Advanced NVH Measurement Data Processing of Electric Motors under Electromagnetic Excitations

Abstract

This paper presents several Noise, Vibration, Harshness (NVH) post-processing techniques used on a dynamic acquisition system to troubleshoot acoustic noise and vibration issues due to electromagnetic forces in e-powertrains. Standard NVH post processing techniques based on Order Tracking (OT), Operation Deflection Shapes (ODS) and Experimental Modal Analysis (EMA) are presented and as well as their application to discriminate the frequencies of magnetic forces responsible for NVH issues. However, they do not filter the different wave-numbers of vibration waves. Some special NVH post processing techniques are introduced to go deeper in the analysis and quickly capture electromagnetically-excited NVH root cause. They are based either on “spatiogram” or on flux sensor waveform post processing. “Spatiogram” relies on the Discrete Fournier Transformation of accelerations measured on the machine. It aims at introducing a space information besides the standard time and frequency information. It can be seen as an extension of the spectrograms done at variable speed as it efficiently discriminates wavenumbers of magnetic forces responsible for NVH issues. Experimental measurements run on a Permanent Magnet Synchronous Motor (PMSM) are interpreted and confirmed by simulation results. Similarly flux sensor waveforms can be post-processed to quantify geometrical and magnetic asymmetries, to estimate radial magnetic forces per tooth and derive Frequency Response Functions (FRF) of stator teeth under radial electromagnetic excitations.