240 



PRINCIPLES OF ELECTRICAL DESIGN 



netic lines in the manner indicated in Fig. 89. Here we have a 

 diagrammatic representation of single-phase, two-phase, and 

 three-phase, windings. In each case, the system of alternate 

 pole pieces is supposed to move across the armature conductors 

 in the direction indicated by the arrow. It will be noted that 

 the conductors of each phase are shown connected up to form a 

 simple wave winding; but this is only done to simplify the dia- 



FIG. 89. Single-phase, two-phase, and three-phase, armature windings. 



gram, and it will be readily understood that each coil may con- 

 tain a number of turns, attention being paid to the manner of 

 its connection to the succeeding coil, in order that the e.m.fs. 

 generated in the various coils shall not oppose each other. 



The upper diagram shows a single winding, in which an alter- 

 nating e.m.f. will be generated. In the middle diagram there 

 are two distinct windings, A and B, so placed on the armature 

 surface that the complete cycle of e.m.f. variations induced in 



