Crystal orientation control of multipole ring magnets for a surface permanent magnet rotor

Abstract

The effects of the crystal orientation on the surface magnetic flux density and cogging torque were investigated for multipole ring magnets. A high magnetic field was applied to pole positions during the pressing process for the fabrication of ring magnets using anisotropic NdFeB powders. The radial orientation of the c axis of these ring magnets is 10% higher than that of previous ring magnets at pole positions. The ring magnets with a high orientation at the pole positions show a smaller distortion wave form of the surface magnetic flux density and a 20% higher surface magnetic flux density than previous ring magnets. The surface permanent magnet rotors using these ring magnets have a 75% smaller cogging torque with a basic period.