CHAPTER VIII. 

 SYNCHRONOUS MOTORS. 



A Synchronous Motor is in construction similar to an 

 alternator. It requires consequently a supply of direct 

 current for exciting the magnets, and a supply of alternating 

 current to the armature. 



Mode of Operation. Let Fig. 127 represent the armature 

 of a 2 pole alternator or synchronous motor. If current is 

 supplied at the brushes so as to flow in the direction indicated, 

 the action will be like that of a direct-current motor. The 

 armature will exhibit the polarity indicated in the Figure 

 by the arrow n s, and rotation will take place in the 

 direction shown. If current flowed in the opposite 

 direction through the armature, rotation would take 



FIG. 127. DIAGRAM OF ARMATURE CURRENT IN SYNCHRONOUS MOTOR. 



place in the opposite direction. A rapidly alternating 

 current supplied to the armature while at rest would 

 produce a series of impulses tending to drive the 

 armature first in one direction and then in the other. 

 The result would be a rapid vibration of the armature, but 

 no rotation, the inertia of the moving part being too great 



