| Popis: |
A.c. superconductor stability within the framework of four basic models is analysed, with each model illustrating specific features in a.c. superconductor behaviour. Expressions are obtained for the minimum zone existence current, minimum propagation current, the limiting current at high frequencies (large Ω parameter), and also the parameter α corresponding to a fully stabilized a.c. superconductor. A.c. superconductors are shown to have a larger stability factor than d.c. ones. The propagation of normal and resistive zones in a.c. superconductors is studied numerically within a wide frequency range. The current dependences of the zone propagation velocity for each model are obtained. It is shown that taking into account a variable magnetic field gives rise to a system in which the conductor within the cycle becomes fully superconducting. |
