Passive IGBT turn-off during short-circuit type V

Abstract:
A new short-circuit type with a passive turn OFF of the IGBT is presented. It can occur in an active neutral point clamped (ANPC) 3L inverter, when the IGBT is turned OFF without taking blocking voltage. The plasma inside the IGBT is not removed until the short-circuit occurs. The di/dt of the plasma removal is given by the short-circuit inductance and results in a high dv/dt. An active-clamping interference in the gate-emitter voltage is impaired by the switched OFF gate. The influence of the DC link voltage, the current before the short-circuit and the delay between switching and short-circuit is analyzed with the help of measurements on a 3,3 kVIGBT. The plasma removal can be explained with an equivalent capacitance. This effect is simulated and described with a causal chain and an equivalent circuit.