International Correspondence Schools.

Electric railway systems ; Electric-railway line construction ; Track construction ; Electric-railway calculations ; Railway motors ; Electric-car equipment ; Speed control ; Efficiency tests ; Switch-gear ; Electric stations ; Electric substations ; Operation of electrical machinery online

. (page 1 of 45)
Online LibraryInternational Correspondence SchoolsElectric railway systems ; Electric-railway line construction ; Track construction ; Electric-railway calculations ; Railway motors ; Electric-car equipment ; Speed control ; Efficiency tests ; Switch-gear ; Electric stations ; Electric substations ; Operation of electrical machinery → online text (page 1 of 45)
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/I



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Electric Railway Systems;
Electric-railway Lin e ...

International Correspondence Schools



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K.F.WENDT LIBRARY

UV¥ COLLEGE OF ENGR.

215 N'. RANDALL AVENUE

MADISG.vWI 53706




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INTERNATIONAL
LIBRARY OF TECHNOLOGY



A SERIES OF TEXTBOOKS FOR PERSONS ENGAGED IN THE ENGINEERING

PROFESSIONS AND TRADES OR FOR THOSE WHO DESIRE

INFORMATION CONCERNING THEM. FULLY ILLUSTRATED

AND CONTAINING - NUMEROUS PRACTICAL

EXAMPLES AND THEIR SOLUTIONS



ELECTRIC RAILWAY SYSTEMS

ELECTRIC-RAILWAY LINE CONSTRUCTION

TRACK CONSTRUCTION

ELECTRIC-RAILWAY CALCULATIONS

RAILWAY MOTORS

ELECTRIC-CAR EQUIPMENT

SPEED CONTROL

EFFICIENCY TESTS

SWITCHGEAR

. ELECTRIC STATIONS

ELECTRIC SUBSTATIONS

OPERATION OF ELECTRICAL MACHINERY



SCRANTON
INTERNATIONAL TEXTBOOK COMPANY

136



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Electric Railway Systems: Copyright. 1015, by International Tkxtvook CpMi>ANT.

Electric-Railway Line Conatruction: Copyright, 1915, by Intbrnational Textbook
Company.

Track Construction: Copjrrigfat, 1015, by International Textbook Company.

Electric-Railway Calculations: Copyright, 1016. by International Textbook Com-
pany.

Railway Motors: Copyright, 1015, by International Textbook C<»<pany.

Electric-Car Bquiinaent: Copyright, 1915, by International Textbook C<»<pany.

Speed Control: Cof^yriflfht, 1915, by International TExVbooK Company.

Efficiency Tests': Copyright, 1015, by International Textbook Company.

Switchgear: Copyright, 19 15. by International Textbook Company.

Electric Stilions: Cofilyright. 1915. by International Textbook Comfai^y.

Electric Substotions: Copyriitht, 1915. by International Textbook Company.

Operation of Electrical Machinery. ParU 1 and 2: Copyright, 1915, by International
Textbook Company.

Copyright in Great Britaitu



All rights reserved.



I^RESS OP

IkrrERNATlONAL TbXTBOOK COMPANY

SCRANTON, Pa.



70186
136



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205471

AUG 24 1916
SB

I3G



PREFACE



The volumes of the Intematiotial Library of Technolotgy are
made up of InstrucJtion Papers, or Sections, comprising the
various cburses of instruction fdr students of the International
Correspondence Schools. The original manuscript fof eadi
Instruction Paper is prepared by a person thoroughly qualified,
both technically and by experience, to write with authority
on his subject. In many cases the writer is regularly employed
elsewhere in practical work and writes for us during spare time.
The manuscripts are then catef ully edited to make them suitable
for correspondence work.

The only qualification for enrolment as a student in these
Schools is the ability to read English and to write intelligibly
the answers to the Examination Questions. Hence, our stu-
dents are of all grades of education, and our Instruction Papers
are, therefore, written in the simplest possible language so as
to make them readily understood by all students. If tech-
nical expressions are essential to a thorough imderstanding of
the subject, they are clearly explained when first introduced.

