A dual-stator machine with diametrically magnetized PM: Analytical air-gap flux calculation, efficiency optimization, and comparison with conventional dual-stator machines

Document Type : Article


1 Laboratory of Electrical Machines and Transformers Research, Department of Electrical Engineering, Amirkabir University of Technology, Tehran, P.O. Box 1591634311, Iran

2 Department of Electrical Engineering, University of Larestan, Lar, Iran


This paper presents a design and optimization procedure for a dual-stator machine with a diametrically magnetized PM to improve the electromagnetic performance. First, analytical design equations are presented based on MEC analysis; they are used to design a basic dual-stator machine. Then, by applying an artificial intelligence algorithm, the machine is optimized to achieve high efficiency and torque density, and low pulsating torque for direct-drive applications. A quantitative comparison is performed between the optimized new machine and conventional dual-stator machines to evaluate the performances and improvements of the understudy machine. The machine performance, including air-gap flux density distribution, back electromotive force, electromagnetic torque, cogging torque, and torque ripple are analyzed by the finite element method. The analysis results have demonstrated that benefiting from its topology, the optimized dual-stator machine with diametrically magnetized PM has the comprehensively better performance, including higher torque density, higher efficiency, and lower torque ripple and cogging torque compared to conventional dual-stator machines.


1. Zhao, W., Lipo, T.A., and Kwon, B. "Dual-stator twophase permanent magnet machines With phase-group concentrated-coil windings for torque enhancement", IEEE Trans. Magn., 51(11), pp. 1-4 (2015).
2. Cupertino, F., Leuzzi, R., Monopoli, V.G., et al. "Maximisation of power density in permanent magnet machines with the aid of optimization algorithms", IET Electric Power Applications, 12(8), pp. 1067-1074 (2018).
3. Vukotic, M. and Miljavec, D. "Design of a permanentmagnet flux-modulated machine with a high torque density and high power factor", IET Electric Power Applications, 10(1), pp. 36-44 (2016).
4. Asgari, S. and Mirsalim, M. "A novel dual-stator radial- flux machine with diametrically magnetized cylindrical permanent magnets", IEEE Trans. Ind. Electron., 66(5), pp. 3605-3614 (2019).
5. Feng, C., Jing, X., Bin, G., et al. "Double-stator permanent magnet synchronous in-wheel machine for hybrid electric drive systems", IEEE Trans. Ind. Electron., 45(1), pp. 278-281 (2008).
6. Mo, L., Quan, L., Zhu, X., et al. "Comparison and analysis of  flux-switching permanent-magnet doublerotor machine with 4QT used for HEV", IEEE Trans. Magn., 50(11), pp. 1-4 (2014).
7. Kim, S., Cho, J., Park, S., et al. "Characteristics comparison of a conventional and modified spoke-type ferrite magnet motor for traction drives of low-speed electric vehicles", IEEE Trans. Ind. Appl., 49(6), pp. 2516-2523 (2013).
8. Dalal, A. and Kumar, P. "Design, prototyping, and testing of a dual-rotor motor for electric vehicle application",
IEEE Trans. Ind. Electron, 65(9), pp. 7185- 7192 (2018).
9. Wang, Y., Niu, S., and Fu, W. "A novel dual-rotor bidirectional  flux-modulation PM generator for standalone DC power supply", IEEE Trans. Ind. Electron, 66(1), pp. 818-828 (2019).
10. Li, Y., Bobba, D., and Sarlioglu, B. "Design and optimization of a novel dual-rotor hybrid PM machine for traction application", IEEE Trans. Ind. Electron, 65(2), pp. 1762-1771 (2018).
11. Yang, H., Zhu, Z.Q., Lin, H., et al. "Comparative study of hybrid PM memory machines having singleand dual-stator configurations", IEEE Trans. Ind. Electron, 65(11), pp. 9168-9178 (2018).
12. Baloch, N., Kwon, B., and Gao, Y. "Low-cost hightorque- density dual-stator consequent-pole permanent magnet vernier machine", IEEE Trans. Magn., 54(11), pp. 1-5 (2018).
13. Kwon, J.W. and Kwon, B. "Investigation of dualstator spoke-type vernier machine for EV application", IEEE Trans. Magn., 54(11), pp. 1-5 (2018).
14. Zhao, W., Chen, D., Lipo, T.A., et al. "Dual airgap stator- and rotor-permanent magnet machines with spoke-type configurations using phase-group concentrated coil windings", IEEE Trans. Ind. Appl., 53(4), pp. 3327-3335 (2017).
15. Gao, Y., Qu, R., Li, D., et al. "A novel dual-stator vernier permanent magnet machine", IEEE Trans. Magn, 53(11), pp. 1-5 (2017).
16. Gorginpour, H. "Design modifications for improving modulation flux capability of consequent-Pole vernier-PM machine in comparison to conventional vernier- PM machines", Scientia Iranica, 27(6), pp. 3150-3161 (2019).
17. Baloch, N., Khaliq, S., and Kwon, B.I. "HTS dualstator spoke-type linear Vernier machine for leakage flux reduction", IEEE Trans. Magn., 53(11), 8111104 (2017).
18. Baloch, N., Khaliq, S., and Kwon, B.I. "A high force density HTS tubular Vernier machine", IEEE Trans. Magn., 53(11), 8111205 (2017).
19. Zhu, L., Jiang, S.Z., Zhu, Z.Q., et al. "Analytical methods for minimizing cogging torque in permanentmagnet machines", IEEE Trans. Magn., 45(4), pp. 2023-2031 (2009).
20. Hanselman, D.C., Brushless Permanent Magnet Motor Design, McGraw-Hill, New York (1994).
21. Gieras, J., Wang, R., and Kamper, M., Axial Flux Permanent Magnet Brushless Machines, Springer-Verlag, New York (2008).
22. Zhu, Z.Q., Ruangsinchaiwanich, S., Chen, Y., et al. "Evaluation of superposition technique for calculating cogging torque in permanent-magnet brushless machines", IEEE Trans. Magn., 42(5), pp. 1597-1603 (2006).
23. Sadeghi, S. and Parsa, L. "Multiobjective design optimization of five-phase Halbach array permanentmagnet machine", IEEE Trans. Magn., 47(6), pp. 1658-1666 (2011).
24. Gieras, J.F., Permanent Magnet Motor Technology: Design and Applications, Taylor & Francis Group, New York (2010).
25. Arslan, S., Gurdal, O., and Akkaya Oy, S. "Design and optimization of tubular linear permanent magnet generator with performance improvement using response surface methodology and multi-objective genetic algorithm", Scientia Iranica, 27(6), pp. 3053-3065 (2018).