Design and Characteristic Analysis of a Wide-Narrow Stator Poles Axial Flux Switched Reluctance Machine
Yu Fengyuan1,2, Chen Hao1,2, Yan Wenju1,2, Liu Yongqiang1,2, Dong Linjie1,2
1. School of Electrical Engineering China University of Mining and Technology Xuzhou 221116 China; 2. Xuzhou Key Laboratory of New Energy Electric Vehicle Technology and Equipment Xuzhou 221116 China
Abstract:In recent years, switched reluctance motors (SRM) have been applied in electric vehicles and aerospace due to their simple and robust structure, good fault tolerance, large starting torque, and wide speed range. However, the low torque density and high torque ripple have limited their large-scale application. With the improvement of industrial manufacturing level, the axial flux motor (AFM) has gradually attracted attention due to its shorter axial length and higher power density. In this paper, a novel wide-narrow stator-pole axial flux SRM (WNS-AFSRM) is proposed and investigated. Firstly, the topology and operating principle of the WNS-AFSRM are introduced. The motor has a parallel double-stator structure in which the left and right stator discs maintain a short magnetic path by sharing one single rotor segment. The stator teeth are staggered between the wide and narrow poles, with concentrated windings wound on the wide stator poles and no windings on the narrow stator poles. Hence, better magnetic, thermal and mechanical isolation is achieved, and the reliability of the WNS-AFSRM is ensured. Secondly, the design flow chart is presented, the power equation is also given, and the initial structural parameters of the WNS-AFSRM are determined. The three-dimensional finite element method is employed to analyze the influence of six key dimensional parameters on the torque output capability. Then, four parameters with a considerable impact are selected, and the Taguchi algorithm is carried out to optimize these four key dimensional parameters to improve motor performance. Comparing the torque waveforms before and after the optimization shows that the maximum synthetic torque decreases from 34.21N·m to 31.01N·m, while the minimum synthetic torque increases from 19.46N·m to 21.71N·m. Thus, the torque ripple has been reduced by 39.9% from 63.1% to 37.9%. Besides, the average torque increases from 23.40N·m to 24.48N·m with an increment of 4.6%. Thirdly, the static and dynamic performance of the WNS-AFSRM is simulated, and the performance is compared with two other motors. The radial electromagnetic force is compared with a single-stator WNS-AFSRM under the same outer diameter. It is demonstrated that the proposed double-stator WNS-AFSRM structure could effectively reduce the unbalanced axial electromagnetic force of the rotor. Moreover, a comprehensive performance comparison is conducted with a radial flux SRM with the same wide-and-narrow stator-poles structure under the same outer diameter and axial length. It can be found that the inductance at the aligned position is almost equal for both motors, but the NWS-AFSRM has a lower unaligned inductance. In addition, the core mass, total mass and average torque per unit mass of the NWS-AFSRM are more significant than that of the NWS-SRM, verifying the increased torque density of the proposed NWS-AFSRM. Finally, the final dimensional parameters are given, and a 1.25kW prototype is manufactured. The measured static flux linkage and dynamic current waveforms verify the correctness of the finite element and simulation results. The following conclusions can be drawn from the simulation and experimental results: (1) The left and right stators maintain short magnetic path by sharing a common rotor segment, and the magnetic flux cancels each other at the unaligned position to obtain an appreciable maximum-minimum inductance ratio. (2) The influence of variations in vital dimensional parameters on the rated output torque performance is analyzed using the single variable method, and the multi-objective Taguchi optimization algorithm results in a 39.9% reduction in torque ripple and a 4.6% increase in average torque for the NWS-AFSRM. (3) The proposed double-stator NWS-AFSRM structure is compared with the single-stator NWS-AFSRM using the three-dimensional finite element method. The results show that the proposed structure could effectively reduce the unbalanced axial electromagnetic force and improve the reliability of the motor.
