Single-speed voltage-driven no-load PWM vibro-acoustic simulation with permeance / mmf model

A new project is set-up in tuto_test_SCIM_06 by copy/paste tuto_test_SCIM_01 (or by loading it with the GUI).
The following parameters are modified for asynchronous intersective PWM operation:

Input.Simu.type_gensupply = 1;
Input.Simu.type_skin_effect = 1;
Input.Simu.param_PWM{1} =[0 Inf 1 1500];

The skin effect is activated in the equivalent circuit.
The last parameter means that we apply a 1.5 kHz symmetrical switching frequency independently of the speed.

In the GUI, the PWM is defined in the Workflow/Simulation group :

160. PWM simulation setup with the GUI
PWM simulation setup with the GUI

type_gensupply = 1 correspond to an analytical PWM method. You first need to set the Input to "Voltage (waveform)" then PWM method to "Analytical PWM". For param_PWM, the first 2 parameters (0 Inf) correspond to the starting and ending supply frequency and are not available in the GUI (set to 0 and Inf by default). The third one (1) set type_PWM to Asynchronous and the last one is the switching frequency. Finally, type_skin_effect is in Electrical/assumption and must be set to "Analytical".

Result Interpretation

The voltage spectrum is no longer sinusoidal (plot_voltage_fft)

Voltage Spectrum
Voltage Spectrum

Large sidebands around twice the switching frequency appear.

These harmonics are not as high in the current spectrum due to the effect of inductances. The current waveforms can be plotted with plot_currents

Current waveform
Current waveform

The SWL spectrum is now given by plot_VS_ASWL_modal_cont

Modal contribution
Modal contribution

One can notice that some new acoustic lines have appeared near 1.5, 3, 4.5 and 6 kHz (multiples of the switching frequency). The SWL value of the slotting line near 660 Hz is unchanged compared to the sinusoidal case as it is linked to the fundamental voltage / current. The new lines have necessarily 0 and 2p=6 circumferential wavenumbers, they come from PWM operation.

Note that in this mode, the spectrogram obtained with load extrapolation cannot be generated as the evolution of the force harmonics magnitude with speed depends on the modulation index. One should therefore define a variable speed project with Input.Simu.type_varspeed = 2;

If spectral leakage is too important, choose a fundamental frequency that is a divider of the switching frequency.

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