Study on the Influence of HTS Strip and Harmonics on AC Loss of HTS Transformer

The coil of the high-temperature superconducting (HTS) transformer is made of superconducting material, which has the characteristics of being lightweight, low loss, and having a low burning risk. However, when a superconductor operates or transmits alternating currents in an alternating magnetic field, the changing magnetic field will generate an inductive electric field, which will cause the AC loss of superconductors. On the one hand, the overall efficiency of the HTS transformer will be reduced, and on the other hand, the temperature of the HTS strip will increase, which will affect its critical current. When it is serious, it leads to the quench of the winding, accelerates the aging of the insulation layer, limits the overload capacity of the transformer, and even damages the entire transformer. In this paper, the influence of AC loss on HTS transformer winding is analyzed from two aspects of HTS strip and high-order harmonics. Based on the two-dimensional (2D) axisymmetrical coordinate finite element calculation model, the electromagnetic calculation and AC loss characteristic analysis of the 20 kVA superconducting traction transformer is carried out on the finite element simulation analysis software. Different HTS strips are adopted, and corresponding high-order harmonic currents are set. The influence of the HTS strip and high order harmonics on AC loss of the HTS transformer is obtained.