Rare-earth-free Al-Ni-Co hybrid PMa-SyRM for an air-conditioner compressor

Abstract

A hybrid ferrite-Al-Ni-Co permanent magnet assisted synchronous reluctance motor (PMa-SyRM) for an air-conditioner compressor is proposed. Al-Ni-Co PMs have high residual flux density similar to rare-earth PMs such as Nd-Fe-B and Sm-Co. Therefore, the performance parameters of the PMa-SyRM such as power factor, efficiency etc., with Al-Ni-Co PMs can be improved without significantly increasing the cost of the motor. However, Al-Ni-Co PMs have a steep II^nd-quadrant B-H curve, and the challenge lies in addressing their demagnetisation issues. In the proposed hybrid PMa-SyRM, the rotor geometry is suitably optimised for placing the Al-Ni-Co PMs in the centre flux barriers to address the demagnetisation issues. Further, an analytical magnetic circuit is presented to design the proposed PMa-SyRM. Later, 2-D finite element analysis of the proposed motor including the demagnetisation analysis of PMs and stress analysis of the rotor is carried out and presented. A prototype is fabricated, experimental validation is carried out, and the results of the performance and cost are compared with that of ferrite and hybrid ferrite-Nd-Fe-B PMa-SyRM.