Practical Wide Frequency Approach for Calculating Eddy Current Losses in Transformer Windings

A practical method for calculating eddy current losses in transformer windings is reported. The method improves the classical loss presentation by introducing a loss coefficient, called eddy current factor kc. In this paper, eddy current losses in round conductors are discussed. A graphical approximation of kc as a function of wire diameter, frequency, layer number, copper packing factors in the direction parallel and perpendicular to the layer is provided. The graphs are obtained by analytical expressions compared with FEM simulations. To unify the approach for different cases, a reference diameter, apparent and equivalent frequency are defined. A few short examples for applying the method in transformer design are given. The method is applicable for a variety of transformers with different frequencies, wire diameters and conductor fittings. The proposed method is verified by designing several transformers. As an example, a 2.5 kW transformer is fully described. The experiments show good matching with the calculations.