WALKER ALTERNATOR 99 



unsaturated one. The latter effect is, however, much greater than 

 the former one, owing to the high saturation of the main pole. Hence 

 as the current increases the e.m.f. rises. This method of compound- 

 ing an alternator, although capable of yielding excellent results so 

 long as the power factor ( 7) does not fall below about 0'85, is no 

 longer applicable to highly inductive loads ; for in this latter case, as 

 shown by the chain-dotted curve of Fig. 80, the wave of rotating flux 

 is shifted so far back relatively to the poles as to produce a magneti- 

 zation of the auxiliary pole in the wrong direction, thus lowering 

 the e.m.f. 



