AC Loss Distribution in Two-Layer HTS Cable

We measured the influence of the twist pitch, twist direction, and transport current balance of the inner and outer layers on the ac loss characteristics in a two-layer twisted high temperature superconducting (HTS) cable. To measure the ac loss in each layer, we placed the thermo-couples on each tape face with thermal insulation. In the HTS cable, the inner layer is exposed to a longitudinal magnetic field generated by the twisted outer layer, and the outer layer is exposed to a circumferential direction magnetic field generated by the inner layer. When the inner and outer layers connect in series, the ac loss characteristics in the inner layer exhibit the influence of the outer layer arrangement. When the transport current balance of the inner and outer layer changes, the lowest loss condition exists when the inner transport current exceeds the outer transport current. These phenomena are possible explanations for the amplitude and direction of the magnetic field in each layer.