ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
426. 
427%. 
428. 
generating station, transmission line or distribution 
system, will be felt by the motor. If the speed variations 
are not within the standard values, then hunting of the 
synchronous motors will be set up, that is, the speed will 
vary within larger or smaller limits, decreasing and 
increasing at intervals. 
If the motor is fed by slow speed generators, the field system 
should have either solid poles or laminated poles with 
suitable damping arrangements and, as a general design- 
ing rule when damping arrangements are used, it may be 
stated, that the rotating weight of the synchronous motor 
should be comparatively small, so as to permit the taking 
up of the changes in frequency. 
Overload Capacity.—The momentary overload capacity 
of synchronous motors, that is, the greatest output 
before falling out of step, is generally large; standard 
generators used as synchronous motors will stand a 
momentary load of about double, and more, of the normal 
output. 
A generator of small voltage drop, will correspond to a 
synchronous motor of large overload capacity, and vice 
versa. 
Methods of Starting.—The greatest disadvantage of 
a synchronous motor is, that it must be brought up to its 
synchronous speed before it can give the required power, 
see Par. 420. 
This class of motor is generally used in large sizes, in connec- 
tion with continuous current dynamos in substations, or for 
heavy mill work. When starting up on a light load, the 
exciter may be utilized or an auxiliary starting motor 
used, whichever way may be found the most convenient. 
A line of shafting already running also provides a con- 
venient method of starting up. 
Self Starting Motors.—Synchronous motors are not 
usually made self starting, but in cases where a self 
starting motor is required, such a condition can be carried 
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