 
 
 60 
 
 2300 
 
 69 
 
 31 
 
 13.5 
 
 60 
 
 2300 
 
 57.6 
 
 37 
 
 16.5 
 
 60 
 
 2300 
 
 48.3 
 
 46 
 
 21.5 
 
 60 
 
 2300 
 
 46.5 
 
 60 
 
 28 
 
 60 
 
 2300 
 
 46.5 
 
 62 
 
 28.5 
 
 60 
 
 2300 
 
 49.5 
 
 71 
 
 33 
 
 60 
 
 2300 
 
 52.8 
 
 79 
 
 37 
 
 60 
 
 2300 
 
 58.5 
 
 89 
 
 41.5 
 
 60 
 
 2300 
 
 66.6 
 
 100 
 
 46 
 
 60 
 
 2300 
 
 71.4 
 
 106 
 
 48.5 
 
 60 
 
 125 PER CENT LOAD PHASE CHARACTERISTIC 
 
 2300 
 
 85.8 
 
 30.5 
 
 13.2 
 
 60 
 
 2300 
 
 68.4 
 
 42.5 
 
 19.3 
 
 60 
 
 2300 
 
 60 
 
 53.5 
 
 24.8 
 
 60 
 
 2300 
 
 58.5 
 
 62 
 
 28.7 
 
 60 
 
 2300 
 
 57.9 
 
 63.5 
 
 29.5 
 
 60 
 
 2300 
 
 59.4 
 
 71 
 
 32.8 
 
 60 
 
 3300 
 
 61.8 
 
 79 
 
 36.4 
 
 60 
 
 2300 
 
 65.55 
 
 87 
 
 40.3 
 
 60 
 
 2300 
 
 71.4 
 
 100 
 
 45.6 
 
 60 
 
 CALCULATION SHEET NO. 10 
 429 
 
CALCULATING EFFICIENCY 
 
 Standard efficiency test is made by the method of losses and 
 calculations, therefore should be made according to the follow- 
 ing : 
 
 D-c. Generator 
 
 Consider a compound wound commutating pole generator 
 and 
 
 Let Vl = Volts line. 
 
 Il = Amperes line =78+^9 = /io + /ii. 
 I& = Amperes shunt field. 
 1 4 = Amperes armature = Il — Ig- 
 
 Is = Amperes series field = lLrs — , 9 P a • 
 
 Jg = Amperes series field shunt = I l — Is- 
 
 TO 
 
 Iio= Amperes commutating field = Ilz 
 
 '(Rn+Rio) 
 
 Jn = Amperes commutating field shunt = Il—Iiq- 
 R 5 = Brush contact resistance. 
 R& =Hot resistance of shunt field. 
 
 R* = 
 
 Rs = 
 R<> = 
 
 Rio — 
 
 Rn = 
 
 armature, 
 series field, 
 series field shunt. 
 " commutating field. 
 
 " " shunt. 
 
 Then the total IR drop=/ 4 Rt+I 4 R 5 +I s Rs+Iio Rio- 
 Let Wi = Core loss watts taken from the core loss curve 
 corresponding to Vl~\-IR for each load. 
 W 2 = Watts brush friction from core loss test. 
 If the value taken from test appears inconsistent, calculate 
 W2 by the formula: 
 
 W '= 33000 Where . 
 
 F = Circumference of commutator in feet 
 
 N =R.p.m. 
 
 B = Number of brushes 
 
 L =Lb. pressure per brush 
 
 ix = Coefficient of brush friction for the 
 particular type of brush used. 
 In the case of engine- driven machines or those which are 
 furnished without base, shaft or bearings, the bearing friction 
 is omitted from the total losses, and is charged against the 
 prime mover. 
 
 In nearly every case it is preferable to use the calculated 
 brush friction instead of that obtained from test. During a 
 short test, the commutator and brush contact surface cannot 
 get into as good condition as is obtained after a long period of 
 commercial operation. Consequently, the brush friction test 
 does not represent the conditions that will exist after the machine 
 has been in operation for some time. The coefficient of friction 
 determines the value of brush friction, which in turn is deter- 
 
 430 
 

 o 
 
 
 
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 H- Tjl H 
 
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 Ceo j o JoHU 
 
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 C3 03 g 
 
 s so 
 
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 JH <D 
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 CALCULATION SHEET NO. 11 
 431 
 
mined by the condition of the commutator and brush contact 
 surface. This coefficient varies considerably at first and only 
 reaches a constant value after a considerable - period of opera- 
 tion. The coefficient used in the above formula for the calcula- 
 tion of brush friction has been obtained by the Company by 
 means of exhaustive tests on brushes of different types with 
 various pressures and commutators. These tests extended 
 over a long period to obtain constant and satisfactory conditions 
 for both brush and commutator surface. The resulting values 
 of brush friction can, therefore, be relied on to give accurate 
 and final results. 
 
 Wz = Bearing friction from core loss test. 
 
 Wb = Watts output =IlX Vl. 
 The brush contact resistance, R- , is that taken from a curve, 
 made for different types of brushes, corresponding to the brush 
 current density per square inch at any given load. 
 
 Brush current density per square inch =t— — -^i : 
 
 Y2 total brush area 
 
 One-half the total brush area = where 
 
 I = Length of brush parallel to the shaft 
 iv = Width of brush 
 5 = Number of studs 
 t = Number of brushes per stud. 
 For reasons similar to those just given, the Company has 
 made extensive tests to determine the contact resistance of 
 different types of brushes, from which curves have been plotted 
 with brush current densities as abscissae and either brush con- 
 tact resistance per square inch or IR drop in brush contact 
 as ordinates. In order to measure the contact resistance directly, 
 the commutator would have to be short-circuited and the 
 voltage drop measured from the commutator to the surface of 
 each brush. This would be a long operation entailing consider- 
 able expense. The results also could not be reliable owing 
 to the newness of commutator and brushes. It is, therefore, 
 preferable to use the brush contact resistance obtained from 
 the curves mentioned. 
 
 If Wz= bearing friction from core loss test, then total loss 
 in watts = 2 W = W x + W 2 + W 3 + h 2 R 4 + h 2 R 5 + IJR 6 + 
 (/e V L - h 2 Re) +h*Rs + h*R 9 + I 1 o 2 Rio+Iu 2 Rn- 
 
 The quantity IsVl-I<?R*=I 2 R loss in the shunt field 
 rheostats. 
 
 The watts input W a will then be 
 
 W a =Wb + '2W, where Wb = watts output =IlVl 
 
 Theefficiencv£=-^ 
 
 In case a core loss test is not made, the running light is 
 substituted in the formula for the quantity ( Wi + Wi + Wz). 
 If the segregation of the losses in the series and commutating 
 pole fields and their respective German silver shunts is not 
 
 432 
 
required the resistances R$ and R$ may be combined to equal 
 R S F, likewise Rio and R n to equal R C F- 
 
 The total losses then will be 
 
 2 W = Running light + IJR* + 7 4 2 i? 5 + h Vl + Il 2 RsF 
 +Il}RcF. 
 
 To calculate resistances hot when calculating efficiencies, 
 the temperature should be obtained from the formula: 
 
 T = (KX rise by thermometer) +25° cent. 
 K is the ratio between the rise in temperature by thermometer 
 and that determined by resistance measurement. Resistance 
 measurements of temperature have been determined by actual 
 tests on a large number of different armatures and fields. For 
 all armatures, or field spools of revolving field machines K = 1.25. 
 For stationary ventilated field spools IT = 1.7. See Calculation 
 Sheet 11 and Fig. 70 for form used in calculating and plotting 
 efficiency. 
 
 D-c. Motor 
 
 The efficiency of a direct current motor may be calculated 
 as follows: 
 
 Using the same nomenclature as above 
 
 U = lL-h 
 
 Watts Input W = IlVl 
 
 W\ = Core loss taken from the core loss curve corresponding 
 to Vl-IR 
 
 ThenZW=W l + W 2 + W z +IJR 4 + ISR b +I 6 2 R G + 
 (hV L -h 2 R6)+Is 2 Rs+h 2 R*+Iio 2 Rio+Iu 2 Rn 
 
 as before 
 
 Watts output Wb = Tr a — 2 W and 
 
 f- ] 1r 
 
 Wo 
 Since motors are always rated according to horse-power 
 
 output 
 
 «-& 
 
 If, as in the case of d-c. generators, only a running light 
 is taken and it is desired to combine the resistances of the 
 series and commutating pole fields with their respective shunts 
 and to combine the losses in the shunt field and rheostats, 
 then 
 
 2 W = Running light +h*R i +I?R b +hV L +lL 2 RsF+Il 2 RcF 
 
 In the case of shunt motors 
 
 2 W = Running light +I A 2 R A +Ia 2 R 3 + / 6 Vl 
 
 The remarks made above in reference to the calculation 
 of brush friction and brush contact resistance, also in reference 
 to the calculation of hot resistances, as well as to all other effi- 
 ciency calculations, apply here. (See Calculation Sheet 12.) 
 
 It will be seen from Fig. 75 that motor efficiencies are plotted 
 against amperes line as abscissae and per cent efficiency and 
 h.p. output as ordinates. The horse-power curve should be 
 produced to intersect the abscissae line at running light amperes 
 line. 
 
 433 
 
CO 
 
 "*. *°. 
 
 O lO Oq oq' iO iO 
 
 O tH rji 1-1 00 
 
 OS 
 
 00 H 
 IO 00 CO 00 rH O 
 
 ooooco>ooocqido6o»od 
 io co co oq tjh i-h >-h i> co oo os oq 
 co -tf *o oo (N oq to 
 
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 CO 
 
 O CO Oq CO Oq 00 
 
 OH HH00 
 IOH -H r^H 
 
 CO 
 CO 
 
 qi> oq oqq 
 
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 ococoioi>'-'oq»o»ocooocq 
 r^i ^h to i-h i-h oq OS 
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 w 
 
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 Amperes Line 
 Amperes Field 
 Amperes Arm. 
 IR . 
 
 P^ 
 
 l — i 
 
 1 
 
 bpeed 
 Core Loss 
 Brush Friction 
 Bearing Friction 
 PR Armature 
 PR Brush 
 IE Field . 
 Total Losses . 
 Kw. Input 
 Kw. Output . 
 H.P. Output . 
 % Efficiency . 
 Brush Density 
 Brush Contact Res 
 
 3 
 
 Si 
 
 pq 
 
 u 
 
 CD 
 
 a 
 
 CD 
 
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 CALCULATION SHEET NO. 12 
 
 434 
 
Synchronous Converter 
 
 The method employed to calculate the efficiency of a standard 
 synchronous converter is similar to that used for d-c. generators 
 except for the additional PR and friction losses of the a-c. 
 brushes. Because of the neutralizing action of the motor and 
 generator current it should be noted that only a certain per- 
 centage of the PR loss of the armature must be used for cal- 
 culating the efficiency of the machine. This percentage varies 
 for different machines as follows: 
 
 Single-phase 147% 
 
 Two-phase ....... 39% - 
 
 Three-phase 59% 
 
 Six-phase 27% 
 
 $* 
 
 P 
 
 
 
 
 
 
 
 
 s : 
 
 
 
 ^ 
 
 
 
 >^ - 
 
 
 
 %^, 
 
 
 
 
 
 
 
 
 
 
 
 "~~"~~ ■- ~- ^ ■-■ — =. 
 
 
 
 — — 
 
 MOO 2000 3O0O 4000 
 
 FeeC per Aff/7v£e 
 
 sooo 
 
 Fig. 190 
 ►COEFFICIENT OF FRICTION OF A-C. BRUSHES 
 
 The calculation of the a-c. brush contact resistance requires 
 a measurement of the alternating current flowing in the arma- 
 ture. This also varies in different types of machines. The 
 following are the constants by which the direct current should 
 be multiplied to obtain the alternating current. 
 
 For Single-phase 1-41 
 
 Two-phase ....... 0.707 
 
 Three-phase 0.943 
 
 Six-phase 0.472 
 
 As with the d-c. brush contact resistance, a curve must be 
 referred to of the a-c. contact resistance. This should be used 
 and no direct measurement of resistance attempted. In every 
 case the contact resistance should be calculated per ring, the 
 total loss being obtained by multiplying by the number of 
 rings. 
 
 Brush contact area per ring = width of brush in inches X arc 
 of contact in inches X the number of brushes. 
 
 , , , , . Alternating current 
 
 The brush density per ring == r- — ^ Q „ - nrr 
 
 * fe Brush contact area per ring 
 
 * Upper curve taken with copper collector rings. Lower curve taken with 
 gun metal collector rings. 
 
 435 
 
CO CO 
 
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 600 
 
 
 
 2.65 
 2.65 
 
 4760 
 1134 
 2654 
 
 CO 
 
 oooo rHos do 
 
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 OS co oq CO 
 o 
 
 
 % Load . 
 Volts Line . 
 Amps. Line 
 Amps. Shunt Field 
 Amps. Arm. D-C. 
 Amps. Arm. A-C. 
 Core Loss . 
 Brush Friction D-C. 
 Bearing Friction 
 PR Armature 
 
 (.59 X D-C. PR) 
 PR Brushes D-C. 
 PR Shunt Field 
 PR Rheostat . 
 PR A-C. Brushes 
 PR A-C. Brush Fric. 
 Total Losses 
 Kw. Output 
 Kw. Input 
 % Efficiency 
 
 Brush Density [ ^_"£ 
 
 Brush Contact f A-C 
 Resis. { D-C 
 
 00 
 
 
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 3 
 
 
 
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 m 
 
 
 
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 9£ 
 
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 11 
 
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 CALCULATION SHEET NO. 13 
 436 
 
The resistance obtained from the curve, corresponding to 
 this value divided by the brush area per ring is the contact 
 resistance per ring. 
 
 The a-c. brush friction should be calculated in the same 
 manner as used for d-c. measurements, the coefficient of friction 
 being taken from a curve. (See Fig. 190.) Calculation Sheet 13 
 and Fig. 95 show the form used in calculating and plotting the 
 efficiency of a synchronous converter. 
 
 A-c. Generator 
 
 For a-c. generators the method is as follows: 
 Let Vl = Volts line 
 
 Wb = Output = V3 VlIl for three-phase and 2 VlIl for 
 
 two-phase. 
 Il = Amperes line. 
 Ii = Amperes field. 
 
 Rx =Hot resistance of armature between lines. 
 R-2 = Hot resistance of field. 
 Wi= open-circuit core loss corresponding to Vl+IR on 
 
 the core loss curve 
 W 2 = short-circuit core loss corresponding to II on the 
 
 short-circuit loss curve 
 Ws = friction and windage obtained from core loss test 
 Ii is calculated for each load, as when calculating for 
 
 regulation (See Chapter 9, page 182.) 
 
 \/S 
 IR is the drop in the armature = - — Il Ri for three- 
 phase machines and Ll Ri for two-phase. 
 ?W=Wi+i W-2 + Ws+i PL Ri+Ir R-2 for three-phase 
 machines 
 = Wi+% W 2 + W z +2lL 2 Ri+h' 1 R2 for two-phase ma- 
 chines 
 Watts input = W a = Wb + 2 W 
 
 Efficiency =777- 
 
 Wz need not be considered if the machine is furnished 
 without base, shaft or bearings. 
 The above method of calculation is used when the machine 
 is to operate at unity power-factor. 
 
 If it is desired to calculate the efficiency at any other power- 
 factor the following calculations must be made: 
 
 /L= K L XV5Vr c P-F . and W > = Vj X V LXlLX7o P-F. for 
 
 three-phase machines 
 K w 
 
 IL= VlX2XV P-F and W b = 2V L XlLX% P-F. for two- 
 phase machines 
 
 7i should be calculated for various power-factors as given 
 under regulation. 
 
