Result interpretation : Graphical Output (Variable speed)

All the variable speed graphical post processing start with plot_VS, they can be accessed with by using the Matlab auto-completion or in the plot commands documentation.

Note that this first tutorial project tuto_BPMSM_01 results should not be compared directly with the results of the reference article as the permeance/mmf model is used and is less accurate than other models.

Here, the variable speed radial acceleration can be displayed with plot_VS_Ar_spectrogram

Radial acceleration spectrogram
Radial acceleration spectrogram

If you are not familiar with this graph you can refer to our detailed article on what is a spectrogram?. One can see that significant excitation occurs in particular at 2fs and 12fs.

The overall SPL (sound pressure level) can be displayed with plot_VS_ASPL_overall

A-weighted variable speed sound pressure level
A-weighted variable speed sound pressure level

The green line corresponds to the speed above which field weakening is applied. The red line corresponds to the speed above which the spectrum is complete up to specified maximum frequency Input.Simu.freq_max_spec.

To have more information on where noise come from, one can plot the sonogram (variable speed noise spectrum) with plot_VS_ASPL_sonagram

A-weighted sound pressure level sonagram at 1 m
A-weighted sound pressure level sonagram at 1 m

The contribution of the structural modes to the acoustic noise level can also be checked with (plot_VS_ASWL_modal_cont) :

Structural mode contribution to A-weighted SWL
Structural mode contribution to A-weighted SWL

This identification can be also made in a sonagram by using (plot_VS_ASWL_spatiogram) :

90. A-SWL spatiogram: A-weighted sound powel level per magnetic force wavenumber
A-SWL spatiogram: A-weighted sound powel level per magnetic force wavenumber

This powerful post processing allows to discriminate the sound power level radiated by each force wavenumber involved in the lamination vibration. One can see in this example that the dominant wavenumber is clearly 0 as it is the case for most symmetrical traction machines in automotive application.

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