Effect of Size and Position of Pinholes on Transformer Core Loss

Abstract

This paper presents the investigation of the variation of core loss due to the effect of pin holes in the transformer core which are used to stack the core sheets in a step lap pattern. A three-phase distribution transformer with a rating of 160 kVA, 11 kV/ 415 V has been selected for the investigation. The transformer model was developed using SolidWorks software and examined for the no-load loss using finite element analysis software ANSYS Maxwell. Simulation results were obtained for different pin hole sizes and positions. The flux variations in the core, with and without pin holes are analyzed. Based on the core loss, the optimum pin hole diameter and positions are determined. Analysis shows that the hysteresis loss is not significantly affected by the pin holes while the eddy current loss has an effect from pin hole diameters. Analyzing the results, the optimum pin hole diameter is determined as 6 mm corresponding to an increased loss of under 1% of the loss. Results further show that placing the pin holes where the flux distribution is a minimum, reduces the core loss. The results of the analysis are planned to be implemented in an actual distribution transformer.