Mission Profile-Based Hotspot Temperature and Lifespan Estimation of DC-Link Capacitors Used in Automotive Traction Inverters

In electric vehicles (EVs), film capacitors are installed in the traction inverter to reduce ripple current. However, the lifespan of commercial film capacitors is highly sensitive to temperature fluctuations. The high ambient temperature within the traction inverter often leads to the premature failure of these capacitors, severely impacting the reliability of the traction drive system. In existing studies, the internal losses of capacitors have often been treated as constant, overlooking variations caused by changes in operating conditions and aging, which results in discrepancies between predicted and actual lifespans. This paper first proposes a new finite element analysis (FEA) modelling strategy to more accurately determine the hotspot temperature rise by considering the distribution of losses within the capacitor core. Next, based on the Federal Testing Procedure -75 (FTP-75) driving cycle, the operating profile of capacitors during EV operation is obtained. Following that, the cumulative damage of the capacitor is evaluated according to Miner’s rule, and the lifespan of the film capacitors is assessed. This method can offer a reference for capacitor replacements planning.