# Vibro-acoustic effect of pole displacement

The effect of pole displacement 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_08. To quantify the effect of manufacturing tolerences and introduce a 10 % shift relative to the pole width one can define in the simulation project

`Input.Simu.pole_shift_angle =1.0472*0.1;    % angle of pole shifting of the pole number 1 (0 for no default) [rad] in case of manufacturing error`

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

Airgap rotor magnetomotive force

One can see that a pole has been moved. 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

Similarly to the demagnetization case, the pole displacement manufacturing error has introduced additional sidebands in the acoustic spectra.

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

Structural mode contribution

One can compare these graphs with the ones obtained in the healthy case (no pole displacement). Pole misalignement 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. One can see that a 10% variation of a pole position has a much stronger effect (+20 dB) that the 10% variation of pole magnetization experienced in previous tutorial.