Study on oil cooling method for the powertrain of electric vehicles

Abstract

This study presents a thermal-fluid analysis of an electric vehicle (EV) powertrain to evaluate the effectiveness and limitation of oil cooling. A validated numerical model was developed to investigate oil flow behavior, churning effects, and temperature distribution. Results show uneven oil distribution in the motor chamber. Only 22.6 % of the cooling oil reached the drive-end winding, while 46 % reached the non-drive end. As a result, the drive end experienced a 4.2 % higher temperature than the non-drive end. The stator temperature was 4.9 % higher than the windings, and the rotor exhibited the highest temperature due to inefficient heat dissipation. Additionally, oil recirculation from the reducer (0.02 L/s) reduced cooling efficiency, particularly under high-load conditions. These findings provide critical insights into the thermal challenges of EV powertrains and serve as a foundation for optimizing oil flow, developing hybrid cooling strategies, and improving thermal management in next-generation EVs.