NVH Aspects of Electric Drives-Integration of Electric Machine, Gearbox and Inverter 2018-01-1556

The rate in the electrification of vehicles has risen in recent years and, despite that electric vehicles are quiet, NVH remains a major requirement of vehicle development. The typical NVH issues are gear whine from the gearbox, noise from the E-machine or electromagnetic whine, as well as the noise from the inverter, and noise from inverter harmonics effect on E-machine.

Simulation methodologies and CAE workflows are being enhanced to contribute to electric drive systems development. Front loading in the concept and layout design phase are necessary to avoid significant NVH issues at the end of development. The authors previously presented a workflow for combining the electric and mechanical noise for electric drives for the concept and layout design phases. This paper shows an application of the formerly presented workflow for NVH simulation and validation of a system with an Interior Permanent Magnet (IPM) E-machine. Other than E-machine noise two main other aspects relevant for NVH in electric drives, the gearbox and inverter. The inverter has two effects on NVH: it radiates noise itself, often not a significant source, but also creates an excitation supplied to the electric machine as current. The effect of these inverter harmonics on the E-machine is shown. The simulation of this current from an inverter is presented and compared with measurements. The gearbox simulation workflow is briefly discussed and a guideline for selecting the gear ratios depending on the number of slots and poles is deliberated. Lastly, integration aspects of subsystems in a full electric drive unit also discussed.