THE SINGLE-PHASE SERIES MOTOR. 



317 



The repulsion motor may be shown to be fundamentally equiva- 

 lent to the simple series motor in its action and in its torque-speed 

 characteristics as follows : The stator winding t, Fig. 272, pro- 

 duces the pulsating flux T and acts like the primary of a trans- 

 former of which the secondary is the short-circuited armature 

 winding. Let us assume that this transformer action is ideal 

 (zero reluctance for flux T) and let us assume that the ratio of 

 transformation is i : i. Then the armature current is identical 



Fig. 272. 



in value and in phase * to the current in the coil / just as if the 

 armature were included in the primary circuit. 



The stator winding f produces the pulsating flux F. The 

 armature is an open circuit with respect to the electromotive 

 forces induced by the pulsations of this flux, but the electromo- 

 tive forces produced by the cutting of F by the rotating arma- 

 ture act through or around the short-circuit formed by the 

 brushes and these electromotive forces are reproduced in the 



*The secondary current of a transformer is usually thought of as exactly opposite 

 in phase to the primary current, but whether it be considered as opposite to or in phase 

 with the primary current depends on a mere convention as to the choice of the direc- 

 tion in the secondary coil which is to be considered as the positive direction. 



