Permanent magnet (PM) shifting method is one of the ways to improve performance characteristics of PM machines. In this paper, PM shifting method is employed to reduce total harmonic distortion (THD) of the back EMF and torque ripple of a TORUS type nonslotted axial flux permanent magnet (TORUS NS‐AFPM) machine. To fulfill this goal, a formula for calculating back EMF waveform of the machine with shifted PMs is proposed. A 3.7 kW, 1400 rpm TORUS NS‐AFPM machine is selected as case study machine and the accuracy of the proposed formula is confirmed with the help of three‐dimensional finite element method (3‐D FEM). Then by using proposed formula, the effect of PM shifting angle on the back EMF waveform of the machine is investigated. In addition, the case study machine is fabricated and back EMF waveform of the machine with different value of PM shifting angle is analyzed using experimental results. With the help of proposed formula and 3‐D FEM the effect of PM shifting angle on the torque ripple of the machine is studied. In addition, a procedure for calculating optimum value of PM shifting angle is proposed. The obtained results show the effectiveness of the PM shifting method on improving machine back EMF waveform and torque ripple.

中文翻译：

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磁滞位移可改善TORUS型无槽轴向磁通永磁电机的反电动势并降低转矩脉动

永磁（PM）移位方法是改善永磁电机性能特性的方法之一。本文采用PM位移法来减小TORUS型无槽轴向磁通永磁体（TORUS NS-AFPM）机器的反电动势总谐波失真（THD）和转矩脉动。为了实现这一目标，提出了一种计算带偏移永磁电机反电动势波形的公式。选择一台3.7 kW，1400 rpm的TORUS NS‐AFPM机作为案例研究机，并借助三维有限元方法（3‐FEM）确认了所提出公式的准确性。然后，通过提出的公式，研究了PM偏移角对电机反电动势波形的影响。此外，制造了案例研究机，并使用实验结果分析了具有不同PM偏移角值的机器的反电动势波形。借助提出的公式和3D FEM，研究了PM换向角对电机转矩脉动的影响。另外，提出了用于计算PM偏移角的最佳值的过程。获得的结果表明，PM移位方法对于改善机器反电动势波形和转矩脉动是有效的。