# Fixed-speed partial-load sinusoidal voltage-driven vibroacoustic simulation

In this new project tuto_SPMSM_04 the voltage is imposed instead of the current. This means the equivalent electrical circuit must be calculated in MANATEE. The variable speed mode based on spectrogram synthesis is still activated but this means a constant excitation current is applied during the run-up.

By default all the electrical circuit parameters (resistances, inductances, iron losses etc) are calculated analytically. One important parameter is how to calculate the back emf of the machine. Here the calculation is carried using fast subdomain models using

`Input.Simu.type_comp_PhiPM = 4;`

The result of the back emf and flux linkage calculation is displayed in the command line text output:

PM RMS fundamental flux linkage: 0.091452 Wb
PM RMS fundamental back emf (phase to neutral): 28.7306 V
PM RMS fundamental back emf (line to line): 49.7629 V

The value of the fundamental flux linkage can also be accessed in the usual output structure of MANATEE with

`Output.Magnetics.PhiPM0`

The fundamental RMS back electromotive force (phase to neutral) is in

`Output.Magnetics.EPM0`

The waveforms of flux linkage and back emf can be displayed with plot_bemf:

Back emf

The fundamental phase to neutral voltage and voltage angle is imposed in this project as

```Input.Simu.U0 = 45.7304/sqrt(2); Input.Simu.Phi0 = 2*pi/3;```

The voltage angle Phi0 is chosen to obtain a current vector that is close from q-axis. The phasor diagram can be plot using plot_phasor_PMSM command line. The Id and Iq current waveforms can also be obtained using plot_currentscommand line:

Current magnitude
Id and Iq current waveforms

Usual electromagnetic and vibroacoustic post processings presented at the beginning of the tutorial can be applied.

In particular the fixed-speed sound power level spectrum due to magnetic forces is given by plot_ASWL_modal_cont:

Modal contribution to A-weighted SWL

Based on spectrogram synthesis technique which here assumes that the armature excitation is independent of speed, one can also calculate the variable-speed acoustic noise spectrogram using plot_VS_ASPL_sonagram

A-weighted sound pressure level sonagram at 1 m