Abstract
The separation of core loss plays an important role in the transformer loss calculation. To obtain more accurate core loss, based on the comparison and analysis on two traditional loss separation methods, an improved loss separation method was proposed for the core loss calculation of the transformer in a wide magnetic flux density range. Firstly, through analysis the eddy current loss was obtained by direct calculation, while the hysteresis loss was obtained by performing the quasi-static magnetization process. And the coefficient corrections for the hysteresis loss and eddy current loss calculation were conducted by using the experimental data. The result comparison between the proposed method and traditional ones were made. Secondly, by setting up the Epstein frame platform, the total loss and static hysteresis loss of 14 types of industrial silicon steel were measured. In addition, the suggestive values and the corresponding value range of the loss coefficients of 14 kinds of industrial silicon steel were given. The results obtained by the proposed method were in good agreement with the measured data in the wide magnetic flux density range, while the suggestive values and the corresponding value range of 14 kinds of industrial silicon steel can provides an effective data support for the accurate core loss calculation.
Highlights
The excitation characteristics and no-load loss of a transformer are important indicators to evaluate its performance
According to the mechanism of the loss generated by ferromagnetic materials under the action of alternating magnetic field, the iron loss can be decomposed into three parts, named the hysteresis loss, the energy loss caused by the friction between the domains; eddy current loss, the joule loss caused by the induced current in ferromagnetic materials; abnormal loss respectively, caused by eddy currents in alternating leakage magnetic fields [9]
Where Ptot is the total core specific loss per unit mass, W/kg; Ph, Pe and Pex respectively represent the hysteresis loss per unit mass, eddy current loss per unit mass and abnormal loss per unit mass, W/kg; f is frequency, Hz; Bm is the amplitude of magnetic flux density, T; kh, ke, kex and are the coefficients related to the microstructure of ferromagnetic materials
Summary
The excitation characteristics and no-load loss of a transformer are important indicators to evaluate its performance. The methods for core loss calculation of different silicon steel types in a wide magnetic flux density range still remain problematic, which makes the calculation of the iron loss an important issue under study [4]. The direct application of the Bertotti model or other improved method to certain types of silicon steels during the loss separation, and it works well in the low magnetic flux density range. Due to the typical non-linear characteristics of the oriented silicon steel sheet, serious distortion emerges in the high magnetic flux density range (over 1.5 T) [14], resulting in a large calculation error of about 50%.
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