Abstract：Axial flux permanent magnet motor is suitable for the field with high requirements on motor perfor- mance and installation space due to advantages such as high-power density, small volume, and light mass. In the field of high-power density motors, flat copper wire is used for its high slot-filling rate and excellent heat dissipation performance. However, due to the influence of skin effect, proximity effect, and external magnetic field, the flat copper wire has a higher AC copper loss, which can seriously affect the motor performance and the insulating material life. Therefore, accurate calculation and suppression of AC copper loss of flat copper wire are significant. Although accurate results can be obtained using the three-dimensional transient field to calculate AC copper loss, some issues, such as long computing time and high computer performance requirements, could be improved. Therefore, a hybrid analytical calculation method is proposed to balance calculation accuracy and calculation time. This method combines the three-dimensional finite element with the analytical method, which can consider the influence of skin effect, proximity effect, and external magnetic field on AC copper loss. Meanwhile, a conductor arrangement of flat wire vertical winding is proposed to suppress AC copper loss. Firstly, according to the actual size of the winding, a detailed three-dimensional model of flat copper wire is established in the eddy current field, and the magnetic flux density is calculated. Secondly, the combined sampling method of parts, segments, and layers is adopted. Finally, the sampling magnetic flux density is combined with the analytical model to calculate the AC copper loss. A 60 kW, 18-slot, 20-pole double-rotor single-stator axial flux permanent magnet motor was taken as an example. Firstly, the proposed method analyzed the AC copper loss of different conductor arrangements, verified by a three-dimensional transient field finite element. The AC copper loss of the flat wire vertical winding is reduced by 36.9% compared with that of the flat wire parallel winding, and the hybrid analytical calculation time is reduced by 97.96% compared with the three-dimensional transient finite element. Secondly, the AC copper loss and motor efficiency under different working conditions were analyzed. The flat wire vertical winding motor's performance is better than the flat wire parallel winding motor in all working conditions, and its advantages are more obvious with the increase in frequency. Finally, the prototype was tested. The experimental results, the finite element results, and the hybrid analytical calculation results were almost consistent, which verified the accuracy of the hybrid analytical calculation and the effectiveness of the flat wire vertical winding. The following conclusions can be obtained by comparing the calculation results of the three methods: (1) The conductor arrangement of flat wire vertical winding is proposed, effectively suppressing the AC copper loss of flat copper wire and improving motor efficiency. The number of conductors at the slot opening should be reduced, and the conductor arrangements should be changed to suppress AC copper loss without changing the motor topology structure. (2) The influence of skin effect, proximity effect, and external magnetic field on AC copper loss of flat copper wire can be considered by the hybrid analytical calculation method. This method has the advantages of high accuracy and short calculation time in calculating AC copper loss, which is also suitable for rapidly analyzing the effect of different flat copper wire conductor arrangements on AC copper loss.
武岳, 张志锋. 轴向磁通永磁电机扁铜线交流铜耗的混合解析计算及抑制[J]. 电工技术学报, 2023, 38(24): 6609-6618.
Wu Yue, Zhang Zhifeng. Hybrid Analytical Calculation and Suppression of AC Copper Loss of Flat Copper Wire in Axial Flux Permanent Magnet Motor. Transactions of China Electrotechnical Society, 2023, 38(24): 6609-6618.
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