Effects of Magnetizing Yoke Design on the Magnetic Properties of Nd2Fe14B Permanent Magnet for Electric Vehicle Motor Applications

Abstract

When the uniformity of the magnetization yoke is low, a mismatch occurs between the physical rotation center and the center due to the magnetic force after magnetization. This discrepancy in rotation can cause issues such as vibration and noise during high-speed rotation, which in the long term leads to a decrease in the lifespan of the motor. In addition, in order to minimize the problem of motor lifespan when a vehicle is used for more than 10 years after purchase, the problems caused by magnetization should be solved as far as possible. In this study, magnetization yokes were designed in various ways to optimize the factors that affect the magnetic properties after the magnetization of the Nd2Fe14B permanent magnets used in electric motors. In the case of a 50 µm deviation between the coils wound inside the magnetization yoke, the magnetic property imbalance of the Nd2Fe14B magnets and the motor characteristics are not significantly affected after magnetization. However, when the center of the coil wound inside the yoke is shifted from the center of the yoke, the magnetic field is generated unevenly, which degrades both the magnetic and motor characteristics of the Nd2Fe14B magnet. Therefore, it is very important to control the center of the coil that generates the external magnetic field in the magnetized yoke in order to magnetize the Nd2Fe14B magnet with excellent magnetic properties.