High-Temperature Superconducting Motor Using Y-Ba-Cu-O Bulk Magnets

A DC motor equipped with melt-processed Y-Ba-Cu-O (YBCO) superconductors as field magnets was constructed. The YBCO bulks were magnetized at temperatures of 65-77 K in a liquid nitrogen vessel by applying a pulsed magnetic field. The maximum output power was 940 W when the YBCO bulks were cooled to 65 K. Continuous running tests were carried out for up to 6 h. We found that the trapped magnetic fluxes are hardly affected by the magnetic field of 7500 A/m generated by the armature current and that cooling of the YBCO bulks to low temperatures is very effective for holding the trapped field at a high level and, hence, substantially elevating the performance of a high-temperature superconducting (HTSC) motor.