Influence of AC Transport Current Balance on AC Loss in a Two Layered Polygonal YBCO Assembled Conductor

In high temperature superconducting (HTS) AC applications, HTS tapes are assembled into high current capacity conductors. We previously reported our experimental results showing the AC loss reduction in a polygonal arranged single layer YBCO assembled conductor. The AC loss reduction is greatest in round shape arrangements. To get more detailed information, we investigated the influence of AC transport current balance on AC loss characteristics in a two layered hexagonal YBCO assembled conductor. We transported different AC currents in the outer and inner layers of YBCO tapes using two power sources, and the currents were in-phase with each other. The results show the effects of the balance of the transport currents on the AC loss characteristics. The minimum AC loss in the two layered YBCO assembled conductor occurs when the transport current in the inner layer is greater than the outer layer.