SYNCHRONOUS MACHINERY 



253 



(3) A current leading the generated e.m.f. by 90 degrees 

 magnetizes the field, increases the flux and increases the generated 

 e.m.f. ' 



If the current lags behind the e.m.f. by angle <, it may be 

 resolved into two components, 7 cos <f> in phase with the e.m.f. 



o 



o 



o 



Motor 



0) 



J?>nchronous 

 Motor 



N | w S 



on 



FIG. 229. Armature reaction. 



and, therefore, cross magnetizing and I sin <j> lagging 90 degrees 

 behind the e.m.f. and demagnetizing. 



The effect of armature reaction increases almost directly with 

 the current. When the magnetic circuit, or that part of it in- 

 cluding the pole tips, air gaps and teeth, becomes saturated the 



