CHAPTER X. 

 THE ROTARY CONVERTER. 



The Rotary Converter. The currents induced in the con- 

 ductors of a direct-current generator are actually 

 alternating currents which have given to them a single 

 direction in. the external circuit, owing to the action of 

 the commutator.^/. Thus, an alternator with rotating 

 armature is essentially the same machine as a direct- 

 current generator, except for the substitution of simple 

 collecting rings directly connected to the. armature 

 winding, in the place of a commutator of which the 

 segments are connected to a great number of separate 

 conductors. 



A closed circuit armature may be provided with both 

 commutator and slip rings, and may then be used 

 alternatively as a direct or alternating current generator. 

 It may also be used to give simultaneously direct and 

 alternating currents. A more frequent application of a 

 machine constructed in this way is to drive it as a motor 

 by means of current of one kind, and to take current of 

 the opposite kind from the armature winding. In this 

 way the machine acts as a motor-generator, with the 

 important difference from the true motor generator, that 

 the sani armature winding receives the driving current 

 and gives out the generated current. 



As in the case of direct-current motor-generators, 

 the fact that both generator and motor currents circulate 

 round a single armature core renders the resultant 

 armature magnetic reaction very small. This is due to 

 the motor and generator currents always being in 

 opposite directions, and consequently exerting magnetis- 

 ing forces which approximately neutralise each other. 



In the rotary converter a further advantage is secured 

 by the fact that the individual conductors carry only the 

 difference between the two currents which they receive as 

 motor conductors and give out as generating conductors. 



The value of the current carried by any conductor 

 consequently varies with the position of the armature, 

 and goes through a complete cycle of changes as the 

 conductor passes from one pole to the next similar pole. 



