STRUCTURE OF INDUCTION MOTORS. 165 



the stampings of which need not be so thin as those of the stator, 

 since the frequency of the flux is there much smaller than in the 

 stator. A rotor stamping is depicted in Fig. 65. The rotor wind- 

 ing sometimes consist simply of bars of copper, short-circuited at 



FIG. 65. 



each end by heavy copper rings. This is called a " squiPPCl- 

 eag?e" winding. When a squirrel-cage winding is not used, a 

 tri-phase star winding is almost universally employed, in which 

 case three ends are jointed together, while the remaining three are 



FIG. 66. The several parts of a Heyland monophase induction motor. 



connected to three collector-rings mounted on the shaft. Three 

 brushes rub on these rings, and are held by holders connected to 

 the end shields of the case. 



Fig. 66 shows the several parts of a Heyland monophase induc- 

 tion motor, manufactured by Messrs. Witting Bros., London. 



