Structure of Transfer Function of Transformers with Special Reference to Interleaved Windings

Transfer function (TF) is computed during impulse tests on transformers. The structure and shape of TF depends on the type of winding, viz., disc, layer-type, or interleaved winding. There are certain features specific to TF of an interleaved winding, which have, over the years, been attributed to its increased series capacitance. However, reasons for why an increase in series capacitance should introduce such differences, the presence of only a few (lower frequency) poles in interleaved windings, etc., is as yet unknown. By analytically solving the equivalent circuit model, mathematical explanations are deduced. It is demonstrated, for the first time, how pole-zero cancellation and winding resistance are both instrumental in determining the structure of TF of interleaved windings.