CHAPTER XV 



SYNCHRONOUS MOTORS 



The preliminary tests taken on synchronous motors 

 consist of drop on spools, air gap, resistance measure- 

 ment, balancing of phase voltages, phase rotation and 

 running free minimum output. 



Complete tests consist of special tests and normal 

 and overload heat runs. 



Special tests consist of starting tests, open and short 

 circuited core loss, saturation, synchronous impedance, 

 no load and full load phase characteristics, and wave 

 form. The method of taking phase characteristics has 

 previously been described. 



Fig. 36 



Starting tests should be made both with and without 

 a compensator, if the motor is of a new type and rating 

 and is to be started with a compensator when installed. 

 If the motor does not form part of a motor-generator set, 

 it should be belted to a generator so that it will have 

 some load at starting. 



The motor should first be tested for starting without 

 the compensator. The center line of one pole is placed 

 in line with the center line of the frame and 180 electrical 

 degrees marked off in a clockwise direction from this 

 line on the head end of the motor. The total length of 

 this scale should be two-thirds of the distance between 

 the center lines of adjacent poles for three-phase 



[120] 