 437 
 
o 
 
 2 ° 
 
 M 
 
 IOONNOOOOOOOOOIOCO 
 NOHiOiOiOOOOOOO»ONO> 
 
 HomiN oo»ohooo^(n^ 
 
 i-i i-H N(M 1-1 OS lO iO CO CO 
 
 i-i HTf COH(M(M 
 
 i-i CM 
 
 OON»0 00 00OOOOOOOOO 
 OOCO^^h-^OOOOOOOi-iOi 
 HON<M OHCOCOOONOIM 
 
 i-l HTf MHNO 
 
 rH cm 
 
 iooco'iococoooooooooo»o 
 
 NOffiCOCOCOOOOOOOOiO^O 
 O i-i CM OCO>OOCOONNCD 
 rH r-i CO CM CO lO I> CO CO 
 
 ,_, ,_, ^ ^ rH CM OS 
 
 OOi-iOO^^OOOOOOOO)CO 
 
 >OOo:(MN(MOO(MOO(M00005 
 
 OH(M O i-i CM CO CO O CM lO CO 
 
 i-H rH CO iO LO iO OS CM CM 
 
 r-l rH ^ rH CM 00 
 
 iO 
 i-O O lO Th CM CM o 
 
 CM O CO CM rH i-H O 
 O CM O O 
 
 rH rH CO 
 
 rH HrJ- 
 
 CO 
 
 ooooo^i> 
 
 CO O O CO *0 CO 00 
 CO O O CO CM HH 
 
 HIQIO^HH 
 rH CM 00 
 
 oooo o o 
 
 O CM OO 
 
 O CM OO 
 
 rH rH CO 
 
 rH rH ^ 
 
 IO 
 
 OOOOOCM O 
 O O O 00 
 
 lOOlO rH 
 
 HH iO CM 
 
 rH CM 00 
 
 ■0-U 
 
 <D in <L> 
 
 ^! . . . « 4J >* 
 
 O a; t* o 
 
 W rH rj g 
 i» << B > O rH^H rnfeHMM^ 
 
 CALCULATION SHEET NO. 14 
 
 438 
 
 Ph". 
 
 o 
 
 M 
 
 w 
 
 I- 
 
 CM C 
 
 f§ 
 
 ^ o 
 °g 
 
 ,— ; 
 
 IO ° 
 
 J! ° 
 
 0?o 
 r^ cm 
 
 CM t/: 
 
 t° 
 
 <V LO 
 C OS 
 
 -1 l> 
 
 ►H CM 
 
 <Ph 
 
 #r* 
 
The change in the line current will affect: 
 hi W\, W 2 , and the PR of the armature. See Fig. 87 and 
 Calculation Sheet 14. 
 
 Synchronous Motors 
 
 Using the same nomenclature as for a-c. generators the 
 following method is used for synchronous motors: 
 
 Ix is either taken from the phase characteristic or is calculated 
 W a = watts input = V3 VlIl + I\ 2 Ri for three-phase or 
 
 2 VlIl +I\ 2 Ro for two-phase. 
 Wb = watts output = W a ~ 2 W 
 
 Efficiency =ttt 
 W a 
 
 W\ = open-circuit core loss corresponding to Vl~ IR on the 
 core loss curve. 
 
 Wb 
 
 Horse-power output =^-- 
 /4o 
 
 See Calculation Sheet 15 and Fig. 90. 
 
 Induction Motors 
 
 The calculation of the efficiency of induction motors is made 
 from the results of the separate special tests taken as given in 
 Chapter 12, according to the following method: 
 
 CALCULATING THE CHARACTERISTICS OF AN 
 INDUCTION MOTOR 
 
 In calculating the characteristics of an induction motor 
 the tabulation given on Calculation Sheet 20 is followed through. 
 The slip at maximum load is first calculated and then values 
 of slip below that amount are assumed so as to give several 
 approximately equally spaced points on the curve and the 
 horse power outputs corresponding to these values of slip are 
 found by following the tabulated form. Curves are then 
 plotted with horse power as abscissae and slip, torque, efficiency, 
 etc., as ordinates. 
 
 439 
 
w 
 o 
 
 Ph 
 
 I 
 
 -co 
 
 rig 
 
 o O 
 
 go 
 
 w 
 
 GO 
 CO 
 
 o 
 p 
 
 o 
 
 & 
 w 
 
 dosoc'ioioo 
 
 LO O LO CO O OS o 
 
 r-t CM CM Oi CO 
 
 CO CM CO 
 
 b- CO rH 
 
 OOO(M(McD0ioC0 
 
 (OOHN^oiOCOOJ 
 
 OCDCONHHH 
 
 (M ^ 
 
 looq 
 
 iCONMNOOO 
 
 IMO^CONIMO 
 
 i-H <M i-i O rH 
 
 CO CO CO 
 
 00 00 CO 
 COOOCMLOoicioOCD 
 NONNHOO^OOi 
 
 ■^ LO CO O i— i i— • i— i 
 
 1- T* 
 
 b- 
 
 oooo oioocq o 
 
 O O CO iO CO CO o 
 
 H(M 1-1 O tO 
 
 CO CO CO 
 
 LO 
 
 qoi th 
 
 OOONNHicnd 
 
 rHTHLOb-b-b-C0<MO5 
 
 WOONH00 00H 
 
 Oi LO CO ^ rH 
 
 CO 
 
 lO i-H 
 
 lo o 06 io ro n o 
 
 NO(M>00©0 
 CM i-H O CO 
 CO CO CO 
 
 CO 00 LO 
 O O O (M CM rH rH b- LO 
 
 05OON(D»0(MC0 0i 
 
 rHrHCOCMrHCOCCOO 
 LO rH CO O 
 CM 
 
 50 
 
 13200 
 
 19 
 
 51 
 
 69 
 
 13131 
 
 13700 
 
 00 CO 
 COCO r-J 
 
 MOON^CDOO^' 
 OCDOONNWHiOOJ 
 1-|(MCOCMO^^LO 
 CM CO CO CD 
 CM 
 
 LO CO LO 
 LO O OJ O TjH LO O 
 
 (MO LO CO CO O 
 (M hoo 
 
 CO CO CO 
 
 CO <M 
 
 co co c^j 
 
 b-LOOCMrHOcOCOO 
 
 Tfcocot^i-icMaicDoo 
 
 LO CO CM CO CM rH CM 
 
 CO CD rH 
 CM 
 
 
 13200 
 
 50.1 
 
 oo 
 oo 
 
 <M CT> 
 
 CO CO 
 
 CM 
 
 t> 
 
 O CM <M CO O O O 
 iOb- CM CM 
 LO CM b- 
 CO CO CO 
 CM 
 
 
 % Load . 
 Volts Line . 
 Amps. Line 
 Amps. Fid. 
 
 (V-IR) . 
 Core Loss . 
 1/3 Short Cir. 
 
 Core Loss 
 PR Arm. . 
 PR Fid. . 
 Friction 
 Total Losses 
 Kw. Input 
 Kw. Output 
 H.P. Output 
 % Efficiency 
 
 CI) 
 
 
 o 
 
 
 a 
 
 
 b- 
 
 
 ~H 
 
 -P 
 
 +J 
 
 c 
 
 O 
 
 0) 
 
 w 
 
 a 
 
 
 
 
 CO 
 
 b 
 
 rH 
 
 A 
 
 +j 
 
 n 
 
 o 
 
 00 
 
 ffi 
 
 T— 1 
 
 CO 
 
 ^ 
 
 £ 
 
 
 ^ 
 
 -M 
 
 O 
 
 o 
 
 CM 
 
 o 
 
 LO 
 
 rH 
 
 CM 
 
 -P 
 
 CO 
 
 c 
 
 H 
 
 cu 
 
 ^a 
 
 
 o 
 
 LO 
 
 co 
 
 CM 
 
 00 
 
 m 
 
 co 
 
 B 
 
 ^ 
 
 rC 
 
 cu 
 
 o 
 
 J 
 
 rH 
 
 CO 
 
 
 
 
 i— i 
 
 s 
 
 tS 
 
 <fe 
 
 r/i 
 
 xr 
 
 <U 
 
 <v 
 
 Ph'Ph' 
 
 CALCULATION SHEET NO. 
 
 440 
 
 15 
 
EXCITATION ON 100 H.P., 440 V., 6-POLE, 500 R.P.M., 
 3-PHASE INDUCTION MOTOR 
 
 Volts 
 
 Amperes 
 
 Watts No. 1 
 
 Watts No. 2 
 
 + 
 
 Total Watts 
 
 544 
 
 57 
 
 13900 
 
 18000 
 
 4100 
 
 497 
 
 46.5 
 
 9550 
 
 13180 
 
 3630 
 
 467 
 
 41.0 
 
 7700 
 
 11000 
 
 3300 
 
 437 
 
 36.5 
 
 6310 
 
 9350 
 
 3040 
 
 398 
 
 31.8 
 
 4800 
 
 7490 
 
 2690 
 
 348 
 
 27 
 
 3300 
 
 5640 
 
 2340 
 
 299 
 
 22.5 
 
 2310 
 
 4300 
 
 1990 
 
 248 
 
 18.4 
 
 1440 
 
 3130 
 
 1690 
 
 197 
 
 14.8 
 
 686 
 
 2110 
 
 1425 
 
 174 
 
 13.2 
 
 497 
 
 1840 
 
 1343 
 
 148 
 
 11.7 
 
 239 
 
 1440 
 
 1201 
 
 124 
 
 10.2 
 
 124 
 
 1240 
 
 1116 
 
 98.5 
 
 9.5 
 
 + 149 
 
 895 
 
 1044 
 
 81 
 
 9.3 
 
 239 
 
 745 
 
 984 
 
 61.4 
 
 9.5 
 
 273 
 
 696 
 
 969 
 
 SINGLE-PHASE 1-2 
 
 477 
 
 70 
 
 
 3900 
 
 
 437 
 
 60 
 
 
 3430 
 
 
 397 
 
 52.5 
 
 
 3060 
 
 
 
 SIN 
 
 GLE-PHASE 
 
 2-3 
 
 
 477 
 
 70 
 
 3950 
 
 
 
 437 
 
 60 
 
 3430 
 
 
 
 397 
 
 52.5 
 
 3060 
 
 
 CALCULATION SHEET NO. 16 
 
 441 
 
POSITION CURVE ON 100 H.P., 440 V., 6-POLE, 500 R.P.M., 
 3-PHASE, FORM M INDUCTION MOTOR 
 
 Position 
 
 Volts 
 
 Amp. 
 
 Amp. at Normal 
 Volts 
 
 1 
 
 63 
 
 118 
 
 824 
 
 2 
 
 63 
 
 124.5 
 
 870 
 
 3 
 
 63 
 
 134 
 
 935 
 
 4 
 
 63 
 
 121 
 
 845 
 
 5 
 
 63 
 
 116 
 
 810 
 
 6 
 
 63 
 
 130 
 
 907 
 
 7 
 
 63 
 
 129 
 
 900 
 
 8 
 
 63 
 
 119.5 
 
 835 
 
 9 
 
 63 
 
 124 
 
 866 
 
 CALCULATION SHEET NO. 17 
 
 SLIP CURVE ON 100 H.P., 440 V., 6-POLE, 500 R.P.M. 
 3-PHASE, FORM M INDUCTION MOTOR 
 
 Volts 
 
 Amp. 
 
 R.P.M. 
 
 Per Cent Slip 
 
 440 
 
 88 
 
 9 
 
 1.8 
 
 440 
 
 118 
 
 14 
 
 2.8 
 
 440 
 
 148 
 
 19 
 
 3.8 
 
 440 
 
 177 
 
 24 
 
 4.8 
 
 CALCULATION SHEET NO. 18 
 
 442 
 
IMPEDANCE TEST ON 100 H.P.,440 V., 6-POLE, 1200 R.P.M., 
 3-PHASE, FORM M INDUCTION MOTOR 
 
 Volts 
 
 Amperes 
 
 Watts. Xo. 1 
 
 + 
 
 Watts No. 2 
 
 Total Watts 
 
 6.7 
 
 14 
 
 90 
 
 
 
 90 
 
 16.6 
 
 36 
 
 425 
 
 25 
 
 400 
 
 21.3 
 
 45 
 
 749 
 
 74 
 
 675 
 
 28.8 
 
 60 
 
 1413 
 
 198 
 
 1215 
 
 34.7 
 
 72.3 
 
 1923 
 
 248 
 
 1675 
 
 38.2 
 
 79.6 
 
 2380 
 
 397 
 
 1983 
 
 44.2 
 
 92.5 
 
 3150 
 
 546 
 
 2604 
 
 49.6 
 
 104 
 
 3920 
 
 596 
 
 3324 
 
 56.5 
 
 118 
 
 5200 
 
 893 
 
 4307 
 
 63.7 
 
 132.5 
 
 6500 
 
 1115 
 
 5385 
 
 74.5 
 
 154 
 
 8740 
 
 1500 
 
 7240 
 
 85.6 
 
 177 
 
 11300 
 
 2010 
 
 9290 
 
 103.7 
 
 214 
 
 
 
 
 115.5 
 
 239 
 
 
 
 
 146 
 
 300 
 
 
 
 
 
 SINGLE-PHASE 
 
 1-2 
 
 
 75.7 
 66.3 
 56 
 
 134.5 
 
 119 
 
 101 
 
 3520 
 2765 
 2010 
 
 
 SINGLE-PHASE 2-3 
 
 / 5.7 
 
 135 
 
 3640 
 
 
 66.3 
 
 119 
 
 2820 
 
 
 
 56 
 
 101 
 
 2010 
 
 
 
 CALCULATION SHEET NO. 19 
 
 443 
 
CHARACTERISTICS OF A 100 H.P., 440 VOLT, 6-POLE, 500 
 R.P.M., 3-PHASE, FORM M, INDUCTION MOTOR 
 
 EXPLANATORY NOTES 
 
 b = Susceptance. 
 
 E = Rated terminal volts 
 
 £o = Volts per phase 
 
 e = Counter e.m.f. of rotor in terms of stator 
 
 eso = E — reactive component of e.m.f. 
 
 F = Friction watts from curve 
 
 F = Friction watts per phase 
 
 go = Conductance 
 
 I = Assumed full load amperes per line 
 
 I I = Calculated amperes per phase 
 
 Ih = Core loss component of exciting current 
 
 I m = Exciting current (running light) 
 
 P = Mechanical power of rotor in watts per phase 
 
 P-Fo = Output of rotor in watts per phase 
 
 R — Resistance of stator per phase 
 
 Ri = Resistance of rotor per phase 
 
 Ri = Resistance of rotor per phase in terms of stator 
 
 5 =Slip at normal voltage and current, taken from slip 
 
 curve 
 
 S\ = Assumed slip at various loads 
 
 T — Torque in synchronous watts 
 
 V = Impedance volts at normal amperes, from curve 
 
 W = Impedance watts at normal amperes, from curve 
 
 W\ = Core loss watts 
 
 X = Reactance of stator 
 
 Xi = Reactance of rotor in terms"of 'stator 
 
 FORMULAE 
 
 3-PHASE MOTORS 
 
 b 
 E 
 
 eso 
 E 
 
 V3 
 eso = Eo — ImX 
 
 Fo =— for motor; f — for motor-generator set 
 
 Ih 
 
 eso 
 Wx 
 3 Eo 
 Im = Running light amperes 
 
 I 2 R =7j- (res. between lines at 25 deg.) X(Im 2 ) 
 
 R =3^ (res. between lines at 65 deg.) 
 R _ 1.1 EoS 
 
 444 
 
TT'i = Excitation watts - (7 2 i? + F) 
 
 * = ^(vfc)' : - (i?+ ^ 
 
 _ 21.12 T 
 
 Torque = - 
 
 Syn. r.p.m. 
 
