Vibro-Acoustic Analysis of an Electric Powertrain: An Evaluation of the Relative Contribution of Gear Whine Noise and Electromagnetic Excitations on the Overall Response

The NVH (Noise, Vibration, Harshness) performance of electric vehicles is gaining critical importance nowadays. Sources of different nature are responsible for the production of vibrations and noises in electric powertrains: namely, mechanical and electromagnetic excitations are worth investigating, both leading to relevant vibroacoustic responses. The mechanical source considered in this paper is the transmission error (TE); radial and tangential forces acting on stator teeth, as well as torque ripple acting on the rotor are the electromagnetic sources included. The modelling and simulation of the vibroacoustic performance of an electric powertrain for vehicle traction is carried out using a specialised commercial software, Romax. The NVH problem is first approached with the aim of weighting separately the contributions to the acoustic response due to mechanical and electromagnetic excitations. The difference between spur and helical gears is analyzed in terms of TE excitation harmonics, and the benefits brought by microgeometry corrections discussed. Waterfall and operational deflection shapes analysis has been used to identify the cause of some resonances (e.g. stator breathing mode) excited by the different vibrational sources.