Modelling the interactions between magnets and granular high-Tcsuperconductor material with a finite-element method

A computational model for the interaction of magnets with HTS material of arbitrary grain size and critical current density is presented. The two-dimensional solution technique is based on a finite-element method and the superconductor is assumed to obey a power-law voltage-current characteristic. The currents inside the grains are generated by the periodic movement of a magnet stack consisting of permanent magnets and iron shims which gives an exciting field with a strong gradient. The considered application of this is a so-called high magnetic gradient bearing. The motivation for this work was to investigate the dependence of the levitation force and loss on the grain size and the intragrain jc.