Rational approach for self-limiting current injection transformers confirmed by coupled electromagnetic-thermal FEM simulation

Current injection transformer (CIT) systems are within the major group of the standard-type test of high current components in the electrical industry. The present precious approach contemplates an arrangement for a rational design of a self-current limiting transformer (SLT) being integrated by a single unit 25 kA CIT system for fast overcurrent detection in stipulated current tests. This paper describes mathematical formulations based on an electric models and the dominant effects of an auxiliary winding on the rate of the self-limiting process of the system. This requires the evaluation of multiphysical (i.e. coupling of the electromagnetic and thermal parts) finite element modelling and simulations for three different approaches to suit the designer's choice. An overcurrent causes a considerable distortion of axial leakage flux, which in turn produces high radial forces. The transient analysis of the leakage flux densities and the corresponding electromagnetic forces on windings of the CIT and proposed SLT are the other objects of this paper. Moreover, the distribution of the flux density and the corresponding localized losses within the SLT core are further objects of this paper. However, this paper will mark another important event in superconductor technology and augment efficiency and compactness from which a lower overall cost of the CIT system could be attainable.