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FEM EquationMagnetodynamic2D

From FreeCAD Documentation

FEM EquationMagnetodynamic2D

Menu location
Solve → Electromagnetic Equations → Magnetodynamic 2D Equation
Workbenches
FEM
Default shortcut
None
Introduced in version
0.21
See also
Magnetodynamic equation

Description

This equation performs analyses using a 2D version of the Maxwell's equations when the unknown is the z-component (or φ-component).

For information about the math of the equation, see the Elmer models manual, section Computation of Magnetic Fields in 2D.

For more general analyses in 3D using Maxwell's equations, FreeCAD supports Elmer's Magnetodynamic equation. Nevertheless, if it is possible to perform the analysis in 2D, this is recommended since the math behind this is then simpler and the calculation time is therefore faster.

Usage

  1. Add an Elmer solver.
  2. Select it in the Tree View.
  3. There are several ways to invoke the command:
    • Press the Magnetodynamic 2D Equation button.
    • Select the Solve → Electromagnetic Equations → Magnetodynamic 2D Equation option from the menu.
  4. Change the equation's solver settings or the general solver settings if necessary.

Solver Settings

For the general solver settings, see the Elmer solver settings.

The magnetodynamic 2D equation provides these special settings:

  • DataAngular Frequency: The harmonic actuation frequency. It is only used if DataIs Harmonic is set to true.
  • DataCalculate Current Density: Calculates the current density.
  • DataCalculate Electric Field: Calculates the Electric vector field.
  • DataCalculate Elemental Fields: Calculates the electromagnetic fields for every mesh element. This is useful to see discontinuities in meshes.
    Note: at the moment, FreeCAD cannot display these results properly. Therefore, it is at the moment of no practical use.
  • DataCalculate Harmonic Loss: Calculates the linear and quadratic harmonic power loss. See the Elmer models manual, section Loss Estimation Using the Fourier Series for details
  • DataCalculate Joule Heating: Calculates the Joule heating.
  • DataCalculate Magnetic Strength: Calculates the Magnetic field strength.
  • DataCalculate Maxwell Stress: Calculates the Maxwell stress tensor field.
  • DataCalculate Nodal Fields: Calculates the fields for every mesh node. The default is true. If no other DataCalculate * is set to true, it only calculates the magnetic flux density.
  • DataCalculate Nodal Forces: Calculates the forces for every mesh node. The results can be used for further mechanical analysis.
  • DataCalculate Nodal Heating: Calculates the Joule heating scalar field for every mesh node.
  • DataIs Harmonic: If the driving force is harmonically actuated (AC current). If set to true, DataAngular Frequency must have a value > 0.

Analysis Feature Information

The magnetodynamic 2D equation takes the following analysis features into account if they are set:

Results

The available results depend on the solver settings. If none of the DataCalculate * settings were set to true, only the electric potential (called av in the results) is calculated. Otherwise, the corresponding results will also be available.

The possible results are:

  • Current density in A/m2
  • Electric field vector values in V/m
  • Harmonic power loss in W
  • Magnetic flux density in T
  • Maxwell stress tensor values in As/m3
  • Magnetic field strength in A/m
  • Nodal force in N
  • Joule heating in J
  • Potential in V

Notes

  • Despite the name, the Magnetodynamic equation can be used to perform magnetostatic analyses.
  • To properly use this equation, it's also necessary to have the surface model contained strictly on the XY plane and to choose a proper 2D coordinate system for the Elmer solver (typically Cartesian 2D).