The great majority of our students wish to prepare them-
selves for advancement in their vocations or to qualify for
other and more congenial occupations. Their time for study
is usually after the day's work is done and is limited to a few
hoiu^ each day. Therefore, every effort is made to give them
practical and acciu*ate information in clear, concise form, and
to make this information include all of the essentials but none
of the non-essentials. To effect this result derivations of rules
and formulas are usually omitted, but thorough and complete
instructions are given regarding how, when, and imder what
conditions, any particular rule, formula, or process should be

iii



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iv PREFACE

applied. Whenever possible one or more examples, such as
would be likely to arise in actual practice, together with their
solutions, are given for illustration.

As the best way to make a statement, explanation, or descrip-
tion clear is to give a picture or a diagram in connection with
it, illustrations are very freely used. These illustrations are
especially made by our own Illustrating Department in order
to adapt them fully to the requirements of the text. Projec-
tion drawings, sectional drawings, outline drawings, perspec-
tive drawings, partly shaded or full shaded, are employed,
according to which will best produce the desired result. Half-
tone engravings are used only in those cases where the general
effect is desired rather than the actual details.

In the table of contents that immediately follows are given
the titles of the Sections included in this volvime, and under
each title is listed the main topics discussed. At the end of
the volume will be found a complete index, so that quick
reference can be made to any subject treated.

Intbrnational Textbook Company



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CONTENTS



Electric Railway Systems Section Page

Introduction 17 1

Direct-Current Railway Systems 17 2

Current-Collection Systems 17 2

Energy Distribution Systems for Direct-
Current Operation 17 6

Alternating-Current Railway Systems ... 17 23
Energy Distribution Systems for Alternating-
Current Operation 17 23

Energy Calculations 17 27

General Consideration 17 27

Passenger Factor and Length of Track ... 17 28

Number of Cars 17 29

Size and Weight of Cars . 17 30

Tractive-EflFort Formulas 17 31

Power Formulas 17 43

Energy Tests 17 47

Location of Power House 17 54

EnergyCosts ' 17 67

Electric-Railway Line Construction

Overhead Systems 18 1

Line Poles 18 1

Feeders 18 6

Trolley Wires 18 13

Line Lightning Arresters 18 30

Catenary Line Construction 18 30

Third-Rail Systems 18 49

Conduit Systems 18 67

V



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vi CONTENTS

Track Construction Section Page

Roadbeds *. . 19 1

Hints on Construction 19 1

Typical Roadbeds 19 3

TheTrack 19 6

Ties ; 19 6

Rail and Tie Acces^Hcs 19 9

Rails 19 12

Rail Joints 19 18

RallSonds 19 26

Special Work 19 32

Maintenance of Track 19 39

Electric-Railway Calculations

Line Calculations 20 1

Conditions Affecting the Size of Feeders . . 20 1

Feeder Formulas 20 3

Track Resistance 20 5

Feeder Problems 20 11

Importance of Low- Voltage Drop 20 25

Line Tests • 20 26

Bond Tests 20 26

Feeder and Track-Return Tests 20 32

General Engineering Features 20 33

Rail Calculations 20 33

Curve Calculations 20 .34

Grade Calculations 20 38

Track Tests 20 38

Electrolysis 20 40

Railway Motors

Preliminary Considerations 21 1

Operating Requirements 21 1

Gear deduction 21 2

Motor Rating 21 4

Direct-Current Motors . 21 4

Description of Motor 21 4

Features of Construction 21 7

Alternating-Current Motors 21 12



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CONTENTS vii

Railway Motors — Continued Section Pfige

Description of Motor 21 12

Featxires of Operation 21 14

Motor Characteristics 31 17

Motor Installation and Maintenance ... 21 20

Electric-Car Equipment

Motor-Circuit and Auxiliary Apparatus . . 22 1

Trunk Connections 22 1

Lightning Arresters 22 16

Lighting, Heating, and Auxiliary Apparatus 22 19

Electric-Car Lighting 22 19

Electric Car Heating 22 27

Auxiliary Car Devices . 22 34

CarHouse 22 56

Pit Room 22 57

Repair Shop 22 58

Speed Control

Methods of Speed Control 23 1

Rheostatic Control .23 2

Series-Parallel Cylinder Control 23 3

Series-Parallel Multiple-Unit Hand C<^trpl 23 12
Series-Parallel Multiple-Unit Automatic

