A core loss model for laminated transformers

The exciting current and core loss properties of stacked EI transformer structures depend on the distribution of flux in each lamination. Although flux is uniformly distributed in a butt Joint stack, there is a nonuniform distribution of flux in a 1 × 1 stack. The analysis of flux distribution presented here is based on Ampere's law together with conservation of magnetic flux, and is not applicable if any portion of the core material saturates. The derived expressions for flux are combined with a simple expression for Epstein sample loss data to obtain models for transformer core loss and exciting ampere-turns which are useful for computer aided design and analysis. These models include the major effects of flux density, frequency, lamination geometry, and material properties. Comparisons of corresponding calculated and measured results indicate the reasonableness of the models.