Effect of Core Magnetic Saturation on Cogging Torque of Motor

Abstract

This paper discusses what effects of magnetization saturation has on the cogging torques of 12-pole motors with 9-slot cores, using Nd-Fe-B ring magnets. The core flux density is changed with sintered, bonded and thermally demagnetized magnets. Cogging torques especially 36th harmonics, increase with the higher flux densities of the core at the teeth, and then magnetic saturation makes cogging torques larger. However, the harmonics of core flux densities are low although 36th cogging torques are related to the harmonics of core flux. Therefore, increasing cogging torques with magnetization saturations may be affected by the reduction in permeabilities due to magnetic saturations and the generation of core-flux density harmonics.