Reduction of the cogging torque is preferred during the design process of a permanent magnet (PM) synchronous machine (PMSM), especially in the low-speed traction applications. This article presents a dual-skew magnet technique to minimize the cogging torque in the axial-flux permanent-magnet (AFPM) motor with a yokeless and segmented armature (YASA). The theoretical expression of the cogging torque of the AFPM machine is deduced, and the advantages of the dual-skew magnet are verified by comparing with a sector shape magnet and a conventional skew magnet using the 3-D finite-element method (FEM). The simulation results show that, compared with the other two magnet topologies, the machine equipped with the dual-skew magnet shows its advantages in the reduction of cogging torque, torque ripple, and magnet eddy current loss.

This paper presents a 3-D magnetic equivalent circuit (MEC) network that integrates the hysteresis model for the analysis of the axial field flux-switching (AFFS) memory (AFFSM) machine. Similar to finite element method, meshing is used to subdivide the model into smaller domains called elements, over which a set of element equations and a reluctance network equation are built. Newton-Raphson method is adopted to handle the nonlinear problems. The fixed-point technique is introduced to cope with the problem involving hysteresis. The proposed method is capable of predicting the operation of the low coercive force permanent magnet during flux regulation and the electromagnetic field distribution of the machine. Finally, the proposed 3-D MEC method is implemented for analysis of the AFFSM machine. MEC results are compared with 3-D finite element analysis and experimental results. The results show that the proposed method offers reasonable accuracy with moderate computational effort.

Hybrid axial field flux‐switching permanent magnet (HAFFSPM) machine exhibits a high‐cogging torque due to its doubly salient structure and flux focusing effect. In consideration of the armature and field windings are both equipped in the HAFFSPM machine, a cogging torque reduction method by the harmonic field current injection is proposed in this study. Initially, the mathematical model of the HAFFSPM machine is analysed. Moreover, the theoretical principle of the proposed method is investigated based on the analytical model of the machine. The amplitude and phase angle of the injected current are calculated according to the harmonic component of the cogging torque. The feasibility of the proposed method is analysed and validated by both the finite‐element analysis method and experiments on the prototype. Finally, the comparison between the proposed method and several topology optimisation methods of the HAFFSPM machine is given to indicate the priority of the harmonic field current injection method on cogging torque reduction.

This paper presents a new topology of an axial flux-switching memory machine with series-type permanent magnets (SPMs) to improve the flux regulation capability. The key idea was to combine low coercive force (LCF) PMs, which can be magnetized and demagnetized readily, with high coercive force (HCF) PMs in series to provide a variable air-gap magnetic flux. The flux regulating principle and the forward magnetization effect of HCF PMs on LCF PMs are presented and discussed. Based on 3D finite element analysis (FEA), the magnetization variation of LCF PMs and the electromagnetic performances of the machine under different magnetization states were investigated. Simulation results showed that the air-gap magnetic flux could be weakened by up to 45% by using a magnetization current impulse, significantly extending the PM motor’s flux-weakening speed range. Finally, a prototype machine was built, and experiments were performed to validate the predictions. The basic experimental validation shows that the measured back-EMF and the flux regulating characteristic matched the 3D FEA results well.

In this paper, the structure parameters of a novel high-performance magnetic transmission for converting between rotary and rectilinear motion is studied by finite element method (FEM). The structure parameters include the length of air-gap and design parameters of ferromagnetic pole-pieces. In order to explore the influence of individual parameter on force and torque, the variation tendency of force and torque varies with each parameter are described. Response surface method (RSM) is applied into design of experiment (DOE) to find out the relationship between response and parametric variables. A mathematical model is achieved by RSM, which predicts a best set of parameters. The finite element calculation is done to verify the correctness of mathematical model. The study results demonstrate that ferromagnetic pole-pieces have great influence on MT.