Comparative Study on Variable Flux Memory Machines With Different Arrangements of Permanent Magnets

Compared with conventional permanent magnet synchronous motor, variable flux memory motor (VFMM) possesses the advantage of adjusting the magnetization state online. Because of its wide speed range and large high-efficiency region, it becomes a competitive candidate for the electric drive system. This paper presents a novel parallel hybrid magnets VFMM which is obtained by updating a conventional series hybrid permanent magnets VFMM. The proposed motor adopts a new permanent magnet arrangement and the combination of low coercive force permanent magnet and high coercive force permanent magnet is used. The proposed parallel hybrid permanent magnets VFMM and the series hybrid permanent magnets VFMM are compared. The equivalent magnetic circuit models of the motors are used to explain the principle of the motors. The finite element analysis method is used to study the fundamental properties, such as open circuit radial flux density, unintentional demagnetization with q-axis current, intentional demagnetization with d-axis current, torque capability, and efficiency characteristics. It was shown the efficiency of the parallel hybrid permanent magnets VFMM is higher in the high-speed region and the magnetization state adjustment range of the parallel hybrid permanent magnets VFMM is larger.