A Study on Characteristic of Cogging Torque due to Assembly Tolerances of Magnet on Rotor and Evaluation of Noise and Vibration in Brushless DC Motor

BLDC 전동기에서 회전자 자석의 조립 공차에 따른 코깅토크 특성변화와 소음진동 불량 평가에 관한 연구

  • Received : 2016.06.01
  • Accepted : 2016.06.14
  • Published : 2016.06.30


The cogging torque of a brushless dc (BLDC) motor results from the interaction between permanent magnets and iron core, and it causes noise and induce vibrations. During a manufacturing process, assembly tolerances lead to the change of the electromagnetic structure of a BLDC motor where permanent magnets are not properly glued to the surface of rotor core. In this paper, the effect of magnet separation from the surface of rotor core on the cogging torque is investigated due to assembly tolerance. The relationship with key design parameters is considered such as separation between magnets and rotor core, the number of magnets having separation, as well as the several types of arrangements among neighboring magnets. Finite element method (FEM) has been used to analyze a BLDC motor, and the allowable assembly tolerance is proposed to prevent generating noise and vibrations. Within proposed assembly tolerance, it is concluded that the cogging torque of a BLDC motor is decreased, and hence noise and vibrations.


cogging torque;assembly tolerances;permanent magnet (PM);noise and vibration;brushless motor


  1. K. J. Han, H. S. Cho, D. H. Cho, and H. K. Jung, IEEE Trans. Magn. 36, 1927 (2000).
  2. L. Gasparin, A. Cernigoj, S. Markic, and R. Fiser, IEEE Trans. Magn. 45, 1210 (2009).
  3. H. J. Park, D. W. Kang, W. H. Kim, H. W. Lee, S. B. Lim, and J. Lee, KIEE EMECS Conf. 134 (2010).
  4. S. Y. Kim, J. H. Cho, S. G. Song, B. T. Kim, and J. Lee, KIEE Conf. 661 (2013).
  5. J. R. Hendershot Jr. and T. J. E. Miller, Design of Brushless Permanent-Magnet Motors, Motor Design Books, Venice (2010) pp. 107-108.
  6. C. K. Kim, S. G. Lee, and S. Y. Jung, Trans. KIEE 58, 1923 (2009).


Supported by : 한국연구재단