FFT2 analysis of radial force with expression of main lines (plot_Fr_fft2_stem)

Post-processing documentation
Matlab commandplot_Fr_fft2_stem
Module EM.pp
Description PLOT_FR_FFT2_STEM plots the FFT2 of radial magnetic force per unit area with a stem plot
Parameters
Restrictions
See also plot_Fr_fft2, plot_Ft_fft2_stem, plot_Fr_cfft2

Result

This MANATEE software post processing plots the 2D Fourier transform of radial magnetic pressure as a 3d stem plot:

Airgap radial pressure FFT2
Airgap radial pressure FFT2
plot_fr_fft2_stem

Contrary to the contour plot of radial magnetic forces given by plot_Fr_fft2, the scale is here linear and the largest magnetic forces are automatically labelled by identifying the closest analytical expression.

The largest force harmonics should occur at r=2p (twice the number of pole pairs), f=2fs (twice the fundamental electrical frequency), and at r=0 f=0 (static force). Note that only the lowest force wavenumbers are important in magnetic noise and vibration process.

To avoid that this large force damps all the other harmonics using a linear scale, one can automatically exclude the 0 and 2f components with

Input.Plot.is_remove2f=1
Input.Plot.is_remove0f=1

In some electrical machines, the 2f components might be important for noise and vibrations. For further plot options (e.g. change axis) see How to change plot options.

When spectral leakage occurs (e.g. due to slip in induction machines with a too low number of revolutions, or when importing flux or current data that is not exactlty periodic) one can obtain:

Airgap radial force FFT2
Airgap radial force FFT2
plot_Fr_fft2_stem

This representation of magnetic force harmonics, including their analytical expression, allows to confirm the physical origin of magnetic noise in electrical machines.

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