Practical Limits of Liquid Cooling Electric Vehicle Power Modules

Intelligent power modules (IPMs) are critical components within electric vehicle (EV) power inverters that require effective liquid cooling. IPM manufacturers are constantly evolving their designs in lockstep with advancements in switching transistor technology to deliver more power with increased efficiency. In particular, the imminent arrival of new IPMs based on wide-bandgap semiconductors poses new thermal challenges due to smaller die areas and increased heat fluxes. The question arises whether the traditional liquid cooling strategies will be sufficient to cool the next generation of EV IPMs as semiconductor technology transitions from Si IGBTs, to SiC MOSFETs and GaN power HEMTs, with progressively decreasing die areas. In this paper, this question is explored through an analytical solution of the heat equation in a representative model of a typical EV IPM heat exchanger (HX). It is shown that there exists a practical thermal limit to traditional EV IPM IIXs which must he addressed by IPM and automotive parts manufacturers together. Thermal benchmarking experiments, supported by numerical simulations, of two commercially available IPMs are performed, confirming no violations of the derived thermal limit.