Transport current properties of double-pancake coils wound by Ag-sheathed Bi-2223 tapes

In order to apply high T-c superconducting (HTS) tape to the power apparatu s, it is necessary to evaluate the property of coil shape. In particular, t he stability of coil is important, because it is expected to influence both the machine design and the operating conditions. In order to study the fea sibility of HTS power application, we used double-pancake coils wound by Ag -sheathed Bi-2223 multi-filament tapes, and measured the transport current properties. From the experimental and analytical results, it was noted that the HTS double-pancake coils exhibited very stable properties, even beyond the critical current of coils. We believe that we can show the possibility of application of the HTS tape to the winding of power apparatus although further improvements in superconducting properties of the tapes are needed. The stabilities of HTS and LTS (low T-c superconductor) are quite differen t, so it is also necessary to establish an analytical method for determinin g the stability of HTS winding.