382 ELECTRICAL ENGINEERING 



(359) 



n n 







Since is the current in the coil when the machine is operating as 



Zi 



a direct-current generator, the ratio of the power lost in the coil 

 when operating as a converter to that lost when operating as a 

 direct-current generator with the same output is 



16 cos 



p] f _ 8 



"Tfl ^ 



-+1 . . (360) 



n TT sin - 

 n 



and this is the ratio of the coil heating under the two conditions. 

 This ratio is a maximum for the coil next to the alternating 



leads h or k, where ft = -, and it is 



(361) 



It is a minimum for the centre coil of the phase, where = 0, and is 



n z sin 2 - mr sin - 

 n n 



The ratio of the total power lost in the armature of the converter 

 to that lost when the machine is operating as a direct-current 

 generator with the same output is found by integrating the ratio 



hp over one half phase from /3 = - to /3 = and taking the aver- 



71 



age. It is 



H-?A#=5f/-J li^ + iU 



v *** \ n 2 sin 2 - mr sin - 



\ n n I 



