The active part of the transformer is created by mutual connecting of core and low voltage and medium voltage windings, see Fig. 1.

Fig. 1 The active part from the LV side of transformer

Fig. 2 The active part from the lateral side

Fig. 3 The active part from the MV side and bringing out the taping leads

Source: MRAJCA, Miroslav. Design of Oil Distribution Transformer. Brno, 2021. Also available from: Semestral thesis. Brno University of Technology, Faculty of Electrical Engineering and Communication Technologies, Department of Power Electrical Engineering and Electronics. Thesis supervisor Čestmír Ondrůšek.