A Novel Hybrid-Variable-Flux Permanent Magnet Machine

This article proposes and investigates a novel hybrid-variable-flux permanent magnet machine (HVF-PMM), which incorporates a variable leakage flux (VLF) property into a hybrid PM variable flux memory machine (VFMM) to broaden the design space. Thus, the conflicts of conventional variable flux PMMs between low- and high-speed key performance metrics balance. The proposed HVF-PMM is geometrically characterized by a leakage flux bypass beside the second layer high coercive force (HCF) PMs, of which the magnetic saturation can be flexibly adjusted by load current and magnetization state (MS) of low coercive force (LCF) PMs jointly. Consequently, the tradeoff issue between HCF and LCF PMs existing in conventional VFMMs can be well addressed, and hence, high torque capability at low speeds and high efficiency under high-speed operation can be realized simultaneously. First, the design concept and operating principle of the proposed machine are introduced and analyzed, respectively. Subsequently, the HVF property of the proposed design is investigated using a simplified magnetic circuit model and finite element (FE) method. Furthermore, the electromagnetic characteristics of the proposed machine are analyzed and compared with its counterpart. Finally, a prototype is manufactured and tested to validate the feasibility of both theoretical and FE analyses.