THE ALTERNATOR 



125 



reetanirle i> equal to the coil spread. In Fig. 131 (a) and (c) 

 there are three coils per pole. Each coil produces a rectangle of 

 mmf. If there are the same number of turns in each of the three 

 coils, the height of each mmf. rectangle is the same. The re- 



Retailing Flux 

 Magnetomotive 



Fio. 131. Distributed field winding and resulting magnetomotive force 



flux waves. 



sultant mmf. is found by superposing the three mmf. rectangles, 

 as shown in Fig. 131 (c). The resulting magnetomotive force 

 wave is "stepped," as shown. Due to fringing, the resultant flux 

 wave is nearly sinusoidal, as indicated in the figure. Therefore, a 



ooooooooooooooooooooooo 



!t<-rn;itor roils in V. 



ilient pnle altern.-iinr. having a distributed winding, lias 

 usually a better v. i H> than a salient -pole alternator. 



69. Phasing Alternator Windings. Three-phase altni 

 windings may be .-nnnreied either in V or in delta. ln>' 



uccur in practice \\ i com'- from the machine, 



