Till: SYNCHRONOUS 



310 



switching, short-circuit.-, etc., and also by sudden changes of 

 load on the motor shaft. Hunting due to such causes usually 

 -in at a rapid rate, Imt the first oscillations may be great 

 to cause the motor to tall out of synchronism. 

 action of the damper winding involves the principle of 

 both the induction motor and the induction generator. So long 

 as the rotor is rotating at synchronous speed, the rotating field 

 of the armature or stator does not cut the dampers and they have 



Fio. 295. Rotor of a 600- volt. .,! >yn lin.nou.- motor >ho\viim 



rinding. 



Thai fa, the armature mini', rotates synchronously 

 with the field and there is no relative motion between the field flux 

 and the dampers. Assume that the rotor slows down moment- 

 arily. For an instant the rotating field due to the armature mmf. 

 j faster than the field structure. This is equivalent to 

 tin- rotor .-lipping temporarily, and current- are induced in the 

 dampers. This i- induction motor action and the cum-i 



mipers are in such a direction that they tend to pull the 

 rotor back again towards synchroni.-m. 



