A new approach for AC loss reduction in HTS transformer using auxiliary windings, casestudy: 25 kA HTS current injection transformer

Abstract

AC loss is one of the important parameters in HTS (high temperature superconducting)AC devices. Among the HTS AC power devices, the transformer is an essential partin the electrical power system. The AC losses in an HTS tape depend on themagnetic field. One of the techniques usually adopted to mitigate the unwantedmagnetic field is using a system of coils that produce a magnetic field oppositeto the incident one, reducing the total magnetic field. In this paper adding twoauxiliary windings to the HTS transformer to produce this opposite magneticfield is proposed. The proper use of these auxiliary windings could reduce theleakage flux and, therefore, the AC loss. A mathematical model is used to describethe behaviour of a transformer operating with auxiliary windings, based on thetheory of electromagnetic coupled circuits. The influence of the auxiliary windingson the leakage field is studied by the finite element method (FEM) and the ACloss of an HTS transformer was calculated. Also, the simulation results showthat employing auxiliary windings will improve the HTS transformer efficiency.