What can I do if the natural frequencies calculated by MANATEE are a bit far from the experimental ones?

The fact a natural frequency is overestimated or underestimated in MANATEE can come from different reasons:

In case you have too high differences, the possibilities are the following:

  • enforce the experimental natural frequencies using the variables Input.Simu.ExpFreq, ExpModes, ExpDamp input values with Input.Simu.is_force_natfreq = 1
  • use the tuning factor Knat_freq_user to tune the 2D analytical model - these tuning factors can account for the difference between the model and the real structure
  • use the 3D FEM structural model (longer calculation time but more accurate results) of MANATEE

It is anyway recommended to carry an experimental modal analysis of the electrical machine, as the manufacturing process can affect the natural frequencies and the damping, and use these experimental values to tune MANATEE model and have more realistic results. You can contact EOMYS if you need help to run this type of experimental characterization.

Note that this methodology is not necessary in a relative design analysis at variable speed (ex: influence of the slot number on the maximum sound power level): as resonances occur usually far from the minimum and maximum speeds, a +/-10% change of the natural frequencies will not change the largest noise and vibration levels.

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