Calculation of the circulating current and short- circuit impedance of a 3000kVA HTS transformer with split types of windings

A conceptual design of a 3000 kVA high-temperature superconducting (HTS) transformer with split types of windings for locomotives is developed in this paper. The primary winding of it has four coils which are arranged on two core limbs respectively and connected in parallel, so the branch currents are probably not equal to each other. In this paper, on the basis of the 3-D magnetic field analysis by finite element method (FEM), an inductance matrix (IM) for multi-branch of the primary winding and one of the secondary split windings is first calculated, and then the circulating current among the primary branches is determined by circuit theory. Finally, the short-circuit impedance between the primary winding and one of the secondary split windings is obtained.