THE INDUCTION MOTOR. 



Let us now suppose that the motor is at work. The primary field 

 produced by the supply currents makes ~j complete revolutions per 

 second, whilst the armature follows with a speed of ~ a complete rev- 

 olutions per second. The magnetic slip 5 is then 



If the field revolves clockwise, the armature must also revolve clock- 

 wise, but at a slightly slower rate. Relatively to the field, then, the 



FIG. 49. 



armature will appear to revolve in a counter clockwise direction, with 

 a speed of 



revolutions per second. As far as the electro-magnetic action within 

 the armature is concerned, we may therefore assume that the pri- 

 mary field is stationary in space, and that the armature is revolved 

 by a belt in a backward direction at the rate of ~ revolutions per 

 second. The effective tangential pull transmitted by the belt to the 



90 