 H.P.= P 
 
 248.7 
 
 Exc. watts 
 
 P-F. (at zero load) = 7= 
 
 A/3 Elm 
 
 Slip at max. output = , 
 
 Ri+V(R+Ri) 2 + (X+X^ 
 
 2-PHASE MOTORS 
 
 £0 
 
 eso — E — ImX 
 
 eso 
 £0 =E 
 
 F (F \ 
 
 Fo =— for motor; ( — for motor-generator set 1 
 
 Ih 
 
 go = — 
 eso 
 
 Ih = 7r ~^r 
 2 Eo 
 
 Im = Running light amperes 
 
 PR =2(res. between lines at 25 deg.) X(im 2 ) 
 
 R =Res. between lines at 65 deg. 
 
 Rl = — -J— 
 
 R - W 7? 
 R* ~2P ~ R 
 
 Wi = Excitation watts - (PR + F) 
 
 * -i 
 
 X x =X 
 
 x -iJ(f) f -^+* 
 
 ~ 14.08 r 
 
 Torque =- 
 
 Syn. r.p.m. 
 
 373 
 
 ■r, -p, , , , n Exc. watts 
 
 P-F. (at zero load) = _ __ 
 
 I Elm 
 
 Ri 
 
 Slip at max. output 
 
 Rx+ViR + RiV + iX+Xiy- 
 445 
 
035 
 
 001225 
 
 00002046 
 
 004393 
 
 00441346 
 
 00232 
 
 00 
 
 to 
 oq 
 
 to 
 
 010435 
 536235 
 0001584 
 
 os 
 to 
 
 CO 
 
 o 
 
 to to to to 
 
 cq i-i ^h to os 
 
 NMNCOO 
 ■^ 00 00 CO Cq 
 
 HHNOm 
 
 0000CO t-h 
 CO OS CO CO CO to 
 CO t-h CO to Oi 1> 
 
 co cq cq ^ co o 
 tooooo o 
 
 i—i 
 
 028 
 
 000784 
 
 00001309 
 
 004393 
 
 00440609 
 
 001856 
 
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 cq 
 
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 431835 
 00010135 
 
 CO 
 
 cq 
 
 o 
 
 to to OS OS 
 cq oq ^ os co 
 J> O CO 00 to 
 
 ^ i> oo cq i-h 
 
 t-H t-H t-H o <M 
 
 00 
 b- b- 00 OS 
 
 rM r> cq os to co 
 co i-H cq co to o 
 tooooo 
 
 
 021 
 
 000441 
 
 000007362 
 
 004393 
 
 004400362 
 
 0013915 
 
 CO 
 
 CO 
 
 CO 
 
 010435 
 326735 
 000057 
 
 CO 
 OS 
 Cq 
 
 o 
 
 iO H lO N (M 
 
 <m cq i> co «* 
 
 i> o co to cq 
 Tti co o cq co 
 
 l— 1 T-H i— 1 O i— 1 
 
 OS t-H O H CO 
 
 co b- t-h cq to 
 ^ co o ^ cq co 
 co t-h cq co ■* o 
 coooooo 
 
 T— I 
 
 014 
 
 000196 
 
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 CO 
 
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 o 
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 14725 
 
 153011 
 
 04905 
 
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 07246 
 
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 OS OS OS 00 00 CO 
 
 co o h cq cq o 
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 n _ 
 
 o, N <N rt e^ «H 
 
 1 
 
 3 ►© 5 
 
 ^ -O 3 r© <S ~CS 
 II 
 
 3 i-C> 
 
 + <? 
 
 Us 1 ~ «* - M 
 
 ii 
 
 G* 
 
 CALCULATION SHEET NO. 20 
 
 446 
 

 
 
 
 
 tO 
 
 to 
 
 
 iOiO XX 
 
 
 
 
 tO 
 
 tO 
 
 to 
 
 
 OS l-H X T-H ^H 
 
 
 
 
 CO 
 
 1—1 
 
 CM 
 
 
 i> cm cc x xx 
 
 lO 
 
 iq 
 
 x* OS 
 
 OS 
 
 OS 
 
 X 
 
 HOHOomroo 
 o lOOiOO o o 
 
 q 
 
 CM d 
 
 ^ o 
 
 CM 
 
 t^ o ' d d d d 
 
 CO CM "^ O t^ X 
 HO) X CO to CM 
 
 
 
 X 
 
 H 
 
 f " r "^ '- h ' 
 
 
 
 X 
 
 O OS OS CM 
 CO CM CM CO 
 
 
 
 
 to to 
 
 
 
 
 CM 
 
 X 
 
 "* 
 
 
 (M Hffi OS OS 
 
 
 
 
 CD I> 
 
 r-( 
 
 T— 1 
 
 
 X X CO CD tO X CO 
 
 
 CO 
 
 CO OS 
 
 OS 
 
 OS 
 
 T— 1 
 
 xxxo Oi-h cm 
 -* tP O rt X ox 
 
 otjj o^ poo 
 
 q 
 
 CM CD 
 
 cod ' d>d>Sd> 
 
 HlO T}H O^ O 
 i-H i-H Th COtHCO 
 
 
 
 1> 
 
 OS 
 
 r ' \ '** '^ 
 
 
 
 OS 
 
 lO 
 
 tO tH ^ CD 
 CM CM CM CM 
 
 
 
 
 
 
 
 
 
 to 
 
 
 
 co X CM 
 
 
 
 
 OS 
 
 t> 
 
 CM 
 
 
 ■^ O OS I>1> 
 
 
 
 
 I> 
 
 1—1 
 
 X 
 
 tO 
 
 O l> O OS CM CM 
 
 
 CO 
 
 CO OS 
 
 OS 
 
 X 
 
 1> 
 
 Kmc?:ocN 
 q co o co q q q 
 
 ic 
 
 q 
 
 to d 
 cm : 
 
 as © 'dodo 
 
 X Tf TH O-HH OS 
 
 O CD CO CO OS 
 
 
 
 CO 
 
 1> 
 
 f " l" '^ '^ 
 
 
 
 o 
 
 CO 
 
 OS X X OS 
 
 
 
 
 i> x cm ba Oi 
 
 
 
 
 CO 
 
 CD 
 
 
 
 -t — x ea o 
 
 
 
 
 tO X 
 
 O 
 
 1— 1 
 
 -* 
 
 co x ^ co Tf Tt 
 
 
 Oa 
 
 -^ OS 
 
 q 
 
 X 
 
 X 
 
 CM I> CO Tf X O X 
 
 CM N C N C C C 
 O CM O CM O O O 
 
 OS 
 CM 
 
 q 
 
 CD d 
 
 do ' d>d><6<6 
 
 
 
 OS 
 
 C<1 ffr 
 
 co t> coc;n 
 
 X CO CO CO CO 
 
 
 
 ^ 
 
 \ ' \ "^ "^ 
 
 
 
 o 
 
 CM CM CM CO 
 
 »— 1 T— 1 T— 1 T— 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 w w 
 
 * -S ,. 
 ' t + 
 
 <S -C -C ►© N _ „^ „ 
 
 ^t <o <o <o G* <o C 
 
 Vi 
 
 + o 
 
 > 
 
 + 
 
 -6 ,-s £ 
 + co f- 
 
 1 
 3i 
 
 o 
 
 Po 
 
 (See note 
 (See note 
 
 II 
 
 
 
 1 
 
 II II II II 
 
 II 
 
 II 
 
 II II 
 
 s 
 
 
 « 
 
 
 
 ^ ^ £ 
 
 
 
 H.P. 
 
 orque 
 
 
 
 
 
 
 
 
 
 H 
 
 CALCULATION SHEET NO. 20 (Continued) 
 447 
 
SUMMARY OF SPECIAL TEST 
 
 EXCITATION RUNNING LIGHT 
 
 
 Volts 
 
 Amperes 
 
 Watts • 
 
 Polyphase 
 
 Single-phase 
 
 Friction watts 
 
 440 
 440 
 
 36.7 
 60.5 
 
 3026 
 
 3460 
 
 900 
 
 STATIONARY IMPEDANCE 
 
 Polyphase 
 Single-phase 
 
 118 
 102 
 
 4375 
 2050 
 
 Impedance amp. at rated volts =910. Max. =936. Min. = 
 810. Slip (S)=2.8 per cent at normal load of 440 volts, 118 
 amperes. 
 
 Resistance between lines at 25 deg. cent. =0.071 ohms; at 
 65 deg. cent. =0.082 ohms. 
 
 
 CALCULATION CONSTANTS 
 
 E n 
 
 = 254. 
 
 X = 0.12926 
 
 Ih = 2.601 
 
 R 
 
 = 0.041 
 
 Xi = 0.12926 
 
 I m = 36.7 
 
 JRi 
 
 = 0.06627 
 
 X x 2 = 0.0167 
 
 e S o =249.26 
 
 £i 2 
 
 = 0.004393 
 
 PR= 143.4 
 
 go = 0.010435 
 
 Rt 
 
 = 0.06377 
 
 Wx =1982.6 
 F =300 
 
 b = 0.14725 
 
 
 SUMMARY OF CHARACTERISTICS 
 
 Per cent load . 
 
 50 
 
 75 
 
 100 
 
 125 
 
 Horse power . 
 
 50 
 
 75 
 
 100 
 
 125 
 
 Amperes line . 
 
 67 
 
 93 
 
 120 
 
 143 
 
 Per cent efficiency 
 
 90.4 
 
 , 91.6 
 
 91.8 
 
 9.1.1 
 
 Per cent power-factor . 
 
 81 
 
 88.8 
 
 92 
 
 92.9 
 
 CALCULATION SHEET NO. 21 
 
 448 
 
o 
 ft 
 
 a* 
 
 ft O 
 
 Z 
 
 o 
 
 w 
 ta 
 <y 
 
 pa 
 o 
 
 H 
 
 o 
 
 I— ' 
 H 
 
 < 
 
 H 
 GO 
 
 O— i 
 
 •OOO'-tCOCO'^COOSQO 
 
 00 ^O t^ X *-< ^ LC CO CI 
 
 HrHHHH 
 
 h 
 
 LC LC >-C ic 
 
 t^ LO <N l> O- ^O 
 
 tHOOCOCO^^+CD^OO 
 
 En 
 
 + 
 
 lC LO LC LC lO 
 l> I> CI IO t> C3 
 
 rooii>"^cdt>-ooo»H 
 
 W ^ H; IC X! O N ^ LC 
 
 * 
 
 iC LO iC >C C lO lC lC lO 
 <N l> 1> I> CI ININNN 
 
 + 
 1 
 
 t- [^ I> I- l^ 
 
 CO Tf Tf >-C CD CO I> LO LO 
 
 + 
 + 
 
 li™*' LT*" LT"* Lf^ lO 
 
 r> i> t> r^ i> 
 
 cc d t- -1- 1- x x rn — '< 
 
 r~ io - 1 - lc co CO t^ cc lo 
 
 W+F W-F 
 
 LCiCiCiOiOLOiOiCiO 
 W N N N (M N (N (N N 
 -r -t CO CO I> l> CO CO LC 
 
 LC LC lC lC lC lC LT LC 'C 
 
 N (M N CI (M CI N N <N 
 
 CONNNNNCONO 
 
 t— It-It— 1 t— 1 t— It— It— It— 1 t— 1 
 
 Amp. 
 
 <M 
 
 >-h OS t^ -t -f LC CI I> CO 
 
 -frcrcrc-f-tCic3i'- J 
 
 1 1 I 1 1 1 1 1 1 
 
 -coaNCMr-ncco 
 
 <M CO CO »0 Ci OS CI CC 1^- 
 
 > 
 
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 C3 CI CI CI CI CI o X t^ 
 CI N CI CI CI CI C, - -i 
 
 Con- 
 troller 
 Pos. 
 
 — Cl CI :c -r -f co I - X 
 
 " 
 
 Lewi- 
 Arm. 
 
 2 ft. 
 2.292 ft. 
 
 CI c 
 
 55 o 
 
 CALCULATION SHEET NO. 
 
 449 
 
 22 
 
w 
 
 CO 
 
 < 
 H 
 
 Ph 
 
 i 
 
 § r 
 
 Ph' 
 
 « 
 
 v© 
 J> 
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 P=f 
 
 O 
 
 Ph 
 vo # 
 
 n o 
 
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 H 
 
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 w 
 
 H 
 
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 P 
 C 
 
 o 
 
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 CDIOC^O<NCOIO<M1>Ot-i,-h0 
 CDOOiCKMt^i-ieOt^O^iO^CO 
 
 COCO^^^h(MOOO»OOl>l?<ICO 
 <M <M <M <N <M <M <N 1-1 t-i t-h ,-h (M 
 
 h& 
 
 &+ 
 
 ooooooooooooo 
 
 r-i00--lCO'*00CCCO<OC<IC0O:i-l 
 
 OtSOJrtGHMiOiOiOONn 
 
 OOCOI>rHCO<Ot^O<MiOC01>00 
 
 r-lrH<M<N<N<NC0COCOCOC0 
 
 ooooooooooooo 
 
 00NOO(DONC4OO'tN 
 
 OOOOOOOOOOOOO 
 0>0--ICOOOOOOCOO<N<MCOCO 
 (MiOmai'-iCOiOOOO'-KM'OTt' 
 l>^C0«O00O5O(M-*t^000H> 
 >-<C<l<M<N<M<MCOCOCOCOCOCO<-l 
 
 5 I OOOOOOOOOOOOO 
 
 W ooioioowooiomoooo 
 
 „ NOiONNOOOOOONON 
 
 l^ 3 ! 00<M^t^O<N|iOCT><Ml>OCCOOO 
 
 > ! ^iiOiOiOOCOO<OI>t^t^OO^ 
 
 hooochnconhmohh 
 <m<m<m<ncococococococo^<n 
 
 
 
 qqqqqqqqqqqqq 
 
 CO CO CO CO CO CO CO CO CO 00 CO CO co 
 
 OOi--<^COtOI>OCOCOCOiOO 
 OOlOONOOOWNNNffiO 
 CDOO^-iCOCOOOSOSOOCD'-HOCO 
 NQOJHNMN(MHO:05N(N 
 
 t«A 
 
 w2 
 
 OOOOOOiOOOOOOO 
 OWON^OOHOiOiONOOO 
 O^C0r-lO001>i0'-H>O-#C0 
 NCKNIMMHHHH <M 
 
 OtOOOOMMOOiOiOHO 
 H^00O-*CHiOO)0)M 
 
 r-l ,H rH M <N <M <N CO 
 
 OOOOOOOOOOOOO 
 IOCOO©OHHIOO)N(M 
 ^I^OrHC3iO^HC0^O^H 
 
 ^(DOOOHHOOOOOtO 
 
 6S 
 
 ►J 9 
 
 iO <N_iq 
 
 Oco»OCDCq00<N06c0Ol05(MO 
 HClCO^^iOiOCOCtDN 
 
 * 'J. . 5 
 
 f- ^ Jj TJ 
 
 O/ -OS 
 
 O00^HO(MI><Mt-IC0C0t>>0O 
 
 <N<M(M<M<M<Mr-<.-lr-(.-l 
 
 CALCULATION SHEET NO. 
 
 450 
 
 23 
 
2 ° 
 
 in & 
 
 Time to 
 Syn. 
 
 Sec. 
 
 o 
 c/2 
 
 o 
 
 00. 
 
 O 
 
 CD 
 
 oo 
 
 o 
 
 CD 
 00 
 
 CO 
 
 o 
 1> 
 
 o 
 
 00 
 
 CO 
 
 CO 
 
 t-. 
 
 
 cm 
 
 CO 
 
 Tf 
 
 LO 
 
 
 
 
 
 
 
 1. Volts 
 r Spool 
 
 t^ 
 
 -^ 
 
 l> 
 
 00 
 
 
 CM o 
 
 t^ 00 
 
 "* 00 
 
 ^* 00 
 
 -tf 00 
 
 ,_, p. 
 
