INDUCTION-MOTOR REGULATION

139

and of a size very large compared with the motor, over a supply
circuit of negligible impedance, so that a sudden change of
motor current can not produce even a momentary tendency of
change of the terminal voltage of the motor, the stability curve,
ks, of Fig. 54 gives the performance of the motor. If, however,

Y- 0.01 -0.13 Z-0.l-hO.3j
CONSTANT POTENTIAL HO VOLTS
GENERATOR IMPEDANCE Z»0.02+ 0.5J
LINE Z"-0.1+0.2j
TRANSFORMER IMPEDANCE Z = 0.04*0.1j

REGULATION COEFFICIENT OF SUPPLY kr-$
STABILITY COEFFICIENT OF MOTOR lc,-^ $

STABILITY COEFFICIENT OF- SYSTEM Jcs-kT
MAXIMUM OUTPUT POINT ®

\

7

Bfe

gg

o^5
*o.

180
170
160
150

40

30

20

10

FIG. 54.—laduction-motor load curves.
at a change of load and thus of motor current the regulation
of the supply voltage to constancy at the motor terminals re-
quires a finite time, even if this time is very short, the maximum
output of the motor is reduced thereby, the more so the more
rapidly the motor speed can change.
Assuming the voltage control at the motor terminals effected