Stray Losses in Power Transformers: A Comparative Study of Modeling Frameworks for Mild Steel

Abstract

Accurately predicting eddy-current and hysteresis losses in mild steel components such as the structural parts and tank of power transformers remains a challenge in transformer design. Conventional numerical approaches for eddy-current loss analysis require discretization at a fraction of the skin depth. While accurate, such fine volumetric mesh becomes computationally prohibitive for large power transformers. Moreover, hysteresis loss is not always included in this analysis. To investigate the trade-off between computational cost and accuracy, this work presents a comparative analysis of eight distinct modeling frameworks for predicting both eddy-current and hysteresis losses in mild steel. These include efficient methods avoiding meshing, such as standard impedance boundary conditions, and more accurate approaches retaining full volumetric meshing, namely complex permeability, nonlinear single-valued B-H curve, and Jiles-Atherton hysteresis modeling. To accurately represent the material's electromagnetic behavior, the properties of the mild steel used are measured directly from samples. Finally, loss measurements are conducted to benchmark all eight frameworks, demonstrating mean absolute percentage errors between predictions and measurements generally below 20%.