A new hybrid method for the fast computation of airgap flux and magnetic forces in IPMSM

In this paper, a new hybrid method is developed for the fast and accurate computation of air gap flux density in the open-circuit Interior Permanent Magnet Synchronous Machines (IPMSM). The rotor magnetomotive force is estimated using a single non-linear FEA simulation. Then, rotor motion and stator slotting effect are included without loss of calculation performance using the semi-analytical subdomain method initially developed for Surface Permanent Magnet Machines. This hybrid method calculates the time and spatial distribution of radial and tangential airgap flux in a few seconds. It can be used to quickly estimate electromagnetic quantities (cogging torque, back emf) as well as magnetic forces for the electromagnetic and vibroacoustic design optimization of electric motors. The method is applied to the vibroacoustic analysis of the IPM machine of the Toyota Prius 2004 at open-circuit state and variable speed. Results show that the maximum sound power level occurs when the air gap magnetic pressure harmonics excite the breathing mode of the stator structure.