Chapter I: Front Matter

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

HAWKINS
ELECTRICAL GUIDE
NUMBER
FIVE

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. 5.

~ALTERNATING CURRENTS~ 997 to 1,066

The word "_alternating_"--advantages of alternating
current--direct current apparatus; alternating current
apparatus--disadvantages of alternating current--~alternating
current principles~--the sine--application and construction of
the sine curve--~illustrated definitions~: cycle, alternation,
amplitude, period, periodicity, frequency--commercial
frequencies--advantages of low frequency--~phase~--phase
difference--phase displacement--synchronism--"in phase"--curves
illustrating "in phase" and "out of phase"--~illustrated
definitions~: in phase; in quadrature, current leading;
in quadrature, current lagging; in opposition--~maximum~
volts and amperes--~average~ volts and amperes--elementary
alternator developing one average volt--~virtual~ volts and
amperes--~effective~ volts and amperes--relation between
shape of wave and ~form factor~--wave form--oscillograph
wave form records--what determines wave form--effect of one
coil per phase per pole--~single phase current~; hydraulic
analogy--~two phase current~; hydraulic analogy--two
phase current distribution--~three phase current~;
hydraulic analogy; distribution--~inductance~--~the
henry~--inductive and non-inductive coils--hydraulic analogy
of inductance--inductance coil calculations--~ohmic value of
inductance~--~capacity~: hydraulic analogy--the farad--specific
inductive capacity--condenser connections--~ohmic value of
capacity~--lag and lead--mechanical analogy of lag--lag
measurement--steam engine analogy of current flow at zero
pressure--~reactance~--examples--choking coil--impedance
curve--~resonance~--critical frequency--skin effect.

~ALTERNATING CURRENT DIAGRAMS~ 1,067 to 1,100

~Definitions~: impressed pressure, active pressure,
self-induction pressure, reverse pressure of
self-induction--rate of change in current strength--properties
of right angle triangles--equations of the right
triangle--representation of forces by wires--parallelogram
of forces; ~the resultant~--~circuits containing resistance
and inductance~--graphical method of obtaining the
impressed pressure--~equations for ohmic drop and reactance
drop~--examples--diagram for impedance, angle of lag,
etc.--~circuits containing resistance and capacity~--capacity
in series, and in parallel--amount of lead--action of
condenser--the condenser pressure--capacity pressure--equation
for impedance--- examples and diagrams--~circuits
containing resistance, inductance, and capacity~--impedance
equation--examples and diagrams--equation for impressed
pressure--examples and diagrams.

~THE POWER FACTOR~ 1,101 to 1,124

Definition of power factor--true watts--- apparent watts--ferry
boat analogy of power factor--limits of power factor--effect
of lag or lead--~how to obtain the power curve~--nature of
the power curve--synchronism of current and pressure; ~power
factor unity~--case of synchronism of current and pressure
with power factor less than ~unity~--steam engine analogy of
power factor--"wattless current;" ~power factor zero~--examples
of phase difference nearly 90 degrees--mechanical analogy
of wattless current--~why the power factor is equal
to cos φ~--graphical method of obtaining the active
component--examples and diagrams--effect of capacity--diagrams
illustrating why the power factor is ~unity~ when there is
no resultant reactance in the circuit--~usual value of power
factor~--power factor test--~how alternators are rated;
kva.~--curves illustrating power factor--~how to keep the
power factor high~--why power factor is important in station
operation--wattmeter method of three phase power measurement.

~ALTERNATORS~ 1,125 to 1,186

Uses of alternators--classes of alternator--~single phase
alternators~; essential features; width of armature
coils--elementary single phase alternator--~polyphase
alternators~--uses for two and three phase current--elementary
three phase alternator--starting difficulty with single phase
motors--six and twelve phase windings--~belt or chain driven
alternators~--sub-base and ratchet device for tightening
the belt--~horse power transmitted by belts~--best speeds
for belts--advantages of chain drive; objections--~direct
connected alternator~--"direct connected" and "direct
coupled" units--~revolving armature alternators~; their
uses--~revolving field alternators~--marine view showing
that motion is purely a relative matter--essential parts
of revolving field alternator--the terms "stator" and
"rotor"--inductor alternators: classes, use, defects--hunting
or surging in alternators--~amortisseur~ windings--~monocyclic
alternators~--diagram of connections--teaser coil--~armature
reaction~--distortion of field--strengthening and
weakening effects--superpositions of fields--three phase
reactions--~magnetic leakage~--~field excitation of
alternators~--self-excited alternator--direct connected
exciter--gear driven exciters--~slow speed alternators~--~fly
wheel alternators~--~high speed alternators~--~water wheel
alternators~--construction of rotor--~turbine driven
alternators~--construction--step bearing--~alternators of
exceptional character~--asynchronous alternators--image current
alternators--extra high frequency alternators--self-exciting
image current alternators.

CONSTRUCTION OF ALTERNATORS~ 1,187 to 1,266

~Essential parts of an alternator~--field magnets--~methods
of excitation~: self-excited, separately excited,
compositely excited--magneto--construction of stationary
magnets--revolving field--slip rings--spider for large
alternator--provision for shifting armature to give access
to field--~armatures~--core construction--advantages of
slotted core armatures--~armature windings~--~classification~:
revolving and stationary windings--half coil and whole coil
windings--~concentrated~ or uni-coil winding; features;
waveform--~distributed~ or multi-coil windings: breadth
of coil, partial and fully distributed coils--the Kapp
coefficient--general equation for voltage--wire, strap, and
bar windings--condition, governing type of inductor--coil
covering--single and double layer multi-wire inductors and
methods of placing them on the core--~insulation~--core
stamping--single and multi-slot windings--- arrangement in
slot of two layer bar winding--table of relative effectiveness
of windings--~single phase windings~--advantage of half coil
winding--~two phase windings~--shape of coil ends--three
phase windings--shape of coil ends--kind of coil used with
three phase windings--~grouping of phases~--two phase
~star connection~--two phase ~mesh connection~--three
phase star connection--winding diagrams with star and
Δ connections--three phase Δ connection--three phase
winding with "short" coils--three phase lap winding star
connection--three phase wave winding star connection--~output
of star and delta connected alternators~--gramme ring
armatures showing three phase star and mesh connections
with direction of currents in the coils--features of star
connection--characteristics of delta connection--proper
ends to connect to star point--determination of path
and value of currents in delta connection--points to be
noted with ~Y~ connection--diagram of ~Y~ connection with
return wire--chain or basket winding--skew winding--fed-in
winding--imbricated winding--spiral winding--mummified
winding--shuttle winding--creeping winding--~turbine alternator
winding~: how the high voltage is obtained with so few poles;
table of frequency and revolutions--~turbine alternator
construction~--form of armature generally used--two pole radial
slot field--parallel slot field--difficulty experienced with
revolving armatures--how the field design is modified to reduce
centrifugal force--examples of revolving fields.