RECTIFYING DEVICES 375 



to make the equation simple, we may now write for the 

 single-phase converter, 



a-c. input = c-c. output 



Hence, 4it. = 



which gives the relative values of the continuous current 

 and the virtual alternating current. We know that the 

 maximum value of an alternating current is equal to 

 1.4 IX the virtual value, so that 



7 a i t . (maximum) = 1. 4 17 alt . (virtual) =2X/ CO n. 



Therefore, if the machine running as a single-phase 

 synchronous converter is supplying 10 amperes to the 

 c-c. line ( 5 amperes in the individual coils, as shown in 

 Fig. 245), the maximum value of the current in the a-c. 

 supply line is 20 amperes and the maximum value of the 

 alternating current in a coil is half of this value, or 10 

 amperes. 



Actual Current in a Coil. The actual current in any 

 coil of the converter is the resultant of a sine wave of 

 current (maximum value equal to 10 amperes) and the 

 rectangular current shown in Fig. 245. Fig. 246 shows 

 the result of subtracting the continuous current in a coil 

 from the alternating current, on the supposition that the 

 alternating current has its maximum value when coil 1 

 is undergoing commutation. 



Peculiar Current Forms. From Fig. 246 it is seen that 

 the currents in the individual coils are very different in 

 magnitude and form; this makes the heating of the various 

 coils different, it being much greater in those coils near the 

 a-c. taps. In case the converter is operating with a power 



