Compared with a standard permanent magnet synchronous motor, a line-start permanent magnet synchronous motor (LSPMSM) has additional features that include two-sided slots on its stator and rotor. Thus, due to its complex air gap form, there is no simple method to calculate the cogging torque of this kind of motor at present. This paper presents a new analytical method that models the rotor as an equivalent magnetic motive force (MMF) distribution in the air gap which avoids the influence of rotor slotting in the air gap. Based on the energy method, an analytical method is presented here to analyze the pole-slot match of stator and the influence of number of slots per pole of rotor on the cogging torque. The effect of auxiliary slots on cogging torque of LSPMSM is studied and by changing the number of auxiliary slots to reduce the cogging torque, the correctness of the above method has been validated by the finite element method.
1. Akeshi, T., K. Satoshi, M. Kenji, and B. Andreas, "Asynchronous torque of line-starting permanent-magnet synchronous motors," IEEE Trans. Energy Convers., Vol. 30, No. 2, 498-506, 2015. doi:10.1109/TEC.2014.2361836
2. Mahmoudi, A., S. Kahourzade, N. A. Rahim, H. W. Ping, and N. F. Ershad, "Slot less torus solid rotor ringed line-start axial flux permanent magnet motor," Progress In Electromagnetics Research, Vol. 131, 331-355, 2012. doi:10.2528/PIER12070308
3. Villani, M., M. Santececca, and F. Parasiliti, "High-efficiency line-start synchronous reluctance motor for fan and pump applications," 2018 XIII International Conference on Electrical Machines (ICEM), 2178-2184, 2018. doi:10.1109/ICELMACH.2018.8507230
4. Mahmoudi, A., S. Kahourzade, N. A. Rahim, and H. W. Ping, "Improvement to performance of solid-rotor-ringed line-start axial-flux permanent-magnet motor," Progress In Electromagnetics Research, Vol. 124, 383-404, 2012. doi:10.2528/PIER11122501
5. Tian, M. M., X. H. Wang, and D. H. Wang, "The analysis of the influences of switching opportunity for a novel 6/8 pole changing line-start permanent magnet synchronous motor," 20th International Conference on Electrical Machines and Systems (ICEMS), 1-5, 2017.
6. Isfahani, A. H. and S. V. Zadeh, "Effects of magnetizing inductance on start-up and synchronization of line-start permanent-magnet synchronous motors," IEEE Trans. Magn., Vol. 47, No. 4, 823-829, 2011. doi:10.1109/TMAG.2010.2091651
7. Lee, B. H., J. W. Jung, and J. P. Hong, "An improved analysis method of irreversible demagnetization for a single-phase line-start permanent magnet motor," IEEE Trans. Magn., Vol. 54, No. 11, ID: 8206905, 2018.
8. Aliabad, A. D. and F. Ghoroghchian, "Design and analysis of a two-speed line start synchronous motor: Scheme one," IEEE Trans. Energy Convers., Vol. 31, No. 1, 366-372, 2016. doi:10.1109/TEC.2015.2481929
9. Ugale, R. T. and B. N. Chaudhari, "Rotor configurations for improved starting and synchronous motor," IEEE Trans. Ind. Electron., Vol. 64, No. 1, 138-148, 2017. doi:10.1109/TIE.2016.2606587
10. Stioa, D., K. Hameyer, and B. Drago, "The behavior of the LSPMSM in asynchronous operation," 14th Int. Conf. Power Electronics and Motion Control, 45-50, 2010.
11. Aliabad, A. D., M. Mojtaba, and F. E. Nima, "Line start permanent magnet motors: significant improvement in starting torque, synchronization, and steady state performance," IEEE Trans. Magn., Vol. 46, No. 12, 4066-4072, 2010. doi:10.1109/TMAG.2010.2070876
12. Wei, F. L., Y. L. Luo, and H. S. Zhao, "Influences of rotor bar design on the starting performance of line start permanent magnet asynchronous motor," 6th Int. Conf. Electromagnetic Field Problems and Applications, 1-4, 2012.
13. Edgar, P. S. and A. C. Smith, "Line start permanent magnet machines using a canned rotor," IEEE Trans. Ind. Appl., Vol. 45, No. 3, 903-910, 2009. doi:10.1109/TIA.2009.2018981
14. Wu, D. and Z. Q. Zhu, "Design tradeoff between cogging torque and torque ripple in fractional slot surface mounted permanent magnet machines," IEEE Trans. Magn., Vol. 51, No. 11, ID: 8108704, 2015.
15. Azar, Z. and Z. Q. Zhu, "Investigation of torque-speed characteristics and cogging torque of fractional-slot IPM brushless AC machines having alternate slot openings," IEEE Trans. Ind. Appl., Vol. 48, No. 3, 903-912, 2012. doi:10.1109/TIA.2012.2190962
16. Ren, W., Q. Xu, Q. Li, and L. B. Zhou, "Reduction of cogging torque and torque ripple in interior PM machines with asymmetrical V-type rotor design," IEEE Trans. Magn., Vol. 52, No. 7, ID: 8104105, 2016.
17. Kahourzade, S., A. Mahmoudi, A. Gandomkar, N. A. Rahim, H. W. Ping, and M. N. Uddin, "Design optimization and analysis of AFPM synchronous machine incorporating power density, thermal analysis, and back-EMF THD," Progress In Electromagnetics Research, Vol. 136, 327-367, 2013. doi:10.2528/PIER12120204
18. Tiang, T. L., D. Ishak, C. P. Lim, and M. R. Mohamed, "Analytical method using virtual PM blocks to represent magnet segmentations in surface-mounted PM synchronous machines," Progress In Electromagnetics Research B, Vol. 76, 23-36, 2017. doi:10.2528/PIERB17041501
19. Nguyen, V. T. and T. F. Lu, "Analytical expression of the magnetic field created by a permanent magnet with diametrical magnetization," Progress In Electromagnetics Research B, Vol. 87, 163-174, 2018.
20. Wang, X. H., T. T. Ding, and Y. B. Yang, "Study of cogging torque in line-start permanent magnet synchronous motors," Proceedings of the CSEE, Vol. 25, No. 18, 167-170, 2005.
21. Kang, G. H., Y. D. Son, and G. T. Kim, "A novel cogging torque reduction method for interior-type permanent magnet motor," IEEE Trans. Ind. Appl., Vol. 45, No. 1, 161-167, 2009. doi:10.1109/TIA.2008.2009662