PURPOSE: To reduce the capacity of a reactor and to prevent the deterioration in the rectification of a control device for an electric rolling stock by flowing an armature current through a GTO thyristor during an ordinary operation and flowing the current through the reactor only when the current abruptly increases.

CONSTITUTION: An armature current flows through a GTO thyristor 8 during power drive operation, and flows through a GTO thyristor 9 during the regenerative operation. On the other hand, when a line voltage abruptly varies so that the armature current rapidly increases, the varied component is supplied through a transformer 10 to a gate circuit of the thyristor 8 or 9. The secondary side voltage generating direction of the transformer 10 is determined to the direction of flowing a gate current to turn the thyristor 8 or 9 OFF when the armature current is abruptly increased. Accordingly, when the armature current is increased rapidly due to the variation in the line voltage, the thyristor 8 or 9 is interrupted, the current flows through the reactor 4, thereby suppressing the peak current.