Cooling and dynamic performance of electric vehicle traction motor adopting direct slot cooling method

Heat loss in an electric vehicle traction motor can be an important cause of insulation breakdown in coil winding and demagnetization of rotor magnets, resulting in a gradual or permanent malfunction of the motor. Thus, a motor cooling technique that immediately removes a large amount of heat released under extremely tough driving conditions is needed. In this study, the cooling and dynamic performances of two motors adopting the direct slot cooling (DSC) and water jacket cooling (WJC) methods were tested. The coolant in the DSC model directly cools the main heat source of the coil winding using the open slot of a motor stator as the cooling channel. Through thermal and electromagnetic simulations, the motor maximum and average motor temperatures under constant-current and real-driving conditions, marginal current density in a given coolant pumping power, and maximum torque and power of both motors are presented in detail.