Variable-speed partial-load current-driven vibro-acoustic simulation with subdomain model

To include the effect of the load in this new project tuto_SPMSM_03 one must activate the armature field calculation with

Input.Simu.is_mmfs=1;

The armature current can either be included specifying the voltage or the current. In this simulation the RMS phase current is imposed with

Input.Simu.type_extsupply=1;

A 90 Arms value of the phase current is specified with

Input.Simu.I0=90;

The associated current angle is specified with

Input.Simu.Phi0=pi/2;

For surface PMSM, pi/2 means that the Iq current and torque production is maximized (full load case). The spectrogram synthesization to still activated with

Input.Simu.is_spectro_synthesis = 1

This means that at variable speed the current is kept constant with Id=0 (no flux weakening).

The airgap flux density at nominal speed 1500 rpm can be plot with plot_B_space:

Radial and Tangential airgap flux density (subdomain)
Radial and Tangential airgap flux density (subdomain)

One can notice that the armature field distorts the airgap field for torque production.

The full load radial force spectrum can be plot using plot_Fr_fft2_stem. The plot can be rescaled to focus on high frequency harmonics with

Input.Plot.is_remove2f=1;

The following graph is obtained:

Radial airgap force spectrum
Radial airgap force spectrum

Some additional magnetic force harmonics compared to open-circuit case appear linked to the armature field such as f=6fs, r=0 and f=8fs, r=4.

The noise spectrum at nominal speed can be plot using plot_ASWL_modal_cont. The radial vibration spectrum at nominal speed can be plot using plot_Ar_modal_cont

The acoustic noise due to Maxwell forces at variable speed is given by plot_VS_ASPL_sonagram:

Acoustic noise due to Maxwell forces at variable speed
Acoustic noise due to Maxwell forces at variable speed

Note that the spectrogram frequency resolution can be improved by increasing the number of revolutions, for instance with Input.Simu.Nrev=5 one obtains

spectrogram with better frequency resolution
spectrogram with better frequency resolution

There is no additional resonance but the open-circuit resonances have been amplified by armature field reaction. This illustrates how the current angle can increase or decrease noise level due to magnetic forces.

This also shows that noise mitigation actions should therefore focus on rotor field harmonics in this particular machine.

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