Iterative Electrical–Thermal Coupled Simulation Method of Automotive Power Module Used in Electric Power Steering System

This paper presents a multi-physics analysis coupling the electrical and thermal properties of a power module. As power modules have multi-physical behaviors, it is important to simulate their multi-physical characteristics. Simulations of these characteristics have been separately conducted using specific software; however, as these characteristics are often coupled, it is difficult to fully understand the multi-physical nature of power modules. This paper proposes a method to analyze the coupled characteristics of a power module in an iterative manner. The analyzed module is designed for an automotive electric power steering (EPS) system. We fabricated the EPS module and measured its electrical and thermal characteristics, which were used for reference. For the coupled simulation, we employed ANSYS Icepak and Q3D Extractor for thermal and electrical simulations, respectively, linked them to the ANSYS workbench environment, and conducted an iterative feedback simulation until the simulated results converged. The coupled simulation demonstrated that the parasitic resistance and volume loss density of the power module are increased by ~50% compared to the those obtained from a separately conducted electrical simulation due to the impact of the linked thermal simulation. As a result, the simulated thermal resistance increased to 0.26 K/W, which is almost identical to the measured value of ~0.27 K/W. Therefore, our iterative electrical–thermal coupled simulation exhibits more accurate results than the conventional separate simulations.