Effective thermal management scheme foradvanced traction motors with internal oil-and external water-cooling systems

In this study, we present a new mixed cooling system that combines internal oil with water-cooling, and the effective temperature control of the motor resulted in long-term stable operating conditions. Mass, momentum, and energy equations were obtained by adopting the volume of fluid and moving reference frame methods for an in-depth heat transfer analysis of motor cooling systems. In addition, various cooling systems, such as churning and drop methods were carefully selected by considering the maximum temperature and heat transfer path of the advanced motor. To ensure the reliability of the computational model, the internal thermal resistance of the motor was adjusted based on the analysis results of the reference case. The churning effect facilitated heat transfer through the air gap, thus minimizing the local temperature difference between the rotor magnets and stator coils. The drop effect directly cooled the end coil, thereby resulting in a high cooling efficiency.