Analysis of PM Magnetization Field Effects on the Unbalanced Magnetic Forces due to Rotor Eccentricity in BLDC Motors

S. Mahdiuon-Rad, S. R. Mousavi-Aghdam, M. Reza Feyzi, M. B. B. Sharifian


This paper investigates both static and dynamic eccentricities in single phase brushless DC (BLDC) motors and analyzes the effect of the PM magnetization field on unbalanced magnetic forces acting on the rotor. Three common types of PM magnetization field patterns including radial, parallel and sinusoidal magnetizations are considered. In both static and dynamic eccentricities, harmonic components of the unbalanced magnetic forces on the rotor are extracted and analyzed. Based on simulation results, the magnetization fields that produce the lowest and highest unbalanced magnetic forces are determined in rotor eccentricity conditions.


finite element method; single phase brushless DC (BLDC) motor; static and dynamic eccentricity; unbalanced magnetic force

Full Text:



H. S. Chen, M. C. Tsai ,“Effect of rotor eccentricity on electric parameters in a PM brushless motor with parallel winding connections”, Journal of Applied Physics, Vol. 105, No. 7, pp. 07F121-07F121-3, 2009

U. Kim, D. K. Lieu, “Magnetic field calculation in permanent magnet motors with rotor eccentricity: without slotting effect”, IEEE Transactions on Magnetics, Vol. 34, No. 4, pp. 2243–2252, 1998

T. Yoon, “Magnetically induced vibration in a permanent-magnet brushless DC motor with symmetric pole-slot configuration”, IEEE Transactions on Magnetics, Vol. 41, No. 6, pp. 2173–2179, 2005

S. Rajagopalan, J. M. Aller, J. A. Restrepo, T. G. Halbetler, R.G. Harley, “Analytic-wavelet-ridge-based detection of dynamic eccentricity in brushless Direct Current BLDC motors functioning under dynamic operating conditions”, IEEE Transactions on Industrial Electronics, Vol. 54, No. 3, pp. 1410-1419, 2007

S. Salon, K. Sivasubramaniam, L. T. Ergene, “The effect of asymmetry on torque in permanent magnet motors”, IEMDC 2001, IEEE Electric Machines and Drives International Conference , Cambridge, USA, pp. 208-217, 2001

Z. J. Liu, J. T. Li, M. A. Jabbar, “Prediction and analysis of magnetic forces in permanent magnet brushless dc motor with rotor eccentricity”, Journal of Applied Physics, Vol. 99, No. 8, pp. 08R321- 08R321-3, 2006

C. L. Chiu, Y. T. Chen, W. S. Jhang, “Properties of cogging torque, starting torque, and electrical circuits for the single-phase brushless DC motor”, IEEE Transactions on Magnetics, Vol. 44, No. 10, pp. 2317-2323, 2008

K. T. Kim, S. M. Hwang, G. Y. Hwang, T. J. Kim, W. B. Jeong, C. U. Kim, “Effect of rotor eccentricity on spindle vibration in magnetically symmetric and asymmetric BLDC motors”, ISIE 2001, IEEE International Symposium on Industrial Electronics, Pusan, South Korea, Vol. 2, pp. 967–972, 2001

C. I. Lee, G. H. Jang, “Experimental measurement and simulated verification of the unbalanced magnetic force in brushless DC motors”, IEEE Transactions on Magnetics, Vol. 44, No. 11, pp. 4377-4380, 2008

eISSN: 1792-8036     pISSN: 2241-4487