260 



ALTERNATING CURRENTS 



electrical space-degrees apart. The rotor or armature of B is 

 wound three-phase and the coils are connected to a commutator 

 in the same manner as they are in a direct-current armature. 

 The three-phase slip-ring currents of the main motor are carried 

 into the armature of B through the brushes and commutator, 

 the brushes being spaced 120 electrical space-degrees apart as 

 shown. Series compensating windings Ci, C% and Ca act along 

 their respective brush axes and assist commutation. 



Mechanical 

 Load 



Generator 



Neutralized Shunt 

 3-Phase Commutator Motor 



FIG. 246. Connections for adjusting speed of an induction motor by means 

 of a neutralized three-phase commutator motor connected to slip-rings of in- 

 duction motor. 



A three-phase auto-transformer B is Y-connected across the 

 slip-rings. A tap on each phase of this transformer feeds one 

 of the shunt fields FI, F z , F 3 , the shunt fields being connected in 

 Y. 



A constant speed generator G, usually of the induction type, is 

 mechanically connected to the motor B, and delivers back into 

 the line the power received from the motor. 



