CHAPTEB XI. 

 THE INDUCTION MOTOR. 



General Principles of the Induction Motor. Production of a Rotat- 

 ing Field. Let the diagrams iu Fig. 170 represent a ring- 

 shaped iron core with two separate windings upon it in 

 positions at right angles to each other. The two windings 

 are each wound in halves on opposite sides of the ring. 

 For briefness we will call the winding composed of the 

 top and bottom coils the " vertical " winding, and the 

 other the " horizontal " winding. A current sent through 

 either winding will have the effect of magnetising the ring, 

 producing north and south poles at points in the ring 

 half-way between the two coils composing the winding. 



FIG. 170. PRODUCTION OF A ROTATING FIKLD BY 2-PHASE CURRENTS. 



Imagine a magnet needle to be pivoted in the centre of 

 the iron ring so as to be free to rotate in the plane of the 

 ring. This is represented by the long arrow in the centre 

 of the ring. 



If a current is sent through the horizontal winding 

 only, as indicated in Diagrams I. and V., the ring will be 

 magnetised with a north pole at the top or bottom, 

 according to the direction of the current, and the needle 

 will set itself at right angles to the lines of this page, as 

 shown. If the same current is sent through both vertical 

 and horizontal coils (Diagrams II. and VI.) the needle 



