Practical method to determine additional load losses due to harmonic currents in transformers with wire and foil windings

A method is presented to determine the additional load losses in transformers caused by harmonic currents. Several blackbox short circuit tests at different harmonic frequencies have to be conducted on existing transformers or have to be simulated in the design stage. A 'K-factor'-related formula allowing for the estimation of the total augmented losses in the transformers is derived. This approach is also valid for transformers containing windings of the foil type. It is shown by means of measurements and simulations that the rise of the losses does not follow a squared dependency as it is the case with traditional wire winding transformers. An alternative K-factor definition to be used with these transformers seems to be necessary and is provided here.