192 



ARMATURE CONSTRUCTION 



and for three phases, 3x3 = 9 coils in all. If we wish this to be 



g 



a two-range winding, we should have o = 4J co ^ s i n eac ^ range, or 



four coils in one range and four coils in the other, with the extra 

 coil half in each range. 



8 



<o 



v 



FIG. 231. Three-phase Six-pole Half-coiled Winding (nine coils in two ranges). 



This latter winding has already been shown in Fig. 223, where 

 there are six poles, three phases, and nine coils. 



Laid out as a two-range winding with a bent coil, the appear- 

 ance of the ends of the armature coils is shown in Fig. 231, where 

 we have coils 1, 3, 5, 8 in one range, coils 2, 4, 6, 9 in the other 

 range, and coil 7, the bent one, half of which is really in each range. 



A considerable advantage of the two-range over the three-range 

 winding is that the former only requires two kinds of coil, whereas 



