ALTERNATING-CURRENT WINDING 199 



total number of poles are subtended by coils, i.e. every other pole 

 has a coil opposite it on the armature, every alternate pole having 

 no coil opposite to it. 



This is so in all the windings in Fig. 237, g, h, k, m, and n, where 

 it will be seen that the portion of the armature opposite alternate 

 poles is not occupied by coils. 



Similarly, in the two phase windings of Fig. 238, the whole- 

 coiled windings of Figs, a, b, c, e, and/ have two coils for each pole, 

 i. e. one coil per phase per pole, and the half -coiled windings Figs. 

 e, g, A, k, m, and n have two coils subtending every alternate pole, 

 i.e. one coil per phase per pair of poles. 



Also in the three phase windings of Fig. 239, the whole-coiled 

 windings, Figs, a, b, c, e, and f t have three coils for each pole, i.e. 

 one coil per phase per pole, and the half-coiled windings, Figs. 

 g, h, k, m, and n, have three coils subtending every alternate pole, 

 i.e. one coil per phase per pair of poles. 



Thus, as explained, the distinction between the " whole-coiled " 

 and " half-coiled " varieties is that the " whole-coiled " has one coil 

 per phase per pole, while the " half-coiled" has one coil per phase 

 per pair of poles. 



It may be noted that for a given number of poles and phases 

 the half-coiled winding has one-half the total number of coils that 

 the whole-coiled winding would have. 



By way of illustrating the nomenclature, the winding in Fig. 

 238, h, would be designated a " two-phase, half-coiled, double-coil, 

 spiral winding " ; or that in Fig. 239, /, a " three-phase, whole- 

 coiled, triple-coil, lap winding." 



We have already on pp. 191 and 192 summarised the properties 

 of spiral coil windings with regard to the number of ranges in 

 which the winding may be laid up. We are now in a position to 

 make out from Fig. 239 a table showing the number of ranges 

 possible with each of the windings (lap coil windings are 

 exempted, as, by reason of the two arms of the V end 

 connectors being formed in two separate planes, they lie up 

 together in order). 



Table XIII. shows the number of ranges for all the spiral coil 

 windings in Fig. 239, from which the following conclusions may 

 be drawn : 



(a) All the whole-coiled three-phase windings, Figs, a, b, and c, 

 must be three-range. 



(b) The half-coiled windings may be three-range, Figs. G, H, and 

 K, or two-range, Figs, g, h, and k, the possibility of three or two- 



