Comparison of different electromagnetic forces calculation methods for the analysis of NVH behaviour of electric motors

This paper deals with NVH (Noise Vibration and Harshness) analysis of electric motors for automotive applications. A comparison between numerical and analytical magnetic force computation methods is conducted. Altair Flux, Ansys Maxwell and Ansys Motor-CAD are the commercial software considered, while the analytical expression of the airgap magnetic field is defined by means of the image method. A 12 pole 18 slot combination Permanent Magnet Synchronous Motor (PMSM) is considered as benchmark machine. In order to evaluate the acoustic emission of the PMSM a 2D circular beam model is considered. The main spatial-temporal components of the calculated radial and tangential harmonic forces are used as input for the NVH analytical model. Differences at the force calculation level are analyzed to investigate how they affect the prediction at the acoustic noise level for the considered electric motor.