Hysteretic ac loss of a superconductor strip subject to an oscillating transverse magnetic field: Geometrical and electromagnetic effects

摘要

Numerical simulations of geometrical and electromagnetic effects on the distributions of the magnetic induction, the electric field, the current density, the power loss density, and the hysteretic ac loss of a type-Ⅱ superconductor strip exposed to an oscillating transverse magnetic field are performed by resorting to the quasistatic approximation of a vector potential approach. The underlying definition of the superconducting constituent makes use of a generalized "smoothed" Bean model of the critical state, which includes the field dependence of the induced current as well. Based on the Jacobian-free Newton-Krylov approach and the backward Euler scheme, the numerical analysis at hand is tailored to the problem of a variable width/thickness aspect ratio of the superconductor strip. Assigning representative materials characteristics and conditions of the applied magnetic field, the main findings include: (ⅰ) at high amplitudes of the applied magnetic field, variations of the magnetic induction, the induced electric field, the induced current density, and the power loss density across the thickness of the strip die away as the latter quantity abates; (ⅱ) at low and moderate amplitudes of the applied magnetic field, the hysteretic ac loss abates rapidly, as the aspect ratio of the strip augments, the field dependence of the induced current merely playing an insignificant part thereby; conversely, whereas the geometrical effect controlled by the aspect ratio of the strip is minute at high amplitudes of the applied magnetic field, a reduction of the hysteretic ac loss occurs due to Kim's extended Ansatz for the critical state.