GTO traction chopper with snubber energy recovery

The sequential operation of a snubber energy recovery circuit for a traction propulsion GTO chopper is described, with explanatory waveforms. The circuit has no additional active components. It has fewer components than the conventional circuit and results in lower GTO switching losses. The application of the circuit to vehicles of the Mass Transit Railway Corporation in Hong Kong is described. In this application, the low GTO losses resulting from the new circuit enabled the chopper equipment to be naturally ventilated and the heat sinks to be electrically isolated from the power semiconductors and earthed