Result

The flux density distribution is the main output of the electromagnetic model of MANATEE software as it is used to calculate the Maxwell stress tensor responsible for electromagnetically-excited audible noise.

This particular post processing plots the radial airgap flux as a function of airgap angle, including the corresponding Fourier analysis:

Airgap radial flux density as a function of space

plot_Br_space

The largest harmonic should correspond to the number of pole pair (displayed in red).

In this example of an induction machines with Zs=36 stator slots and Zr=28 rotor slots and p=3 pole pairs, one can see significant slotting harmonics at Zs-p=33 and Zs+p=39 due to stator slots and stator stepped magnetomotive force. The rotor slotting effect at Zr-p=25 and Zr+p=31 is smaller due to the fact that rotor slot openings are much smaller compared to stator slot openings.

Note that this 1D FFT graph gives only a partial view of the harmonics, as both space and time frequencies are involved in noise and vibration generation. A 2D Fourier transform of the flux is available with plot_Br_cfft2.

To change the default plot options you can read How to change post processing plot options ? article.

This graph help identifying the space harmonics involved in flux density which may affect the noise and vibration behaviour of the electrical machine.