202 



ARMATURE CONSTRUCTION 



ranges depending on the grouping of the coils, which will be seen 

 on comparing Figs, g, h, and k with G, H, and K respectively. 



TABLE XIII. 



NUMBER OF RANGES FOR THREE-PHASE SPIRAL COIL WINDINGS 

 IN FIG. 239. 



The windings in Figs. G, H, and K are, strictly speaking, 

 grouped as six-phase windings (and in connecting them up Y or 

 A one phase must be reversed, as noted on p. 183), while Figs, g, 

 h, and k are true three-phase windings. 



Figs. 237, 238, and 239 show that the number of slots per pole 

 per phase is determined simply by (1) whether the winding is 

 single, double, or triple coil, and (2) whether it is whole-coiled or 

 half-coiled. 



Examination of the numbers of slots in the various windings 

 enables us to draw up Table XIV., which shows the number of slots 

 per pole per phase for single and polyphase windings. For instance, 

 a triple-coil whole-coiled winding (Figs, c and / in Figs. 237, 238, 

 and 239) has six slots per pole per phase, but a triple coil half-coiled 

 winding (Figs, k and n) has only three slots per pole per phase. 



In single-phase windings the total number of slots per pole 

 is simply the number of slots per pole per phase, and thus in 

 Table XV. the number of slots per pole for single-phase windings 

 is copied from Table XIV. With two-phase windings the total 

 number of slots per pole is twice the number of slots per pole 

 per phase, and with three-phase windings three times. Thus we 

 are able to fill up the number of slots per pole in Table XV. for 

 two and three phase by multiplying the corresponding 

 phase values by 2 and 3 respectively. 



