470 'ELECTRICAL APPARATUS
Starting Devices.—Polyphase induction motor:
Resistance of high temperature coefficient, 2. Gives good torque
curve at low speed and good regulation at speed, but requires
high temperature in the resistance.
Hysteresis device, 4. Gives good speed regulation and good
torque at low speed and in starting, but somewhat impairs the.
power-factor.
Eddy-current device, 5; double and triple squirrel-cage, 18, 20,
24; and deep-bar rotor, 7. Give good speed regulation combined
with good torque at low speed and in starting, but somewhat
impairs the power-factor. (See " Double Squirrel-cage Induction
Motor" and "Deep-bar Induction. Motor.57)
Single-phase induction motor:
Phase-splitting devices, 67. Resistance in one phase, 68. In-
ductive devices, 72. Shading coil, 73. (See "Shading Coil.")
Monocyclic devices, 76. Resistance-reactance device or rnono-
cyclic triangle. Condenser motor, 77. (See " Condenser Motor.")
Repulsion-motor starting.
Series-motor starting.
Synchronous-induction Generator.—XIII, 113. Induction
machine, in which the secondary is connected so as to fix a definite
speed. This may be done:
1. By connecting the secondary, in reverse phase rotation, in
shunt or in series to the primary: double synchronous generator.
(See "Double Synchronous Machine.")
2. By connecting the secondary in shunt to the primary
through a commutator. In this case, the resultant frequency is
fixed by speed and ratio of primary to secondary turns.
3. By connecting the secondary to a source of constant low
frequency: Stanley induction generator. In this case, the low-
frequency phase rotation impressed upon the secondary may be
in the same or in opposite direction to the speed. (See "Con-
catenation (2).")
Synchronous-Induction Motor.—IX, 97. An induction motor
with single-phase secondary. Tends to drop into step as syn-
chronous motor, and then becomes generator when driven by
power. Its low power-factor makes it unsuitable except for
small sizes, where the simplicity due to the absence of direct-
current excitation may make it convenient as self-starting "syn-
chronous motor. As reaction, machine, 150.
Thomson-Houston Arc Machine.—141-144. Three-phase F-