DIRECT-CURRENT MACHINERY 



183 



The interpoles have the same effect as moving the brushes since 

 they move the poles magnetically. 



FIG. 147. Interpole generator or motor. 



The m.m.f. of the interpole winding must oppose the m.m.f. of 

 the armature and must be strong enough to overbalance it and 

 produce a field under the interpole of the proper intensity to reverse 



a 



FIG. 148. Flux distribution in interpole generator or motor. 



the current in the short-circuited coil. Since the interpole wind- 

 ing is in series with the armature the commutating field increases 

 with load and satisfactory commutation up to and beyond the 



