Electric powertrain NVH simulation

EOMYS uses Manatee software to efficiently assess and mitigate noise and vibrations due to magnetic forces at all design stages of electric powertrains, from e-machine to vehicle level.

Early design stage

In early design stage, Manatee is used to quickly rank different e-motor topologies based on simple inputs such as lamination dimensions or slot/pole combinations. Fast electromagnetic and vibro-acoustic models can be used to run quick sensitivity studies on the NVH effect of electromagnetic design variables. Once e-motor topology and slot/pole combination is frozen, Manatee is then used to identify the root cause of main resonances occuring at variable speed and load. 

Intermediate design stage

Once the magnetic circuit of the electrical machine is frozen, more accurate electromagnetic and NVH models can be used at intermediate design stage to refine calculations and further optimize the design. As an example, a 3D FEA mechanical model of the stator stack can be used in combination with electromagnetic FEA. e-machine dimensions are then optimized to reduce magnetic air-borne noise levels by shifting some lamination modes or cancelling some magnetic force harmonics. Noise control techniques such as pole shaping or notching can be applied during multiobjective optimization with respect to NVH and electromagnetic performances.
At this stage, the effect of control (e.g. switching frequency, current angle) on the NVH performances can also be studied.

Detailed design stage

Once a detailed CAD model of the full e-powertrain (housing, stator and rotor, gearbox, etc) is available, Manatee calculations can be refined to include both air-borne and structure-borne noise. Whatever the design stage, Manatee unique Electromagnetic Vibration Synthesis algorithm naturally provides the contribution of Load Cases and structure modes, providing insightful results on the e-NVH transfer path and how to mitigate it.

As structure-borne noise can come from unbalanced forces induced by eccentricities, non idealities may be introduced at this design stage. Robust NVH design can be carried by comparing different e-machine designs NVH performances under faults or manufacturing tolerances (e.g. eccentricities, uneven magnetization, uneven airgap). Mechanical tolerances specification can also be carried more accurately by quantifying the NVH levels as a function of tolerance levels.

Further noise mitigation actions can be carried depending on the transfer path analysis. Magnetic and control techniques may include skewing or harmonic current injection. Mechanical techniques may include change of bearing types, boundary conditions (shrink fit, bolting), or stiffeners.

Vaildation stage

Once a prototype is available, EOMYS can run e-NVH tests and compare Manatee simulation results with measurements. This comparison allows to identify non idealities that were not included in first simulation runs (e.g. current unbalance), and to refine e-NVH models (e.g. by fitting modal damping). 

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