Investigation of Dual-Effect Air-Gap Field Regulation Mechanism in Variable Flux Memory Machines

This article investigates the mechanism of dual-effect air-gap field regulations in variable flux memory (VFM) machines, based on which series-parallel permanent magnet (PM) VFM machines are focused. It is revealed that the field regulation is composed of two factors, i.e., the variable flux effect directly due to the variable PM (VPM) magnetization state regulated by current pulses, and the variable reluctance effect of rotor iron bridges relevant to the VPM leakage flux variation. The basic electromagnetic performance of the VFM machines is evaluated and the contributions of the two factors are quantitatively identified based on finite element analysis and frozen permeability technique. Moreover, the design parameters of iron bridges directly influencing the variable flux and variable reluctance effects are analyzed, and it is found that the field regulation capability of VFM machines can be enhanced by carefully designing the iron bridges and synthesizing the two effects. A VFM prototype machine is fabricated and tested to validate the analyses.