A Magnetic Circuit Model for an IPM Synchronous Machine Incorporating Moving Airgap and Cross-Coupled Saturation Effects

A new magnetic circuit model is presented for an interior permanent magnet (IPM) synchronous machine, using a machine with three-phase distributed stator windings and three layers of flux barriers in the rotor as an example topology. The model accounts for: i) the effects of cross-coupled magnetic saturation caused by the salient rotor; ii) variation of magnetic saturation levels in the iron rotor bridges that are key elements of the unitary rotor laminations; iii) the effects of stator lamination slots on the airgap mmf distribution; and iv) the local variation of airgap permeance due to the stator slotting and the relative position of the rotor with respect to the stator. As a result of these features, the new model is capable of significantly improving the accuracy of electromagnetic performance predictions for aggressively-designed IPM machines compared to previously-available magnetic circuit models. Comparisons with finite-element analysis and measurement results are provided showing that the new model is much faster while delivering appealing accuracy compared to the FE method.