Inductances of a fractional-slot concentrated-winding interior PM synchronous machine considering effects of saturation and cross magnetization

The Fractional Slot Concentrated Winding (FSCW) configuration increases spatial harmonics of the magneto motive force (MMF) waveform of an electric machine. Therefore, saturation level in such machines is typically higher than that of the conventional machines with distributed windings. Since the characteristic of Interior Permanent Magnet (IPM) machine principally depends on inductances variation, this paper attempts to investigate the effect of saturation on the machine inductances in a FSCW IPM machine. Variations of apparent, incremental and cross-magnetization inductances were measured by flux-linkage calculation method and the dq-axis voltage equations were modified to take into account for these variations. The effect number of slot and pole combinations in the variations of the inductances was also investigated. Experimental test was carried out in a prototype machine to verify the finite element results.