Semi-Empirical Model for Precise Analysis of Copper Losses in High-Frequency Transformers

Accurately estimating the copper losses is essential for the elaborate design of high-frequency (HF) transformers used in high-power isolated dc-dc converters. Higher is the frequency of the transformer, more significant is the edge effect of the windings, which makes the classic analytical methods for the calculation of copper losses inaccurate. In this paper, for the accurate evaluation of HF copper losses in layered windings, we gather intensive 2-D finite-element method (FEM) simulations into a base formula by means of a multivariable regression process to establish a novel semiempirical formula with five determinant geometrical parameters. The selected variation range for each of these parameters ensures that the formula is suitable for the majority of practical applications. Two HF transformer test models with core-type and shell-type structures are built, and “double 2-D”FEM simulation and measurement are carried out to verify the proposed formula. We also investigate the impact of the porosity factor and the interleaving winding configuration on the overall copper losses.