Saturation vibro-acoustic effects with permeance / mmf model

A new project is set-up in tuto_test_SCIM_08 by copy/paste tuto_test_SCIM_01. The following parameters are modified for variable speed operation:

Input.Simu.U0 = 600/sqrt(3);
Input.Simu.type_satmodel= 1;
Input.Simu.Nsatharm = 1;

In the GUI, U0 is in Workflow, type_satmodel and Nsatharm are not yet in the GUI.

The voltage is doubled to increase saturation effects, and the modelling of saturated permeance is activated (type_satmodel=1) with only one additional harmonic (Nsatharm=1).

The behaviour of the B(H) curve during saturation can be modelled in three different ways:

  • by using the special curve specified in the MaterialData folder by “M400-50Asat.txt”, suitable for high H operation (Input.type_BHsat=0)
  • by using the 4 parameters of an analytical B(H) curve defined in the machine script : Input.Magnetics.Bmax_BHsat, Input.Magnetics.mur0_BHsat, Input.Magnetics.a_BHsat, Input.Magnetics.mur1_BHsat (To set in the machine file, not available in the GUI)
  • by using the B(H) graphical interface to manually fit the B(H) curve with the 4 parameters of the analytical model

Result interpretation

The effect of saturation permeance wave can be checked using plot_Per_space :

210. Saturated permeance
Saturated permeance

On can see an additional harmonic of space wavenumber 2p=6, which is going to flatten the airgap flux density distribution with a 3p=9 spatial wavenumber (plot_B_space) :

210. Airgap radial flux
Airgap radial flux

The new sonogram is given by plot_VS_ASWL_sonagram

210. Sonogram

One can notice a new force line close to the slotting harmonic force of wavenumber 2. This saturation line has a wavenumber 4 and a frequency fs(Zr/p+4), it was already identified in the theoretical analysis (eps=2). Here it does not create any resonance, but in some squirrel cage designs this saturation harmonic can generate significant acoustic noise.

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