An Improved Variable Flux Memory Machine Topology With Multi-Stage Magnetization Strategy

Variable Flux Memory Machine (VFMM) is capable of regulating the air-gap flux density flexibly by applying current pulses. This paper proposes an improved Y-structure VFMM topology, which features wide flux-regulation range and excellent on-load Demagnetization Withstand (DW) capability, and a novel multi-stage magnetization strategy is proposed. By injecting current pulse directly into the low-coercive-force (LCF) permanent magnet (PM) positions instead of the d-axis, the magnetization states of all PMs are varied sequentially, which decreases the amplitude of the required magnetization current. Magnetic circuit model is established to illustrate the operating principle, and optimization work is performed to further enhance the overall performance. Electromagnetic characteristics and magnetization property are investigated with 2D Finite Element Analysis (FEA). The FEA results show that the proposed topology takes the advantage of wide flux-regulation range and superior on-load DW capability. Moreover, less magnetization current is required with proposed magnetization strategy compared with conventional strategy.