Reducing Torque Ripples of the Axial Flux PM Motors by Magnet Stepping and Shifting

E. Cetin, F. Daldaban


Higher efficiency on electric machines is the research goal of many studies. An example is the axial flux permanent magnet machines. These machines have some advantages like their watt/kg efficiency and torque density. This study aims to develop the performance characteristics of the axial flux permanent magnet machines. A new rotor magnet poles design in axial flux machines is suggested to mitigate the torque ripples. The method of stepping and shifting of the magnets is used. Two different designs are compared to verify the proposed approach. 3D finite element analysis is used for simulations. Torque ripple and back electromotive force waveforms are obtained from computer analysis. As a conclusion, the suggested method is found to be useable and mitigates the torque ripples. In addition to that, back EMF waveforms are turned to sinusoidal by the suggested design.


axial flux machines; step and shift; rotor magnet poles; torque ripple; back emf; permanent-magnet machines

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F. Giulii Capponi, G. De Donato, F. Caricchi, “Recent advances in axial-flux permanent-magnet machine technology”, IEEE Transactions on Industry Applications, Vol. 48, No. 6, pp. 2190-2205, 2012

J. F. Gieras, R. J. Wang, M. J. Kamper, Axial Flux Permanent Magnet Brushless Machines, Springer Science & Business Media, pp.3-19, 2005

T. M. Jahns, W. L. Soong, “Pulsating torque minimization techniques for permanent magnet ac drives - A review”, IEEE Transactions on Industrial Electronics, Vol. 43, pp. 321-330, 1996

M. Aydin, Z. Q. Zhu, T. A. Lipo, D. Howe, “Minimization of Cogging Torque in Axial-Flux Permanent-Magnet Machines: Design Concepts”, IEEE Transactions on Magnetics, Vol. 43, No. 9, pp. 3614-3622, 2007

S. J. Sung, S. J. Park, G. H. Jang, “Cogging torque of brushless DC motors due to the interaction between the uneven magnetization of a permanent magnet and teeth curvature”, IEEE Transactions on Magnetics, Vol. 47, No. 7, pp. 1923 -1928, 2011

D. G. Dorrell, M. Popescu, “Odd stator slot numbers in brushless dc machines—An aid to cogging torque reduction”, IEEE Transactions on Magnetics, Vol. 47, No. 10, pp. 3012-3015, 2011

M. Aydin, T. A. Lipo, “Axial Flux Permanent Magnet Disc Machines: A Review”, SPEEDAM, pp. 61-71, 2004

Z. Q. Zhu, D. Howe, “Analytical prediction of the cogging torque in radial-field permanent magnet brushless motors”, IEEE Transactions on Magnetics, Vol. 28, No. 2, pp. 1371–1374, 1992

L. Gasparin, A. Cernigoj, S. Markic, R. Fiser “Additional cogging torque components in permanent-magnet motors due to manufacturing imperfections”, IEEE Transactions on Magnetics, Vol. 45, No. 3, pp. 1210 -1213, 2009

M. A. Khan, I. Husain, M. R. Islam, J. T. Klass , “Design of experiments to address manufacturing tolerances and process variations influencing cogging torque and back EMF in the mass production of the permanent-magnet synchronous motors”, IEEE Transactions on Industry Applications, Vol. 50, No. 1, pp. 346-355, 2014

C. Y. Hsiao, S. N. Yeh, J. C. Hwang, “A Novel Cogging Torque Simulation Method for Permanent-Magnet Synchronous Machines”, Energies, Vol. 4, No. 12, pp. 2166-2179, 2011

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