ALTERNATING-CURRENT WINDING 185 



phase windings, as such are not in common use ; the latter, however, 

 will be referred to in connection with rotary converter windings at 

 a later part of this chapter. 



In connection with the winding diagrams already given, and 

 given subsequently, it is desirable to point out that it is immaterial 

 which of the several coils of each phase have their ends form the 

 terminals of the phases so long as they are all connected up 

 successively round the armature. For example, in Fig. 219 we 

 started with conductor IA and connected up phase A successively, 

 making conductors IA and GA the terminal connections. 



Similarly, for phase B we had conductors IB and 6B. It would 

 have been quite in order if we had taken, say, SB and 2B, or SB 

 and 4B, instead of IB and GB, or similarly for phase A. It does 

 not matter from what points the terminals are brought out, so long 

 as the coils of one phase are all connected up in their proper order. 



FIG. 226, A. FIG. 226, B. 



Two-phase Groupings. 



As, however, in the actual armature it is desirable to have the 

 terminals all coming out at about the same spot on the armature 

 (near the machine terminals), we shall adopt this plan in all our 

 diagrams and bring out the terminals of the phases as near together 

 as possible. 



It will have been noticed that the windings in Figs, 221, 222, 

 and 223 are all of the half-coiled variety (see p. 170) i.e. there is 

 one coil for each phase under each pair of poles. Thus in Fig. 223 

 the total number of coils is nine, and as there are three phases, 

 there are 9/3 = 3 coils per phase. The number of poles is, however, 

 six, which is double the number of coils per phase. 



Suppose, now, instead of connecting the whole of the conductors 

 forming the group IA (in Fig. 222) to the group 2A, we only 

 connected half of them to half of the conductors in group 2A ; 

 then it is quite permissible to connect half of IA in an opposite 

 direction back to half of the group GA in a similar fashion to 

 Fig. 212. By so treating each group, IA, 2A, 3 A, etc., we obtain 