[1] 闫文举, 陈昊, 马小平, 等. 不同转子极数下磁场解耦型双定子开关磁阻电机的研究[J]. 电工技术学报, 2021, 36(14): 2945-2956. Yan Wenju, Chen Hao, Ma Xiaoping, et al.Development and investigation on magnetic field decoupling double stator switched reluctance machine with different rotor pole numbers[J]. Transactions of China Electrotechnical Society, 2021, 36(14): 2945-2956. [2] Ding Wen, Bian He, Song Kaidi, et al.Enhancement of a 12/4 hybrid-excitation switched reluctance machine with both segmented-stator and-rotor[J]. IEEE Transactions on Industrial Electronics, 2021, 68(10): 9229-9241. [3] 闫文举, 陈昊, 刘永强, 等. 一种用于电动汽车磁场解耦型双定子开关磁阻电机的新型功率变换器[J]. 电工技术学报, 2021, 36(24): 5081-5091. Yan Wenju, Chen Hao, Liu Yongqiang, et al.A novel power converter on magnetic field decoupling double stator switched reluctance machine for electric vehicles[J]. Transactions of China Electrotechnical Society, 2021, 36(24): 5081-5091. [4] 许爱德, 任萍, 陈加贵, 等. 基于电感特殊位置点的开关磁阻电机转子位置检测及误差补偿[J]. 电工技术学报, 2020, 35(8): 1613-1623. Xu Aide, Ren Ping, Chen Jiagui, et al.Rotor position detection and error compensation of switched reluctance motor based on special inductance position[J]. Transactions of China Electrotechnical Society, 2020, 35(8): 1613-1623. [5] 卿龙, 王惠民, 葛兴来. 一种高效率开关磁阻电机转矩脉动抑制方法[J]. 电工技术学报, 2020, 35(9): 1912-1920. Qing Long, Wang Huimin, Ge Xinglai.A high efficiency torque ripple suppression method for switched reluctance motor[J]. Transactions of China Electrotechnical Society, 2020, 35(9): 1912-1920. [6] 匡斯建, 张小平, 刘苹, 等. 基于相电感非饱和区定位的开关磁阻电机无位置传感器控制方法[J]. 电工技术学报, 2020, 35(20): 4296-4305. Kuang Sijian, Zhang Xiaoping, Liu Ping, et al.Sensorless control method for switched reluctance motors based on locations of phase inductance characteristic points[J]. Transactions of China Electrotechnical Society, 2020, 35(20): 4296-4305. [7] 阮俊峰, 杨明发, 周海鸿. 基于瞬时转矩控制的开关磁阻电动机转矩脉动抑制研究[J]. 电气技术, 2019, 20(4): 37-41. Ruan Junfeng, Yang Mingfa, Zhou Haihong.Torque ripple minimization for switched reluctance motor based on DITC[J]. Electrical Engineering, 2019, 20(4): 37-41. [8] 孙玉坤, 袁野, 黄永红, 等. 磁悬浮开关磁阻电机及其关键技术发展综述[J]. 电工技术学报, 2015, 30(22): 1-8. Sun Yukun, Yuan Ye, Huang Yonghong, et al.Development of the bearingless switched reluctance motor and its key technologies[J]. Transactions of China Electrotechnical Society, 2015, 30(22): 1-8. [9] 徐妲, 林明耀, 付兴贺, 等. 混合励磁轴向磁场磁通切换型永磁电机静态特性[J]. 电工技术学报, 2015, 30(2): 58-63. Xu Da, Lin Mingyao, Fu Xinghe, et al.Static characteristics of novel hybrid axial field flux-switching PM machines[J]. Transactions of China Electrotechnical Society, 2015, 30(2): 58-63. [10] 徐磊, 朱孝勇, 张超, 等. 磁极径向组合轴向磁场永磁电机转矩品质分析与优化设计[J]. 中国电机工程学报, 2021, 41(6): 1971-1982. Xu Lei, Zhu Xiaoyong, Zhang Chao, et al.Torque quality analysis and optimization design of axial field machine with radial combined permanent magnet poles[J]. Proceedings of the CSEE, 2021, 41(6): 1971-1982. [11] He Mingjie, Li Weiye, Peng Jun, et al.Multi-layer quasi three-dimensional equivalent model of axial-flux permanent magnet synchronous machine[J]. CES Transactions on Electrical Machines and Systems, 2021, 5(1): 3-12. [12] 颜建虎, 汪盼, 费晨. 模块化开关磁阻式横向磁通电机设计与分析[J]. 