CONVERSION OF ALTERNATING CURRENT. 187 



whence 



-1/2- 



I, = J>7|- / o = a544/ o (iH) 



7 4 = o. 500/ (iv) 



Current entering at each collector ring. Figure 154 shows the points of attach- 

 ment of collector rings to the armature winding of a synchronous converter, the two 



Armature winding 



Fig. 154. Fig. 155. 



arrows / and /,/ show the directions in which the currents in the two armature 

 sections are considered as positive, and the arrow 7 r shows the positive direction of the 

 current 7 r . From this figure it is evident that I T ^=zI n 7 n ' (the vector difference 

 of course). Therefore, since 7 n and 7 n ' differ in phase by the angle 2Tr/n, as shown 

 in Fig. 155, it is evident that the value of 7 r is 



7 r = 2/ n sin- (vi) 



whence, using the value of 7 n from equation (i) above, we have 



For a two-ring converter 7 r = I.4I47 



For a three-ring converter T r = o.9427 



*This entire article applies to the two-pole machine (armature winding having 

 two paths). In case of a multipolar machine having p f current paths through the 

 armature, this equation becomes 



. TT 

 p'n sin 



