136 ARMATURE CONSTRUCTION 



distinguish between the " back end " .and the " front end " pitches 

 by designating them as 



2/6 = ("back end pitch") 

 and 



yf= ("front end pitch"). 



In the winding of Fig. 162 we have 



2/6-49 

 2//=47. 



We may denote the mean pitch as y i.e. 

 _ 



Thus y (i.e. the mean pitch) is equal to the total number of 

 face conductors divided by the number of poles. In this case 



192 



11= =48. 

 4 



The precise values of the front and back pitches are deter- 

 mined by taking the one greater by 1 than the value of the mean 

 pitch, and the other less by 1 than that value ; thus in the present 

 case we have 



yf=y- 1=48- 1 = 47. 



Let us employ this same number of face conductors, i.e. 192, 

 but connect them up into a 6-pole winding. 



^6 = 32 + 1=33; ^=32-1=31. 



The winding diagram is given in Fig. 163. 



The present treatise deals with questions relating to the 

 constnwtion of armatures, and for this reason questions of electro- 

 magnetic design are not entered upon, or, at the most, are kept in 

 the background. It is necessary to allude to this plan in the 

 present chapter, since otherwise the method of dealing with 

 armature windings would not be clearly appreciated. In carrying 

 out the design of the winding in the draughting office and in the 

 construction work in the shop, a considerable degree of familiarity 

 with the electro-magnetic properties of windings is highly desir- 

 able. It is, however, neither necessary nor desirable to deal 