Control .23 20

Single^Ph^se Speed Control 23 28

Control for Storage-Battery Car 23 34

Control for Gasoline-Electric Car 23 35

Efficiency Tests

Comparison of Methods 52 1

Losses K 2

Direct-Current Machines 52 4

Resistance Measurements 52. 4

Running-Light Test 52 8

Generator Test 52 8

MotorTest 52 ' 17

Loading^Back Test 52 19

Series-Motor Test 52 25



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vui CONTENTS

Efficiency Tests — Continued Section Page

Altonating-Current Machines 52 28

Alternator Running-Light Test 52 28

Synchronous-Motor Running-Light Test . . 52 31

Alternator Test With Auxiliary Motor ... 52 31

Induction-Motor Test 52 37

Transformer Test . 52 40

SWITCHGEAR

Requirements of Switchgear Construction . 53 1

General Classifications 53 3

Direct-Current Switchgear 53 3

Circuit-Opening Devices 53 3

Direct-Current Regulating Devices .... 63 14
Lightning Arresters for Direct-Current Cir-
cuits 53 20

Alternating-Current Switchgear 53 23

Circuit-Opening Devices . 53 23

Alternating-Current Regulating Devices . . 53 35
Lightning Arresters for Alternating-Current

Circuits 53 35

The Assembled Switchboard 53 39

Definition and General Requirements ... 53 39

Pressure Wiring 53 40

Direct-Current Switchboards 53 40

Alternating-Current Switchboards .... 53 43

Electric Stations

Number and Capacities of Units 54 1

Conductors and Current Densities 54 3

Direct-Current Generating Stations .... 54 4

Railway Stations 54 4

Direct-Current Light and Power Stations . . 54 14

Alternating-Current Stations 54 28

Parallel Operation of Alternators 54 28

Synchronizing Circuits 54 29

Small Alternating-Current Stations .... 54 38

Medium-Size Alternating-Current Stations . 54 45

Large Alternating-Current Stations .... 54 50 '



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CONTENTS ix

Electric Substations Section Page

Purpose of Substations 55 1

Similarity Between Substations and Gener-
ating Stations 55 3

Direct-Current Substations 55 4

* Miscellaneous Equipment 55 6

Transformers 55 9

Choice Between Synchronous Converters and

Motor-Generators 55 13

Motor-Generator Substations With Induc-
tion Motors 55 15

Motor-Generator Substations With Synchro-
nous Motors 55 23

Sjnichronous-Converter Substations for Rail-

wajrs 55 26

Sjnichronous-Converter Stations for Light

andPower 55 38

Synchronizing Circuits for Rotary Con-
verters 55 50

Automatic Synchronous-Converter Substa-
tions 55 52

Alternating-Current Substations ..... 55 54

Frequency-Changer Substations 55 54

Transformer Substations 55 57

Operation op Electrical Machinery

Safe Operating Temperatures 56 1

Operation of Electric Motors 56 4

Direct-Current Motors 56 4

Alternating-Current Motors 56 10

Operation of Direct-Current Generators . . 56 16

Preliminary Inspection 56 16

Shunt Generators 56 16

Compound Generators 56 22 •

Series Generators 56 24

Field Circuits of Direct-Current Generators 56 26

Edison Three-Wire System 56 27

Tirrill Regxilators With Direct-Current

Generators 56 28



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X CONTENTS

Operation op Electrical Machinery — Continued

Section Page

Routine Care and Insp^tion 56 30

Operation of Alternating-Current Generators 66 31

Preliminary Inspection 56 31

Operation of Single Alternator 56 32

Series Operation 56 33

Parallel Operation -56 33

TirrillRegulators With Alternators .... 56 39

Operating Troubles of Alternators 56 43

Operation of Motor-Generators and Syn-
chronous Converters 57 1

Motor-Generators for Current Conversion . 57 1
Induction-Motor-Driven Frequency Chang-

ere 57 4

Synchronous - Motpr - Driven Ereq|Liency

Changers 57 4

Sjmchronous Converters 57 18

Miscellaneous Equipment . . , 57 29

Storage Batteries 57 29

Series Booster Generators . 57 35

Transformers 57 36

Potential Regulators on Distributing Cir-
cuits ... 57 36

Care and Maintenance of Electrical

Machinery 57 37

General Instructions 57 37

Troubles of Direct-Current Machines . . *. 57 41

Troubles of Alternating-Current Machines . 57 52

Dangers of Physical Injury 57 54

Tests for Faults in Electrical Circuits ... 57 57

Classification 57 57

Qualitative Tests 57 57

Quantitative Tests . 57 64



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ELECTRIC RAILWAY SYSTEMS



INTRODUCTION

1. A ntimber of railway systems have been developed in
which electric motors installed on the cars are utilized to drive
the cars and trains. Electric energy for the operation of these
motors is generated at one or more main stations and, for the
larger systems, is distributed through substations to conductors
leading to the moving cars.

