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Experimental Extraction of Winding Resistance in Litz-Wire Transformers - Influence of Winding Mutual Resistance

par Niyomsatian, Korawich ;Gyselinck, Johan ;Sabariego, Ruth
Référence IEEE transactions on power electronics, 34, 7, page (6736-6746), 8493262
Publication Publié, 2019-07-01

Article révisé par les pairs

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Résumé :

The extraction of winding resistance from impedance measurements needs a compensation of undesirable effects, e.g., core loss and distributed winding capacitance. This paper rigorously shows that the core loss (or core-loss resistance) measured with the two-winding method always includes the effect of the winding mutual resistance. At high frequencies, this effect becomes more prominent and can cause an overestimation of the measured core-loss resistance. As a result, the compensated winding resistances can be significantly underestimated. To mitigate this effect, this paper proposes to measure the core-loss resistance on an auxiliary 1:1 transformer with single-turn windings. Consequently, it is scaled to obtain the actual core loss. The proposed analysis and method is applicable to multiwinding systems. For validation, this paper considers a gapped transformer with litz-wire winding for high-frequency operations. The experimental results are validated against the results from its three-dimensional finite-element (FE) model. The litz-wire winding is considered in the FE model by means of a homogenization approach. With the method proposed in this paper, the experimentally extracted winding resistances become more accurate and are in good agreement with the FE results.