Calculation of Electromagnetic Excitation Forces in Double Skewed Motors

  • Bao, Xiaohua (School of Electrical Engineering and Automation, Hefei University of Technology) ;
  • Di, Chong (School of Energy System, Lappeenranta University of Technology) ;
  • Zhou, Yang (School of Electrical Engineering and Automation, Hefei University of Technology)
  • Received : 2016.10.12
  • Accepted : 2017.11.25
  • Published : 2018.03.01


An electromagnetic excitation force is caused by the air-gap flux density, which greatly influences the noise and vibration of the motor. In many real projects, skewed slot technology is widely used to reduce the harmonic components of the air-gap flux density to reduce the noise and vibration of the motor. However, a skewed slot has several side effects such as a transverse current and axial drifting. Thus, a double skewed slot rotor is selected with the aim of eliminating these side effects. This paper presents the exact structure of the double skewed slot rotor and the mechanism whereby the electromagnetic excitation force can be reduced. A multi-slice method is adopted to model the special structure. Finite element simulation is used to verify the theory.


Supported by : National Natural Science Funds of China


  1. S. B. Yu, and R. Y. Tang. "Electromagnetic and mechanical characterizations of noise and vibration in permanent magnet synchronous machines," IEEE Trans. Magn., vol. 42, no. 4, pp. 1335-1338, Apr. 2006.
  2. D. H. Cho, and K. J. Kim. "Modelling of electromagnetic excitation forces of small induction motor for vibration and noise analysis," IEE Proceedings-Electric Power Applications, vol. 145, no. 3, pp. 199-205, May. 1998
  3. C. L. Xia, Z. Zhang, and Q. Geng. "Analytical Modeling and Analysis of Surface Mounted Permanent Magnet Machines With Skewed Slots," IEEE Trans. Magn., vol. 51, no. 5, Article#:8104508, May. 2015.
  4. H. Karmaker, and A. M. Knight. "Investigation and Simulation of Fields in Large Salient-Pole Synchronous Machines With Skewed Stator Slots," IEEE Trans. Energy Convers., vol. 20, no. 3, pp. 604-610, Sept. 2005.
  5. I. Hirotsuka, Y. Tsubouchi, and K. Tsuboi. "Effects of slot combination and skew slot on the electromagnetic vibration of a 4 pole capacitor motor under load condition," Electrical Machines and Systems, 2005. ICEMS 2005. Proceedings of the Eighth International Conference on. IEEE., Nanjing, China, Sept. 2005.
  6. D. H. Im, J. H. Chang, S. C. Park, and et al. "Analysis of radial force as a source of vibration in an induction motor with skewed slots," IEEE Trans. Magn., vol. 33, no. 2, pp. 1650-1653, Mar. 1997.
  7. H. Kometani, Sakabe, Shigekazu, and et al. "3-D analysis of induction motor with skewed slots using regular coupling mesh," IEEE Trans. Magn., vol. 36, no. 4, pp. 1769-1773, Jul. 2000.
  8. K. Yamada, Y. Takahashi, and K. Fujiwara. "Simplified 3D Modeling for Skewed Rotor Slots with End-ring of Cage Induction Motors," IEEE Trans. Magn., vol. 52, no. 3, Article#:8101604, Mar. 2016.
  9. K. Yamazaki. "A quasi 3D formulation for analyzing characteristics of induction motors with skewed slots," IEEE Trans. Magn., vol. 34, no. 5, pp. 3624-3627, Sept. 1998.
  10. Y. Kawase, T. Yamaguchi, Z. P. Tu, and et al. "Effects of Skew Angle of Rotor in Squirrel-Cage Induction Motor on Torque and Loss Characteristics," IEEE Trans. Magn., vol. 45, no. 3, pp. 1700-1703, Mar. 2009.
  11. G. D. Kalokiris, T. D. Kefalas, A. G. Kladas, and et al. "Special air-gap element for 2-D FEM analysis of electrical Machines accounting for rotor skew," IEEE Trans. Magn., vol. 41, no. 5, pp. 2020-2023, May. 2005.
  12. J.J.C. Gyselinck, L. Vandevelde, J.A.A. Melkebeek. "Multi-slice FE modeling of electrical machines with skewed slots-the skew discretization error," IEEE Trans. Magn., vol. 37, no. 5, pp. 3233-3237, Sept. 2001.
  13. S. L. Ho, W. N. Fu, and H. C. Wong. "Direct modeling of the starting process of skewed rotor induction motors using a multi-slice technique," IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 1253-1258, Dec. 1999.
  14. G. H. Muller, and C. F. Landy. "A novel method to detect broken rotor bars in squirrel cage induction motors when interbar currents are present," IEEE Trans. Energy Convers., vol. 18, no. 1, pp. 71-79, Mar. 2003.
  15. A. Lamine, and E. Levi. "Dynamic induction machine modelling considering the stray load losses," Universities Power Engineering Conference, 2004. UPEC 2004. 39th International. IEEE, Bristol, UK, Sept. 2004.
  16. L. Wang, X. H. Bao, C. Di, and et al. "Effects of Novel Skewed Rotor in Squirrel-Cage Induction Motor on Electromagnetic Force," IEEE Trans. Magn., vol. 51, no. 11, Article#:8114204, Nov. 2015.
  17. W. Fei, and Z. Q. Zhu. "Comparison of cogging torque reduction in permanent magnet brushless machines by conventional and herringbone skewing techniques," IEEE Trans. Energy Convers., vol. 28, no. 3, pp. 664-674, Sept. 2013.
  18. H. Ahn, G. Jang, J. Chang, and et al. "Reduction of the torque ripple and magnetic force of a rotatory two-phase transverse flux machine using herringbone teeth," IEEE Trans. Magn., vol. 44, no. 11, pp. 4066-4069, Nov. 2008.
  19. T. J. Wang, F. Fang, X. S. Wu, and et al. "Novel Filter for Stator Harmonic Currents Reduction in Six-Step Converter Fed Multiphase Induction Motor Drives," IEEE Trans. Power Electron., vol. 28, no. 1, pp. 498-506, Jan. 2013.
  20. D. G. Dorrell. "Calculation of unbalanced magnetic pull in small cage induction motors with skewed rotors and dynamic rotor eccentricity," IEEE Trans. Energy Convers., vol. 11, no. 3, pp. 483-488, Sept. 1996.
  21. W. Bernhard, O. Biro, S. Rainer, and et al. "Computation of rotating force waves in skewed induction machines using multi-slice models," IEEE Trans. Magn., vol. 47, no. 5, pp. 1046-1049, May. 2011.
  22. Ho, S. L., W. N. Fu, and H. C. Wong. "Estimation of stray losses of skewed rotor induction motors using coupled 2-D and 3-D time stepping finite element methods," vol. 34, no. 5, pp. 3102-3105, Sept. 1998.
  23. J. Pyrhonen, T. Jokinen, and V. Hrabovcova. Design of rotating electrical mechines. John Wiley& Sons, Ltd, 2008, pp. 250-251.