June 2016 : FEMM automesh, Force wave visualization, 3th anniversary

MANATEE new features

MANATEE (Magnetic Acoustic Noise Analysis Tool for Electrical Engineering) software logo

We are currently working on the next major release MANATEE 1.06.01. We have added and validated the following features in this version :

  • time and space symmetries of the airgap flux distribution are automatically identified and used, further reducing calculation time of MANATEE
  • the effect of boundary conditions (clamped, simply supported, free) on the analytical computation of the lamination natural frequencies has been included and validated
  • possibility to include a DC current & voltage component
  • possibility to simulate locked rotor electromagnetic & vibroacoustic behaviour
  • possibility to plot the overall vibration level as a function of speed

We have also started to work on the simulation setup GUI, for a next release. More information about this new GUI will be provided in the following newsletter.

MANATEE coupling with FEMM

As you may know, MANATEE is fully coupled to the electromagnetic finite element freeware FEMM for non-linear magnetostatics. All the machines defined with MANATEE graphical user interface can therefore be exported to FEMM. The FEMM automated meshing process has now been optimized with some default values depending on the machine geometry. All the mesh parameters of the main electrical machine regions can also be user-defined (airgap, stator and rotor teeth, stator and rotor yoke, magnets, ventilation ducts etc) if necessary. All these parameters will be available in the GUI for the definition of the simulation.

Electrical machines automatically defined in FEMM by MANATEE
Electrical machines automatically defined in FEMM by MANATEE
Harmonic current injection

MANATEE now includes harmonic current injection in the DQ frame. In the following example, a resonance occurs at full-load on a PMSM due to the interaction between the lamination breathing mode natural frequency and the radial pulsating force at LCM(Zs,2p)fs/p=18fs (18 times the electrical frequency). The noise and vibration levels can be greatly reduced by an optimal current injection.

In a few minutes of calculation the optimal magnitude and phase of Id and Iq harmonic currents can be found. The following curves show the effect of the phase of Id and Iq harmonic currents (magnitude fixed to 0.5% of the fundamental current, frequency=18fs) on the overal acoustic noise levels and torque ripple. The Id harmonic current injection is the most effective reducing radial force ripple, with more than 11 dB of variation and nearly no influence on torque ripple. Iq harmonic current injection can also be used as an alternative in this case, but a compromise must be made between acoustic noise and torque ripple reduction.

Compromise between acoustic noise and torque ripple reduction
Compromise between acoustic noise and torque ripple reduction

Zoom on MANATEE feature

All MANATEE graphs can be plot in terms of "orders": frequencies can be plot as "electrical order", representing the multiplication coefficient between the frequency and the fundamental electrical frequency, or as "mechanical order", for the ratio with the rotational mechanical frequency ; wavenumbers can be plot as "space order", representing the multiplication coefficient between the wavenumber and the number of pole pairs. This options can be accessed in the Plot structure initialized in plot_init. As an example the following graph of radial force harmonics is obtained with the post processing plot_Fr_fft2:

Stator radial pressure FFT2 and natural frequencies
Stator radial pressure FFT2 and natural frequencies

By changing the plot options with Input.Plot.type_electrical_order=1;Input.Plot.is_spatial_order=1; and replotting the graph, one can see that the units have changed and zooming on the largest components one obtains :

plot_Fr_fft2 with electrical orders
plot_Fr_fft2 with electrical orders

This visualization allows to easily find the analytical expression of the force waves, in this case the largest forces have wavenumber r=2p at frequency f=2fs (twice the electrical frequency) and r=0 at frequency f=0. These two harmonic forces are called "fundamental forces" because they are present in any electrical machine, even in case of slotless lamination, ideal airgap winding and sinusoidal PM field: these forces are proportional to the square of the fundamental airgap flux density wave at wavenumber r=p and frequency f=fs.

EOMYS News

EOMYS has celebrated its third anniversary this month. It is the opportunity to thank all our customers worldwide for their trust on our simulation and experimental R&D activities, and EOMYS engineering team for its high-level technical work and innovation spirit. During the last years, EOMYS has reinforced its position as a key partner for the analysis of electromagnetically-excited noise and vibrations in electrical systems.

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