Analysis and Design of SPM Type Variable Flux Memory Motor Considering Demagnetization Characteristic of Permanent Magnet

Permanent magnet (PM) of variable flux memory motor (VFMM) with a distributed winding is demagnetized by the opposite direction magnetic field at rear edge of PM. Moreover, average torque, performance, and power of VFMM are decreased when the PM is demagnetized. Therefore, method to prevent the demagnetization of PM is an important issue for VFMM design. In this paper, some methods are proposed to reduce the demagnetization of the PM. First method is to replace certain regions of PM that is vulnerable to demagnetization with higher grade PM material, as demagnetization is highly effected by magnetic field intensity. However, the cost of the high grade PM material and manufacturing complexity may be problematic. Therefore, other methods that are based on magnetic resistance concept are introduced, which alters different design variables to solve the issue. To verify the validity of the methods, demagnetization ratio of the base model is compared to that of the suggested method applied models under same operating condition.