THE ALTERNATOR 



117 



At higher speeds, centrifugal forces require that the poles be 

 Hnvr-tailed to the spider. In small machines, the spider may be 



IK;. 123. Revolving field spider with dove-tailed poles. 



of solid steel, as shown in Fig. 123. The pole pieces dove-tail to 

 this spider and are wedged in by keys driven one from each end. 



: 



Fio. 124. Twelve-pole, 000 r.p.m. rotor. 



In ratnr, thr spider is made of steel 



riveted together, as shown in Fig. 124. The poles are 



