CHAPTER IX 



ALTERNATING-CURRENT ARMATURE WINDING SYSTEMS 



IN the present chapter we shall study the question of winding 

 schemes and diagrams for alternating-current armatures, following 

 much the same plan employed in Chap. VIII. for continuous- 

 current armature windings. 



We shall regard the matter chiefly from the standpoint of 

 the practical possibilities of the various windings considered in 

 conjunction with their diagrams, and questions relating to the 

 electrical and magnetic properties of the windings will not enter 

 further than is necessary. 



In the case of alternating-current windings, it is possible to 

 represent by means of a diagram the aspects of the winding as it 

 actually appears on the armature, with more precision than is the 

 case with continuous-current diagrams. Thus, such questions as 

 the shape of the coils and end connectors, their arrangement in 

 layers and their location in the slots, may be intelligently repre- 

 sented in the diagrams by adhering to a few simple conventions, 

 which will be explained in the course of this chapter. 



When considering polyphase windings, we are able to distin- 

 guish between the windings of the various phases by the use of 

 different colours for each phase, which is of great assistance in 

 studying these windings from their diagrams. 



Alternating-current windings fall at once into two broad 

 classes : 



I. Open circuit windings. 



II. Closed circuit windings. 



The windings of Class I. are in most common use for alternators 

 and induction motors. 



The term " open circuit " signifies that the winding (or more 

 precisely the winding of each phase) consists of a continuous 

 path through the conductors which terminates at two ends the 



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