Abstract: A switched reluctance machine is energized by phase circuits with four active switches, for example MOSFETs, arranged in a bridge configuration. The switches are capable of conducting current in both a first direction and a second direction and are capable of operating as a diode. The direction of current flow through the phase winding is reversed when changing from motoring to generating and from generating to motoring. The ratings of the switches are set in accordance with the energy supply and energy return currents.

Abstract: A regenerative ac to dc convertor includes a thyristor bridge invertor and a rectifier having a dc link capacitor. A second capacitor is connected across the invertor. In a regenerative braking mode of the motor the invertor is arranged to return energy from the second capacitor to the ac supply. Circulating currents are inhibited by diodes connecting the dc link and second capacitor. A first diode is arrange to conduct from the positive terminal of the second capacitor to the positive terminal of the dc link capacitor. A second diode is arranged so that it conducts from the negative terminal of the dc link capacitor to the negative terminal of the second capacitor.