374 ELEMENTS OF ELECTRICAL ENGINEERING. 



in the stator windings are at their maximum values in the regions 

 in the middle of the polar areas. It will be noticed, furthermore, 

 that the currents in the rotor conductors are at their maximum 

 values in the regions where the flux density in the gap space has 

 its maximum values. The torque which acts upon the rotor is 

 due to the side forces with which the flux pushes on the rotor 

 conductors. 



16. Induced electromotive forces in the rotor of a single-phase 

 induction motor. The theory of the single-phase induction motor 

 as developed in Art. 139, Chapter XIII, is based upon a proposi- 

 tion concerning the relationship between the electromotive forces 

 which are induced in the rotor rods by a pulsating flux, and the 

 electromotive forces which are induced in the rotor rods by the 

 cutting of the same flux. Consider, for example, the flux 4> in 

 Fig. 253 of Chapter XIII. Let n be the frequency of the single- 

 phase alternating-current supply, let n r be the speed of the 

 rotor, and suppose, for the sake of simplicity, that the motor is of 

 the two-pole model as shown in Fig. 253. Consider (a) the 



Fig. 7. 



electromotive forces induced in the rotor rods by the cutting of 

 4> and (fr) the electromotive forces induced in the rotor rods by 

 the pulsation of <f>. The electromotive forces (a) are in time 

 quadrature with the electromotive forces (b), the electromotive forces 

 (a) are distributed about the axis A A' in exactly the same way 

 that the electromotive forces (b) are distributed about the axis J3B' ', 



