The relationship between levitation force and stiffness in symmetrical and unsymmetricalapplied fields

Abstract

The two key parameters for levitation performance over a permanent magnet (PM)guideway are the levitation force and the stiffness of the high temperature superconductor(HTS) YBaCuO bulk. Their distributions along a lateral displacement (LD) were measuredin zero-field-cooling (ZFC) and in field-cooling (FC) conditions. There are two cases ofapplied magnetic field for a single HTS bulk: symmetrical or unsymmetrical about the bulkaxis. Although the levitation force has a linear relationship with the applied field in thesymmetrical case, such a linear relationship disappears once the applied field becomesunsymmetrical. Furthermore, the levitation stiffness is measured in FC, and they stillchange more drastically than the levitation force in ZFC. In particular, the levitationstiffness has a linear relationship with the associated levitation force, whether the appliedfield is symmetrical or unsymmetrical. Its lateral distribution at a gap of 20 mmin FC agrees with the levitation force distribution at a gap of 10 mm in ZFC.