DC motor thyristor rectifier - has protection against thyristor turn-off overloads with quenching thyristors turning on alternately

摘要

The thyristor rectifier, for d.c. motors, is protected against overload voltages resulting from its thyristor turning off or being quenched. The a.c. supply is obtained from a transformer whose secondary is connected at one end to the junction between two series-coupled diodes bridging the load and at the other end over an inductor to the junction between two series-coupled main thyristors also bridging the load. The main thyristors are bridged by two series-coupled quenching thyristors in the same conduction direction as the main thyristors. The anode/cathode junctions between the two thyristors in each pair are connected together over the quenching capacitor. A quenching thyristor is turned on when the capacitor voltage exceeds the supply voltage.