Influence of Transport Mode on AC Loss Characteristics of a Bi-2223 Tape in a Multi-Tape Conductor

The high-temperature superconductor (HTS) with large current capacity has been developed for power applications such as power transmission cables and fault current limiters. Especially, in these power applications, AC loss is very important in an economic point of view but this issue has not been completely elucidated due to its many complexities. In this work, two HTS conductors with very different critical current densities, which consist of several Bi-2223 tapes placed on a cylindrical former, were fabricated in an attempt to arrive at a clear understanding of their AC loss characteristics. AC loss characteristics for such two cylindrical multi-tape conductors have been experimentally investigated. Moreover, the influence of current transport mode on the AC loss of the Bi-2223 tape in the conductors was investigated. DC voltage-current characteristics of the Bi-2223 tapes were also measured for discussions on the measured AC losses. The results show that for the conductor with high critical current density, the measured AC loss strongly depends on the transport mode as in the conductor with low critical current density. However, the transport mode dependence of the conductor with high critical current density becomes weaker and weaker as transport current increases. In the simultaneous mode, the measured AC loss of the conductor with low critical current density is in good agreement with the calculated loss from the monoblock model. However, the measured loss of the conductor with high critical current density does not coincide with both the numerically calculated loss and loss calculated from the monoblock mode.