Thermal Modeling and Sensitivity Analysis of a Traction Motor in a Production EV

Thermal design is critical to the performance and reliability of electric vehicle’s traction motor which may suffer from issues such as de-magnetization of permanent magnets and aging of insulation layer of copper winding wires at high temperature. In this work, CFD simulation was first conducted using ANSYS FLUENT to study the heat transfer and fluid flow inside the stator-rotor air gap and the end space of an electric traction motor used in a production vehicle (GAC’s pure electric GE3 SUV). To study the effect of air gap thickness, analytical results based on thermo-fluid theory were also computed and compared to CFD results. We then conducted lumped-parameter thermal network (LPTN) simulation of the traction motor. The model consists of 74 nodes, in which each stator end winding was modeled as three-layer structure to capture the inner temperature gradient. A sensitivity analysis was also performed over a range of parameters, e.g., material thermal conductivity, thermal contact resistance at interfaces, stator-rotor air gap thickness, convective heat transfer coefficient at the two end spaces. This systematic work is highly valuable to understand the motor’s critical thermal design parameters and to further improve the motor thermal, mechanical and electro-magnetic management design.