轴向磁通电机中Halbach阵列永磁体的解析优化方法

To further increase the electromagnetic torque of the axial flux permanent magnet (AFPM) motor using the soft magnetic composite cores, this paper performs analytical optimization for the two-segment Halbach array of permanent magnets with unequal width. The air-gap magnetic field and electromagnetic performance are calculated by using the slotless 2D equivalent model and the relative permeability of the slotted air gap. Based on the derivative of electromagnetic torque and the composite integration rule, the expression for the optimal pole-arc coefficient of the axial magnetization segment to maximize the electromagnetic torque is derived. The accuracy of the analytical solutions of the air-gap magnetic field, back electromotive force, electromagnetic torque, and optimal pole-arc coefficient of the Halbach array is verified by a 3D finite element analysis of an AFPM motor. The analytical optimization results of the Halbach array show that: when the pole-arc coefficient is 0.82, the electromagnetic torque of the AFPM motor reaches the maximum; the optimal pole-arc coefficient depends on the number of pole pairs, the permanent magnet thickness, the radial size of motor, and the width of air gap, etc. When the number of pole pairs is 5, the optimal pole-arc coefficient decreases with the increase of the permanent magnet thickness, and the rise in the motor radial size results in the increase of the optimal pole-arc coefficient. The impact of the width of air gap on the optimal pole-arc coefficient is small enough and can be ignored in applications.