Torque ripple minimization under unbalanced phase resistance in a five-phase permanent magnet assisted synchronous reluctance motor

This paper presents an analysis of the torque ripple minimization under unbalanced phase resistance (UPR) in a five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM). There are many reasons for arising UPR conditions in a motor. One of the key reasons can be the shortening winding turns of the motor which significantly reduces the winding insulations. Therefore, over the times, the torque ripple increase gradually. Excessive torque ripple leads to early degradation of the drive train components with an increased acoustic noise that reduces the performances of a PMa-SynRM. Especially, under UPR conditions, the torque ripple becomes prominent which require smart and easy mitigation approach to retain the advantages of a PMa-SynRM. This paper investigates three different UPR conditions that commonly arise a five-phase PMa-SynRM. A simple phase voltage compensation technique has been utilized to improve the torque ripple under different UPR conditions. Extensive theoretical analysis has been carried out through finite element analysis (FEA) to verify the proposed idea. The effectiveness of the method has been evaluated by the experimental tests that are conducted by utilizing 3.7 kW dynamo system.