Abstract：Snubber capacitance is usually parallel connected to switches in power converters made up of IGBT to suppress voltage overshoot during the process of turn-off so as to protect the IGBT and converters. Based on a dynamic model of IGBT, the paper theoretically analyzed the impact law of snubber capacitance on turn-off voltage. Then the voltage-overshoot results with two different snubber capacitances were compared in detail.As a conclusion, the snubber capacitance can reduce the turn-off voltage of IGBT and produce the voltage-current oscillation in a DC-bus as well. Some simulation and experimental results reflecting voltage-oscillation caused by snubber capacitance during the turn-off process of IGBT were shown. At last one method to cancel or decries snubber capacitance was proposed.

Keyword：snubber capacitance;IGBT;converter;turn-off voltage;current oscillation;