 
 
 
 
 
 
 CM 05 
 
 CO CM 
 
 I> 
 
 oo »o 
 
 (M CO 
 
 M 
 
 lO 00 
 
 co Oi 
 
 CM O 
 
 CO OS 
 
 cooq o 
 
 H CO 
 
 z 
 ►J 
 
 cn 
 
 «3 
 
 CO 
 
 CM 
 
 00 CO 
 
 OS «- ' 
 
 t> lO OS 
 
 co c a> 
 
 TJH O 
 
 CM OS 
 
 CO Ci 
 
 CM 
 lo OS 
 
 3 O O 
 
 X LO LO 
 
 -t CO CO 
 
 — i CM cm 
 
 O OOO LO O CM O 
 
 co cm x x co as o cm 
 
 lO COCOCO '-< LO CO CO 
 
 CM rH CM CM r-t CM —I CM 
 
 o o 
 
 CO io 
 
 -rf CO 
 
 -h CM 
 
 OOO 
 Tf CO CO 
 CO lo lO 
 ^h CM CM 
 
 O O OOO X o 
 
 O X CO CT> OJ O CM 
 
 CO CO CM to lO CO CO 
 
 i-i CM -h CM CM h CM 
 
 o o 
 
 "t iO 
 
 CO CO 
 
 iO o 
 
 lO CO 
 
 CM iO 
 
 ^ CM 
 
 iO O X 
 LO X -h 
 — CO CM 
 
 O OOO 
 
 C3 O CM CM 
 
 lO -t CO CO 
 
 CM ^ CM CM 
 
 la |i& |l& |1& 
 
 oooo Koooo Pdoooo P^oqoq 
 
 ">N SPTPiTCT NO 24. 
 
 ft 
 
 w '£ C 
 P4oQOO 
 
 CALCULATION SHEET NO. 24 
 
 451 
 
MOTOR CORE LOSS AND SATURATION ON A 1000 KW., 
 
 600 V., 8-POLE, 375 R.P.M., 6-PHASE 
 
 SYNCHRONOUS CONVERTER 
 
 Direct 
 
 Amp. 
 Arm. 
 
 
 
 
 
 Core Loss 
 
 Volts 
 
 Volts 
 Arm. 
 
 Amp. 
 Field 
 
 Speed 
 
 IE 
 
 I 2 R 
 Arm. 
 
 and 
 Friction 
 
 A-C. 
 . Side 
 
 258 
 
 54 
 
 2.36 
 
 375 
 
 13920 
 
 30 
 
 13890 
 
 179 
 
 273 
 
 51 
 
 2.50 
 
 375 
 
 13910 
 
 20 
 
 13890 
 
 188 
 
 300 
 
 49 
 
 2.81 
 
 375 
 
 14710 
 
 20 
 
 14690 
 
 210 
 
 348 
 
 44 
 
 3.3 
 
 375 
 
 15300 
 
 20 
 
 15280 
 
 240 
 
 415 
 
 39.5 
 
 4.05 
 
 375 
 
 16400 
 
 10 
 
 16390 
 
 288 
 
 452 
 
 38.5 
 
 4.45 
 
 375 
 
 17400 
 
 10 
 
 17390 
 
 309 
 
 503 
 
 37.6 
 
 5.24 
 
 375 
 
 18900 
 
 10 
 
 18890 
 
 350 
 
 565 
 
 37 
 
 6.22 
 
 375 
 
 20900 
 
 10 
 
 20890 
 
 389 
 
 600 
 
 37 
 
 7.12 
 
 375 
 
 22200 
 
 10 
 
 22190 
 
 421 
 
 630 
 
 37.9 
 
 7.89 
 
 375 
 
 23850 
 
 10 
 
 23840 
 
 439 
 
 660 
 
 38.1 
 
 8.88 
 
 375 
 
 25100 
 
 10 
 
 23090 
 
 462 
 
 687 
 
 41.1 
 
 9.8 
 
 375 
 
 28200 
 
 10 
 
 28190 
 
 479 
 
 
 
 
 
 
 BRUSHES 
 
 600 
 
 35.5 
 
 7.1 
 
 375 
 
 21300 
 
 D-c. down, A-c. up 
 
 600 
 
 33.5 
 
 7.1 . 
 
 375 
 
 20100 
 
 D-c. up — (except 2), 
 A-c. up 
 
 600 
 
 35.1 
 
 7.1 
 
 375 
 
 21050 
 
 D-c. up — (except 2), 
 A-c. down 
 
 D-c. brush friction — 1200. 
 
 A-c. " " — 950. 
 
 Total friction windage from curve 11800. 
 
 Res. of armature at end of C.L. =0.0088. 
 
 CALCULATION SHEET NO. 25 
 
 452 
 
c 9, 
 
 n^n^oo»coo^^ 
 
 0.2 
 
 ^^N00O33OH03 00 
 
 00 00MXO:0C3:^.00 00 
 
 ^m 
 
 
 
 
 3i2 
 
 CDOOWCONiO»00>0 
 
 
 ©x©i-i 10 oi co co co CO 
 
 i- c x :i - i- 32 oi Lt po 
 
 i — — M oj co 
 
 
 oooooooooo 
 
 
 ^'-CH^OCMOIOO 
 
 
 NOJOONOCCXSCOOO 
 
 ~> 
 
 io^>aicocoair-iTfiooi> 
 
 H r-l H N N (M CO 
 
 
 
 
 
 •d 
 
 o 
 
 QJ 
 
 p, 
 
 ^cN'tCKNccDCOOCOOOO 
 
 CD N N N 30 X C 1 , 35 O W 
 
 as 
 
 
 X N N iC C 
 
 cqosb-b-<3»cco5TiH i-i cm 
 
 h i-i i-h CM CM CO CO to 
 
 2? 
 
 a«2 
 
 »o io t^ x co co 
 
 NiQcOO-tXi-OXOJN 
 
 m ro»oo6ai'-Hco»oi> t^' 
 
 
 05 
 
 > 
 
 ^CON(N(MOOO>00«l 
 t^ I> l> t> t^ I> b- CO CO CO 
 
 
 
 NOiQOOOiC^W©'* 
 OOCQMNHOOffiOOCO 
 t^ t^ l> t^ O I- t^ co co CO 
 
 
 Amp. 
 Shunt 
 Field 
 
 O LO CO O X lO CM O iO O 
 COCOCOCOMMCNCNt-^^ 
 EN CM CM IN Ol CM CM 01 CM CM 
 
 g 
 
 oooooooooo 
 
 q 
 
 
 
 a 
 
 d* 
 
 CN^^iO»Ob-00O 
 
 x co lo — co x m co ^h ci 
 
 
 
 co -rf co cr. o oi -t -o cr. ic 
 
 
 Ji 
 
 U3 U3 l.0 iO l.0 >0 iO >0 u6 lO 
 
 CALCULATION SHEET NO. 26 
 
 453 
 
<U to 
 u to 
 O O 
 
 
 I— I r! 
 
 O (U Ih 
 
 £a2 
 
 ac2 
 
 
 
 OcOiOCOOHOOiWOOOH 
 »OC0C0Cqr^OiO05C0»O00CvJ 
 
 ^lOCDNOOOJOiOiOOOH 
 
 i-HO^KM^cooOiOfNOOCiiO 
 
 OOC'HiOOOOfN^^COOOOi 
 
 <MCOI>>0(M(M(M»00^0010 
 
 0005rHCq^COCCl>0000050 
 rHi-HrHT-lT-li-li-lr-li-ICQ 
 
 OCOOCOOCD(MOOO(MCOO 
 
 X^(MH0300NOCOCO(MIO 
 (MOO^OJ^CDOCOMOOOO 
 
 onooNOfflmoacooo 
 
 r-it--C0I>C0»O00i-ii-tCOCO00 
 
 ioooio»ooo 
 
 OCXMCOOOOOTtHcDOOOOOXM^ 
 
 dddddddddddo 
 
 COOiOOOiOOOO(NCO^»0© 
 CBOOOHH(N(N(N(N(N(M 
 
 NO(MON00OiO00OcD(M 
 COt>-Oia>0»Oi-HCOt>.(NI><N 
 
 CALCULATION SHEET NO. 27 
 
 454 
 
c 
 o 
 "■5 
 o 
 'u 
 ft 
 
 coooaj^^cooioqiO'-Hr-ir-ioo 
 
 *T3 
 
 OtDcOiCiOiOiOiOiOiOiOiO-* 
 
 I— 1 u 
 
 < 
 
 
 Ol^iOHCJHiONOCDCOOM 
 
 R.P.M. 
 
 O^NiOOiOOOOOffiWH© 
 N^OiOOcOCOffiiOOCDWOO 
 
 ^^TjlCOW(M(MHHH0005 
 
 Volts 
 Generator 
 
 OCOiCiOiOCOOOO(MiO>OOM 
 
 Amp. 
 Motor 
 
 lOiOOOiOiOOOiOOiOO 
 (MHO3500NCO>OT)<fCNHH 
 
 |3 
 
 ONCC»ONONiOOtOOON 
 
 O 
 
 So 
 1 
 
 xn 
 
 O 
 
 -J • G 
 
 O « 3 
 
 X 
 
 CALCULATION SHEET NO. 27 (Continued) 
 455 
 
SHUNT REGULATION ON A 100 KW, 600 R.P.M., 
 125 VOLT D-C. GENERATOR 
 
 
 Volts 
 
 Amp. 
 
 Volts 
 
 Amps. 
 
 Speed 
 
 
 Line 
 
 Line 
 
 Fid. 
 
 Fid. 
 
 No load, normal volts 
 
 125.0 
 
 
 
 66.2 
 
 7.56 
 
 600 
 
 yi load, rheostat as above 
 
 118.8 
 
 200 
 
 62.0 
 
 7.1 
 
 600 
 
 34 load, normal volts . 
 
 125.0 
 
 200 
 
 71.0 
 
 8.1 
 
 600 
 
 }/2 load, rheostat as above . 
 
 114.2 
 
 400 
 
 65.0 
 
 7.5 
 
 600 
 
 }/2 load, normal volts . 
 
 125.0 
 
 400 
 
 73.0 
 
 8.4 
 
 600 
 
 % load, rheostat as above . 
 
 113.1 
 
 600 
 
 66.0 
 
 7.6 
 
 600 
 
 % load, normal volts . 
 
 125.0 
 
 600 
 
 92.0 
 
 10.6 
 
 600 
 
 Full load, rheostat as above 
 
 112.2 
 
 800 
 
 83.0 
 
 9.5 
 
 600 
 
 Full load, normal volts 
 
 125.0 
 
 800 
 
 103.0 
 
 11.9 
 
 600 
 
 No load, rheostat as above 
 
 145.3 
 
 
 
 117.0 
 
 13.5 
 
 600 
 
 CALCULATION SHEET NO. 28 
 
 456 
 
EFFICIENCY AND REGULATION ON HT-60-400- 
 6600/11400Y-480 
 
 Connection (primary) 6600, (secondary) 480. 
 
 Temp. deg. cent, (efficiency) 25, (regulation) 25. 
 
 Core loss (per cent) 0.62 at 1.0 P-F. 
 
 Core loss (per cent) 0.775 at 0.8 P-F 
 
 Core loss (watts) 2480. 
 
 PR primary 
 
 PR secondary 
 
 Total loss 4576. 
 
 IR per cent 0.524. 
 
 IZ per cent 4. 
 
 Per cent total loss 1.14, at 1.0 
 
 Kw. input 404.58, at 1.0 P-F. 
 
 2096. 
 
 P-F.; 1.43 at 0.8 P-F. 
 324.58 at 0.8 P-F. 
 
 Kw. output 400, at 1.0 P-F.; 320 at 0.8 P-F. 
 
 Per Cent 
 Load 
 
 100 PER CENT POWER FACTOR 80 PER CENT POWER-FACTOR 
 
 Test 
 
 Guar. 
 
 Test 
 
 Guar. 
 
 
 
 PER 
 
 CENT EFFICIENCY 
 
 
 
 150 
 
 
 
 
 
 
 125 
 
 98.9 
 
 98.5 
 
 98.6 
 
 
 
 100 
 
 98.9 
 
 98.5 
 
 98.6 
 
 
 
 - 5 
 
 98.8 
 
 98.4 
 
 98.5 
 
 
 
 50 
 
 98.5 
 
 97.9 
 
 98.2 
 
 
 
 25 
 
 97.5 
 
 96.2 
 
 96.9 
 
 
 PER CENT REGULATION 
 
 100 
 
 Resistance at 25 deg. cent, (primary) 3.13, (secondary) 
 0.0105. 
 
 CALCULATION SHEET NO. 29 
 
 457 
 
EFFICIENCY AND REGULATION ON WCT-25-2800- 
 38100/66000Y-2300 
 
 Connections (primary) 66,000, (secondary) 2300. 
 
 Temp. deg. cent, (efficiency) 25, (regulation) 25. 
 
 Core loss (per cent) 0.54 at 1.0 P-F. 
 
 Core loss (per cent) 0.676 at 0.8 P-F. 
 
 Core loss (watts) 15140. 
 
 PR primary \ 4Q 0Q 
 
 PR secondary / 
 
 Total loss 56040. 
 
 IR per cent 1.46. 
 
 IZ per cent 4.52. 
 
 Per cent total loss 2, at 1.0 P-F.; 2.5 at 0.8 P-F. 
 
 Kw. input 2856, at 1.0 P-F.; 2296 at 0.8 P-F. 
 
 Kw. output 2800, at 1.0 P-F.; 2240 at 0.8 P-F. 
 
 
 100 PER CENT POWER-FACTOR 
 
 80 PER CENT POWER-FACTOR 
 
 Per Cent 
 
 
 
 Load 
 
 
 
 
 
 
 Test 
 
 Guar. 
 
 Test 
 
 Guar. 
 
 
 PER CENT EFFICIENCY 
 
 150 
 
 
 
 
 
 125 
 
 97.8 
 
 97.6 
 
 97.3 
 
 
 100 
 
 98.0 
 
 97.9 
 
 97.6 
 
 
 75 
 
 98.2 
 
 98.0 
 
 97.8 
 
 
 50 
 
 98.2 
 
 98.0 
 
 97.8 
 
 
 25 
 
 97.5 
 
 97.2 
 
 96.9 
 
 
 PER CENT REGULATION 
 
 100 
 
 1.55 1.7 
 
 3.76 
 
 
 Resistance at 25 deg. cent, (primary) 36.45, (secondary) 
 0.1151. 
 
 CALCULATION SHEET NO. 30 
 
 458 
 
NOMENCLATURE 
 Type 
 
 The following abbreviations are used to designate the type 
 
 of the apparatus listed: 
 
 AB Transformer, air blast, single-phase. 
 
 ABO Transformer, air blast, two-phase. 
 
 ABT Transformer, air blast, three-phase. 
 
 ABH Transformer, air blast, six-phase. 
 
 AS Alternator, revolving armature, single-phase. 
 
 AQ Alternator, revolving armature, two-phase. 
 
 AT Alternator, revolving armature, three-phase. 
 
 AH Alternator, revolving armature, six-phase. 
 
 ASB Alternator, revolving field, single-phase. 
 
 AQB Alternator, revolving field, two-phase. 
 
 ATB Alternator, revolving field, three-phase 
 
 AHB Alternator, revolving field, six-phase. 
 
 ACS Double current generator. 
 
 ASI Synchronous motor, revolving field, single-phase. 
 
 AQI Synchronous motor, revolving field, two-phase. 
 
 ATI Synchronous motor, revolving field, three-phase. 
 
 AHI Synchronous motor, revolving field, six-phase. 
 
 BR Feeder potential regulator. 
 
 C D-c. generator, turbine driven. 
 
 CC D-c. generator, turbine driven, with comm. pole. 
 
 CB Enclosed d-c. motor. 
 
 CBC Enclosed d-c. motor with comm. poles. 
 
 CDM Dynamotor. 
 
 CL D-c. motor or generator. 
 
 CLC D-c. motor or generator with comm. pole. 
 
 CO D-c. motor for crane service. 
 
 CP Air compressor with d-c. motor. 
 
