Result interpretation : Text Output

In this part the text outputs of MANATEE are reviewed before using the post processing commands.

The overall text output should look like this:

MANATEE Simulation text output
MANATEE Simulation text output

If one wants to remove all the text outputs in the command line, the parameters Input.Simu.is_com must be set at 0.

Some warnings may appear, one should carefully read them and check that they do not represent an issue.

In the following text output one can find the theoretical vibroacoustic study:

Theoretical vibroacoustic study
Theoretical vibroacoustic study

This table sweeps the slot/pole interactions force harmonics at no-load and identifies potential harmful force harmonics. These harmonics represent both radial and tangential force harmonics.

  • The wavenumber r is the "spatial frequency" of the magnetic force wave (half the number of nodes). For instance, the fundamental flux density has a wavenumber r=p (number of pole pairs).
  • The integers ks are the ranks of the stator slotting permeance harmonics (ranks of the Fourier transform of the airgap reluctance, ks=1 for the principal slotting harmonic, ks=0 for the average airgap permeance).
  • The integers hr are the ranks of the rotor magnetomotive force harmonics (ranks of the Fourier transform of the magnetization waveform along the airgap, hr=0 corresponds to the fundamental flux density created by the magnets).
  • The variable eps equals +/-1 in the wavenumber expression r for slotting harmonics (force harmonics resulting from the interaction between stator slots and magnet poles).
  • The variable k is the proportionality factor between the force harmonic frequency and the fundamental stator frequency.
  • The boolean resonance indicates if there is a resonance that should theoretically occur, based on the minimum and maximum speed specified, and based on the natural frequencies calculated by the structural model (in our case, a 2D analytical model).
  • freso indicates the supply frequency at which this resonance occurs.
  • Nreso indicates the speed at which this resonance occurs.

The lower are hr and ks, the higher are the reluctance harmonics magnitude and the higher are vibration and noise at resonance.

In this example, one can see that some resonances occur with the breathing-mode of the stator stack (r=0) at 36 times the electrical frequency due to slot/pole interactions. More especially the (2*17+1)p=35p and (2*18+1)=37p ranks of magnet field interact with the first stator slot harmonic to create a force wave at 36fs of wavenumber 0 - a pulsating magnetic force at 36 times the electrical frequency. The general expression of this force harmonic frequency is LCM(Zs,2p)fs where LCM stands for the Least Common Multiple. One can see that the smallest wavenumber is 4 which corresponds to the theoretical value of the Greatest Cemmon Divider between slot and pole numbers GCD(Zs,2p)=GCD(36,4)=4.

Note that this theoretical study does not include higher space harmonic effects, in particular the space harmonics present in the stator winding mmf.

The next text outputs sums up the main parameters of the machine:

Machine main characteristics
Machine main characteristics

The rotation direction of the main flux is determined based on the winding pattern. To reverse the rotation direction one can permute the phase in the simulation project using Input.Simu.perm_cur=[2,1,3].

In the following outputs one should check the slot fill factor and the weight calculation:

Slot fill factor and machine weight
Slot fill factor and machine weight

The mean turn length depends on the overhang end winding geometry. For random wound winding the effective length of the winding overhang is difficult to estimate, so a tuning factor can be introduced in Input.Geometry.Kwoh. If the slot fill factor is above 100% a wrong slot geometry or winding turn number or wire section might have been used.

Here one can check the discretization is high enough:

Discretization validation
Discretization validation

The vibration model outputs are then summarized:

Vibration model outputs
Vibration model outputs

The acoustic model outputs are summarized:

Acoustic model outputs
Acoustic model outputs

Note that the numerical accuracy of MANATEE acoustic noise calculation is below +/-0.3 dB.

Previous Next