This paper proposes a novel hybrid-magnetic-circuit variable flux memory machine (HMC-VFMM) by combining series and parallel hybrid magnet structures. Thus, the synergies of wide flux regulation range in parallel type and excellent on-load demagnetization withstand capability in series type can be simultaneously obtained with the proposed HMC design. Meanwhile, two sets of the permanent magnets (PMs) with high coercive force (HCF) and low coercive force (LCF), i.e. NdFeB and AlNiCo PMs, are employed to achieve high torque density and energy-efficient magnetization state (MS) adjustment. The topologies and tradeoffs of traditional parallel and series VFMMs are addressed first. In addition, the structure evolution, features and operating principle of the proposed HMC-VFMM are described, respectively. A simplified equivalent magnetic circuit is modelled to reveal the performance improvement of the machine. Then, the design improvements with q-axis barriers are presented to elevate the LCF PM working point for preventing the on-load demagnetizing effect, while maintaining the torque capability. The electromagnetic characteristics of the HMC design are investigated and compared with the parallel/series counterparts. Finally, the experiments have been carried out to validate the finite element (FE) analyses.

This paper proposes a novel topology of consequent-pole switched flux permanent magnet (SFPM) machine with U-shaped permanent magnets (PMs) for torque improvement, which is attractive for traction applications. The proposed machine is geometrically derived from a conventional sandwiched SFPM machine by introducing airspace flux barriers and flat-type PMs. The proposed design can provide an effective circulating path for low-order field harmonics. This property is beneficial for the torque capability enhancement. The machine topologies and operating principle are introduced first. Moreover, a magneto-motive force (MMF) permeance based model for the proposed SFPM machines is employed to analytically reveal the underlying working mechanism. The electromagnetic characteristics of the two proposed SFPM machines are investigated by finite element (FE) analyses, and compared with those of the conventional sandwiched SFPM machine. Finally, a 6/13-pole SFPM machine with U-shaped PM structure is manufactured and tested to experimentally validate the theoretical and FE analyses.

This paper investigates and compares the electromagnetic performance of two novel hybrid-magnetic-circuit variable flux memory machines (HMC-VFMMs) with different hybrid permanent magnet (PM) configurations. The investigated HMC-VFMMs are both geometrically characterized by a combination of series and parallel magnetic circuit topologies, but with different positions of series and parallel PM branches. The developed HMC design can combine the merits of wide flux adjustment range in parallel structure and excellent unintentional demagnetization (UD) withstand capability in series structure. The topologies, features and working principles of the studied HMC-VFMMs with different hybrid magnet configurations are described, respectively. The magnetic circuit model is utilized to analytically reveal the performance metrics of the two machines. The electromagnetic characteristics of the radially-magnetized (RM-) and circumferentially-magnetized (CM-) LCF types of HMC-VFMMs are evaluated and compared by the finite-element (FE) method. Furthermore, the performance comparison of the proposed RM-type HMC-VFMM with a benchmark IPM machine is conducted. The experiments on RM-type HMC-VFMM prototype with RM-structure are carried out to validate the FE analyses.

This article focuses on a newly developed 30-kW hybrid-magnetic-circuit variable flux hybrid magnet memory machine (HMC-VFMM) with a delta-type magnet arrangement for automotive traction applications. The proposed HMC-VFMM can improve the torque capability with effective utilization of flux concentration due to delta-type hybrid magnet arrangement while decreasing the required magnetization current level due to the dual-layer (DL) permanent magnet (PM) design. The presence of the parallel magnetic circuit can permit a satisfactory magnetization state (MS) manipulation range. Meanwhile, the DL series-type PM configuration can maintain beneficial unintentional demagnetization withstand capability. The machine topology and operating principle are described. Furthermore, the magnetic circuit model of the proposed machine structure is developed to identify and confirm the feasibility of the electromagnetic performance enhancement. Besides, the electromagnetic characteristics of the proposed HMC-VFMM are comprehensively analyzed and compared with those of a benchmark delta-type PM machine based on the Nissan Leaf drive motor. Finally, a 30-kW prototype is manufactured and tested to verify the feasibility of the proposed HMC-VFMM design in the potential context of electric vehicle applications.