Abstract
The magnetic properties of the magnetic steel sheets, which are used for the magnetic cores of motors, vary with stress. This variation affects the characteristics of motors, e.g. the cogging torque of permanent magnet motors. In this paper, a novel, highly precise motor analysis method is proposed, which consists of the combination of structural analysis and electromagnetic field analysis-that is, the electromagnetic field analysis considering the stress distribution in the stator core. The cogging torque, which arises from the stress by shrink fitting of the frame to the core, is estimated using the proposed method. The validity of the proposed method has been verified by comparing the calculated results to the experimental result. Moreover, the better expression of the stress distribution in the coupled analysis is examined, and the result is that the principal stress is suitable rather than the von-Mieses stress. The reason is that the principal stress can distinguish the magnetic properties under compressive stress from the properties under tensile stress, and it can also consider the magnetic anisotropy caused by the stress.
