316 THE ROTARY CONVERTER. 



conductors to one ring will be equal to the angle between 

 one N pole and the next N pole. The total number of 

 connections from the armature will thus be the same as 

 the number of the poles. 



Assuming the case of a two-pole converter fed from 

 the direct-current side to give a single-phase alternating 

 current, the armature will have two connections to the slip 

 rings which will in two positions in every revolution 

 receive the full voltage given to the commutator. The 

 value of the alternating voltage produced will consequently 

 have a maximum value equal to the direct current voltage, 



and a virtual value of ~m~ or '707 times this voltage. 



In the case of a two-pole three-phase converter the 

 conductors connected to slip rings will be situated 120 

 apart. 



The maximum voltage bet ween two rings will occur when 

 the conductors joined to the rings are in such a position 

 as the conductors a, b shown in Fig. 157, since the conductors 

 between a and b will then be moving iu the strongest part 

 of the field. In this position the flux being cut by the con- 

 ductors will be less .than the maximum flux, which would 



FIG. 157. VOLTAGE OP THREE-PHASE CONVERTER. 



be cut by the conductors between A and B in the ratio of 

 ab to AB, if we assume the armature to rotate in a uniform 

 field. 



Since the angle aOb = 120, the length a c = a sin 60 

 = A sin 60. Thus the line a b = A B sin 60 



Hence maximum voltage = F D sin 60, where F D = 

 voltage induced in the armature when employed for 

 generating direct current, i.e., direct-current voltage of the 

 converter. 



