The ac losses of high critical-temperature superconducting (HTS) wires are numerically calculated by means of a finite element method (FEM), which is formulated with a self magnetic field due to an induced current as unknown. The numerical model is straight HTS wires carrying an alternating transport current in an external ac magnetic field perpendicular to the wire axis. In this situation, the electromagnetic field around the wires is given by two-dimensional (2D) Maxwell's equations. It is also assumed that the transport property is represented by either the critical state model or the power-law model, in which the electric field is proportional to the power of the current density. The obtained losses are compared with conventional theoretical curves in several simple geometries.
When an AC magnetic field was applied in the axial direction to a linear array of superconducting monofilamentary wires in the presence of a DC magnetic field perpendicular to the axes of the wires, it was found that the component of flux along the DC field changed its semi-quasistatic distribution in each cycle of the AC field and finally reached a uniform distribution after several tens of cycles. In the steady state, the AC component of flux showed a distribution of the Bean-London type with a reduced pinning force. For a small amplitude of AC field, the observed hysteresis loss increased with increase in the DC field. All of these characteristics exhibit a striking contrast to those of the so-called longitudinal-field effects, and may be called abnormal transverse-field effects; they have not been observed until now.
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