Improvement of magnetic circuit in levitation system using HTS and soft magnetic material

In this paper, we used, thin bulk Dy/sub 1/Ba/sub 2/Cu/sub 3/O (DBCO) samples cooled adjacent permanent magnets in the close magnetic circuit to enhance both the magnetic levitation force and stiffness values. Then soft magnetic material (yoke) is opposed to the surface of field cooled high temperature superconductor (HTS) sample. It is obvious that, when the yoke is approached to the surface, of trapped-field HTS, the attraction force will be increased. However, in the small air gap (<0.8 mm), the reduction of force causing "positive stiffness" effect which is the key point in this suspension system. In this report, the relation between attractive force and air gap is investigated when cross section of air gap is selected as a parameter. By this system, it is possible to levitate a mass by the weight of 150 N with positive stiffness of 8 N/mm.