Vol. 85

Front:[PDF file] Back:[PDF file]
Latest Volume
All Volumes
All Issues

Influence of Rotor Magnet Shapes on Performance of Axial Flux Permanent Magnet Machines

By Praveen Kumar and Rakesh Kumar Srivastava
Progress In Electromagnetics Research C, Vol. 85, 155-165, 2018


Axial flux Permanent Magnet (AFPM) machines, due to its high torque capability, high power density and compact size, are the most suitable candidates for in-wheel Electric Vehicle application. However, the presence of cogging torque in AFPM machines, resulting from the interaction of PMs and stator slots, introduces torque ripples, noise and vibrations which deteriorates the performance of the machine. To overcome this, several techniques for cogging reduction are utilized. Out of various techniques, rotor magnet shape variation is most commonly utilized. This paper investigates the effect of some preferred magnet shaping techniques in AFPM machines on several performance parameters such as magnetic flux density distribution in air gap, cogging torque, flux linkage, no load-induced emf, emf harmonics, electromagnetic torque and torque ripple. These parameters were analyzed using 3-D Finite Element Method (FEM) based simulations. It was found that a maximum cogging reduction by 62.49% and output torque ripple by 63.25% were obtained by using short-pitched and skewed rotor magnets. This also resulted in a reduction of induced emf by 14.18% and electromagnetic torque by 15.17%.


Praveen Kumar and Rakesh Kumar Srivastava, "Influence of Rotor Magnet Shapes on Performance of Axial Flux Permanent Magnet Machines," Progress In Electromagnetics Research C, Vol. 85, 155-165, 2018.


    1. Zhu, Z. Q. and D. Howe, "Influence of design parameters on cogging torque in permanent magnet motors," IEEE Trans. Energy Convers., Vol. 15, No. 4, 407-412, Dec. 2000.

    2. Bianchi, N. and S. Bolognani, "Design techniques for reducing the cogging torque in surface-mounted PM motors," IEEE Trans. Ind. Appl., Vol. 38, No. 2, 1259-1265, Sep./Oct. 2002.

    3. Aydin, M., "Magnet skew in cogging torque minimization of axial gap permanent magnet motors," Proc. IEEE ICEM, 1-6, Vilamoura, Portugal, Sep. 2008.

    4. Wanjiku, J., M. A. Khan, P. S. Barendse, and P. Pillay, "Influence of slot openings and tooth profile on cogging torque in axial-flux PM machines," IEEE Trans. Ind. Electron., Vol. 62, No. 12, 7578-7589, Dec. 2015.

    5. Aydin, M., Z. Q. Zhu, T. A. Lipo, and D. Howe, "Minimization of cogging torque in axial flux permanent magnet machines --- Design concepts," IEEE Trans. Magn., Vol. 43, No. 9, 3614-3622, Sep. 2007.

    6. Ocak, C., I. Tarımer, and A. Dalcalı, "Advancing pole arc offset points in designing an optimal PM generator," TEM Journal, Vol. 5, No. 2, 126-132, 2016.

    7. Ocak, C., I. Tarımer, A. Dalcalı, and D. Uygun, "Investigation effects of narrowing rotor pole embrace to efficiency and cogging torque at PM BLDC motor," TEM Journal, Vol. 5, No. 1, 25-31, 2016.

    8. Libert, F. and J. Soulard, "Investigation on pole-slot combinations for permanent-magnet machines with concentrated windings," Proc. IEEE ICEM, 5-8, Cracow, Poland, Sep. 2004.

    9. Guemes, J. A., A. M. Iraolagoitia, P. Fernandez, and M. P. Donsion, "Comparative study of PMSM with integer-slot and fractional-slot windings," 2010 XIX International Conference on Electrical Machines (ICEM), 1-6, 2010.

    10. Li, J., D.-W. Choi, S.-G. Lee, J.-H. Jang, and Y.-H. Cho, "Minimization of cogging torque in fractional-slot axial flux permanent magnet synchronous machine with conventional structure," Proc. IEEE ICEF, 1-4, Dalian, China, 2012.

    11. Aydin, M. and M. Gulec, "Reduction of cogging torque in double-rotor axial-flux permanent-magnet disk motors: A review of cost-effective magnet-skewing techniques with experimental verification," IEEE Trans. Ind. Electron., Vol. 61, No. 9, 5025-5034, Sep. 2014.

    12. Tarımer, I., S. Sakar, and A. Dalcalı, "Effects of structural design of pole arc offset in a salient pole generator to obtaining sinusoidal voltages with the least harmonics," Przeglad Elektrotechniczny, R. 86, 367-372, NR 11a/2010, 2010.

    13. Arslan, S., S. A. Oy, and I. Tarımer, "Investigation of stator and rotor slits’ effects to the torque and efficiency of an induction motor," TEM Journal, Vol. 1, 117-125, Feb. 2017.

    14. Tarımer, I., "Investigation of the effects of rotor pole geometry and permanent magnet to line start permanent magnet synchronous motor’s efficiency," Elektronika Ir Elektrotechnika, Vol. 90, No. 2, 67-72, 2009.

    15. Tarımer, I. and A. Dalcalı, "Effects of permanent magnets on torque and power density of spherical motors," TTEM (Technics Technologies Education Management), Vol. 10, No. 2, 144-149, 2015.

    16. Tarımer, I. and C. Ocak, "Performance comparison of internal and external rotor structured wind generators mounted from same permanent magnets on same geometry," Elektronika Ir Elektrotechnika, Vol. 92, No. 4, 65-70, 2009.

    17. Tarımer, I., S. Sakar, and A. Dalcalı, "Computer aided design of permanent magnet linear synchronous generator," Przeglad Elektrotechniczny, R. 86, 230-234, NR 3/2010, 2010.

    18. Tiegna, H., Y. Amara, and G. Barakat, "Study of cogging torque in axial flux permanent magnet machines using an analytical model," IEEE Trans. Magn., Vol. 50, No. 2, Art. ID. 7020904, Feb. 2014.