Proposal of transformer using magnetic shielding with bulk high T/sub c/ superconductors

As for a general transformer using a ferromagnetic core, the magnetic flux may leak by using the high frequency and the overload. When the magnetic flux leaks from the core, the secondary voltage and its power transfer efficiency decrease. Bulk high T/sub c/ superconductors (HTS's) with the high critical current density have the strong magnetic shielding characteristic at the static magnetic field and the AC magnetic field. Thus, we examined to surround a magnetic circuit of a transformer with bulk HTS's. From this research, when the magnetic circuit of the transformer was surrounded with plural HTS's, it was confirmed that the secondary voltage and the power transfer efficiency of the transformer increased especially in the high frequency range.