Optimization of the Magnetization Direction of Magnets in a Permanent Magnet Assisted Synchronous Reluctance Machine to Minimize Demagnetization

Surface Permanent Magnet (PM) machines owe their high performance to the use of strong rare-earth magnets which typically makes them an expensive option. A potential lower cost alternative is a PM-assisted Synchronous Reluctance Machine (PMASynRM) which potentially use relatively lower magnet grades to achieve comparable performance because of its reluctance torque contribution. However, the use of relatively weaker magnets poses a higher risk of demagnetization as a result of cross-coupling due to armature reaction and other magnet sets. This paper proposes to reduce the level of demagnetization in the magnets by optimizing their direction of magnetization. Additionally, the effect of varying the magnetization direction on other performance parameters including magnetic flux linkages, torque, torque ripple and back EMF reduction due to demagnetization have also been studied. The results for both rare-earth free designs as well as designs that include a blend of rare-earth and rare-earth free magnets have been presented.