IO-A] 



SYNCHRONOUS MOTOR. 



running a little too fast or too slow, the line and motor electro- 

 motive forces are first opposed and then added, giving rise to 

 " beats " shown by the periodic flickering of the lamps which are 

 dark and bright alternately. 



The lamps do not show whether the motor is running too fast 

 or too slow; but, when a change of speed (increase or decrease) 

 makes the flicker less rapid, the change is in the proper direction 

 for bringing the motor into synchronism. It is not necessary, and 

 usually would not be possible, to bring the motor to exact syn- 

 chronous speed. When synchronous speed is practically reached, 



Supply Line 



Supply Line 



FIG. i. Arrange- 

 ment of synchronizing 

 lamps (one phase). 



Lamp or 

 Voltmeter 



FIG. 2. Synchroniz- 

 ing with a voltmeter, 

 or one lamp or other 

 indicator. 



shown by the slow changes of the lamps between dark and bright, 

 the switch should be closed when the lamps are dark. 



14. Synchronizing with Lamps Bright. To synchronize with 

 the lamps bright instead of dark, interchange the two lamp 

 terminals on the line or motor side (as the two upper lamps in 

 Fig. 4). 



15. Synchronizing with a Single Lamp or Voltmeter. By 

 closing one switch-blade, one lamp (or series of lamps) of twice 

 the voltage may be used instead of two, as in Fig. 2 ; a voltmeter, 

 or other indicator, may be used in place of the lamp and will 

 show more accurately the exact moment of synchronism. 



1 6. Use of Transformers with Synchronizing Devices. Syn- 

 chronous motors and converters are usually made for potentials 



