What is the EVS (Electromagnetic Vibration Synthesis) method?


The EVS (Electromagnetic Vibration Synthesis) is an algorithm designed to speed up electromagnetically-excited noise and vibration calculations and get more physical insights on the e-NVH behaviour of the machine.

It consists in decoupling the vibrational characterization of the electric motor structure from the operational electromagnetic excitation, as one would do experimentally using an impact hammer or an electrodynamic shaker to carry an Experimental Modal Analysis.

As electromagnetic forces due to Maxwell stress can be decomposed in a discrete series of rotating force waves with specific wavenumbers which depends on slot / pole combination and winding pattern, this characterization can be carried by artificially exciting the structure with some specific rotating force patterns at variable frequency in radial and tangential directions. One obtains some normalized Frequency Response Functions (FRF) that can be stored for later use. This EVS method can be called the "rotating wave excitation method". Another EVS method consists in exciting each tooth of the stator with variable frequency radial and tangential excitations. This method is called the "tooth excitation method".

The interest of EVS method is presented in the paper Numerical simulation of structural-borne vibrations due to electromagnetic forces in electric machines – coupling between Altair Optistruct and MANATEE software.

Once the FRF are calculated, the electromagnetic loads are projected on the excitation basis and the vibration response is synthesized without additional calculations. The example of rotating wave vibration synthesis is illustrated here:

770. Rotating wave vibration synthesis
Rotating wave vibration synthesis

Application to MANATEE software

MANATEE software v1.04.06 mechanical module can apply EVS algorithm to the following structural models:

  • MANATEE built-in semi-analytical vibroacoustic models (rotating wave only)
  • Optistruct structural FEA commercial software
  • GetDP structural FEA free software (distributed with MANATEE)

Coupling with other FEA software are under study.

In MANATEE software scripting mode the vibration synthesis method is chosen using the input parameter

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