374 



ELECTRICAL MACHINERY 



from one direction to the opposite direction, but while the 

 coil is moving from one brush to the other its current is con- 

 stant in magnitude and direction. Each coil would have 

 its current commutated, or changed in direction, 30 (one- 

 twelfth of 360) later than its neighbor and so the current 

 forms of Fig. 245 are seen to be correct. 



Current Due to A-C. Input. Now consider the current 

 in each coil, supposing the machine running as a single- 



Time 



Fia. 245. Currents in the Different Coils Due to c-c. Load. 



phase synchronous motor. The current in each coil will 

 be a sine wave (supposing a sine wave of e.m.f. to be 

 impressed) and the maximum value of the current in any 

 one coil is equal to one-half the maximum of the current 

 in the single-phase line supplying the power; this is true 

 because there are two paths in the armature between 

 which the line current divides equally. 



Ratio of Alternating Current to Continuous Current in a 

 Single-phase Converter. Neglecting the losses in the machine, 



