ii8 ALTERNATING CURRENTS 



eight conductors, and these conductors have to be connected in series 

 in such a manner that two conductors in immediate connection 

 belong to two neighbouring groups. Let us suppose all the con- 

 ductors to be numbered, and let conductor 1 be connected at one end 

 to the neutral point of the winding. The four groups of conductors 

 forming the winding of the first phase are then as follows : 



Group 1 : 1, 2, 3, 4, 5, 6, 7, 8 



II : 25, 26, 27, 28, 29, 30, 31, 32 

 III : 49, 50, 51, 52, 53, 54, 55, 56 

 IV : 73, 74, 75, 76, 77, 78, 79, 80 



Between Groups I and II are the sixteen conductors belonging to 

 the other two phases, and there are similar intervals between the 

 remaining groups. 



In arranging the connections, we select conductors which are as 

 nearly as possible separated by a distance corresponding to the 

 pole-pitch. Now, the pole-pitch is, in terms of the number of 

 conductors comprised in it, equal to 8 4 6 = 24. But this value could 

 not be adopted for the pitch of the winding, since with a double layer 

 of conductors the pitch must correspond to an odd number.* Hence 

 we select a double pitch for our winding, namely, 23 and 25, using 

 these numbers alternately ; the mean pitch of the winding is thereby 

 made to correspond to the pole-pitch. 



We must commence with a pitch of 25, since a pitch of 23 would 

 lead us to conductor 1 + 23 = 24, which does not belong to our 

 phase at all. Hence our winding proceeds thus 



1264974 



A difficulty occurs at this point. We have travelled once round 

 the rotor periphery, and the next step (assuming that we go on using 

 the pitches 25 and 23 alternately) would bring us to conductor 

 74 + 23 = 97, which is conductor 1. But this would close the 

 winding. Hence we select the odd conductor in Group I, which is 

 nearest conductor 1. This is obviously conductor 3, and the step 

 from 74 to 3 (or 99) corresponds to a pitch of 25. We thus find it 

 necessary to break the alternate sequence of the two pitches at the 

 end of the first round, and to use the same pitch twice in succession. 

 The same difficulty occurs, and is similarly overcome, at the end of 

 each revolution. Bearing this in mind, we obtain the following for 

 the first half of the winding table, each horizontal line representing 

 one complete revolution : 



* Otherwise, starting from conductor No. 1, which is in the top layer, we should be 

 using up odd conductors, all of which are in the top layer ; this would not allow of the 

 compact arrangement of end connections, which becomes possible when odd and even 

 conductors (i.e. conductors in the top and bottom layer) are connected alternately. 



