CONTENTS
PAG K
PREFACE............................. v
CHAPTER I.—SPEED CONTROL OF INDUCTION MOTORS.
/. Starting and Acceleration
1. The problems of high torque over wide range of speed, and of
constant speed over wide range of load—Starting by armature
rheostat......................... 1
2. A. Temperature starting device—Temperature rise increasing
secondary resistance with increase of current—Calculation of
motor........................ 2
3. Calculation of numerical instance—Its discussion—Estimation
of required temperature rise............... 4
4. B. Hysteresis starting device—Admittance of a closed mag-
netic circuit with negligible eddy current loss—Total secondary
impedance of motor with hysteresis starting device ...*.. 5
5. Calculation of numerical instance—Discussion—Similarity of
torque curve with that of temperature startin gdevice—Close
speed regulation—Disadvantage of impairment of power factor
and apparent efficiency, due to introduction of reactance—Re-
quired increase of magnetic density........... 6
6. C. Eddy current starting device—Admittance of magnetic cir-
cuit with high eddy current losses and negligible hysteresis—
Total secondary impedance of motor with eddy current starting
device—Numerical instance............... 8
7. Double maximum of torque curve—Close speed regulation—
High torque efficiency—Poor power factor, requiring increase
of magnetic density to get output—Relation to double squirrel
cage motor and deep bar motor.............10
77. Constant Speed Operation
8. Speed control by armature resistance—Disadvantage of in-
constancy of speed with load—Use of condenser in armature or
secondary—Use of pyro-electric resistance.........12
9. Speed control by variation of the effective frequency: con-
catenation—By changing the number of poles: rnultispcod
motors........................ l.'J
10. A. Pyro-electric speed control—Characteristic of pyro-
electric conductor—Close speed regulation of motor—Limita-
tion of pyro-electric conductors..............14
11. B. Condenser speed control—Effect of condenser in secondary,
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