A Novel Pole-Changing Memory Machine with Hybrid-Pole Configuration

In this paper, a novel pole-changing memory machine (PCMM) with hybrid-pole (HP) topology is proposed and optimized. The rotor topology is characterized by the hybrid pole configuration of V-type high-coercive force (HCF) permanent magnet (PM) and flat-type low coercive force (LCF) PM with auxiliary magnetic bridge, which solves the crucial problem of unbalanced magnetic field distribution of PCMMs. The magnetization states (MSs) of LCF PM can be flexibly varied to form either 4- or 8-pole magnetic circuits, respectively. The armature winding has convenient switching process since only a swapping of two phases is needed to match the pole numbers, which facilitates the online pole-changing manipulation. A variable-speed-based finite element (FE) analysis process is developed to comprehensively consider the operational modes with different pole numbers. The sensitivity analysis is carried out to determine the high- and low-sensitivity design parameters. Then a two-round multi-objective optimization is conducted on the proposed HP-PCMM to achieve high torque, high efficiency and low torque ripple. Finally, the electromagnetic performance of the HP-PCMM is evaluated and compared with those of the reference machines, i.e., flat-type PM PCMM (FPM-PCMM) and equal-pole-arc HP-PCMM (EHP-PCMM), respectively.