VP12-16: Optimization Study on Local Anti-demagnetization Ability of Rotor Permanent Magnet of High-speed Motor
Creators: Weizhou Li
Jungang Cheng
Xusheng Lu
Yangyang Li
Dong Zhao
Weili Pei and Ruilin Pei
Publisher: name: IEEE
Year: 2023

Sensors, High Frequency Devices, and Power Devices (Virtual)
Permanent magnet in High-speed motor rotor works in a harsh environment and is affected seriously by temperature, stress, reverse magnetic field and other multi-physical fields. Among them, temperature and reverse magnetic field have magnitude influence and are prone to local irreversible demagnetization under extreme operating conditions [1]. In the literature [2] [3], by analyzing the mixed structure of permanent magnets, the permanent magnets of different materials are mixed and spliced to reduce the amount of rare earths while achieving better performance, but the splicing method has high process requirements and the low performance magnets will affect the overall performance of the motor. Therefore, new paths and methods need to be further explored for the optimization of the local demagnetization resistance of magnets. In section II, a high-speed built-in PM motor model is established, as shown in Figure 1. The demagnetization distribution model of two structural magnets is given through finite element analysis (FEA), and the local anti-demagnetization optimization is carried out with this model as the target. Based on the principle of grain boundary diffusion, three optimization treatments are designed: I. Dy permeation in the demagnetization-prone region; II. Tb penetration in the demagnetization-prone region; III. Dy/Tb co-infiltration in the demagnetization-prone region. Multiple sets of experiments were conducted by varying the concentration, temperature and time to analyze the infiltration process from the material perspective. In section III, multi-physical field experiments are carried out. Comparative experiments close to the actual operating environment of the motor are designed to validate the local demagnetization resistance of the optimized permanent magnets. In section IV, in order to improve the local demagnetization performance, Dy infiltration, Tb infiltration and mixed co-infiltration are employed in the demagnetization-prone area of high-speed motor magnets, and the effectiveness of the proposed method is validated by multi-physics field experiments, which provides a reference for the subsequent research on rare-earth-less permanent magnets and their application in high-speed motors.References: [1] M. Baranski, W. Szelag and W. Lyskawinski, "Experimental and Simulation Studies of Partial Demagnetization Process of Permanent Magnets in Electric Motors," in IEEE Transactions on Energy Conversion, vol. 36, no. 4, pp. 3137-3145, 2021. [2] B. Poudel, E. Amiri, P. Rastgoufard and B. Mirafzal, "Toward Less Rare-Earth Permanent Magnet in Electric Machines: A Review," in IEEE Transactions on Magnetics, vol. 57, no. 9, pp. 1-19, 2021. [3] Y. Zhang, Z. Xiang, X. Zhu, L. Quan and M. Jiang, "Anti-Demagnetization Capability Research of a Less-Rare-Earth Permanent-Magnet Synchronous Motor Based on the Modulation Principle," in IEEE Transactions on Magnetics, vol. 57, no. 2, pp. 1-6, Feb. 2021.