Iron Loss Separation And Magnetic Characteristics Of Power Transformers

The power transformer is one of the most vital equipment in power system,whose iron loss is a crucial part of the power loss.But for a long time it is difficult to be modeled and calculated because of the complicated electromagnetic characteristics.An iron loss model proposed by Bertotti in 1988,which is summarized through the experimental data,divides the iron loss into three components—hysteresis,eddy current and abnormal loss.The coefficients of this model is obtained by fitting the measured data.Based on this model,several different kinds of traditional iron loss separation algorithms are studied in this paper and an improvement is presented for the calculation method.The iron loss for transformers under different working conditions can be analyzed by this new developed model with a higher computational accuracy.The main work is as follows:1.Research about silicon steels of transformers under normal working condition is conducted.A loss and magnetic characteristic measurement system is established with an Epstein frame to test different types of oriented silicon steels.The waveform of the excitation is sinusoidal.Loss separation methods are compared based on Bertotti’s model and an improved calculation procedure is presented.The hysteresis loss is measured by the static-hysteresis test system and the data shows the presented method is more accurate than the traditional ones.2.Based on the analysis conducted under sinusoidal excitations,the iron losses under excitations with harmonics are studied.The loss components can be calculated from the loss data under sinusoidal excitations,based on the hysteresis loss characteristics.Besides,the computed results for a wide range of silicon steels are compared with the experiment data,which demonstrates the efficiency and applicability of this method for the loss separation under the excitation with higher harmonics.3.Transformer model with product level—the laminated cores are tested with multiple groups of experiments.The piecewise fitting procedure of the loss separation under different excitation conditions is shown with examples.Besides,the variation rules of the hysteresis,eddy current and abnormal losses with the excitation are summarized.Finally,the calculated value of the coefficients and advised fitting data range for this model are given for common silicon steels in this paper,which is the reference for loss prediction for other types of steels,and can also provide a reliable data support for the refined iron loss calculation in transformer designation and manufacturing.