CHAP. V] 



EXCITING AMPERE-TURNS 



99 



of a and $s. See Adams, loc. cit., p. 332. The formula can be used only 

 when s is larger than 2a. 



Prob. 24. Show that Jt/a =2.93 log (1 +frs/a), if the fringing lines 

 of force are assumed to consist of concentric quadrants (Fig. 27, to 



FIG. 27. Two simplified paths for the fringing flux. 



the right), with the point cf as a center, continued as straight lines. 

 See Arnold, Die Gleichstrommachine, Vol. 1, p. 269. 



Prob. 26. Show that formula (50) applies to synchronous ami dim t- 

 current machines with salient poles as well, if // is the width of the 

 pole shoe, corrected for the fringe, and A 2 is the pole pitch. 



PROPERTY OF ELECTRICAL LA80RATO 



FACULTY Of 



S 





OCX 2 7 1513 



