Halbach永磁阵列无刷直流电机转矩的解析计算和分析

Halbach永磁阵列具有灵活配置电机气隙磁通密度、磁屏蔽的特点,将其用于无刷直流电机以增加电磁转矩、降低齿槽转矩。在保角变换求解电磁场基础上,给出无刷直流电机电磁转矩与齿槽转矩的解析计算模型,通过有限元仿真对该模型的准确性进行证明;使用该模型分析每极两块(1P2p)、每极三块(1P3p)Halbach永磁阵列中主磁钢弧角和辅磁钢充磁方向角对无刷直流电机电磁转矩与齿槽转矩的影响,对比分析径向充磁、平行充磁和Halbach永磁阵列的无刷直流电机电磁转矩与齿槽转矩随永磁体厚度的变化规律。分析结果表明,合理配置无刷直流电机Halbach永磁阵列中主磁钢弧角和辅磁钢充磁方向角可提高电磁转矩、降低齿槽转矩,当永磁体厚度增加时,Halbach永磁阵列更有利于电磁转矩增加。

Analytical Calculation and Analysis of Torque for Brushless DC Motors with Halbach Magnet Array

Since the Halbach magnet array offers self-shielding magnetization and can easily change the waveform of air gap flux density, in this paper it is used in brushless DC motors to increase the electromagnetic torque and reduce the cogging torque. The model for calculating electromagnetic torque and cogging torque is presented according to the no-load magnetic field and the armature magnetic field calculated by conform transformation. Then, the calculated electromagnetic torque and cogging torque are compared with those calculated by the finite-element method (FEM). For the brushless DC motors with Halbach magnet array, the electromagnetic torque and the cogging torque are analyzed when the arc angle of the main segment of two permanent magnets in one pole is different, and they are also calculated when the arc angle of the main segment and the magnetizing angle of lateral permanent magnet (PM) of three PMs in one pole are changed. Furthermore, when the thickness of the PM is changed, the electromagnetic torque and the cogging torque in the brushless DC motor with Halbach magnet array are compared with those in the brushless DC motor with radial magnetization and parallel magnetization. The results show that, if the arc angle of main segment and the magnetizing angle of lateral PM in the Halbach magnet array are properly chosen, the electromagnetic torque can increase and the cogging torque can decrease. As the PM thickness increases, Halbach permanent magnet array is more conducive to increase the electromagnetic torque.