8 1 \< '/- K-rilASE MOTORS 



297 



motor being shown. The main winding, which is highly induct- 

 ive, is connected across the line in the usual manner. Between 

 tin- main poles arc auxiliary poles which have a high-resistance 

 winding and this winding is also connected across the line. As 



'Auxiliary Polei 



Fio. 275. Split-phase method of starting a single-phase induction motor. 



the auxiliary winding has a high resistance, its current will ho 

 more nearly in phase with the voltage than the current in the 

 main winding. For the best conditions, the two currents should 

 differ in phase by 90, but this condition is not readily obtainable, 



81n|!e-FhM 



Supply 



KeiUtane* 



-> Inductance 



Motor staior 



.. 276. Splitting tin- ph.-isi- with rrsist.-uice and inductance. 



and in fact is not necessary. Those two sets of poles produce a 

 sort of rotating field which starts the motor. When the motor 

 oomei up to speed, a centrifugal device in the mtor opens the 

 s\\ itch S and di.-mnnects the auxiliary winding. 



