NVH Technologies and Challenges on Electric Powertrain 2018-01-1551

In this article, NVH performance of fully electric vehicles and some key technologies for NVH improvement are presented. A focus is made on a global NVH simulation methodology able to take into account the electromagnetic excitation sources and all the powertrain structure. Examples of simulation results are shown which allow us not only to predict the NVH performance, but also to understand better the fundamental NVH behavior of an electric motor. In an electric motor, the most important NVH phenomenon is the whistling noise, which is caused by the electromagnetic forces and amplified by the powertrain structure. With the current NVH simulation technology, e-motor whistling noise levels can be accurately simulated up to 4500 Hz.

The improvement of e-motor whistling noise can be achieved both by reduction of the electromagnetic forces at the source and by optimization of powertrain structure. As far as the powertrain structure is concerned, there are two modes which have predominant effects on the e-motor whistling noise: the torsional mode (<1000 Hz) and the breathing mode (5000-6000 Hz) of the stator-housing assembly. In the low motor speed range, the dominant phenomenon is the coupling between the 24^th order tangential electromagnetic forces and the torsional mode of the stator assembly. In the high speed range, the dominant phenomenon is the coupling of radial excitations of 48^th order with the radial breathing mode of the stator assembly. The choice of powertrain structure design must be made according to NVH targets and according to the constraints for powertrain layout and weight-lightening.