THE INDUCTION MOTOR 349 



rotor. This motor starts on the same principle as the 

 repulsion motor which is discussed in the next chapter. 

 A view of the commutator end of the motor is shown in 

 Fig. 227. 



Polyphase Motor Superior to Single-phase Motor. It 

 is evident that the polyphase motor is much more suitable 

 for ordinary installations than the single-phase motor; 

 in the first place the polyphase motor costs less per h.p. 



FIG. 227. View of a Single-phase Motor Using Commutator and 

 Brushes for Starting. Wagner Electric Mfg. Co. 



than the single phase and is more efficient in operation. 

 In addition no extra devices are necessary with the poly- 

 phase motor to produce a starting torque. Because of 

 these facts the single-phase motor is used only in small 

 sizes, and where polyphase power is not available. 



100. Induction Motor Used as a Generator. If an 

 induction motor, connected to a polyphase line and running, 

 is driven by some outside source of power at a speed greater 



