Chapter I: Front Matter

THE THOUGHT IS IN THE QUESTION THE INFORMATION IS IN THE ANSWER

HAWKINS
ELECTRICAL GUIDE
NUMBER
SIX

QUESTIONS
ANSWERS
&
ILLUSTRATIONS]

A PROGRESSIVE COURSE OF STUDY
FOR ENGINEERS, ELECTRICIANS, STUDENTS
AND THOSE DESIRING TO ACQUIRE A
WORKING KNOWLEDGE OF

ELECTRICITY AND ITS APPLICATIONS

A PRACTICAL TREATISE
by
HAWKINS AND STAFF

COPYRIGHTED, 1914,
BY
THEO. AUDEL & CO.,
NEW YORK.

Printed in the United States.

TABLE OF CONTENTS

GUIDE NO. 6.

~ALTERNATING CURRENT MOTORS~ 1,267 to 1,376

Classification--~synchronous motors~--essential
parts--_synchronous motor principles:_ condition for
starting; effective pressure; dead centers; speed; limit
of lag; effect of load changes--effect of altering the
field strength--disadvantages of synchronous motors;
advantages--~the "V" curve~--adaptation--efficiency--~hunting
of synchronous motors;~ mechanical analogy--use as
condenser--surging--characteristics of synchronous motors:
starting; running; stopping; effect upon circuit; power
factor; auxiliary apparatus; adaptation--~induction
(asynchronous) motors~--essential parts--types--_oscillating
magnetic field--rotating magnetic field_--operation of
single phase motor; why not self starting; provision for
starting--operation of polyphase induction motor; why called
asynchronous--speed; classification according to speed--the
terms _primary_ and _secondary_--why polyphase induction
motors are explained before single phase--~polyphase induction
motors~--features--essential parts--_principles_--production
of rotating field--Tesla's rotating field--method of
obtaining resultant flux of Tesla's field--_Arago's
rotations;_ explanation--Faraday's experiment--production
of two phase rotating field; resultant poles--six and
eight pole two phase rotating fields--_physical conception
of two phase rotating field_--production of three phase
rotating field; with ring winding--_physical conception
of three phase rotating field_--three phase six pole
winding--~slip~--_copper cylinder illustrating principle of
operation of induction motor_--calculation of slip--table
of synchronous speeds--variation of slip; why so small;
variation with load; table of variation--sector method of
measuring slip--_evolution of the squirrel cage armature;_
construction--~the field magnets;~ parts; construction--~field
windings for induction motors~--calculation for
revolutions of rotating field; objection to high speed of
field--difficulty with low frequency currents--general
character of field winding--formation of poles--grouping of
coils--_starting of induction motors:_ external resistance,
auto-transformer, internal resistance methods--~internal
resistance induction motors;~ adaptation--how resistance
is cut out--why not desirable for large sizes--~external
resistance or slip ring motors~--operation--armature
connections--~single phase induction motors~--service
suitable for--disadvantage--parts--why not self-starting--how
started--~phase splitting; production of rotating field
from oscillating field~--methods--starting coils--~shading
coils~--character of the starting torque--modification of
armature for starting with heavy load--clutch type of single
phase induction motor; its action in starting--~commutator
motors~--classification--_action of closed coil rotating
in alternating field_--the transformer pressure--generated
pressure--self-induction pressure--local armature currents;
reason for sparking; how reduced--high resistance
connectors--effect of low power factor--effect of
frequency--~series motor~--features--adaptation--~neutralized
series motor~--conductive method--inductive method--~shunt
motors--repulsion motors~--difficulty with early motors--means
employed to stop sparking--~essentials of single repulsion
motors~--the term repulsion induction motor--compensated
repulsion motor--~power factor of induction motors~--its
importance--false ideas in regard to power factor--~speed and
torque of motors~.

~TRANSFORMERS~ 1,377 to 1,456

Their use--essential parts--~basic principles~--the primary
winding--the secondary winding--_magnetic leakage_--~the
induced voltage~--no load current--magnetizing current--action
of transformer with load--classification--~step up
transformers~--use--construction--copper economy--~step
down transformers~--use--construction--~core
transformers~--construction--advantages--~shell
transformers~--comparison of core and shell
types--choice--~combined core and shell transformers~--economy
of construction--~single and polyphase transformers~--features
of each type--choice of types for polyphase
currents--operation of three phase transformer with one phase
damaged--~transformer losses~--~hysteresis~--what governs
the loss--how reduced--~eddy currents~--lamination--thickness
of laminæ--importance of iron losses--how to reduce
iron losses--~copper losses~--how caused--effect
on power factor--effect of resistance--~cooling of
transformers~--cooling mediums employed--heating of
transformers--objection to heating--~dry transformers~--~air
cooled transformers~--natural draught type--forced
draught or air blast type--construction of coils for air
cooling--requirements with respect to air supply--quantity
of air used--~oil cooled transformers~--circulation of
the oil--action of the oil--objection to oil--kind of
oil used--oil requirements--moisture in oil--~water
cooled transformers~--internal coil type--external coil
type--_thermo-circulation_--quantity of circulating
water required--~transformer insulation~--the
~"major"~ and ~"minor" insulation~--mica--outdoor
transformers for irrigation service--oil insulated
transformers--efficiency of transformers--efficiency
curve--~all day efficiency of transformers~--transformer fuse
blocks--auto-transformers--~constant current transformers
for series arc lighting~; elementary diagram illustrating
principles--regulation--transformer connections--single phase
connections--combining transformers--precautions--operating
secondaries in parallel--connections for different
voltages--precautions--two phase connections--~three phase
connections:~ delta, star, delta star, star-delta--comparison
of star and delta connections--three phase
transformers--comparison of air blast, water cooled, and oil
cooled transformers--standard transformer connections--~how
to test transformers~--transformer operation with grounded
secondary--transformer capacity for motors--transformer
connections for motors--arc lamp transformer--transformer
installed on pole--static booster or regulating transformer.

~CONVERTERS~ 1,457 to 1,494

Where used--kinds of converter--A.I.E.E.
classification--~rotary
converters~--operation--speed--principles--relation
between input and output pressures--single and polyphase
types--advantage of polyphase converters--armature
connections of polyphase converter--pressure
relation--voltage variation--advantage of unity power
factor--effect of field too strong--~compounding of
rotary converters~--~ratio of conversion~--~voltage
regulation~--split pole method--regulating pole method--best
location of regulating poles--~reactance method~--~multi-tap
transformer method~--~synchronous booster method~--winding
connections--field connections--adaptation--~motor generator
sets~--classification--standard practice--behavior of
rotary when hunting; comparison with motor generator
sets--racing--~frequency changing sets~--~parallel operation
of frequency changers~--~cascade converter~--speed--action in
motor armature winding--advantages--how started--comparison of
cascade converter with synchronous converter.

~RECTIFIERS~ 1,495 to 1,530

Classification--~mechanical rectifiers~--essential
features--construction--application--~electrolytic
rectifiers~--principles of operation--Mohawk rectifier--the
term "_valve_"--metals for electrodes--electrolyte--Nodon
valve--Audion valve--Buttner valve--Churcher valve--De Faria
valve--Fleming oscillation valve--Grisson valve--Pawlowski
valve--Giles electric valve--Buttner valve--~mercury vapor
rectifiers~--principles--the terms "arc" and "vapor"--three
phase mercury vapor rectifier--construction--auxiliary
apparatus--series mercury arc rectifier--dissipation
of heat from bulb--replacement of bulb--advantages of
rectifier--precautions in installing--~electromagnetic
rectifiers~--construction and operation.