Analysis of Temperature Rise in High-Speed Permanent Magnet Synchronous Traction Motors by Coupling the Equivalent Thermal Circuit Method and Computational Fluid Dynamics

To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors, the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics. Also, a cooling strategy is proposed to solve the problem of temperature rise, which is expected to prolong the service life of these devices. First, the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed, then the fluid flow for the considered motor is analyzed, and the equivalent thermal circuit method is introduced for the calculation of the temperature rise. Finally, the stator, rotor loss, motor temperature rise, and the proposed cooling method are also explored through experiments. According to the results, the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68°C and 76°C, respectively. By monitoring the temperature of the air outlets inside and outside the motor at different speeds, it is also found that the motor reaches a stable temperature rise after 65 min of operation. Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point. We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors. © 2020