Analysis of PMSM NVH performance in electric propulsion systems using FE models

The stator of the PMSM is the main transfer path for the Electro Magnetic (EM) force from stator teeth to the drive unit (DU) through its mounting ears. First, a FE model of full winding stator model along with connection ring is analyzed for modal behaviors. Time domain EM force excitations are converted into frequency domain and applied at the stator teeth. This enables stator mounting forces analysis at all critical NVH orders. Next, the detailed FE modelling approach is compared with response calculated form a simplified modelling approach, with stator end windings modelled as lumped mass and inertia to reduce computational time. The comparison study of two approaches clearly shows the benefits of using simplified FE models for studying motor whine with reduced modelling and computational costs. Furthermore, the frequency-dependent stator damping measured from modal test is applied in electric DU analysis to evaluate NVH performance excited by motor EM force excitations using simplified stator model. The sound power level radiated from the DU and the mount vibration response show negligible influence of stator damping at DU unit level NVH response in the low frequency range. Analysis and test results correlate reasonably well at the dominant motor whine orders for the DU, which validates the proposed method.