Optimum reduction of self field effects in a Bi-2223 stacked superconducting busbar

High T/sub c/ superconductors, such as Bi-2223, have been promising candidates for an electrical busbar because the busbar has a relatively low self magnetic field. It has been found that the critical current of Bi-2223 stacked tapes is much less than the total summation of critical currents of each tape, which is mainly attributed to the self magnetic fields. Furthermore, since the critical current degradation of Bi-2223 tape is greater in the normal magnetic field (to the tape surface) than in the parallel one, detailed magnetic field configurations are required to reduce the self-field effects. Conceptually, by rearranging each stacked tape properly, the self field effects could be minimized. In this paper, we calculate the self field effects of a stacked conductor, defining self field factors of normal and parallel magnetic fields to the tape surface. We propose an optimum shape of octagonal structured busbar which has minimum self field effects.