Litz Wire Losses with Custom Twisting

This MATLAB tool extracts the losses of a litz wire winding with custom twisting. A 2.5D method is used to simulate the impact of the twisting imperfection on the losses.

The code is a simplified version of the method used in the following paper:

• T. Guillod, J. Huber, F. Krismer, and J. W. Kolar
• Litz wire losses: Effects of twisting imperfections
• IEEE COMPEL 2017, Stanford, CA, USA
• https://doi.org/10.1109/COMPEL.2017.8013327

The following method is used to compute the losses:

• the geometry of the wire is given (coordinates of the strands)
• the twisting is defined with a permutation matrix (twisting of the strands)
• the DC inductance and DC resistance matrices are extracted (analytical solution)
• the permutation matrix is applied to the impedance matrix (twisting of the strands)
• the current sharing problem between the strands is solved (parallel connected strands)
• the magnetic field is computed for the different strands (internal and external field)
• the losses of the different strands is computed (analytical solution with Bessel functions)

The following approximations are made:

• The DC inductance and DC resistance matrices are used (and not the AC matrices)
• The current and field distribution inside the strands is assumed to be constant

Examples

The following examples are included:

• run_straight.m - Simulation of a Litz wire with untwisted strands
• run_twisted.m - Simulation of a Litz wire with fully twisted strands
• run_random.m - Simulation of a Litz wire with random twisting

Gallery

Compatibility

The tool is tested with the following MATLAB setup:

• Tested with MATLAB R2018b / 2019a / 2024b
• No toolboxes are required.
• Compatibility with GNU Octave not tested but probably easy to achieve.

References

References for the litz wire losses:

• Guillod, T. / Litz Wire Losses: Effects of Twisting Imperfections / 2017
• Muehlethaler, J. / Modeling and Multi-Objective Optimization of Inductive Power Components / 2012
• Ferreira, J. / Electromagnetic Modelling of Power Electronic Converters / 1989

Author

• Thomas Guillod, ETH Zurich, Dartmouth College - GitHub Profile

License

• This project is licensed under the BSD License, see LICENSE.md.
• This project is copyrighted by: (c) 2016-2020, ETH Zurich, Power Electronic Systems Laboratory, T. Guillod.
• This project is copyrighted by: (c) 2025-2025, Dartmouth College, Thayer School of Engineering, T. Guillod.