Improved Finite Element Method of Winding Loss and Leakage Inductance for Planar Transformer Used in LLC Converter

The finite element method is often used to accurately calculate the performance parameters such as winding loss and leakage inductance of planar transformers. However, due to high storing and calculating costs, in the case of a tight design cycle, the number of design schemes that can be accurately calculated is limited, which increases the risk of selecting the local optimum point as the final design scheme. Therefore, the process of constructing and solving linear equations that occupy many resources is improved. Firstly, by analyzing the magnetic field intensity distribution of the planar transformer, according to the strength of the edge effect, the solution region of the planar transformer is divided into the strong edge effect region and the weak edge effect region. Secondly, a one-dimensional linear element that is more suitable for the weak edge effect region is introduced to reduce the number of nodes and elements necessary to describe the solution region’s field, saving computing and storing resources. Thirdly, by restricting the distribution of adjacent element nodes, the problems of element compatibility and coefficient matrix construction caused by the introduction of one-dimensional linear elements are solved. Finally, planar transformer models are built. The winding loss and leakage inductance of calculated and experimental values, as well as the calculating and storing costs of the proposed method and the finite element method, are compared, which verifies the proposed method. © 2022 Chinese Machine Press. All rights reserved.