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ELECTRICAL MACHINERY 



of winding. The number of turns per coil is very low in 

 the a-c. motor and these coils are not connected directly 

 to the commutator bars but through resistance leads, to be 

 explained later. 



105. Power Factor Compensating Winding. If a c-c. 

 series motor were operated on an a-c. circuit, the power 

 factor would be very low, probably not more than .30 or 

 .40. This low power factor would be due to the high 



FIG. 230. View of the Wound Field Structure of a Series Single- 

 phase Railway Motor. Westinghouse Elec. and Mfg. Co. 



inductance of the field and armature windings and could 

 be increased only by decreasing the self-induction of these 

 two windings. 



Compensating Winding. We know that an a-c. system 

 with a low power factor is very inefficient, both from the 

 standpoint of first cost and of operating cost; the series 

 a-c. motor must therefore be designed with low self- induc- 

 tion if it is to be successful. The self-induction of the field 

 winding is kept low by using fewer turns than would be 



