THE INDUCTION MOTOR 



337 



heavy copper rings. The rotor slots are always semi- 

 closed (see p. 46) so that the bars must be pushed in from 

 the ends of the rotor core. As the voltage generated in 

 such a winding is low, very little insulation is required on 

 the bars; in fact, a heavy coat of insulating enamel gen- 

 erally proves sufficient. 



An illustration of a squirrel-cage rotor, showing the 

 bars and short-circuiting ring is given in Fig. 220. The 



FIG. 220. View of End Rings and Bars of a Squirrel-cage Rotor, to 

 Show the Style of Winding. General Electric Co. 



bars are not always placed parallel to the shaft, but are 

 sometimes " skewed " to some extent. This skewing tends 

 to give a more uniform torque in starting and also to reduce 

 the humming noise made when the machine is running. 



Wound Rotor. The wound rotos is equipped with a 

 winding very similar to that of a revolving-armature alter- 

 nator. The different conductors are insulated from one 

 another and arranged in coils. These coils are generally 



