Calculation of the hysteretic force between a superconductor and a magnet

Abstract

The magnetic levitation forces exerted on a high-temperature superconducting ͑HTS͒ disk by a cylindrical permanent magnet ͑PM͒ are calculated from first principles for superconductors with finite thickness. The current j( ,z) and field B( ,z) profiles in the HTS in the nonuniform magnetic field generated by the PM are derived. The levitation force depends nonlinearly on the critical current density j c and on the thickness of the HTS. The flux creep is described by a current-voltage law E( j)ϭE c ( j/ j c ) n , from which we show that the levitation force depends on the speed at which the PM approaches or recedes from the HTS, which accounts for the experimentally observed force creep phenomenon. The stiffness of the system is derived by calculating minor force loops. The numerical results reproduce many of the features observed in experiments.

Levitation characteristics of HTS tape stacks

“…For thicknesses greater than 6-8 mm F z rep (h) dependence flattens and tends to a constant. Such a result is expected and is typical for bulk samples [4,5]. In FC mode (Fig.…”

Magnetic Properties of the Stack of HTSC Tapes in a Wide Temperature Range

“…Thus, for stacks of less than 30 tapes linear increase in force is observed, and at 90-120 tapes F max (n) dependence is saturated. Such a result is typical for bulk HTS samples [6]. Figure 3(a) shows the normalized dependences of maximum repulsive force and magnetization on the number of tapes in the stack at temperature T= 77 K. It is clear from the figure that both dependences are well correlated.…”

Verification of levitation force between an HTS levitator and a permanent magnet

“…Numerical methods have been developed towards to solve the J c (B) and the levitation force [3,4]. Analysis and simulation can be carried out based on above models and various parameters, as example results illustrated in Fig.…”