Oil Injection Cooling Design for the IPMSM Applied in Electric Vehicles

In recent years, the power, torque, speed, and other performance of interior permanent magnet synchronous motor (IPMSM) for electric vehicles have improved. The temperature rise is an important factor limiting the performance of the motors. In this article, a novel hollow shaft oil injection cooling structure is proposed. The cooling oil is passed in from one end of the hollow shaft and enters the permanent magnet cavity through the radial oil channel. The centrifugal force generated by the rotation of the rotor causes the oil to be sprayed from the oil injection holes on the end caps at both ends of the rotor, and the winding ends and the stator are directly cooled, which reduces the internal temperature of the motor. The Taguchi method is used to analyze the influence of the novel hollow shaft oil injection cooling structure on the average temperature of the winding and the difference in the injection flow rate at both ends of the motor. Considering various operating conditions, the optimization scheme of the cooling structure is determined. Finally, the reliability of the structure is verified by stress calculation and modal analysis.