Method for detecting an inverter hardware failure in an electric power train

A method for detecting an inverter hardware failure in an electric power train comprising a high voltage battery having positive and negative terminals, high voltage cables, at least one electric machine and at least two inverter legs with two power electronic switches respectively for pulse-width-modulating a DC voltage from the high voltage battery for energizing the at least one electric machine, the power train being connected to the high voltage battery via a link comprising a bulk capacitance and a Y-capacitance, both being connected to the positive terminal and to the negative terminal of the high voltage battery and a center tapping of the Y-capacitance additionally being connected to a metallic housing electrically isolated from the battery, and including at least one mid-pack voltage sensor for detecting isolation faults, the method comprising the steps of:

• requiring all power electronic switches open;
• alternately closing and opening the two power electronic switches of one of the inverter legs at a certain time at a given duty cycle, a given dead time and a given frequency;
• measuring a mid-pack voltage using the mid-pack voltage sensor;
• identifying both switches of the leg as functional if, with the switches closed, a common mode voltage is detected by the mid-pack voltage sensor or, otherwise, identifying the leg as non-functional.