SYNCHRONIZING INDUCTION MOTORS 165
circuited armature. This is to be expected, as the two motor
armatures short-circuit each other.
The synchronizing torque is a maximum for r — 45°, and is,
by (14), (15), and (16):
Ds = wo2 —~b- (20)
As instances are shown, in Fig. 59, the motor torque, from
equation (18), and the maximum synchronizing torque, from
equation (20), for a motor of 5 per cent, drop of speed at full-
load and very high overload capacity (a maximum power nearly
two and a half times and a maximum torque somewhat over
three times the rated value), that is, of low reactance, as can bo
produced at low frequency, and is desirable for intermittent
service, hence of the constants:
Zi = Z0 = 1+ j, .
. Y = 0.005 - 0.02 j,
eQ = 1000 volts,
for the values of additional resistance inserted into the armatures:
r = 0; 0.75; 2; 4.5,
giving the values:
1 1 + 2 r
01 = m? g =.....~~^T'
i 2 $ , sxi
hi = , b = ,
m\ w>
mi = (1 -f s)2 + 4 <S2? m = (X + s + 2 r)'2 + 4 ,s'2.
As seen, in this instance the synchronizing torque is higher
than the motor torque up to half speed, slightly below the motor
torque between half speed and three-quarters speed, but above
three-quarters speed rapidly drops, due to the approach to syn-
chronism, and becomes zero when the last starting resistance
is cut out.