 CPA Air compressor with a-c. motor. 
 
 CPI Air compressor with induction motor. 
 
 CQ Small d-c. motor (Lynn make). 
 
 CV Small d-c. motor (Lynn make). 
 
 CYC Small d-c. motor (Lynn make) with comm. pole. 
 
 CY D-c. motor for mine service. 
 
 DLC D-c. motor or generator with comm. poles. 
 
 DMC D-c. motor or generator with comm. poles. 
 
 GE D-c. railway motor. 
 
 GEA A-c. railway motor. 
 
 GEI Railway induction motor. 
 
 H Transformer (core type) single-phase. 
 
 HQ Transformer (core type) two-phase. 
 
 HT Transformer (core type) three-phase. 
 
 HC Synchronous converter, six-phase. 
 
 HCC Synchronous converter, six-phase, with comm. poles. 
 
 HCB Synchronous converter, six-phase, split pole. 
 HCBC Synchronous converter, six-phase, split pole, with comm. 
 
 poles. 
 
 HM D-c. motor for mining service. 
 
 I Induction motor, three-phase. 
 
 459 
 
IQ Induction motor, two-phase. 
 
 IS Induction motor, single-phase. 
 
 KT Induction motor, three-phase for crane service. 
 
 IRH Potential regulator, induction type, six-phase. 
 
 IRQ Potential regulator, induction type, two-phase. 
 
 IRS Potential regulator, induction type, single-phase. 
 
 IRT Potential regulator, induction type, three-phase. 
 
 ISB Induction alternator, single-phase. 
 
 IQB Induction alternator, two-phase. 
 
 ITB Induction alternator, three-phase. 
 
 LM Mining locomotive. 
 
 MCF D-c. generator or motor with compensating winding in 
 
 the pole face. 
 
 MD D-c. mill motor, totally-enclosed. 
 
 MDO D-c. mill motor. 
 
 MDS D-c. mill motor. 
 
 MI A-c. mill motor induction type. 
 
 MP D-c. generator or motor (multipolar). 
 
 MPC D-c. generator or motor (multipolar) with comm. poles. 
 
 NR Starting compensator for induction motor. 
 
 OC Transformer (oil-cooled) single-phase. 
 
 OCQ Transformer (oil-cooled) two-phase. 
 
 OCT Transformer (oil-cooled) three-phase. 
 
 OCH Transformer (oil-cooled) six-phase. 
 
 PCS A-c. commutator motor for variable speed. 
 
 PCR A-c. commutator motor for regulating. 
 
 QC Synchronous converter, two-phase. 
 
 QCB Synchronous converter, two-phase, split pole. 
 
 QCC Synchronous converter, two-phase, with comm. pole. 
 
 RI Repulsion induction motor. 
 
 TA Voltage regulator for a-c. generators. 
 
 TD Voltage regulator for d-c. generators. 
 
 RLC D-c. motor comm. poles variable speed. 
 
 RC D-c. motor comm. poles for machine tools. 
 
 TC Synchronous converter, three-phase. 
 
 TCB Synchronous converter, three-phase, split pole. 
 
 TCC Synchronous converter, three-phase with comm. pole. 
 
 WC Transformer (water-cooled) single-phase. 
 
 WCQ Transformer (water-cooled), two-phase. 
 
 WCT Transformer (water-cooled), three-phase. 
 
 WCH Transformer (water-cooled), six-phase. 
 
 YC Synchronous converter, split pole, comm. pole. 
 
 Class Rating 
 
 Following the type letters is a set of figures denoting the 
 "class rating" of the apparatus. This class rating is variable, 
 but for the more common apparatus conforms usually to the 
 following: 
 
 Generators, Motors, and Synchronous Converters 
 
 Poles— kw.— speed, e.g., MPC-6-500-720. 
 
 Some ratings give the size of frame, or use an arbitrary number. 
 
 e.g., DLC-201 (30 h.p.-llOO) CB 14; CP-21; GE-210; MD-108. 
 
 460 
 
 
Transformers 
 
 Cvcles — kv-a. — volts primary — yolts secondary, e.g., AB- 
 
 25-500-4400-220. 
 
 Potential Regulators 
 
 Poles — ky-a. — cycles — yolts primary — yolts secondary — am- 
 peres secondary," e.g., IRH 4-280-25-200-25-3700. 
 
 Form 
 
 Form letters are used to denote details of mechanical con- 
 struction or to show that the apparatus was built for some 
 particular purpose. 
 
 401 
 
SUBJECT INDEX 
 
 Subject Page 
 ADJUSTMENT: 
 
 Comm. Pole Generators 151 
 
 Non-Comm. Pole Generators 137 
 
 Comm. Pole D-C. Motors 161 
 
 Non-Comm. Pole Motors 157 
 
 Comm. Pole Synchronous Converters 205 
 
 AIR BRAKE APPARATUS 360 
 
 AIR COMPRESSORS 314-317 
 
 Commercial Tests 314 
 
 Complete Tests 315 
 
 Oil Leakage 317 
 
 Special Heat Run 316 
 
 Special Tests 315 
 
 Starting Tests 317 
 
 Wearing in Running 314 
 
 AIR GAP 82 
 
 AIR TABLE FOR BLOWER TESTS, USE OF. . . . 307 
 
 AIR VALVES 360 
 
 ALTERNATORS (See Generators, A-C.) 
 
 AMMETER, A-C 50 
 
 D-C 49 
 
 AMMETER SHUNTS WITH MILLIVOLTMETERS 49 
 
 ANEMOMETERS 26 
 
 ANGLE OF SLINGS, STRESSES DUE TO 58 
 
 APPROVED METHODS OF HANDLING MA- 
 CHINES 63-78 
 
 ARMATURE RESISTANCE 112 
 
 Synchronous Converter 190 
 
 ARMATURES, STATIONARY TESTS ON 108 
 
 ASSEMBLY OF MACHINES FOR TEST 58-97 
 
 Approved Methods of Handling 63 
 
 Erecting 79 
 
 Air Gap 82 
 
 Assembly 81 
 
 Balance, Dynamic 91 
 
 Static 90 
 
 Bearings, Filling of 87 
 
 Leakage of 88 
 
 Lubrication of 86 
 
 Oil Gauges for 87 
 
 Temperature Rise of 88, 103 
 
 Thrust 88 
 
 Roller 89 
 
 Belts 92 
 
 Maximum Power to be Transmitted by 92 
 
 Widths, Necessary, of 93 
 
 Blocking 79 
 
 463 
 
Subject Page 
 ASSEMBLY OF MACHINES FOR TEST— Cont'd 
 
 Brushes 83 
 
 Fitting of 84 
 
 Setting of 84 
 
 Spacing of 83 
 
 Bushings 80 
 
 Couplings 80 
 
 End Play, Correcting 96 
 
 Pulleys 91 
 
 Inspection of ■ 92 
 
 Shafts 79 
 
 Truing Commutators 95 
 
 Grinding . 95 
 
 Turning 95 
 
 Hitches 63 
 
 Safe Loads on Eye Bolts 60 
 
 On Manila Ropes and Slings 59 
 
 On Ropes and Chains 60 
 
 On Wire Cable or Slings 59 
 
 Stresses Due to Angle of Slings, Increased 58 
 
 Weights of Various Materials 62 
 
 BAFFLERS, OIL 238, 263 
 
 BAKING COMMUTATORS: 
 
 Comm. Pole D-C. Generators 150 
 
 Non-Comm. Pole D-C. Generators 144 
 
 BALANCE: 
 
 Dynamic 91 
 
 Static 90 
 
 Steam Turbine, Field 246 
 
 Steam Turbine, Wheel 243 
 
 BALANCER SETS 154 
 
 Balancing Tests on 154 
 
 BALANCES 26 
 
 BALLISTIC GALVANOMETERS 31 
 
 BEARINGS: 
 
 Filling of ' 87 
 
 Leakage of . 88 
 
 Lubrication of 86 
 
 Step 238 
 
 Temperature Rise of 88, 103 
 
 Thrust 88 
 
 Roller 89 
 
 Turbine 251 
 
 BELTS 92 
 
 BERM BANK (See Test Tracks) 
 
 BLOCKING 79 
 
 BLOWERS 305-313 
 
 Box Method 311 
 
 Commercial Tests 305 
 
 Complete Tests 305 
 
 Cone Method 310 
 
 464 
 
Subject Page 
 
 BLOWERS— Cont'd 
 
 Double Pitot Tube (Government) Method 306 
 
 Air Table, Use of , for 307 
 
 Calculation for 308 
 
 Pressure and Horse Power Output Curves by 308 
 
 Endurance Run 305 
 
 Formula? for 311 
 
 General Tests 305 
 
 Maximum Air Delivery Heat Run 305 
 
 Minimum Speed Heat Run 305 
 
 Special Tests 305 
 
 Standard Heat Run 305 
 
 BOOSTERS 5 
 
 For Comm. Pole Svn. Converters. . 206 
 
 BOX METHOD FOR* TESTING BLOWERS 311 
 
 BOXES, WATER (See also Limits) 21 
 
 BREAKDOWN TEST ON INDUCTION MOTORS 134 
 
 BRIDGE: 
 
 Slide Wire 38 
 
 Thomson 40 
 
 Wheatstone 37 
 
 BR REGULATORS (See also Transformers) 414 
 
 BRUSH SETTING: 
 
 Comm. Pole D-C. Generator 152 
 
 Non-Comm. Pole D-C. Generator 136 
 
 Comm. Pole D-C. Motors 161 
 
 Synchronous Converter 191 
 
 Svnchronous Converter with Comm. Poles 205 
 
 BRUSH SHIFTING: 
 
 Comm. Pole D-C. Generator 151 
 
 Non-Comm. Pole D-C. Generator 137 
 
 Series Generator 140 
 
 Non-Comm. Pole D-C. Motor 157 
 
 BRUSHES 83 
 
 by Head of Section, Setting of 98, 136 ' 
 
 BUILDING UP OF D-C. GENERATOR 137 
 
 BUSHINGS 80 
 
 CABLE REELS 353 
 
 CABLE, WIRE: 
 
 Safe Loads 59 
 
 CALCULATION SHEETS 421-458 
 
 Dynamotor, Motor Core Loss 454-455 
 
 Efficiency and Regulation 453 
 
 Generator, A-C, Deceleration Core Loss 424 
 
 Open- Circuit Core Loss 422 
 
 Short- Circuit Core Loss 423 
 
 Efficiency Calculating 437 
 
 Efficiency 438 
 
 Saturation 421 
 
 Synchronous Impedance 426 
 
 465 
 
Subject Page 
 CALCULATION SHEETS— Cont'd 
 
 Generator, D-C, Efficiency Calculating 430 
 
 Efficiency 431 
 
 Field Compounding 425 
 
 Shunt Regulation 456 
 
 Motor, D-C, Efficiency Calculating 433 
 
 Efficiency 434 
 
 Railway, Characteristics 428 
 
 Railway, Input-Output 427 
 
 Motor, Induction, Characteristics, Calculating . . . 439 
 
 Characteristics, Formulae 444 
 
 Characteristics, Results 446, 448 
 
 Efficiency Calculating " 439 
 
 Excitation 441 
 
 Impedance 443 
 
 Position Curve 442 
 
 Slip Curve 442 
 
 Stationary Torque 449 
 
 Motor, Synchronous, Efficiency Calculating 439 
 
 Efficiency - 440 
 
 Phase Characteristics 429 
 
 Running Torque 450 
 
 Starting Test 451 
 
 Synchronous Converter, Core Loss and Saturation . 452 
 
 Efficiency Calculating 435 
 
 Efficiency 436 
 
 Phase Characteristics 425 
 
 Transformer, 3-Phase Core Type, Efficiency and 
 
 Regulation 457 
 
 3-Phase Water Cooled, Efficiency and Regula- 
 tion 458 
 
 CALIBRATION CONSTANT FOR INSTRU- 
 MENTS 46 
 
 CARBONS FOR PROJECTORS 380 
 
 CHAINS, SAFE LOAD ON 60 
 
 CHARACTERISTIC CURVES ON INDUCTION 
 
 MOTORS 222 
 
 CIRCUIT BREAKERS, RAILWAY 371 
 
 CLASSES OF RESISTANCE MEASUREMENTS 36 
 COMMUTATION: (See also Adjustment) 
 
 Chart for 138 
 
 On Non-Comm. Pole D-C. Generators 137 
 
 COMMUTATOR: 
 
 Eccentricity of 136 
 
 Grinder 95 
 
 Truing 95 
 
 COMPASS 4 
 
 COMPLETE TEST ON VARIOUS TYPES OF 
 
 MACHINES (See Type Heading) 
 COMPENSATORS: 
 
 For Three- Wire Generators 149 
 
 Starting 347 
 
 466 
 
Subject Page 
 COMPOUNDING: 
 
 Comm. Pole D-C. Generators 153 
 
 With Reactance (Syn. Converters) . . 200 
 
 D-C. Generator (Cold) 138 
 
 D-C. Generator Field 145 
 
 COMPOUNDING CURVE (D-C. GENERATOR).. 145 
 
 COMPRESSORS (See Air Compressors) 
 
 CONDENSER HEAT RUN (Zero Power-Factor). 180 
 
 CONE METHOD FOR TESTING BLOWERS 310 
 
 CONNECTION BLOCKS (A-C. Generators) 173 
 
 CONNECTION BOXES (RAILWAY) 364 
 
 CONSTANT POTENTIAL TRANSFORMERS. ... 384 
 
 CONTACTOR BOXES 370 
 
 CONTACTORS: 
 
 A-C 346 
 
 D-C 345 
 
 Railway 364 
 
 CONTROL": 
 
 For Projectors, Types of 374 
 
 Industrial (See Industrial Control) 
 Train (See Train Control) 
 CONTROLLERS: 
 
 Printing Press 346 
 
 Railway 361 
 
 Trucklight 380 
 
 CONVERTERS, SYNCHRONOUS 190-207 
 
 Brush Setting 191 
 
 Commutating Pole 205 
 
 Adjusting Shunt 205 
 
 Boosters for 206 
 
 Setting Brushes 205 
 
 Complete Test 200 
 
 Compounding Test with Reactance 200 
 
 Core Loss 200 
 
 End Plav Device 191 
 
 Heating Tests 192 
 
 D-C. Booster Method (Circulating Current) . 195 
 
 Potential Regulator Method (Feeding Back) . 196 
 
 A-C. Loss Supply 197 
 
 D-C. Loss Supply 196 
 
 Water Box Method 192 
 
 Current Ratio A-C. to D-C 193 
 
 Phase Characteristics 193 
 
 Precautions in Wiring 193 
 
 Starting up from A-C. End 193 
 
 Input-Output Efficiency 202 
 
 Inverted Converters 203 
 
 Motor-Converters 207 
 
 Phase Rotation 191 
 
 Preliminary Tests 190 
 
 Armature Resistance 190 
 
 467 
 
Subject Page 
 CONVERTERS, SYNCHRONOUS— Cont'd 
 
 Equalizer Spacing 190 
 
 Pulsation Test 201 
 
 Short Commercial Test • 190 
 
 Special Tests 198 
 
 Saturation 198 
 
 Starting Test, A-C 198 
 
 Starting Test, D-C 198 
 
 Synchronous Impedance 198 
 
 Speed Limiting Device 191 
 
 Split Pole 203 
 
 Core Loss and Saturation 204 
 
 Heating Tests 205 
 
 Phase Characteristics, No Load 203 
 
 Phase Characteristics, Full Load 204 
 
 Running Light 205 
 
 Voltage Range Curves 204 
 
 Standard Efficiency 200 
 
 Voltage Ratio 191 
 
 Using Reactance 192 
 
 COOLING-OFF TESTS ON RAILWAY MOTORS 169 
 CORE LOSS: 
 
 Belted . 123 
 
 Deceleration 128 
 
 Running Light 122 
 
 On Various Types of Machines (See Machine 
 Type Heading) 
 
 COUPLERS 370 
 
 COUPLINGS 80 
 
 CRANE MOTOR RUNS 209 
 
 CURRENT: 
 
 From Frame to Shaft ' 173 
 
 £ Measurement of 49 
 
 In Three-phase Circuits 50 
 
 Ratio of Syn. Converters 193 
 
 Transformers 50 
 
 CUT-OUTS 364 
 
 D-C. GENERATORS (See Generators, D-C.) 
 
