230 GENERAL DIAGRAMS FOR SYNCHRONOUS MOTORS 



( \ 



-7 o)J, and the phase of the wth harmonic of 



the resultant E.M.F. with respect to the wth harmonic of slot No. i 

 is, in wth harmonic radians, 



/w \ / w \ 



= Xl -7 to TCI ~ tos ). 



\P' ) \2Nsp ) 



= Belt Span in Degrees 



FIG. 31. 



Thus in passing from the slot E.M.F. to the resultant E.M.F., 

 the relative phase of the wth harmonic with respect to the funda- 

 mental is changed by an amount (in wth harmonic radians), 



= Xm Wi = T(W tos). 



is therefore always a multiple of T. Moreover, w is practically 

 always zero. Therefore, @m is zero when o) is even and x when w 

 is odd; i.e., the wth harmonic can only be reversed and not other- 

 wise changed in phase from the slot E.M.F. In order to see this 

 relation more clearly, consider an infinite number of slots, and 



