Novel Analytical Formulas for Eddy-Current Losses in Semicircle-Section Wound Core of Transformer

摘要

The exploration for estimation of eddy-current losses is of great significance to optimize the design of the transformer. This paper provides a more accurate formula to calculate the eddy-current losses in rectangle section of electrical steel by solving Maxwell's equations rigorously, where the 3-D electromagnetic fields problem can be simplified to the 2-D problem because of the grain-oriented nature of steel sheet. Then an analytical model based on the single-layer trapezium steel sheet is established to validate the formula effectiveness through comparing with 3-D finite-element simulation, and the result shows a good approximation when the slope of trapezium steel is small enough. As for practical transformer core made up of multi-layers trapezium steel sheet, the various parameters of dimension in different layers are determined by geometrical analysis and the formula for power dissipation in wound core is proposed. Finally, the formula describing the eddy-current losses of wound core with the feature of semicircle section is obtained and compared with the experimental values after relevant parameter optimization about a nonlinear ferromagnetic material in the calculation, where the proposed methods are demonstrated to be applicable for engineering.