 D-C. MOTORS (See Motors, D-C.) 
 
 DECELERATION CORE LOSS 128 
 
 DEFECTS: 
 
 Reporting and Correcting 103 
 
 Steam Turbine 273 
 
 DEVELOPMENT TESTS (RAILWAY MOTORS) 165 
 
 DIVING LAMPS 380 
 
 DOUBLE PITOT TUBE METHOD (BLOWER 
 
 TESTS) 306 
 
 DOUBLE SPEED (See Over-Speed) 
 
 DROP ON SPOOLS Ill 
 
 DYNAMOTORS 170 
 
 468 
 
Subject Page 
 
 EFFICIENCY: 
 
 On Various Types of Machines, Standard (See 
 Machine Type Heading) 
 
 Transformer 384 
 
 Calculation of 404 
 
 ELECTRICAL POWER, SHOP 5 
 
 ELECTRIC LOCOMOTIVES 300 
 
 ELECTROMOTIVE FORCE, MEASUREMENT OF 45 
 
 EMERGENCY GOVERNORS 247 
 
 END PLAY: 
 
 Correcting 96 
 
 Device, Magnetic 117 
 
 Device, Mechanical 118 
 
 ENGINE: 
 
 Indicator, Steam 26 
 
 Marine (See Marine Engine) 
 
 Regulation in Compounding Generators, Allow- 
 ance for 140 
 
 EQUALIZERS 136 
 
 For Svn. Converters, Spacing of 190 
 
 EQUIPMENT 5-23 
 
 Boosters 5 
 
 Electrical Power 5 
 
 Exciters 6 
 
 Used as Boosters 6 
 
 Field Rheostats 23 
 
 Floor Stands : 14 
 
 High Potential Testing Sets 7 
 
 Measuring Sets 6 
 
 Motor-Generator Sets 7 
 
 Safety Devices 13 
 
 Shop Motors and Generators 12 
 
 Steam Power 10 
 
 Switchboards 14 
 
 Testing Tables 19 
 
 Transformers 23 
 
 Water Boxes 21 
 
 EQUIVALENT LOAD: 
 
 A-C. Generators 179 
 
 D-C. Generators 144 
 
 Induction Motors 210 
 
 ERECTING 79 
 
 EXCITATION: 
 
 Curves (Induction Motors) 211 
 
 Readings (Induction Motors) 209 
 
 EXCITERS 153 
 
 Used as Boosters 6 
 
 EXCITING CURRENT OF TRANSFORMERS. . . 393 
 
 EYEBOLTS, SAFE LOAD ON 60 
 
 FAILURES OF TRANSFORMERS IN TEST 404 
 
 FAN TESTS (See Blowers) 
 
 469 
 
Subject Page 
 FEEDING BACK: 
 
 A-C. Generators 177 
 
 D-C. Generators ■...." 141 
 
 D-C. Motors 158 
 
 Induction Motors 209 
 
 Synchronous Motors 196 
 
 FIELD: 
 
 Balance (Steam Turbine) 246 
 
 Compounding (D-C. Generators) 146 
 
 Resistance, Measurement of 112 
 
 Rheostats 23 
 
 Tests on 343 
 
 FINGER PRESSURE (Railway Contactors) 366 
 
 FLOOR STANDS 14 
 
 FLOW TANKS 279 
 
 FOCAL LENGTH OF PROJECTOR MIRRORS. . 377 
 
 FORMULA FOR BLOWER TEST 311 
 
 FREQUENCY: 
 
 And Speed 32 
 
 Indicators 33 
 
 FRICTION: 
 
 By Free Running (Electric Locomotive) 304 
 
 From Coasting (Electric Locomotive) 304 
 
 Train 304 
 
 FUSE BOXES 369 
 
 FUSES, RAILWAY 369 
 
 GALVANOMETER, BALLISTIC. . . 31 
 
 GAUGES: 
 
 Pressure 27, 276 
 
 Vacuum. . : 27 
 
 Oil 87 
 
 GENERAL TESTS (INDUCTION MOTORS) 223 
 
 GENERATORS, A-C 172-182 
 
 Commercial Tests 172 
 
 Connection Blocks 173 
 
 Magnetic Leakage (Current from Frame to 
 
 Shaft) 173 
 
 Phase Rotation 172 
 
 Synchronous Impedance 172 
 
 Heating Tests 175 
 
 Actual Load 176 
 
 Feeding Back 177 
 
 Power-Factor Run 176 
 
 Equivalent Load 179 
 
 Long Commercial Test 181 
 
 Open Delta Run 179 
 
 Open-Circuited Run 179 
 
 Short-Circuited Run 179 
 
 Zero Power-Factor Run 180 
 
 Location of Keyway 181 
 
 Marine Engine- Driven (See Marine Engines) 
 
 470 
 
Subject Page 
 GENERATORS, A-C— Cont'd 
 
 Preliminary Tests 172 
 
 Special Tests. 181 
 
 Standard Efficiency 181 
 
 Static Test 182 
 
 Turbine Driven (See Turbines) 
 
 Voltage Regulation 181 
 
 Wave Form 182 
 
 GENERATORS, D-C 136-156 
 
 Balancer Sets 154 
 
 Building up of 137 
 
 Refusal to Generate 137 
 
 Series Generator 137 
 
 Commutating Pole 149 
 
 Baking Commutators on 150 
 
 Compounding, etc 153 
 
 General Notes on 149 
 
 Spacing of Poles of 149 
 
 Locating Neutral on 150 
 
 Shunt Adjustment of 151 
 
 Brush Position, Marking of 152 
 
 Grid Shunts, Position of 152 
 
 Inductive Shunt 152 
 
 Motor Operation 153 
 
 Shifting Brushes 151 
 
 Trammel 152 
 
 Three- Wire 153 
 
 Commutator, Eccentricity of 136 
 
 Equalizers for 136 
 
 Exciters 153 
 
 Stability Test 153 
 
 General Instructions on 136 
 
 Marine Engine- Driven (See Marine Engines) 
 
 Non-Commutating Pole 137 
 
 Complete Test 147 
 
 Heating Tests on 140 
 
 Actual Load 140 
 
 Circulating Current 143 
 
 Feeding Back 141 
 
 Electrical Loss Method 142 
 
 Into Shop Circuit 142 
 
 Mechanical Loss Method 141 
 
 Sets 142 
 
 Water Box Method 140 
 
 Equivalent Load 144 
 
 Baking Commutators 144 
 
 Normal Load Heat Run 144 
 
 Overload Heat Run 145 
 
 Miscellaneous Tests on 145 
 
 Compounding Curve 145 
 
 Field Compounding 146 
 
 High Potential 145 
 
 471 
 
Subject Page 
 GENERATORS, D-C— Cont'd 
 Non-Commutating Pole 
 
 Miscellaneous Tests on 
 
 Rheostat Data 145 
 
 Running Light 146 
 
 Shunt Regulation 145 
 
 Stud Potential Curve 147 
 
 Shunt Adjustment of 137 
 
 Commutation 137 
 
 Chart 138 
 
 Setting Brushes for 136 
 
 Shifting Brushes for 137 
 
 Compounding, Cold 138 
 
 Engine Regulation, Allowance for . . 140 
 
 Reversed Series Field 138 
 
 Series Generator, Series Characteristic . . 140 
 
 Shifting Brushes 140 
 
 Special Tests 147 
 
 Standard Efficiency 147 
 
 Three- Wire 147 
 
 Revolving Compensator 149 
 
 Unbalanced Readings 149 
 
 Preliminary Tests on 136 
 
 GENERATORS, SHOP MOTORS AND 12 
 
 GOVERNOR: 
 
 For Air Brake Apparatus 361 
 
 For Steam Turbine, Emergency 247 
 
 For Steam Turbine, Operating 251 
 
 For Marine Engines 295 
 
 Tests (Steam Turbines) 247 
 
 GRID SHUNTS, POSITION OF 152 
 
 GRINDER, COMMUTATOR 95 
 
 HEATING TESTS: 
 
 On Various Types of Machines (See Machine 
 Type Heading) 
 HEAT RUNS: (See also Heating Tests) 
 
 Preparation for 101 
 
 On Electric Locomotives, Service 303 
 
 HIGH POTENTIAL 113 
 
 On Various Types of Apparatus (See Apparatus 
 Type Heading) 
 
 Testing Sets 7 
 
 HIGH RESISTANCE MEASUREMENTS 42 
 
 HIGH SPEED TEST (See Over Speed) 
 
 HITCHES 63 
 
 HUNTING OF COMM. POLE D-C. MOTORS.... 162 
 
 HYDROMETER 27 
 
 IMPEDANCE: 
 
 Constant Potential Transformers 393 
 
 Curves (Induction Motors) 214 
 
 472 
 
Subject Page 
 
 I M P E D A X C E— Cont ' d 
 
 Position Curve (Syn. Motors) 188 
 
 Readings on Induction Motors, Stationary 209 
 
 INDICATOR: 
 
 Diagrams, Marine Engine 296 
 
 Frequency and Speed 33 
 
 Phase Rotation 25 
 
 Slip 27 
 
 Steam Engine 26 
 
 IXDUCED VOLTAGE: 
 
 Constant Potential Transformers 403 
 
 Synchronous Motors 183 
 
 Synchronous Condensers 193, 198 
 
 INDUCTION GEXERATOR RUNS 209 
 
 Induction: 
 
 Motors (See Motors, Induction) 
 Regulators (See Transformers) 
 
 IXDUCTIVE SHUNTS 152 
 
 IXDUSTRIAL CONTROL APPARATUS 343-352 
 
 Compensators, Starting 34/ 
 
 Heat Runs 351 
 
 Insulation Tests 352 
 
 Magnetizing Current 351 
 
 Ratio 347 
 
 Contactors, A-C 346 
 
 D-C 345 
 
 Controllers, Printing Press 346 
 
 High Potential Tests 347 
 
 Panels, A-C 345 
 
 D-C 345 
 
 Rheostats, Field 343 
 
 For Split Pole Syn. Converters 344 
 
 Starting and Regulating, Hand Operated .... 344 
 
 Shipment 347 
 
 Starters, Automatic 344 
 
 IXDUSTRIAL LOCOMOTIVES 354 
 
 INPUT-OUTPUT TESTS 130 
 
 On Various Types of Machines (See Machine 
 Type Heading I 
 INSPECTION: 
 
 Of Pulleys 92 
 
 Of Apparatus, Preliminary 98 
 
 Of Wiring ' ' 99 
 
 INSTRUMENTS FOR STEAM TURBIXE TESTS 233 
 
 INSTRUMENTS, USE AXD CARE OF 24-57 
 
 Anemometers 26 
 
 Balances 26 
 
 Ballistic Galvanometer 31 
 
 Care of 24 
 
 Compass 4 
 
 473 
 
Subject Page 
 INSTRUMENTS, USE AND CARE OF— Cont'd 
 
 Current, Measurement of 49 
 
 In 3-Phase Circuits - 50 
 
 A-C. Ammeters 50 
 
 Transformers 50 
 
 D-C. Ammeters 49 
 
 Ammeter Shunts with Millivoltmeters 49 
 
 Electromotive Force, Measurement of 45 
 
 Potential Transformers 48 
 
 Potentiometer 45 
 
 Stray Fields, Test for 47 
 
 Voltmeters 45 
 
 Calibration Constant 46 
 
 Millivoltmeters 46 
 
 Hydrometer 27 
 
 Indicators, Steam Engine 26 
 
 Manometers 26 
 
 Phase Rotation Indicator 25 
 
 Planimeter 26 
 
 Power, Measurement of • 51 
 
 Wattmeters 51 
 
 Phase Angle, Correction for 55 
 
 Power-Factor, Measurement of 56 
 
 Pressure Gauges 27 
 
 Resistance Measurements 36 
 
 Classes of 36 
 
 High Resistance Measurements 42 
 
 High Resistance D-C. Voltmeter. . . 42 
 
 Insulation Resistance Testing Sets . . 42 
 
 Megger 44 
 
 Low Resistance Measurements 40 
 
 Drop Method (D-C.) 40 
 
 Thomson Bridge 40 
 
 Medium Resistance Measurements 36 
 
 Slide Wire Bridge , 38 
 
 Ohmmeter 38 
 
 Wheatstone Bridge 37 
 
 Primary Standard of 36 
 
 Unit Employed 36 
 
 Working Standard 36 
 
 Scales 26 
 
 Slip Indicator 27 
 
 Speed and Frequency 32 
 
 Speed and Frequency Indicators 33 
 
 Primary Standard 32 
 
 Speed Indicators 33 
 
 Tachometers 32 
 
 Torque Recorder, Stationary < . . 29 
 
 U-Tubes 26 
 
 Vacuum Gauge 27 
 
 Wave Shapes 34 
 
 Oscillograph 35 
 
 474 
 
Subject Page 
 
 INSULATION RESISTANCE 112 
 
 Testing Sets 42 
 
 On Various Types of Apparatus (See Apparatus 
 Tvpe Heading) 
 
 INSULATORS, PORCELAIN 358-359 
 
 Applying High Potential, Methods of 358 
 
 Inspection 358 
 
 Switchboard Dept., Routine Tests for 358 
 
 Tubes 359 
 
 INTERMITTENT RUNS ON INDUCTION 
 
 MOTORS 209 
 
 INTRODUCTION 4 
 
 INVERTED CONVERTERS 203 
 
 JUMPERS (Railway) 371 
 
 KEYWAY, LOCATION OF 181 
 
 KEYBOARDS 380 
 
 LEAKS IN STEAM TURBINES, WATER 233 
 
 LIMITS: 
 
 Air Gap 83 
 
 Bearings: 
 
 Maximum Temperature Rise Allowed 88 
 
 Maximum Temperature Rise Allowed on 
 
 Commercial Run 103 
 
 Belts: 
 
 Maximum Power to be Transmitted 92 
 
 Maximum Speed Allowed 94 
 
 Compensators: 
 
 Magnetizing Current 351 
 
 Ratio 351 
 
 Core Loss: 
 
 Open-Circuit, Low Limit of Highest Reading 125 
 
 Short-Circuit, Low Limit of Highest Reading 128 
 
 Drop on Spools: 
 
 A-C. Machines Ill 
 
 D-C. Machines Ill 
 
 Exciters: 
 
 Low Limit of Voltage with Full Field 153 
 
 Stability, Voltage Variation in 153 
 
 Governors, Operating: 
 
 Limits of Operation 263 
 
 Manometers: 
 
 Range of Usefulness 26 
 
 Pole Spacing, Commutating: 
 
 Variation 82 
 
 Resistance: 
 
 Grid for Mining Locomotive, Variation in . . . 353 
 
 Cold, Railway Motors 163 
 
 Coil, Reversers '. 363 
 
 Coil, Reversers, Supply Spools 363 
 
 475 
 
Subject Page 
 
 LIMITS— Cont'd 
 Rheostats: 
 
 Solenoid Operated, Voltage for Operation .... 343 
 
 Starting and Regulating, Hand Operated, 
 
 Voltage for Operation 344 
 
 Saturation: 
 
 Range of Curve 120 
 
 Shaft Pressure: 
 
 Usually Required 80 
 
 Lowest Allowable 80 
 
 Speed: 
 
