Abstract: Apparatus for controlling d-c shunt motors of electric cars utilizes first chopper circuits connected in series with the armatures of the d-c motors for controlling armature currents upon receipt of a first set of control signals and second chopper circuits connected in series with the field windings of the d-c shunt motors for controlling the field currents responsive to a second set of control signals, reactors having first and second coils, the first coils being connected in series with the armatures and the second coils being connected in series with the field windings, with the first and second coils magnetically coupled together to maintain a relationship that the field currents decrease with a decrease in the armature currents.

Abstract: When a plurality of shunt motors connected in parallel are used for driving an electric railcar, the differences in the characteristics of the motors introduced during the manufacturing thereof causes the armature currents to vary greatly even when they are running at the same speed. To control the field current by means a single device, therefore, the armature currents must be corrected by armature choppers. In order to fully recover the kinetic energy possessed by the electric railcar, the present invention automatically corrects for the difference in the characteristics of the shunt motors so that the required braking force is uniformly borne by each of the shunt motors.