中国电机工程学报, 2018, 38(22): 6723-6729. Yan Jianhu, Wang Pan, Fei Chen.Design and analysis of modular switch reluctance transverse flux machines[J]. Proceedings of the CSEE, 2018, 38(22): 6723-6729. [13] Sun Wei, Li Qiang, Sun Le, et al.Study on magnetic shielding for performance improvement of axial-field dual-rotor segmented switched reluctance machine[J]. CES Transactions on Electrical Machines and Systems, 2021, 5(1): 50-61. [14] Sun Wei, Li Qiang, Sun Le, et al.Development and investigation of novel axial-field dual-rotor segmented switched reluctance machine[J]. IEEE Transactions on Transportation Electrification, 2021, 7(2): 754-765. [15] Arihara H, Akatsu K.Basic properties of an axial-type switched reluctance motor[J]. IEEE Transactions on Industry Applications, 2013, 49(1): 59-65. [16] Madhavan R, Fernandes B G.Axial flux segmented SRM with a higher number of rotor segments for electric vehicles[J]. IEEE Transactions on Energy Conversion, 2013, 28(1): 203-213. [17] Madhavan R, Fernandes B G.Performance improve-ment in the axial flux-segmented rotor-switched reluctance motor[J]. IEEE Transactions on Energy Conversion, 2014, 29(3): 641-651. [18] Wang Bo, Lee D H, Ahn J W.Characteristic analysis of a novel segmental rotor axial field switched reluctance motor with single teeth winding[C]//2014 IEEE International Conference on Industrial Technology, Busan, Korea (South), 2014: 175-180. [19] 马霁旻, 王杜, 曲荣海, 等. 基于有取向硅钢的轴向磁通开关磁阻电机准三维解析分析与设计[J]. 电工技术学报, 2018, 33(17): 4069-4077. Ma Jimin, Wang Du, Qu Ronghai, et al.Quasi-three-dimensional analysis and design of an axial flux switched reluctance motor based on grain oriented silicon steel[J]. Transactions of China Electrotechnical Society, 2018, 33(17): 4069-4077. [20] 马霁旻. 基于有取向硅钢的轴向磁通开关磁阻电机分析和设计[D]. 武汉: 华中科技大学, 2017. [21] Daldaban F, Ustkoyuncu N.New disc type switched reluctance motor for high torque density[J]. Energy Conversion and Management, 2007, 48(8): 2424-2431. [22] Torkaman H, Ghaheri A, Keyhani A.Axial flux switched reluctance machines: a comprehensive review of design and topologies[J]. IET Electric Power Applications, 2019, 13(3): 310-321. [23] Mecrow B C, El-Kharashi E A, Finch J W, et al. Segmental rotor switched reluctance motors with single-tooth windings[J]. IEE Proceedings - Electric Power Applications, 2003, 150(5): 591. [24] Xu Zhenyao, Lee D H, Ahn J W.Design and operation characteristics of a novel switched reluctance motor with a segmental rotor[J]. IEEE Transactions on Industry Applications, 2016, 52(3): 2564-2572. [25] Sun Xiaodong, Diao Kaikai, Lei Gang, et al.Study on segmented-rotor switched reluctance motors with different rotor pole numbers for BSG system of hybrid electric vehicles[J]. IEEE Transactions on Vehicular Technology, 2019, 68(6): 5537-5547. [26] Diao Kaikai, Sun Xiaodong, Lei Gang, et al.Multimode optimization of switched reluctance machines in hybrid electric vehicles[J]. IEEE Transactions on Energy Conversion, 2021, 36(3): 2217-2226. [27] Cosoroaba E, Bostanci E, Li Yinan, et al.Comparison of winding configurations in double-stator switched reluctance machines[J]. IET Electric Power Applications, 2017, 11(8): 1407-1415. [28] Sun Qingguo, Wu Jianhua, Gan Chun, et al.DSSRM design with multiple pole arcs optimization for high torque and low torque ripple applications[J]. IEEE Access, 2018, 6: 27166-27175. [29] Wang Wei, Luo Mengying, Cosoroaba E, et al.Rotor shape investigation and optimization of double stator switched reluctance machine[J]. IEEE Transactions on Magnetics, 2015, 51(3): 1-4. [30] Chen Hao, Yan Wenju, Gu J J, et al.Multiobjective optimization design of a switched reluctance motor for low-speed electric vehicles with a taguchi-CSO algorithm[J]. IEEE/ASME Transactions on Mechatronics, 2018, 23(4): 1762-1774. [31] Yan Wenju, Chen Hao, Liao Shuo, et al.Design of a low-ripple double-modular-stator switched reluctance machine for electric vehicle applications[J]. IEEE Transactions on Transportation Electrification, 2021, 7(3): 1349-1358.