Effects of Manufacturing Imperfections and Design Parameters on Radial Magnetic Forces in the BLDC Claw-Pole Motor

The demand for overall noise level reduction in cars has increased as of late; meanwhile, the number of auxiliary drives in cars has also increased significantly. Especially in electric vehicles, the application of conventional auxiliary drives, the noise of which is then masked by that of the combustion engine or other dominant noise sources, may not be possible. To address these circumstances, this paper studies the formation of radial magnetic forces in the low-cost sub-fractional hp single-phase outer-rotor BLDC claw-pole motor caused by manufacturing imperfections. Those explored herein include eccentricity, stator part misalignment, and non-uniform magnetization, as well as design parameter variations like air-gap asymmetry and type of magnetization pattern. The findings show that eccentricity and non-uniform magnetization cause unbalanced radial magnetic forces of pulsating character which may trigger system resonances at four times the rotational frequency.