Litz-Wire Winding Loss Calculation Method for Optimal Design of High-Frequency Transformers

The optimal design of high-frequency transformers requires not only an accurate and efficient description of the litz-wire winding but also the precise characterization of the winding electromagnetic field properties that vary with the transformer structure. However, most of the existing methods focus only on the twisting structure of the litz wire itself, neglecting the characterization of the magnetic field variation over the entire winding region in the optimization process. In this paper, a loss calculation method for litz-wire winding that balances accuracy and efficiency is presented, which describes an equivalent process of litz-wire winding. The complicated magnetic fields around the litz-wire winding, which vary with the winding arrangement, are accurately extracted by introducing a meshing process in the method of image. The extracted magnetic fields are analyzed based on the proposed expressions to carry out the description of the litz-wire twisting structure. Finally, the AC resistance evaluation results of the proposed method achieve a good agreement with the measurement values of different inductors and transformers. Due to the accuracy and efficiency of the proposed approach, it is suitable for the optimal design of high-frequency transformers.