Effect of the magnetization direction in permanent magnet on motor characteristics

Two kinds of magnetization types in isotropic permanent magnets are introduced and analyzed by FEM: One is a radial magnetization type, the other is a parabolic one. From the results of FEA, it is found that the permanent magnet with parabolic magnetization has low leakage flux and high interior surface flux density despite using a nonmagnetic material backyoke. The magnetization types are applied to the spindle motor for optical disc media and verified by comparing the results of FEA with experimental results. As a result it is shown that the permanent magnet motor using the parabolic magnetization can consist of the magnet with a nonmagnetic material backyoke. Index terms - NdFeB bonded magnet, parabolic magnetization, isotropic, backyoke, spindle motor