Resistive losses in a high-Tc wire carrying AC current larger than Ic

Abstract

A procedure that allows the calculation of the resistive AC loss in a multifilamentary superconducting wire carrying AC transport current was developed. This loss mechanism, detected by the appearance of a finite drop of electrical potential along the wire, is significant when considering transport currents with amplitudes that exceed the critical current of the wire. The physical model behind our calculation for a common wire, that contains superconducting filaments in a metallic matrix, is the simple parallel combination of two elements: the superconductor standing for the properties of all the filaments, and the normal resistor representing the matrix. The total current carried by two parallel conducting paths is easily calculated for any imposed potential drop. But the inverse task—calculation of the potential drop that would force a defined current to be transported—requires us to resolve a nonlinear equation. We show how it is possible to evaluate the resistive loss by a procedure that needs to perform the root-finding operation in one point of the cycle only. The numerical integration is still necessary, but now it is easily performed because the integrand is explicitly defined. The procedure was successfully tested by comparison with experimental data.