A Novel Dual-Layer PM Variable Flux Hybrid Memory Machine

This paper proposes a novel variable flux hybrid memory machine (VF-HMM) having low-coercive-force (LCF) and NdFeB PMs placed in two layers. The developed machine can be geometrically derived from a conventional VF-HMM with series PM configuration, but the two sets of PMs within one pole are separated into two layers. In the proposed design, a bypass circuit branch for d-axis magnetizing magneto-motive-force (MMF) is designed. This can reduce the required magnetizing current level and inverter rating, which are recognized as the major challenges in the existing series VF-HMMs. Meanwhile, the advantages of on-load demagnetization withstand capability of LCF PMs and the effective reluctance torque utilization in the conventional series VF-HMM can be maintained. The machine topology and features are introduced and addressed, respectively. Then, various possibilities of the machine structures with various available magnet arrangements are presented and compared. Besides, the electromagnetic characteristics of the selected dual-layer VF-HMM model are investigated and compared with those of the conventional counterpart.