Rational approach for self-limiting current injection transformers confirmed by coupledelectromagnetic–thermal FEM simulation

Abstract

Current injection transformer (CIT) systems are within the major group of thestandard-type test of high current components in the electrical industry. The presentprecious approach contemplates an arrangement for a rational design of a self-currentlimiting transformer (SLT) being integrated by a single unit 25 kA CIT system for fastovercurrent detection in stipulated current tests. This paper describes mathematicalformulations based on an electric models and the dominant effects of an auxiliary windingon the rate of the self-limiting process of the system. This requires the evaluation ofmultiphysical (i.e. coupling of the electromagnetic and thermal parts) finite elementmodelling and simulations for three different approaches to suit the designer’s choice.An overcurrent causes a considerable distortion of axial leakage flux, which in turnproduces high radial forces. The transient analysis of the leakage flux densities and thecorresponding electromagnetic forces on windings of the CIT and proposed SLT are theother objects of this paper. Moreover, the distribution of the flux density and thecorresponding localized losses within the SLT core are further objects of this paper.However, this paper will mark another important event in superconductor technology andaugment efficiency and compactness from which a lower overall cost of the CIT systemcould be attainable.