Conventional flux-reversal permanent-magnet (FRPM) machines suffer from large pole leakage flux, which leads to the poor utilization of PMs and reduction of main flux. This paper proposes a consequent-pole FRPM machine, whose magnet usage is halved compared with that of a conventional FRPM machine. Nevertheless, due to the reduction of the pole leakage flux, the proposed machine exhibits larger back EMF and torque than that of the conventional one. In this paper, the operation principles and mechanism of reduced pole leakage flux of the proposed machine are introduced. Moreover, with the employment of finite-element analysis, the electromagnetic performances of the proposed machine are evaluated and quantitatively compared with a conventional FRPM machine in terms of airgap flux density, flux linkage, back EMF, pulsating torque, rated torque, losses, and flux-weakening and overload capabilities.

Permanent-magnet vernier (PMV) machines are attracting more and more attention due to their high torque density and simple mechanical structure. In this paper, a novel PMV machine with an improved permanent-magnet circuit is proposed. Compared with the regular PMV machine, half of the permanent magnets (PMs) in the rotor are moved to the stator slot opening, and Halbach array PMs are employed in the stator while the consequent pole is employed in the rotor. The analysis of this machine indicates that the back electromotive-force amplitude of the proposed PMV machine could be two times that of the regular PMV machine with similar magnet usage, and for the same torque density, viz., 23.1 kNm/m ³ , the power factor of the proposed machine can reach 0.89, while this value is only 0.65 in the regular PMV machine.

In recent years, surface permanent-magnet vernier machines (SPMVM) have been attracting more and more attention for several advantages, including a high torque density and a simple mechanical structure. However, the influence of the pole ratio, which is defined as the ratio of rotor pole pair numbers to winding pole pair numbers, and the winding pole pair numbers on the performance of SPMVMs has not been investigated in literature. This paper mainly focuses on the effects of the pole ratio and the winding pole pair numbers on the torque capacity, power factor, torque ripple, and cogging torque of an SPMVM. The variations of optimal design parameters for maximum torque, such as the split ratio (the ratio of the stator inner diameter to the outer diameter), the slot opening width, and the permanent-magnet thickness, with the pole ratio and the winding pole pair numbers are also investigated by finite-element analysis. The analysis results reveal that the pole ratio and the winding pole pair numbers significantly influence the performance and optimal design parameters of the SPMVM. Finally, an SPMVM prototype is built, and experiments are conducted to validate the aforementioned results.

In recent years, permanent magnet vernier (PMV) machines are attracting more and more attentions owing to their high torque density. The spoke array magnet is widely used in the regular PM machine to improve working flux density. However, the flux barrier effect of spoke array magnet for the PMV machine has been proved, and a large torque reduction may be introduced in the spoke array PMV machine. In this paper, a novel spoke array PMV machine is proposed to improve working flux density and the torque density of PMV machines. The alternate magnetic bridges are added in the rotor core to connect iron pieces with same polarity and provide magnetic circuit for the low-pole number working magnetic field, hence the no-load back EMF and output torque of the proposed machine can be significantly improved. Moreover, analytical airgap flux density distribution based on equivalent magnetic circuit is presented to reveal the mechanism of working flux density improvement, and finite element analysis (FEA) is used to investigate the performance features and structure parameter influence on the key performances, viz. back EMF and torque, of the proposed machine. Finally, a 25Nm prototype has been built and tested to validate these analyses.