 Marine Sets, Regulation 293 
 
 Motors, S.W. or C.W. Comm. Pole, Variation 
 
 from Rated, Cold 161 
 
 Motors, S.W. or C.W. Comm. Pole, Variation 
 
 from Rated, Hot 161 
 
 Motors, S.W. or C.W. Comm. Pole, Variation 
 
 from No Load to Full Load 161 
 
 Motors, S.W. Non-Comm. Pole, Variation 
 
 from Rated, Cold 158 
 
 Motors, S.W. Non-Comm. Pole, Variation 
 
 from Rated, Hot 158 
 
 Motors, C.W. Non-Comm. Pole, Variation 
 
 from Rated, Hot 158 
 
 Motors, S.W. Non-Comm. Pole, Speed Regu- 
 lation 158 
 
 Motors, Series and Railway, Variation from 
 
 Rated, Hot 163 
 
 Shop Machines, Maximum Allowable 13 
 
 Voltage Balance: 
 
 ' Of Balancer Set 154 
 
 Water Box: 
 
 Load 140 
 
 Voltage 176 
 
 LOAD LOSS 132 
 
 LOADING VARIOUS TYPES OF* MACHINES (See 
 "Heating Tests" Under Type Heading) 
 
 LOADS, SAFE 59, 60 
 
 LOCATING NEUTRAL: 
 
 Comm. Pole D-C. Generators 150 
 
 Comm. Pole D-C. Motors 161 
 
 LOCATION OF KEYWAY 181 
 
 LOCOMOTIVES, ELECTRIC 300 
 
 LOCOMOTIVES, MINING AND INDUSTRIAL. . 353-357 
 
 Industrial 354 
 
 Mining 353 
 
 Cable Reels 353 
 
 Winding Devices 354 
 
 Storage Battery 355 
 
 LONG COMMERCIAL TEST 
 
 A-C. Generator 181 
 
 Induction Motors 223 
 
 476 
 
Scbject Page 
 
 LOW RESISTANCE MEASUREMENTS 40 
 
 LUBRICATION: 
 
 Bearings 86 
 
 Marine Engines 288 
 
 Turbines 233 
 
 MAGNETIC LEAKAGE 173 
 
 MAGNETIZING CURRENT OF STARTING COM- 
 PENSATORS 351 
 
 MANOMETERS 26 
 
 MARINE ENGINE SETS 285-299 
 
 Engine 288 
 
 General Instructions 298 
 
 Governor 295 
 
 Indicator Diagrams 296 
 
 Lubrication 288 
 
 Operation 294 
 
 Packing 298 
 
 Pressure, Steam 288 
 
 Starting up 293 
 
 Tests 293 
 
 Valves 293 
 
 Generator 299 
 
 MAXIMUM OUTPUT 133 
 
 MEASURE. COLD, STEAM TURBINE GENER- 
 ATORS : 269 
 
 MEASURING SETS 6 
 
 MEASUREMENT OF VARIOUS QUANTITIES 
 (See the Quantitv i 
 
 MEDIUM RESISTANCE MEASUREMENTS 36 
 
 MEGGER 42 
 
 METERS i See Instruments) 
 
 MILLIVOLTMETERS 46 
 
 MINIMUM PICK UP, RAILWAY CONTACTORS 366 
 
 MINING LOCOMOTIVES 353 
 
 MIRRORS FOR PROJECTORS 377 
 
 MOTOR AND GENERATOR OPERATION (D-C. 
 
 Motors) 162 
 
 MOTOR-CONVERTER 207 
 
 MOTOR FIELDS, WIRING 99 
 
 MOTOR-GENERATOR SETS, SHOP 12 
 
 MOTORING STEAM TURBINES 212 
 
 MOTOR OPERATION (D-C. Generator) 153 
 
 MOTORS | D-C.) 157-171 
 
 Commutating Pole 161 
 
 Adjustment for Commutation 161 
 
 Hunting 162 
 
 Motor and Generator Operation 162 
 
 Running Light 162 
 
 Setting Brushes 161 
 
 Speed Variation 161 
 
 Dynamotors 170 
 
 477 
 
Subject Page 
 MOTORS (D-C.)— Cont'd 
 
 Non-Commutating Pole 157 
 
 Adjustment for Speed and Commutation .... 157 
 
 Heating Tests 158 
 
 Loading for. 158 
 
 Running Light 159 
 
 Special Tests 159 
 
 Speed Curve, Hot 159 
 
 Shifting Brushes 157 
 
 Speed Regulation 158 
 
 Standard Efficiency 161 
 
 Preliminary Tests 157 
 
 Series and Railway Motors 163 
 
 Commercial Tests 167 
 
 Complete Tests 164 
 
 Cooling-off Tests 169 
 
 Development Tests 165 
 
 General Tests 163 
 
 Input-Output 168 
 
 Special Tests 165 
 
 Core Loss 165 
 
 Loading, Method of 167 
 
 Saturation 165 
 
 Speed Curves 165 
 
 Thermal Characteristics 165 
 
 Standard Efficiency Test (Series Motors) .... 168 
 
 Tractive Effort 169 
 
 Starting up 157 
 
 Variable Speed 162 
 
 Ventilation Tests 171 
 
 MOTORS, INDUCTION 208-226 
 
 Commercial Tests 208 
 
 Complete Test 223 
 
 General Test 223 
 
 Heating Tests 209 
 
 Actual Load Runs 209 
 
 Crane Motor 209 
 
 Induction-Generator 209 
 
 Intermittent 209 
 
 Equivalent Load Runs 210 
 
 High Potential 226 
 
 Input-Output and Power-Factor Test. . 223 
 
 Electrical Load Method 225 
 
 String Brake Method 223 
 
 Long Commercial 223 
 
 Preliminary Tests 208 
 
 Special Overload Heat Run 223 
 
 Special Tests 211 
 
 Characteristic Curves 222 
 
 Excitation Curve 211 
 
 Impedance Curve 214 
 
 Position Curve 215 
 
 478 
 
Subject Page 
 MOTORS, INDUCTION— Cont'd 
 Special Tests 
 
 Slip Curve 217 
 
 Starting Test 222 
 
 Torque, Stationary 220 
 
 Standard Efficiency and Power-Factor Test 223 
 
 MOTORS, SYNCHRONOUS 183-189 
 
 Commercial Tests 183 
 
 Complete Tests 188 
 
 Heating Tests 183 
 
 Actual Load 185 
 
 Equivalent Load 185 
 
 Impedance-Position Curve 188 
 
 Phase Characteristics 183 
 
 Preliminarv Tests 183 
 
 Special Tests 185 
 
 Core Loss 185 
 
 Saturation 185 
 
 Starting 185 
 
 Svnchronous Impedance 185 
 
 Wave-Form 185 
 
 Standard Efficiency 188 
 
 Starting Up 183 
 
 Torque Tests 188 
 
 Running 188 
 
 Stationary 188 
 
 MOUNTING MOTORS ON TRUCKS 302 
 
 MS SWITCHES 363 
 
 MU TRIPPING SWITCHES 364 
 
 NEUTRAL, LOCATING: 
 
 Comm. Pole D-C. Generators 150 
 
 Comm. Pole D-C. Motors 161 
 
 NOMENCLATURE: 
 
 General 459 
 
 Turbine 227 
 
 NORMAL LOAD HEAT RUN (D-C. GENERATOR) 144 
 
 NUMBERING FIELD SPOOLS 112 
 
 OHMMETER 38 
 
 OIL: 
 
 Flow (Steam Turbines) 235 
 
 Gauges 87 
 
 OILING (See Lubrication) 
 
 OPEN CIRCUIT RUN (A-C. GENERATORS) 179 
 
 OPEN-DELTA RUN (A-C. GENERATORS) 179 
 
 OPERATING GOVERNORS, STEAM TURBINE 251 
 OPERATION, OBSERVATION AND COMMENTS 
 
 ON 103 
 
 OSCILLOGRAPH 35 
 
 OUTPUT TEST, MAXIMUM 133 
 
 OVERLOAD HEAT RUN (D-C. GENERATOR)... 145 
 
 OVER SPEED TEST 135 
 
 479 
 
Subject Pa 
 
 PACKING: 
 
 Marine Engine - 2! 
 
 Rings, Carbon 2< 
 
 PANELS: 
 
 A-C 3- 
 
 D-C 3^ 
 
 PHASE ANGLE IN WATTMETERS, CORREC- 
 TION FOR I 
 
 PHASE CHARACTERISTICS ON VARIOUS MA- 
 CHINES (See Machine Type Heading) 
 
 PHASE ROTATION: 
 
 Indicator 25 
 
 On A-C. Generators 172 
 
 On Syn. Converters 191 
 
 On Transformers 390 
 
 PIPING, STEAM, EXHAUST AND OIL 232 
 
 PITOT TUBE METHOD FOR BLOWER TESTS, 
 
 DOUBLE 306 
 
 PLANIMETER 26 
 
 POLARITY: 
 
 Of Generators and Motors Ill 
 
 Of Transformers 386 
 
 POLE SPACING, COMMUTATING 149 
 
 PORCELAIN INSULATORS 358 
 
 POSITION CURVE, INDUCTION MOTORS 215 
 
 POTENTIAL CURVE: 
 
 Between Brushes . 134 
 
 Stud 147 
 
 POTENTIOMETER 45 
 
 POWER: 
 
 Electrical 5 
 
 Measurement of 51 
 
 Steam 10 
 
 POWER-FACTOR: 
 
 Measurement of 56 
 
 POWER-FACTOR RUN: 
 
 On A-C. Generator 176 
 
 On Syn. Motor 180, 185 
 
 PRELIMINARY TEST ON VARIOUS MACHINES 
 (See Machine Type Heading) 
 
 PREPARATION OF APPARATUS FOR TEST. . . . 98-105 
 
 Defects, Reporting and Correcting 103 
 
 Heat Runs, Preparation for 101 
 
 Calculating Temperature Rise on 103 
 
 Placing Thermometers for 101 
 
 Inspection, Preliminary 98 
 
 Operation, Observations and Comments During. . 103 
 
 Starting Up 100 
 
 Stationary Apparatus 105 
 
 Temperature Coils 103 
 
 Wiring 98 
 
 480 
 
Subject Page 
 PREPARATION OF APPARATUS FOR TEST— Cont'd 
 Wiring 
 
 Inspection bv Head of Section 99 
 
 Motor Fields _ 99 
 
 Transformers, Grounding of 100 
 
 PREPARATION FOR TEST: 
 
 Steam Turbines 233 
 
 Transformers 385 
 
 PRESSURE: 
 
 Gauges 27 
 
 Steam (Marine Engines) 288 
 
 PRINTING PRESS CONTROLLERS 346 
 
 PROJECTORS 373-381 
 
 Adjustment 375 
 
 Carbons 380 
 
 Inspection 373 
 
 Mirrors, Focal Length of 377 
 
 Rheostats 377 
 
 Signal Apparatus. 380 
 
 Diving Lamps 380 
 
 Keyboards 380 
 
 Trucklight Controllers 380 
 
 Tvpes of Control 374 
 
 PULL" CURVE: 
 
 Electric Locomotive 302 
 
 Railwav Contactors 367 
 
 PULLEYS 91 
 
 PULSATION TEST (SYN. CONVERTERS) 201 
 
 PUMP BACK (See Feeding Back) 
 
 QUANTITY OF OIL FOR BEARINGS 89 
 
 RAILWAY MOTORS (See Motors, D-C.) 
 
 RATIO: 
 
 On Starting Compensators 347 
 
 On Syn. Converters, Current 193 
 
 On Syn. Converters, Voltage 191 
 
 On Induction Motors, Voltage 209 
 
 On Transformers 391 
 
 REACTANCE: 
 
 Changing Ratio of Syn. Converters with . . .• 192 
 
 Compounding Svn. Converters with 200 
 
 REACTANCES (See Transformers) 
 
 RECORDS, TESTING 106 
 
 REELS, CABLE 353 
 
 REGULATION: 
 
 Engine, Allowance for 140 
 
 Shunt (D-C. Generator) 145 
 
 Speed (Comm. Pole D-C. Motors) 161 
 
 Speed (Non-Comm. Pole D-C. Motors) 158 
 
 Voltage (Transformers) 384 
 
 Voltage (Transformers), Calculation of 405 
 
 Voltage (A-C. Generators) 181 
 
 481 
 
Subject p AGE 
 
 REGULATORS, INDUCTION (See Transformers) . . 406 
 
 REGULATORS, VOLTAGE 318-342 
 
 Adjustment 321 
 
 Heat Runs 322 
 
 High Potential 322 
 
 Principle of Operation, General 318 
 
 TypeTA 318 
 
 Form A 2 318 
 
 Principle of Operation 318 
 
 Form F 320 
 
 Type TD, Form G 321 
 
 Form L ; 321 
 
 Form R 321 
 
 Relay Contacts, Adjustment of 322 
 
 Resistance Measurement 322 
 
 TA Form A 2 . 323 
 
 Adjustment of A-C. Magnet Core. . . . . 327 
 
 - Dashpot 323 
 
 Floating Main Contacts 326 
 
 Relay 327 
 
 Setting Springs 329 
 
 Springs 324 
 
 Condensers 332 
 
 Line Drop Compensation 329 
 
 Locating Trouble 331 
 
 Arcing at Relay Contacts 332 
 
 Error Due to Compensating Winding . . . 332 
 
 Error in Voltage 332 
 
 Failure to Build Up 331 
 
 Fall in Voltage 331 
 
 Fluctuating Voltage 331 
 
 TA Form F 333 
 
 Adjustment of A-C. Magnet Core 337 
 
 Dashpot 333 
 
 Floating Main Contacts 337 
 
 Levers and Springs 333 
 
 Relay 337 
 
 Setting Relay Springs 338 
 
 Condensers 338 
 
 Locating Trouble 338 
 
 TA Form K . . . 338 
 
 Form L 333 
 
 TD Form L 340 
 
 Form R 341 
 
 Adjustment of Main Control Magnet. . . 341 
 
 Adjustment of Relay Magnet 341 
 
 Form S 340 
 
 FormT 340 
 
 Form W (Speed Regulator) 342 
 
 RELAYS, RAILWAY 372 
 
 482 
 
Subject Page 
 RESISTANCE: 
 
 Armature 112 
 
 Svn. Converter 190 
 
 Field." 112 
 
 Insulation 112 
 
 Measurements (See also Instruments) 36 
 
 Of Transformers, Cold 386 
 
 Temperature Rise by 112 
 
 REVERSED SERIES FIELD, TEST FOR 138 
 
 RHEOSTAT DATA, D-C. GENERATOR 145 
 
 RHEOSTATS: 
 
 Field (in Testing Dept.) 23 
 
 Field, Testing of 343 
 
 Field, for Split Pole Syn. Converter 344 
 
 Hand Operated Starting and Regulating 344 
 
 For Projectors 377 
 
 RISE BY RESISTANCE FORMULAE, TEMPER- 
 
 TURE 112, 399 
 
 ROLLER BEARINGS 89 
 
 ROPES, SAFE LOADS ON 60 
 
 ROTARY CONVERTERS (See Converters, Syn.) 
 
