Estimation Method of Cogging Torque Probability Distribution of Permanent Magnet Motor Resulting from Asymmetrical Properties

Abstract

This paper examines the cogging torque in permanent magnet (PM) motors resulting from the asymmetrical properties of the rotor and stator such as the variation in magnet properties and slot opening widths of the stator. A PM motor with 10 poles and 12 slots is selected for verification, because the motor with a pole/slot ratio of 5/6 is sensitive to the variation of the rotor and stator. We propose an estimation method of cogging torque using the torque vector, which corresponds to the torque produced on the each magnet or stator core. The validity of this method is confirmed by comparison with the results obtained using FEM. The calculation method of cogging torque probability distribution using the proposed estimation method of cogging torque is also shown.