The larger ntmiber of electric cars are propelled by direct-
current, or continuous-current, energy. In large systems alter-
nating-current energy is usually supplied by the main stations
to the substations, where it is converted by rotary converters
or motor-generators into direct-current energy for the car
motors.

Alternating-current motors are also used to propel the cars
in some railway systems; in such cases, the rotary-converter
substation is not required. Alternating-current energy is gen-
erated in the main station and utilized on the moving cars.

2. Electric railway systems are broadly classified according
to the kind of electric energy supplied to the motors on the cars,
as direcU-current or alternating-current systems, Ftirther classi-
fication is based on the method of current collection or supply
used on the moving cars, as trolley, third-rail, slot, storage-battery
car, and gasoline-electric car systems. The most generally used
is the the direct-current, trolley system. The other systems
mentioned have been adopted where other methods of cturent
distribution and collection must be employed to meet operat-
ing conditions or comply with city laws.

COPVmaHTSD by INTBIINATIONAL textbook company, all mOHTS RKSBRVBO

817

266—2



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ELECTRIC RAILWAY SYSTEMS § 17



DIRECT-CURRENT RAILWAY SYSTEMS



CURRENT-COLLECTION SYSTEMS



TROLLEY SYSTEM

3. The methods of supplying current to the cars usually
depend on the local conditions affecting operation of the sys-
tem. In most of the city and suburban roads, the trolley
system is employed because of its reasonable cost of installa-
tion and the small liability of people or vehicles coming in
cbntact with the trolley wire, which is a bare conductor sus-



PlG. 1

pended over the center of the tracks. This wire is connected
at intervals with large conductors, called feeders, which are often
moimted on the poles supporting the trolley wire. The feeders
are connected to the positive terminals of the main generators
or of the rotary converters. Each car is provided with a device
called a trolley. This consists of a pole moimted on the roof



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§ 17 ELECTRIC RAILWAY SYSTEMS 3

of the car and having at its upper end a wheel that runs in con-
tact with the lower surface of the trolley wire. Current passes
through the wheel and pole to the motors on the car and thence to
the rails. The rails are connected through the earth or through
copper conductors to the negative terminals of the generators or
rotary converters. A complete electric circuit is thus formed.

4. Fig. 1 shows the more important current-collection
features of a trolley system. All cars are in parallel between
the trolley wire and the grotmd ; therefore, the operation of any
car is independent of all others that are in normal condition.
An accident to one car cannot prevent the others from operating
unless the line is short-circuited by the accident.

5. A trolley system using a single trolley wire is called a
ground-return system, because the ground forms at least a part
of the negative side of the circuit, the rails being in contact with
the earth. In some early systems, two trolley wires placed side
by side were used. One wire was connected to the positive bus-
bars and the other wire to the negative bus-bars at the station.
Such a system is a metallic-return system, because both sides of
the circuit are metallic conductors; the rails and earth do not
form a part of the circuit. Two trolleys on each car must be
used and the overhead wiring in the streets is complicated.



THIBD-RAIL SYSTEM

6. The third -rail system is electrically the same as the
trolley system. The trolley wire is replaced by a third rail,
which is usually motmted on insulators to one side of the track
and a little above the level of the track rails. The current
passes to the car circuits through shoes that slide on the con-
tact rail and returns to the station through the track rails.
In a few cases, both positive and negative conductor rails have
been used, the track rails in such cases not being used as a
return circuit.

