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Litz Wire Losses with FEM and MATLAB

Thomas Guillod, ETH Zurich, Power Electronic Systems Laboratory

This MATLAB tool extracts the losses of a litz wire winding from the field patterns.
The losses are computed in the frequency domain with Bessel functions.
The field patterns can be extracted with any simulation software (e.g. COMSOL, ANSYS, OpenFOAM).
The tool be used to compute the losses of different components, e.g., inductors, transformers, and chokes.

The method features several advantages:
* A reduced computational cost, since the discrete strands are not modeled
* The mesh can be coarse, independent of the skin depth
* Method valid up to several megahertz
* The litz wire can feature an arbitrary shape

The following limitations exist:
* The impact of the eddy current on the magnetic field is neglected
* The litz wire is composed of round strands
* The litz wire is ideal (insulated and perfectly twisted strands)
* The litz wire is defined with a fill factor, the exact position of the strands is not considered

The following field patterns are required:
* Integral of the square of the current density over the winding (for skin losses)
* Integral of the square of the magnetic field over the winding (for proximity losses)

This tool is developed by the Power Electronic Systems Laboratory at ETH Zurich and is available under the BSD License. The code is also available on the ETH Data Archive.

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