SPEED CONTROL

For comparison is shown, as T', in dotted lines, the torque
curve of the motor of constant secondary resistance, and of the
constants:

7o = 0.01 - O.lj; -
ZQ = 0.01 + 0.3j;
Zi = 0.1 +6.3 j;

As seen, the hysteresis starting device gives higher torque at
standstill and low speeds, with less slip at full speed, thus a
materially superior torque curve.

INDUCTION MOTOR
Y0=.02-,2j; Z0-.05+.15j; 60*= 100

Z! = (.05 4- .11s)+.335js
SPEED CONTROL BY HYSTERESIS
SPEED CURVES

FIG. 2.—Speed curves of induction motor with hysteresis starting device.

p represents the power-factor, f\ the efficiency, 7 the apparent
efficiency, t\f the torque efficiency and 7' the apparent torque
efficiency.
However, T corresponds to a motor of twice the admittance
and half the impedance of Tr. That is, to get approximately
the same output, with the hysteresis device inserted, as without
it, requires a rewinding of the motor for higher magnetic density,
the same as would be produced in Tr by increasing the voltage
\/2 times.
It is interesting to note in comparing Fig. 2 with Fig. 1, that
the change in the torque curve at low and medium speed, pro-
duced by the hysteresis starting device, is very similar to that
produced by temperature rise of the secondary resistance; at