Analysis of d- and q-axis inductances and saliency ratios in interior permanent magnet machines with fractional-slot concentrated- windings considering harmonic effects

The interior permanent magnet (IPM) machine with fractional-slot concentrated-windings (FSCW) has become a popular research topic owing to their novel structures and attracting potentials. This paper is focused on inductances and saliency ratios in IPM FSCW machines with different pole and slot combinations. Analytical expressions of inductances and saliency ratios are derived using harmonic analysis method (HAM) and their features and trends are concluded. The concept of dq-axis equivalent windings containing harmonic components is proposed to help better understand these features and trends. It explains the phenomenon that configurations with fewer stator slots and fewer winding layers have lower saliency ratio. Theoretical conclusions are verified by finite-element (FE) method.