Study on temperature distribution of permanent magnet synchronous motor for electric vehicles under three-port hybrid cooling structure

Permanent magnet synchronous motors (PMSMs) in electric vehicles operate within highly constrained installation spaces, leading to compact volumes, elevated stator winding current densities, increased losses, and a heightened risk of excessive local temperature rise. This paper investigates a 250 kW double-V interior PMSM for electric vehicle applications. A three-dimensional lumped parameter thermal network (LPTN) model of a single-port housing water jacket cooled PMSM is first developed for both constant-torque and constant-power operating regions. Thermal resistance parameters and heat transfer coefficients for each component are incorporated to calculate the temperature distribution of the stator windings and permanent magnets. To mitigate end-winding overheating under single-port cooling, a dual-port configuration combining housing water jacket cooling and outer-surface oil spray for the end-windings is proposed, and its corresponding LPTN model is established. The hotspot temperature migration under combined water-oil cooling is analyzed. Furthermore, to minimize the temperature difference between the inner and outer end-winding surfaces and enhance rotor cooling, a shaft oil-slinging path is introduced. Integrating this with the previous two methods forms a three-port hybrid cooling architecture that enables coordinated temperature control of the stator straight section, end-windings, and rotor shaft system. During model development, an innovative thermal management evaluation method and an “environmental envelope” concept are incorporated into the LPTN framework to unify the heat exchange boundary between multiple cooling paths and the ambient environment, thereby improving calculation accuracy and model scalability. Finally, an experimental platform for stator-rotor temperature measurement is built. Temperature tests under various operating conditions are compared with simulation results, confirming the accuracy and validity of the proposed three-port cooling LPTN model. The results provide theoretical guidance and engineering reference for temperature rise control and cooling system optimization in high-speed, high-power-density PMSMs for electric vehicles. • Three-port hybrid cooling architecture tailored for high-speed EV PMSMs. • Modular LPTN with an “environmental envelope” unifying multi-path heat exchange. • Port-wise cooling and hotspot migration quantified; model validated by experiments.