Fig. 2 shows the collecting-shoe arrangement for third-rail
equipment. The third rail a is of standard T section and is
supported on insulators b resting on every fifth tie, which is
extended for this purpose. The link-suspended cast-iron shoe c



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4 ELECTRIC RAILWAY SYSTEMS § 17

has a limited vertical movement and the whole collecting device
is moimted on a wooden beam d supported by the truck. A



i



cable e leads to the controlling devices on the car and con-
nection is made to the shoe through a bare, flexible, copper
cable / which is called the shoe shunt because it shtmts the



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§ 17 ELECTRIC RAILWAY SYSTEMS 5

current arotmd the link-pin connections, thereby preventing their
becoming blistered by the current crossing their comparatively
poor contacts. In some cases a shoe fuse is connected in the
circuit at g to cut off the current in case of a short circuit; the
fuse may be of either the enclosed or open type. The third-
rail construction is much used for heavy-traflSc, high-speed serv-
ice over private right of way where the live rail is not a menace
to persons and cattle. As the cross-section of the contact rail
has a large copper equivalent, long stretches of track can be
supplied with current without using feeders.



SLOT SYSTEM

7. The slot system, or open-conduit system. Figs. 3 and 4, is
used only in large cities where heavy traffic warrants the great



Pig. 3



expense of installation and city ordinances prohibit overhead
trolley wires and feeders. Two conductor rails a, one positive



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G ELECTRIC RAILWAY SYSTEMS § 17

and the other negative, are mounted in the conduit and are

connected through feeders run in
adjacent ducts to the positive
and negative terminals of the
generators at the station, thus
forming a metallic-return sys-
t«n. At the top of the conduit
is a f -inch slot between rails e,
through which passes a plow,
suspended from the car truck.
Flat steel springs h press two
cast-iron or soft-steel shoes s,
mounted on the lower part of the

^ plow, against the conductor

I rails. Flexible cables c extend

through the body of the plow

and connect through fuses, or

Fjg-* shoe shtmts, d. Fig. 4, to the

plow shoes. The upper ends of cables c. Fig. 3, connect to the

car circuit.

ENERGY DISTRIBUTION SYSTEMS FOR DIRECT-
CURRENT OPERATION

8. The term energy distribution systems as here used
applies to the arrangement of conductors by which electric
energy is transmitted from the main station, either directly or
through substations to the trolley wire or third rail, from which
the current for the car is taken. Systems using direct-current
motors on the cars are here considered; of these there are two
main divisions: (1) Direct-current generation and supply to
the cars; (2) alternating-current generation and direct-current
supply to the cars.

DIRECT-CURRENT GENERATION AND SUPPLY

9. 550- Volt System. — The simplest method of supply-
ing energy to cars is by direct current transmitted from the
generators in the main station to the trolley wire without any



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§17



ELECTRIC RAILWAY SYSTEMS



intervening transforming devices. The voltage between the
positive and n^ative bus-bars is generally from 600 to 600 volts;




the latter voltage is the later development. This system is
adapted to operation in sections of dense population where the
distances are not too great; it is not adapted to economical



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8 ELECTRIC RAILWAY SYSTEMS § 17

transmission of large amounts of energy over long distances,
because at low voltage the current required is very large and
the line losses excessive. Efforts to decrease these losses by
greatly increasing the copper result tmprofitably.

10. Fig. 5 indicates the more important connections of the
parts of a railway system of this simple type. An engine 5
drives a direct-current generator D, which is connected with
the switchboard K\ this is connected with the trolley and rails
forming a current path as indicated by the arrowheads.

11. Each car requires a current proportional to the power
necessary to operate it. The sum of the currents taken by the
cars forms the load on the station. The total current is indi-
cated by the ammeter connected to the negative bus-bar, as
in Fig. 5.

In a very small system, the trolley wire, if only in one sec-
tion, may be connected directly to the positive bus-bar without
the use of feeder cables. In large systems, the trolley wire is
usually in sections and is too small to carry all the current;
feeder cables are then provided to connect the positive bus-bar
directly with the more distant trolley wire sections.

12. Return cables connecting points on the track to the
negative bus-bars are installed in some systems. The con-
ductivity of the track-return portion of the circuit is thus



Online LibraryInternational Correspondence SchoolsElectric railway systems ; Electric-railway line construction ; Track construction ; Electric-railway calculations ; Railway motors ; Electric-car equipment ; Speed control ; Efficiency tests ; Switch-gear ; Electric stations ; Electric substations ; Operation of electrical machinery → online text (page 1 of 45)