Abstract:In order to look into the influence on the operation performance of a power transformer caused by the direct current (DC) bias, an improved electric and magnetic circuit coupled model is used. The eddy current effects of the core material are taken into consideration. The characteristics of exciting currents, leakage magnetic flux, secondary-side induced voltage, and the level of DC flux in limb are investigated for transformers with different core types and coil connections. The definition of transformer DC bias ratio is presented in the paper, with the aim of assessing the DC bias endurance in an unifed condition. The results indicate that the increasement of the DC bias ratio lead to distortion of the exciting currents waveform, increased harmonic currents and leakage magnetic flux from the coil. Meanwhile, the secondary-side induced voltage remains the same as in normal condition. In all transformer products, the three-phase three-limb transformer has the lowest level of sensitivity to the DC bias, but the single-phase three-limb tranformer bank with YN, yn connected coils has the highest level. The existence of the delta-connected coil has a positive meaning on improving the transformer endurance to the DC bias.
李泓志, 崔 翔, 刘东升, 卢铁兵, 程志光. 直流偏磁对三相电力变压器的影响[J]. 电工技术学报, 2010, 25(5): 88-97.
Li Hongzhi, Cui Xiang, Liu Dongsheng, Lu Tiebing, Cheng Zhiguang. Influence on Three-Phase Power Transformer by DC Bias Excitation. Transactions of China Electrotechnical Society, 2010, 25(5): 88-97.
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