Measurement of AC-Magnetic Loss in Permanent Magnets at High Temperature

Most EV/HEV have adopted Nd-Fe-B sintered magnet having high coercive field strength and remanent flux density. AC-magnetic loss in Nd-Fe-B sintered magnets is relatively large compared to ferrite magnets and other permanent magnets due to low electrical resistivity of Nd-Fe-B sintered magnets and there is a concern that the magnet is demagnetized by heat generated from AC-magnetic loss. The evaluation of the AC-magnetic loss especially at high temperature corresponding to internal environment in the motor during driving is important and the measurement-system for evaluation of the AC-magnetic loss was developed. In this paper, the behavior change of the AC-magnetic loss at high temperature (–200◦C) in Nd-Fe-B sintered magnets having various Hcj and Br was presented. They indicated that the behavior is different between each Nd-Fe-B sintered magnet, and that it is difficult to consider the behavior associating the loss with basic magnetic properties in the magnets such as Hcj and Br. Furthermore, it was clarified that it is unable to understand the loss-behavior from the change of classical eddy current loss. Copyright © 2024 JFE Steel Corporation. All Rights Reserved.