Browse Publications Technical Papers 2018-01-1551
2018-06-13

NVH technologies and challenges on electrical powertrain 2018-01-1551

Electrical motors have the advantage of making less noise compared to internal combustion engines but they create new NVH problems such as noises from gear whine, high frequency electrical whistling noise, noises from auxiliaries, etc. On the other hand, customer’s expectations are much higher with electrical vehicles and they don’t accept any disturbing noise even when the level is low. Therefore, targets for powertrain noises are much more severe in an electrical vehicle than in a classical one. In order to reach these targets, specific NVH methods have to be developed for electrical motors both for mastering the excitations from electromagnetic sources and the NVH responses from the whole powertrain structure. Within Renault, much effort has been made in the development of NVH simulation methodology of the whole e-powertrain, so that potential NVH problems can be detected and solutions found during the early design stages of the electric motor. For new generations of electrical motor, increased power/torque and weight-lightening are the two major requirements. Both of them have negative impacts on electrical whistling noise. Therefore, special NVH counter-measures should be developed in order to keep the whistling noise to an acceptable level. In this article, we will explain the NVH simulation methodology of Renault for e-powertrain development and some examples of results obtained on a new electrical motor with very stringent requirements in terms of power and weight-lightening. For this motor different types of assembly between the stator and the e-motor case have been evaluated (shrink fit, bolt fixing, etc...). Shrink fit assembly gives higher stiffness to the e-motor case, which is favorable to whistling noise, but is limited in terms of torque transmission capacity. Bolt fixing assembly has some advantages in terms of torque capacity and weight-lightening but gives higher whistling noise levels due to some energetic structural modes. Simulation of noise from the whole e-powertrain has been carried out with different stator-case assembly solutions combined to different rotor designs. In parallel, prototypes have been built and tested for correlation with the simulation results, which allowed predictive results on whistling noise. With the predictive simulation model, whistling noise levels have been calculated with some improvements in the powertrain case structure and the stator-case assembly. These predictive simulation results enabled us to choose the best design for the electric motor with respect to NVH requirements while respecting the constraints for powertrain layout and weight-lightening.

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