Method and device for detecting a short circuit of a semiconductor switch element in an inverter for energizing an electric drive in an electric vehicle or hybrid vehicle; inverter comprising such a device

Abstract

A method for detecting a short circuit of a semiconductor switch element in an inverter comprises comprising a plurality of semiconductor switch elements forming a high side and a low side, wherein the high and low sides comprise respective semiconductor switch elements connected in parallel, and the high and low sides are connected in parallel to form an intermediate circuit capacitor. The method includes measuring an intermediate circuit voltage applied to the intermediate circuit capacitor; determining an intermediate circuit capacitance of the intermediate circuit capacitor; determining a short circuit resistance of the inverter; ascertaining a time constant from the intermediate circuit capacitance and the short circuit resistance, by multiplying the intermediate circuit capacitance by the short circuit resistance; ascertaining a change in the measured intermediate circuit voltage within the ascertained time constant to calculate a change rate; and comparing the change rate with a first threshold.