A Novel Asymmetric Variable Flux Memory Machine with Hybrid-Layer Permanent Magnets

In this paper, a novel asymmetric hybrid-layer (AH) variable flux memory (VFM) machine is proposed with the features of hybrid-layer permanent magnet (PM) configuration. For each pole in the proposed FM machine, one part of the PMs includes a single-layer variable PM (VPM), which is in parallel with the other part comprising both a constant PM (CPM) layer and a VPM layer which are in series. This hybrid-layer PM configuration enables a series-parallel magnetic circuit configuration, combining the merits of wide flux regulation range in parallel configuration and high torque in series configuration. Additionally, the asymmetric structure mitigates the intrapolar cross-coupling effect between CPMs and VPMs existing in the symmetrical structure, contributing further to torque improvement. The proposed AH-VFM machine, along with a symmetrical single-layer VFM machine and an asymmetric single-layer VFM machine, is designed and optimized with the same stator, rotor diameter, and PM usage. The electromagnetic performances of the optimized designs for all three machines are investigated and compared, demonstrating that the AH-VFM machine can effectively balance the flux regulation and the torque, as well as an improved constant power speed range and overall efficiency.