Calculating stray losses in power transformers using surface impedance with finite elements

The authors describe the results obtained from a rarely published method of calculating eddy losses in thick conducting materials. The surface impedance formulation is used in a finite element software package which is applied in turn to the design of large power transformers. The transformer and model details are discussed, as are the excellent results obtained by employing these techniques. The authors then discuss the further application of these methods and their implications for transformer design. The transformer tank wall and fittings can be modeled accurately with surface elements, removing the need for complex layers of brick elements to account for skin effects, and this in turn reduces the complexity and size of the models. This method thus yields the advantages of reduced complexity, which is especially important in the analysis of very large devices such as three-phase transformers