Experimental Characterization of Interlamination Shorts in Transformer Cores

Burr-induced interlamination shorts in magnetic circuits increase eddy current loss. In large transformer cores, the short-circuit currents can become so high as to even damage the core. This paper presents contributions to modeling an individual short circuit between two transformer sheets. The aim of the model is to predict the additional eddy current loss caused, depending on the excitation conditions, the placement of the contact points, and the contact resistances. Measurements have been conducted on artificial short circuits between single pairs of transformer sheets. Findings prove that the interlaminar short can be modeled with good approximation by a resistive equivalent circuit, even when the core is saturated. The influence of different parameters on the elements of the equivalent circuit is discussed.