Design optimization of rare-earth free PM-assisted synchronous reluctance motor to improve demagnetization prevention capability

This paper presents the design optimization of rare-earth-free permanent magnet assisted synchronous reluctance motor (PMSynRM) with an objective to improve the demagnetization prevention capability. Ferrite magnet is a common rare-earth-free permanent magnet (PM) which is attracting the manufacturers with its lower price and abundant supply compared to rare-earth materials such as Neodymium, Samarium, and Cerium based PMs. However, due to lower coercive force, Ferrite magnets have a higher risk of getting demagnetized than rare-earth magnets. Therefore, Ferrite based motor should be carefully designed so that the magnets do not get demagnetized at any desired operating condition. This study proposes a Ferrite magnet based PMSynRM (F-PMSynRM) with non-conventional flux-barrier structures to improve its demagnetization prevention capability while maintaining the same output power as a conventional F-PMSynRM. The equivalent magnetic circuit (EMC) has been used to obtain and justify the proposed motor of improved demagnetization prevention capability. Besides, finite element analysis (FEA) results have been presented to compare the proposed motor and conventional motor in terms of their electromagnetic torque, back-emf, stress and demagnetization preventive capability. Experimental results of the no-load induced voltage have been provided to validate the analytical and simulation results.