In a power supply system for a variable reluctance motor, each phase winding (a, b) of the motor is connectible across a pair of supply rails by first (GTO a , GTO b ) and second (T a T e ) switch means located respectively between the first supply rail and the winding and between the winding and the second supply rail. The first switch means (GTO., GTO b ) is a fast switch-off device such as a gate tum-off thyristor or a transistor, while the second switch means (T a , T b ) is a slow turn-off device, such as a thyristor suitable for application to a line-commutation situation. In a two-phase configuration, where the second switch means is a thyristor, force- commutation of the second switch means may be achieved by means of a suitable capacitor (C c ) interconnection between the thyristors switching the respective phases.