Abstract: A gated semiconductor device comprising a substrate defining an active surface area including source regions, and a series of gates formed adjacent and insulated from the source regions. A source electrode contacts the source regions. A termination extends around the periphery of the active surface area, The termination comprises a gate electrode and a layer of conductive material electrically connected between the gate electrode and the gates. The layer of conductive material extends to the source electrode and incorporates a series of regions which are alternately N and P type so as to define a series of breakdown diode junctions distributed around the active surface area and interposed between tie gate electrode and source electrode, In normal operation gate current flows through portions of the conductive layer which do not incorporate diode junctions. In the event that the gate/source voltage exceeds a predetermined level, the diode junctions break down, shorting the gate to the source.

Abstract: A self-excited induction motor variable speed drive using a known self-excitation method in which a capacitor is connected in parallel with the motor. Power is supplied by a supply convertor, a D.C. link and a motor convertor, the latter running at the motor frequency. The motor convertor includes a current bypass switching circuit comprising a capacitor bank connected to the motor terminals and to a neutral point between a pair of thyristors connected across the D.C. link.

Abstract: A rectifier system in which the harmonic content of the A.C. current is reduced in a particularly efficient manner. Two or more 3-phase thyristor bridges are connected in parallel to the A.C. supply, and to the DC output by way of interphase-transformers. For the positive thyristors, and for the negative thyristors separately, the conduction transitions within each bridge are staggered from one bridge to the next so that the total conduction on each phase follows a stepped characteristic approaching a sine wave and thus having a smaller harmonic content than a comparable arrangement having uniform firing angles from bridge to bridge.