Performance Analysis of a Rewound Multiphase Synchronous Reluctance Machine

This article analyses the performance of synchronous reluctance motors (SynRMs) when an existing three-phase stator is rewound (REW) to a higher number of phases. The introduced rewinding technique offers an optimized distribution for air-gap flux, higher winding factor, and higher value for the fundamental component of the magnetomotive force with lower harmonics. The number of turns of the proposed multiphase winding is calculated, keeping fixed copper volume. Finite element simulations verified that the torque density of the REW five- and seven-phase SynRMs is enhanced by 6.56% and 3.37%, respectively, over the existing machine under rated conditions. The torque ripple is also reduced by 17.13% and 15.87%, respectively. Furthermore, the efficiency is enhanced with the REW machines by 0.3% at rated condition. Moreover, the torque gain is greatly increased to 23.48% at higher speed (9000 rpm) and the efficiency is also increased by 3%. The main advantage of the REW machine is clearly observed in case of an open-circuit fault. With one-phase opened, the REW machine can work at 78% of the healthy rated torque, while the three-phase machine works at only 43% with a very huge torque ripple about 228%. Experimental measurements are obtained to validate the theoretical work.