Magnetic gradient levitation using high-Tc bulk superconductors

Magnetic gradient levitation systems using high-T/sub c/ bulk superconductors and iron rails have been studied by numerical analysis of their electromagnetic field. This system enables stable levitation, even at standstill, without active control, by the flux pinning of the superconductors. Emphasis is put on the analysis of the dependence of the levitation characteristics on the critical current density in the superconductor. Numerical analysis results show that levitation characteristics are strongly dependent on the critical current density. Bulk superconductors with a critical current density higher than 2/spl times/10/sup 8/ A/m/sup 2/ are required for stable levitation and sufficient force can be generated in the case of the system model considered in this paper.