Simulation of Proximity Effect in Transformer Due to Harmonic Loads

The AC loss in a transformer winding is mainly due to the sum of the I2R losses produced by the fundamental and harmonic components of the current, recognizing that for each component, R depends on the frequency of that component. For lower-order harmonics, the frequency dependence of the winding resistance is primarily due to the proximity effect, a phenomenon that occurs in coils because the magnetic field surrounding each conductor in a coil depends on the fields produced by other conductors. The proximity effect produces greater losses than those predicted by the skin effect, which is dominant at higher frequencies. The proximity effect therefore accounts for the largest contribution to winding eddy currents under harmonic load current. The proximity effect in transformers which can be the most severe under harmonic conditions are estimated to be proportional to the square of frequency. Finally, the model simulated in MATLAB/Simulink and the losses of 200KVA transformer is then evaluated and results are compared.