A preliminary study of the effect of saturation and cross-magnetization on the inductances of a fractional-slot concentrated-wound interior PM synchronous machine

Accurate determination of the variation of inductances with respect to increase in current is necessary to characterize the behavior of a Permanent Magnet Synchronous Machine (PMSM) under saturation. This is even more crucial in the Fractional Slot Concentrated Wound Interior PM synchronous machine (FSCW IPMSM) because of increased spatial harmonics in the magneto-motive force (MMF) waveform. This paper attempts to determine the variation of inductances of a prototype FSCW IPMSM due to saturation and cross-magnetization effects. The variation of incremental and apparent inductances and their effect on voltage equations are investigated. The flux-linkage calculation method was used to calculate the incremental and apparent inductances for a wide range of operating points including constant torque and flux-weakening regions. The results of a Finite Element (FE) model which agree well with the experimental results were used to further investigate the inductance characteristics.