Overcurrent protection design, failure mode and effect analysis of an electric vehicle inverter

In the light of rapid developments in electric vehicles, it has raised a concern on the functional safety of inverters. Overcurrent is a common fault in the inverter, which could not only damage the inverter but also be hazardous to drivers and passengers due to unintended motive power loss on the road. Hence, an overcurrent protection design in an inverter is highly needed. In this study, the failure mode and effect analysis on the stated problem is systematically analyzed based on the functional safety standard, ISO26262. A two-level overcurrent protection mechanism with modulation limiter and current limiter strategy is proposed and implemented on a 50kW inverter system. Experimental results show the three-phase current amplitude is regulated within the designated current limit effectively during fault injection, which verifies the validity of the proposed strategies for the electric vehicle application.