Skew vibro-acoustic effects with permeance / mmf model

A new machine is set-up in machine_SCIM_C by copy/paste machine_SCIM_A with the following change:

Input.Geometry.skew_rater =  36/28;

In the GUI, this parameter is available in the machine GUI step 9 "Rotor Lamination".

Note that the skew rate is expressed in stator slot pitch for both rotor and stator skew. A skew of the rotor cage of 36/28 stator slot pitch is introduced, meaning a 1 rotor slot pitch.

A new project is set-up in tuto_test_SCIM_11 by copy/paste tuto_test_SCIM_01 with the following changes:

Input.Simu.machine_name = 'machine_SCIM_C';

MANATEE offers two ways to model the skew:

  • the first is to average the flux density along the axial direction and use this for average flux for force calculation (type_skew=1)
  • the second is to calculate the evolution of the flux along the axial distribution (3D distribution along time, angle, and length of the stack) and use that to calculate the magnetic forces.

The latter method is more accurate and should be the default one to be used.

Input.Simu.type_skew = 2;

Another important parameters is the number of slices used in the 3D electromagnetic analytical model along the rotor axis:

Input.Simu.Nskew_slices = 10;

In the GUI, this two parameters can be found in Numerical.Magnetics

240. Skew simulation setup with GUI
Skew simulation setup with GUI

Result interpretations

>> run_MANATEE('tuto_test_SCIM_11');
>> plot_VS_ASPL_overall
Sound pressure level spectrum with skew
Sound pressure level spectrum with skew

One can see that the rotor skew of one rotor slot pitch has drastically reduced the overall acoustic noise level, and that all exciting harmonics linked to rotor slotting have been minimized ( plot_VS_ASPL_spectrogram)

Sonogram with skew
Sonogram with skew
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