Lumped parameter magnetic circuit model for fractional-slot concentrated-winding interior permanent magnet machines

This paper presents a simplified lumped-parameter magnetic circuit model (MCM) of a fractional-slot concentrated-winding (FSCW) interior permanent magnet (IPM) machine that provides rapid estimates of machine performance for use in machine design optimization software. This model incorporates several key nonlinear phenomena including (i) magnetic saturation; (ii) cross-saturation effects between the d- and q-axes affecting both flux linkages and inductances; (iii) stator slotting effects; and (iv) localized effects due to rotor bridges. A coupled permeance element is proposed that captures the cross-coupling saturation effects along with airgap modeling that captures both radial and tangential airgap flux densities. The MCM is configured to predict key machine performance variables including airgap flux densities, back-EMF, phase and dq-axis inductances, characteristic current, and torque. Finite element (FE) analysis results are presented that match the MCM results quite closely, building confidence in the MCM model.