Variable Flux Memory Motor Employing Double-Layer Delta-Type PM Arrangement and Large Flux Barrier for Traction Applications

This article consists of two important topics regarding variable flux memory motors (VFMMs). The first topic is magnetization characteristic analysis of VFMMs having a double-layer permanent magnet (PM). Two-dimensional simulations are executed to clarify relationship between magnetization characteristic and ratio of the double-layer PM. In addition, a prototype of a compact size VFMM is fabricated, and experiments are also carried out to investigate accuracy of magnetization characteristic analysis. The second topic is the proposed VFMM employing double-layer delta-type PM arrangements and extended flux barriers for traction applications. Conventional VFMMs have three critical issues, which are as follows: asymmetric positive and negative magnetizing current pulses, increase in the iron loss due to harmonics caused by demagnetized variable flux PMs (VPMs), and unintentional demagnetization of VPMs under load condition. The proposed VFMM can overcome the abovementioned problems by employing double-layer delta-type PM arrangements and extended flux barriers. In addition, the proposed VFMM achieves much higher efficiency than that of the target motor mounted in TOYOTA Prius fourth-generation over a wide operating range.