Inverter with forced commutation employing gate-turn-off thyristors - has capacitor across each thyristor to suppress dangerous switch off transients

摘要

The inverter supplies a resistive inductive load with power from a dc source. The transient suppression circuit reduces the losses and number of components required. In place of the conventional RC snubber circuit with a diode bypassing the resistor in the direction of current flow for charging the capacitor, a single capacitor only (Cs1-Cs6) is connected across each gate turn-off thyristor (T1-T6). Elimination of the diode permits both capacitors in an inverter bridge arm (Cs1,Cs4; etc.) to take part in each commutation. Therefore the value of capacitance for each unit can be reduced by 50 per cent. Also with this connection the stored energy in the capacitors is returned to the load when the next thyristor turns on. There is thus no power dissipation in resistors thereby increasing efficiency and reducing cooling requirements.