io-C] SYNCHRONOUS CONVERTER. 3 2 3 



Hence, for a single-phase (or 2-phase) machine, the A.C. 

 voltage is 



EA.C. = (i/V2)ac. = .707 D .c.. 



The star voltage Es, measured between one alternating current 

 line and the neutral, is 



s = % ( i/ V 2 ) D.C. = o.354 D .c., 



which is true for a polyphase, as well as for a single-phase, ma- 

 chine. From the star voltage, the line voltage in any case is 

 readily computed; thus, 



In a single-phase or 2-phase machine, the line voltage is twice 

 the star voltage. 



In a 3-phase machine ( 19, Exp. 6-A), the line voltage 3 is 



3 = Vs =- D.C. = .6i2 D . c .. 

 2V2 



In a 6-phase machine, the line voltage 6 is 



6. Current Ratios. Assuming a certain efficiency and power 

 factor, the alternating current in each supply line corresponding 

 to any particular value of direct current output can be computed. 

 Thus, if power factor and efficiency are i .00, each ampere of direct 

 current requires an alternating current of V 2 amp. (=1.414) 

 single-phase, %V 2 amp. (=0.707) 2-phase, %V 2 amp. (=0.943) 

 3-phase, %V 2 am P- ( -47 2 ) 6-phase. 



7. Rating. In a converter, each armature conductor carries 

 an alternating current and a rectified direct current, giving an 

 irregular wave form, with a chopped up appearance, differing in 

 the various conductors according to the time that has elapsed since 

 each conductor has passed under a brush. The rating* of a con- 



* For a good discussion, see paper by O. J. Ferguson, Elect. World, p. 

 214, Jan. 21, 1909, where ratings are derived for various power factors, 

 based upon hottest and coolest coils as well as upon average heating. See 

 also paper by W. L. Durand, Elect. World, p. 235, Jan. 26, 1911. 



