Comparison of Electro-magnet Charateristics of Interior Permanent-Magnet Synchronous Motor according to the Number of Phases

In this paper, the author researches the electromagnetic performances of interior permanent magnet synchronous motor (IPMSM) considering the number of phases. The analysis is carried out by the comparison of three and six-phase models in terms of harmonic components. The harmonics are analyzed by observing torque ripple and iron loss. Distributed winding is applied to both models. The asymmetrical six-phase winding method is used to achieve better torque ripple performance because it has two sets of three-phase winding that have opposite phases. The results of comparison for torque ripple have shown that there is an 11.3 % lower value in the asymmetrical six-phase winding. The iron loss harmonic orders are different at the rotor. In the case of the three-phase motor, 6 kth ($k=1,2,3\ldots$) harmonic losses by phase ripples and 12 kth ($k=1,2,3\ldots$) harmonic losses by slot ripples exist. Therefore 6 kth and 12 kth harmonic orders can be observed. In the case of the six-phase motor, however, only 12 kth harmonic orders can be observed because harmonic losses by phase ripples and slot ripples have identical harmonic order, 12 kth. Lastly, the efficiency of both models is compared.