Vibro-acoustic effect of demagnetization

The effect of pole demagnetization on magnetic forces, magnetic vibration and magnetic noise is studied in this new simulation project. To start you can copy paste tuto_SPMSM_02 (permeance / mmf model) and rename it in tuto_test_SPMSM_07. To demagnetize a magnet of 10 % you can put

Input.Simu.demag_rate=0.1;% rate of demagnetization of the pole number 1

After running the simulation you can check the rotor magnetomotive force with plot_rmmf_space:

Airgap rotor magnetomotive force
Airgap rotor magnetomotive force

One can see that the demagnetization has reduced locally the rotor mmf. The effect on noise can be seen in the sonagram using plot_VS_ASWL_sonagram

To better see the sidebands one can increase the number of revolutions with

Input.Simu.Nrev=4
A-weighted sound power level sonogram
A-weighted sound power level sonogram

The contribution of the structural modes to acoustic radiation can be plot using plot_VS_ASWL_modal_cont:

Structural mode contribution
Structural mode contribution

One can compare these graphs with the ones obtained in the healthy case (no demagnetization). The demagnetization has spred the radial force spectrum, introducing modulation of both wavenumbers and frequencies (at the rotor mmf is rotating). New force wavenumbers appear and excite the mode 2 of the stator stack, although GCD(Zs,2p)=8 in that case.

Previous Next