 RUNNING LIGHT CORE LOSS 122 
 
 On Various Types of Machines (See Machine 
 Tvpe Heading) 
 
 RUNNING TORQUE ON SYN. MOTORS 188 
 
 SAFE LOADS: 
 
 On Eyebolts 60 
 
 On Manila Ropes and Slings 59 
 
 On Ropes and Chains 60 
 
 On Wire Cable or Slings 59 
 
 SAFETY DEVICES 13 
 
 SATURATION: 
 
 Generator 120 
 
 Motor. . . 120 
 
 On Various Types of Machines (See Machine 
 
 Type Heading) 
 
 On Railway Contactors 367 
 
 SCALES 26 
 
 SEARCHLIGHTS (See Projectors) 
 
 SERIES WOUND D-C. GENERATOR: 
 
 Series Characteristic 140 
 
 Shifting Brushes on 137 
 
 SERIES AND RAILWAY MOTORS (D-C.) 163 
 
 SERIES LIGHTING TRANSFORMERS 419 
 
 SERVICE HEAT RUNS (ELECTRIC LOCO- 
 MOTIVES) 303 
 
 SETS: 
 
 Loading 142 
 
 Measuring ' 6 
 
 Motor-Generator, Shop 7 
 
 SHAFTS 79 
 
 483 
 
Subject P AGE 
 SHIFTING BRUSHES: 
 
 On Comm. Pole D-C. Generators , 151 
 
 On Non-Comm. Pole D-C. Generators. 137 
 
 On Series Generators 140 
 
 On Non-Comm. Pole D-C. Motors 157 
 
 SHIFTING PHASES (TO LOAD A-C. GENER- 
 ATORS)' 177 
 
 SHORT-CIRCUIT RUN (A-C. GENERATORS)... 179 
 SHUNT ADJUSTMENT (See Adjustment) 
 
 SHUNT REGULATION (D-C. GENERATOR) 145 
 
 SHUNTS: 
 
 Grid, Position of 152 
 
 Inductive 152 
 
 SHUTTING DOWN STEAM TURBINE SETS. ... 272 
 
 SIGNAL APPARATUS . 380 
 
 SLIDE WIRE BRIDGE 38 
 
 SLINGS, SAFE LOAD ON 59 
 
 SLIP: 
 
 Indicator 27 
 
 Of Induction Motors 217 
 
 SPACING: 
 
 Brushes 83 
 
 Commutating Poles 149 
 
 SPARKING CHART '. 138 
 
 SPECIAL INSTRUCTIONS, STEAM TURBINES. 233 
 SPECIAL TESTS ON VARIOUS TYPES OF MA- 
 CHINES (See Machine Type Heading) 
 SPEED: 
 
 And Frequency ' 32 
 
 Curve, D-C. Motors, Hot 159 
 
 Railway Motors 165 
 
 Railway Contactors 368 
 
 Indicators 33 
 
 Limiting Device, Adjustment of 113 
 
 Regulation, Non-Comm. Pole D-C. Motors 158 
 
 Variation, Comm. Pole D-C. Motors 161 
 
 SPLIT POLE SYN. CONVERTERS (See Converters) 
 
 STABILITY TEST ON EXCITERS : . . 153 
 
 STAGE VALVES 265 
 
 STANDARD EFFICIENCY ON VARIOUS TYPES 
 
 OF MACHINES (See Machine Type Heading) 
 STANDARD TESTS, METHODS OF CONDUCT- 
 ING 108-135 
 
 Armatures, Stationary Tests on 108 
 
 Core Loss, Belted 123 
 
 Deceleration 128 
 
 Running Light 122 
 
 Drop on Spools 
 
 Limits of Variation in Ill 
 
 Numbering Spools 112 
 
 End Play Device, Magnetic 117 
 
 Mechanical 118 
 
 484 
 
Subject Page 
 STANDARD TESTS, METHODS OF CONDUCT- 
 ING— Cont'd 
 
 High Potential 113 
 
 Input-Output 130 
 
 Load Loss 132 
 
 Maximum Output 134 
 
 Overspeed Test 135 
 
 Polarity Ill 
 
 Potential Curve Between Brushes 135 
 
 Resistance 112 
 
 Armature 112 
 
 Insulation 112 
 
 Shunt and Series Fields 112 
 
 Temperature Rise by 112 
 
 Saturation 120 
 
 Generator 120 
 
 Motor 120 
 
 Speed Limiting Device, Adjustment of 113 
 
 Wave Form — Potential Curve Between Brushes . 135 
 
 STANDS, FLOOR 14 
 
 STARTERS, AUTOMATIC 344 
 
 STARTING TEST: 
 
 Induction Motor 222 
 
 Synchronous Converter, A-C 198 
 
 Synchronous Converter, D-C 198 
 
 Svnchronous Motor 185 
 
 STARTING UP: 
 
 General Instructions on 100 
 
 D-C. Motor 157 
 
 Marine Engines 293 
 
 Synchronous Converter (from A-C. End) 193 
 
 Svnchronous Motors 183 
 
 STATIC TEST (A-C. GENERATOR) 182 
 
 STATIONARY APPARATUS 105 
 
 STATIONARY TORQUE: 
 
 On Syn. Motor 188 
 
 Recorder 29 
 
 STEAM CONSUMPTION TESTS: 
 
 On Turbines (See Turbines) 274 
 
 On Marine Engines 294 
 
 STEAM: 
 
 Engine Indicator 26 
 
 Power 10 
 
 Turbines (See Turbines) 
 
 Turbine Generators (See Turbines) 
 
 STEP BEARING 238 
 
 STORAGE BATTERY LOCOMOTIVES 355 
 
 STRAINERS (AIR BRAKE APPARATUS) 361 
 
 STRAY FIELDS, TEST FOR. . . 47 
 
 STRESSES DUE TO ANGLE OF SLINGS 58 
 
 STRING BRAKE METHOD FOR INPUT-OUT- 
 PUT ON INDUCTION MOTORS 223 
 
 485 
 
Subject , p AG e 
 
 STUD POTENTIAL CURVE, D-C. GENERATOR 147 
 
 SWITCHBOARDS 14 
 
 SWITCHES: 
 
 MS 363 
 
 MU Tripping 364 
 
 SYNCHRONOUS CONVERTERS (See Converters) 
 
 SYNCHRONOUS IMPEDANCE 172 
 
 On Various Machines (See Machine Type Heading) 
 SYNCHRONOUS MOTORS (See Motors, Synchro- 
 nous) 
 
 TA FORM A 2 (VOLTAGE REGULATOR) 323 
 
 Form F (Voltage Regulator) 333 
 
 Form K (Voltage Regulator) 338 
 
 Form L (Voltage Regulator) 333 
 
 TABLES, TESTING 19 
 
 TACHOMETERS ; 32 
 
 TAPS: 
 
 Transformers 392 
 
 Starting Compensators 347 
 
 TD FORM L (VOLTAGE REGULATOR) 340 
 
 Form R 341 
 
 Form S 340 
 
 Form T 340 
 
 Form W 342 
 
 TEMPERATURE: 
 
 Coils : 103 
 
 Rise of Bearings 88, 103 
 
 Rise on Heat Runs 103 
 
 Rise, Formula for 112, 399 
 
 TERMINAL BOARD (A-C. GENERATOR) 173 
 
 TESTING: 
 
 Records 106, 107 
 
 Sets (High Potential) 
 
 TEST REPORT 107 
 
 TEST TRACKS (GENERAL ELECTRIC) 300, 304 
 
 Electric Locomotives 300 
 
 Friction by Free Running 304 
 
 Friction from Coasting 304 
 
 Mounting Motors on Trucks 302 
 
 Operating Rules 304 
 
 Order of Tests 300 
 
 Pull Curve 302 
 
 Service Heat Runs 303 
 
 Trolley Bases 302 
 
 Train Friction ■. 303 
 
 THERMAL CHARACTERISTICS (RAILWAY 
 
 MOTORS) 165 
 
 THERMOMETERS: 
 
 Placing of 101 
 
 Reading of, During Heat Runs 144, 14o 
 
 486 
 
Subject Page 
 
 THOMSON BRIDGE 40 
 
 THREE-WIRE: 
 
 Balancer Sets 154 
 
 D-C. Generators, Comm. Pole 153 
 
 Xon-Comm. Pole 147 
 
 THRUST BEARINGS 88 
 
 For Turbines 251 
 
 TIME-CURRENT CURVE (RAILWAY FUSES) ... 369 
 TORQUE: 
 
 Formulae for 220 
 
 On Induction Motors, Stationary 220 
 
 On Synchronous Motors 188 
 
 Recorder, Stationary 29 
 
 TRACTIVE EFFORT 169 
 
 TRAIN CONTROL APPARATUS 360-372 
 
 Air Brake Apparatus 360 
 
 Air Valves 360 
 
 Governors : 361 
 
 Strainers 361 
 
 Circuit Breakers (Railway) 371 
 
 Connection Boxes 364 
 
 Contactors (Railway) 364 
 
 Finger Pressure 366 
 
 Heat Runs 368 
 
 Life Tests 368 
 
 Minimum Pick Up 366 
 
 Pull Curves, A-C 367 
 
 D-C 367 
 
 Saturation Curve 367 
 
 Speed Curve 368 
 
 Wipe 366 
 
 Work Curve . ■ 368 
 
 Contactor Boxes 370 
 
 Controllers 361 
 
 Automatic and Semi- Automatic 362 
 
 Pilot Valves for 363 
 
 Couplers 370 
 
 Cutouts 364 
 
 Fuses 369 
 
 Time-Current Curve 369 
 
 Fuse Boxes 369 
 
 Inspection and High Potential Tests 360 
 
 Jumpers 371 
 
 MS Switches 363 
 
 MU Tripping Switches 364 
 
 Relavs (Railway) 372 
 
 TRAIN FRICTION 303 
 
 TRAMMEL 152 
 
 TRANSFORMERS: 
 
 Current 50 
 
 Potential 48 
 
 4.S 
 
Subject p AGE 
 TRANSFORMERS— Cont'd 
 
 Power (See Transformer Tests) 
 
 Shop ' 23 
 
 TRANSFORMER TESTS 384-420 
 
 Constant Potential 384 
 
 Commercial Tests 384 
 
 Complete Test 384 
 
 Core Loss and Exciting Current 393 
 
 Efficiency 384 
 
 Calculation of 404 
 
 Exciting Current 393 
 
 Failures in Test 404 
 
 Heat Run 395 
 
 High Potential 400 
 
 Impedance 393 
 
 Induced Voltage 403 
 
 Insulation Tests 384 
 
 Order of Tests 385 
 
 Phase Rotation 390 
 
 Polarity 386 
 
 Preparation for Test 385 
 
 Ratio 391 
 
 Regulation . 384 
 
 Calculation of 405 
 
 Resistance, Cold 386 
 
 Taps, Checking 392 
 
 Types of 384 
 
 Air Blast 384 
 
 Natural Draft ? 384 
 
 Oil-Cooled 384 
 
 Water- and Oil-Cooled 385 
 
 Reactances 418 
 
 Tests Required 419 
 
 Double or Triple Voltage 419 
 
 Heat Run 419 
 
 High Potential 419 
 
 Impedance 419 
 
 Resistance, Cold 419 
 
 Regulators, Induction 406 
 
 Type BR 414 
 
 Tests Required 415 
 
 Auxiliary Apparatus 418 
 
 Core Loss 415 
 
 Heat Run 416 
 
 High Potential 418 
 
 Impedance 416 
 
 Induced Voltage 418 
 
 Ratio 415 
 
 Resistance, Cold 415 
 
 Polyphase 410 
 
 Tests Required 411 
 
 488 
 
Subject Page 
 TRANSFORMER TESTS— Cont'd 
 Regulators, Induction 
 
 Auxiliary Apparatus 414 
 
 Core Loss 412 
 
 Heat Run 412 
 
 Polyphase 
 
 Tests Required 
 
 High Potential 413 
 
 Impedance 412 
 
 Induced Voltage 414 
 
 Noise Test 414 
 
 Ratio and Polarity 411 
 
 Resistance, Cold 411 
 
 Single-Phase 406 
 
 Tests Required 407 
 
 Auxiliary Apparatus 409 
 
 Core Loss 408 
 
 Heat Run 408 
 
 High Potential 408 
 
 Impedance 408 
 
 Induced Voltage 409 
 
 Noise Test 409 
 
 Polarity 407 
 
 Ratio 407 
 
 Resistance, Cold 407 
 
 Series Lighting 419 
 
 TRIP RIGGING, EMERGENCY, FOR TUR- 
 BINES 241 
 
 TROLLEY BASES (ELECTRIC LOCOMOTIVES) 302 
 
 TRUCKLIGHT CONTROLLER 380 
 
 TRUING COMMUTATORS 95 
 
 TUBES, APPLYING HIGH POTENTIAL TO 359 
 
 TURBINES, STEAM 227-284 
 
 Bafflers 238, 263 
 
 Balance, Field 246 
 
 Wheel 243 
 
 Bearings, Thrust 251 
 
 Commercial Test 227 
 
 Defects 273 
 
 Generators 265 
 
 Tests 269 
 
 Alternators 269 
 
 *' Motoring" 272 
 
 Record Sheets 273 
 
 Resistance, Cold 269 
 
 Shutting Down 272 
 
 Ventilation 273 
 
 Zero Excitation Heat Run 272 
 
 D-C. Generators 273 
 
 Governor Tests, Emergency 247 
 
 Operating .' 251 
 
 Instruments 233 
 
 489 
 
Subject P AGE 
 TURBINES, STEAM— Cont'd 
 
 Nomenclature 227 
 
 Piping, Steam, Exhaust and Oil ; 232 
 
 Preparing for Test 233 
 
 Oil Flow 235 
 
 Packing Rings, Carbon 241 
 
 Step Bearing 238 
 
 Trip Rigging 241 
 
 Water Leaks 233 
 
 Special Instructions 233 
 
 Special Tests 232 
 
 Steam Consumption Test 274 
 
 Arrangement of Apparatus 283 
 
 Auxiliary Pumps 284 
 
 Cautions 284 
 
 Equipment, Electrical 284 
 
 Steam Controlling 283 
 
 Assembly 274 
 
 Loading . . : 279 
 
 Water Brake 280 
 
 Preparation for Test 274 
 
 Readings ,. . . . 275 
 
 Flow 279 
 
 Tanks 279 
 
 Pressure 275 
 
 Temperature 278 
 
 Tests 281 
 
 Bowl Pressure Curve 283 
 
 Load Curve 282 
 
 Maximum Load, Non-Condensing 282 
 
 No-Load Flow 282 
 
 Shell Pressure Curve 283 
 
 Speed Curve 282 
 
 Superheat Curve 283 
 
 Vacuum Curve 282 
 
 Valves, Stage 265 
 
 TURBO-ALTERNATORS (See Turbines) 
 
 TYPES OF TRANSFORMERS 384 
 
 UNBALANCED READINGS, (3-WIRE GENER- 
 ATORS) 149 
 
 U-TUBES 26, 277 
 
 VACUUM GAUGE 27 
 
 VALVES: 
 
 For Marine Engines 293 
 
 For Railway Controllers, Pilot 363 
 
 Stage 265 
 
 VARIABLE SPEED D-C. MOTORS 162 
 
 VENTILATION TESTS: 
 
 D-C. Motors 171 
 
 Turbine Sets ■ 273 
 
 490 
 
Subject • Page 
 
 VOLTAGE RANGE CURVES (SPLIT POLE SYN. 
 
 CONVERTERS) 204 
 
 VOLTAGE: 
 
 Ratio (Synchronous Converter) 191 
 
 Regulation (See Regulation) 
 
 Regulators (See Regulators) 
 
 VOLTMETERS 45 
 
 Calibration Constant 46 
 
 Milli 46 
 
 WATER BOXES 21, 176 
 
 WATER-BRAKE, USE OF 280 
 
 WATER RATE (See Steam Consumption) 
 
 WATTMETERS 51 
 
 Correction for Phase Angle 55 
 
 WAVE FORM: 
 
 Potential Curve between Brushes 134 
 
 A-C. Generators 182 
 
 WAVE SHAPES 34 
 
 WEIGHTS OF VARIOUS MATERIALS 62 
 
 WHEATSTONE BRIDGE 37 
 
 WHEEL BALANCE, STEAM TURBINES 243 
 
 WINDING DEVICES (MINING LOCOMOTIVES) 354 
 
 WIPE (RAILWAY CONTACTORS) 366 
 
 WIRING 98 
 
 Motor Fields 99 
 
 Transformers 100 
 
 Svnchronous Converters 193 
 
 WORK CURVE (RAILWAY CONTACTORS) 368 
 
 ZERO EXCITATION HEAT RUN (STEAM TUR- 
 BINE GENERATOR) 272 
 
 ZERO POWER-FACTOR HEAT RUN 180 
 
 491 
 
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