102 ARMATURE CONSTRUCTION 



sketch B, the projecting pieces being bent over the end of the 

 bars, as indicated in sketches C and I), the upper row of project- 

 ing teeth being bent to the right hand, and the lower row to the 

 left, and then all the joints are soldered up. In connection with 

 Fig. Ill, one will notice the three large vanes projecting from 

 the end of the core. Vanes are employed rather extensively 

 nowadays, their object being to act as ventilating fans, and to 

 churn air through the machine for cooling purposes. Similar 

 blades will be noticed in Fig. 116 ; they should not, however, be 

 of too large a size, as this will materially add to the windage losses 

 of the motor. It is probable that the blades in Fig. Ill are rather 

 larger than would be desirable, especially if the speed is high. In 



FIG. 111. Squirrel Cage Rotors by Alioth Co. 



latest practice, it is almost universal to locate the end ring on as 

 large a radius as practicable ; thus it is situated directly opposite 

 the ends of the slots, as in all the above constructions. A method 

 which was used earlier, but which does not obtain largely nowa- 

 days, was to bring all the conductors down radially to a small end 

 ring fitting on the shaft. Such a construction is shown in 

 Fig. 113, which represents an old design of the Allmanna Svenska 

 Elektriska Aktiebolaget. In such a construction as this, a high 

 resistance end ring is not easily obtained in a case where it is 

 necessary, as the periphery of the end ring is very much restricted, 

 although the bars are themselves long, and of higher resistance. 

 In addition to this, the structure is not so simple a mechanical 

 job as others of the above methods. 



