Efficiency-Oriented Stepwise Optimization of Variable Flux Memory Machine Considering Torque Requirement and Operation Envelope Expansion

Existing variable flux memory machines (VFMMs) typically suffer from the unavailability of operation envelope expansion and insufficient torque at the high magnetization state (MS), which severely hinders their potential for overall high-efficient operation through MS regulation. In this article, a novel efficiency-oriented stepwise (EOS) optimization strategy for VFMM is proposed. This strategy can innovatively take the coil flux linkage directly as an optimization objective, which can flexibly regulate the operation envelopes and PM torques at different MSs. A 27-slot/4-pole VFMM with the magnetic circuit complementary (MCC) concept is taken as a design example. Firstly, the operation principle, multiple operation conditions, and key requirements of the VFMM are theoretically investigated. Then, the MCC-VFMM and the EOS optimization strategy are introduced and implemented respectively. Furthermore, the key electromagnetic characteristics of the initial and optimized VFMMs are comprehensively compared. Finally, an optimized prototype is fabricated and experimented to confirm the feasibility of the proposed optimization approach.