INDUCTION-MOTOR REGULATION

129

minal voltage, with high impedance in the supply, the starting
torque drops so much that the maximum torque is shifted to
about half synchronism.

In induction motors, especially at overloads and in starting,
it therefore is important to have as low impedance as pos-
sible between the point of constant voltage and the motor
terminals.

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.8 0.2 0.1
Slip Fraction of Synchronism

FIG. 49.—Induction-motor speed current characteristics with a resistance of
1.5 ohms in secondary circuit.

In Table I the numerical values of maximum power, maxi-
mum torque, starting torque, exciting current and starting
current are given for above motor, at constant terminal voltage
and for the three values of impedance in the supply lines, for
such supply voltage as to give the rated motor voltage of 110
volts at full load and for 110 volts supply, voltage. In the first
case, maximum power and torque drop down to their full-load
values with the highest line impedance, and far below full-load
values in the latter case.