Temperature Rise Calculation and Mixed Water Cooling Design of Hairpin Winding Motor for Electric Vehicles

In order to solve the problem of high loss and uneven temperature rise of high-frequency hairpin winding motor of electric vehicles, the electromagnetic field finite element model, field circuit coupling model and thermal network model of the motor are established. The loss and temperature distribution of the conductor and iron core in the slot of the motor at different working points were theoretically deduced and simulated, and the temperature rise of IGBT and SiC driven motors was compared. The results indicate that the losses and temperatures of SiC driven motors are lower than those of IGBT driven motors, and there is an uneven distribution of losses in the conductor and stator core in the slot. The loss density near the slot and tooth top is significantly higher than other parts, and the degree of imbalance increases with the increase of motor speed and frequency. At the peak speed operating point, the temperature of multiple layers of conductors is higher than the maximum insulation operating temperature, and long-term operation is prone to thermal failure. To solve this problem, a composite water cooling structure combining shell water cooling and tank water cooling was proposed, and the relationship between water channel size and cooling effect was analyzed. Compared to a single shell water cooling, composite water cooling can significantly reduce the maximum temperature and temperature imbalance of the conductor.