Short-Circuit Behavior of series-connected High-Voltage IGBTs

In operation of series-connected IGBTs a voltage balancing is necessary, during short circuits it is even more important. Within this paper the behavior of series-connected IGBTs and diodes during the shortcircuit type 2 and 3 is analyzed. The dv/dt during the short circuit is determined by one of two equivalent circuit capacitances. One is the plasma capacitance and the second one is the Miller capacitance. Depending on the gate-drive unit the dv/dt is intrinsic, when the gate current is sufficiently high, and the plasma capacitance determines the desaturation process during short circuit. Or the gate current controls via the Miller-capacitance feedback the dv/dt. The results are obtained with the help of measurement on 3.3 kV-IGBTs.