Evaluation of eddy losses due to high current leads in transformers

An analytical method to calculate eddy loss in a two-dimensional problem is presented. The problem geometry consists of a current carrying conductor of infinite length parallel to a conducting plate of infinite length and width but of finite thickness. The solution method first transforms the original current distribution into sinusoidal current sheets. It is therefore quite general and can be used for different current distributions such as single-phase and three-phase current, different shapes of conductors such as line current, rectangular conductor etc., and different problem geometries such as conducting plate shielded by electromagnetic screen. As an example, eddy loss is evaluated for the case when a line current passes parallel to a conducting plate. A laboratory experiment conducted to verify the theoretical results is also presented. Experimental results are also compared with the loss calculated by two-dimensional (finite-element) analysis. As a particular case of the application of FEM analysis to a practical problem, a 3-D FEM analysis of 40 MVA furnace transformer LV-lead termination is presented. The analysis confirmed the hot-spot locations observed during the testing of the furnace transformer.