ALTERNATING-CURRENT WINDING 183 



In Fig. D we have lettered the terminals S and T according to 

 our convention, and have connected up the winding Y fashion by 

 aid of the arrow-heads on the conductors. We have the three 

 ends T A , T B , T c connected together at the neutral point, and the 

 three beginnings S A , S fi , S c connected to the lines, which is quite 



in accordance with the rule given on p. 179. 



In connecting up the separate windings for a "delta" (A) 

 connection, it is most convenient to examine the conditions at 

 the instant when the conductors of one phase are opposite the 

 middle of a pole piece. Then assume these conductors to be 

 carrying the maximum current, which is illustrated in Fig. E 

 by the arrow-heads on the black conductors. The other two 

 windings have in them at the same instant currents of only 

 one-half this magnitude. The condition of affairs in line and in 

 winding is, for the instant, as represented in the A diagram on the 

 right hand of Fig.- E, and the currents in the windings are as 

 indicated by the arrows in the winding on the left hand of Fig. E. 



It will be seen that the connections agree with those given in 

 Fig. B, according to the rule on p. 179. 



Figs. D and E show two coils of each phase and four poles, but 

 the conditions are exactly the same if the total number of coils 

 are taken in, as for terminals S A> S B , S c we have taken the 

 beginnings of the first coil of each phase connected in, and for 

 terminals T A , T B , T C we have taken the ends of the last coils 



connected in. 



The group of coils in Figs. D and E corresponds to the winding 

 of Fig. 223 and to all of the three-phase two-range windings 

 given subsequently. 



It is safer, in connecting up any three-phase winding, to 

 determine the connections from the directions of the induced 

 currents. In some windings, which are strictly six-phase wind- 

 ings, it is necessary to reverse one phase. 



Thus in the winding of Fig. G (which is the same as Fig. 223), 

 when Y-connected by consideration of the arrow-heads on the 

 conductors, the red phase is reversed and S B instead of T B 

 connected to the neutral point. 



The winding is really a six-phase winding, and the relative 

 currents are as shown by the curves of Fig. F. To convert Fig. F 

 into the true three-phase arrangement of Fig. C the red curve 

 must be reversed, which is effected by reversing the connections 

 of the red phase. 



