Study on Anti-Demagnetization of Magnet for High Speed Permanent Magnet Machine

Compared with common permanent magnet (PM) machine, the high speed PM machine has smaller size and larger power density. However, the heat dissipation of the high speed machine becomes a serious problem due to the small size and high power loss density. More attention should be paid to the protection of the PM rotor from overheating demagnetization. In this paper, the magnetic properties of high speed PM rotor for different machine structure and speed are studied based on the combined analysis of magnetic, temperature and fluid fields. In order to protect the PM rotor from overheating demagnetization, a new structure of high speed machine having PM rotor with nonmagnetic enclosure and stator with inner and outer cooling vents is proposed. The theoretical analysis and experiment result of high speed PM machine show the validity of the proposed anti-demagnetization approach.