Decimation of some specified permeance / magnetomotive force / flux density harmonics

In this part, the harmonic decimation tool of MANATEE is going to be demonstrated. This feature is fully explained in the Howtos article "How to use the harmonic decimation tool". The idea is to cancel a given harmonic wave, defined by its electrical frequency f and its wavenumber r (f=fs and r=p for the fundamental flux wave), in order to check its effect on the acoustic noise and vibration.

The reference simulation is the no-load sinusoidal operation of the SCIM given by tuto_SCIM_01. The main resonance is due to the first slotting harmonic of order Zs-Zr-2p=2 at frequency fs(Zr/p+2).

This can be checked by removing the first harmonic of the permeance linked to stator slotting with the code (tuto_SCIM_25) :

Input.Simu.remove_harm_perm=[[36 NaN]];

In tuto_SCIM_25 all the permeance space harmonic of rank 36 (number of stator slots) are therefore removed. This can be checked with plot_Per_space

300. Permance as a function of space in reference case (left, 01) and without the first stator slot harmonic (right, 25)
Permance as a function of space in reference case (left, 01) and without the first stator slot harmonic (right, 25)

The effect on the noise level is given by plot_VS_ASPL_overall :

300. Overall acoustic noise at variable speed in reference case (left, 01) and without the first stator slot harmonic (right, 25)
Overall acoustic noise at variable speed in reference case (left, 01) and without the first stator slot harmonic (right, 25)

One can see that there is still a strong resonance, although noise level is reduced of 5 dB. This is because the stator to rotor slotting interactions can occur in two ways:

  • stator mmf fundamental x stator permeance harmonic x stator mmf fundamental x rotor permeance harmonic (-p+Zs-p-Zr =2)
  • stator mmf fundamental x stator to rotor permeance interaction harmonic x stator mmf fundamental x average permeance (-p+Zs-Zr-p+0=2)

The stator to rotor slot interaction permeance harmonic has a space order of Zs-Zr=8. To removed this additional space harmonic the code is (tuto_SCIM_26) :

Input.Simu.remove_harm_perm=[[36 NaN];[8 NaN]];
300. Overall acoustic noise at variable speed in reference case (left) and without the first stator slot harmonic and stator to rotor slot harmonic interactions (right)
Overall acoustic noise at variable speed in reference case (left) and without the first stator slot harmonic and stator to rotor slot harmonic interactions (right)

Now the resonance at 1200 rpm is completely cancelled. This harmonic removal tool can also be used at the flux density level.

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