Calculation of the Remnant Magnetization and Magnetic Saturation Characteristics for Sintered NdFeB Permanent Magnets Utilizing Finite Element Transient Simulations

Abstract

This article presents the numerical calculation of the remnant magnetization and magnetic saturation characteristics for sintered neodymium-iron-boron (NdFeB) permanent magnets (PMs) utilizing 3-D finite element (FE) transient simulations. The nonlinear anisotropic properties of the sintered NdFeB PMs are employed to model a sintered NdFeB cylinder magnet. In addition, a magnetizing solenoid is coupled with an external equivalent current pulse circuit to analyze the magnetization process of the sintered NdFeB magnet. The remnant magnetization flux of the sintered NdFeB PM is compared and validated with numerical results and special laboratory magnet measurements published in the literature. On the other hand, a magnet saturation study is carried out; applying different saturation flux densities to the PM and the remnant magnetization flux is computed for each case. The saturation curve is computed, and the minimum saturation flux density is obtained to fully saturate the sintered NdFeB PMs. Finally, some virgin and demagnetized sintered NdFeB PMs are magnetized and saturated in the laboratory, and the minimum saturation flux density and the saturation curve are measured and compared with the FE simulation results. The results presented in this article show that the sintered NdFeB PMs are fully magnetized if a minimum saturation flux density of 3 T is applied during the magnetization process. The FE methodology presented in this article can be utilized by magnetizing fixture manufacturers and PM manufacturers to design efficient magnetizing fixtures and to predict the correct magnetization and saturation of different commercial grades of the sintered NdFeB PMs or other PM materials utilized in the magnetic industry and in special applications as PM motors.