Electromagnetic Properties of Nb-Ti Superconducting Wires with Cu-Ni-Mn Matrix for AC Use

Abstract

There are certain advantages in applying power system superconducting wires. High efficiency, stability of power systems and miniaturizing of power frequency equipment. are all desirable. Decreasing AC loss from superconducting wires constantly generating in AC field is an important factor for AC use. The characteristics of superconducting wires for AC use are the use of high resistant matrix Cu-Ni alloy, a short twist pitch of wires and submicron superconducting filaments. For the achievement of a high current density, however, the rate of occupation of the superconductor in the wire should be high. The result is, a filament spacing of the order of 0.1μm. Electromagnetic coupling at each filament due to the proximity effect causes an increase in the hysteresis loss. Reduction of this proximity effect can be achieved by increasing the filament spacing or by decreasing the value of ξeff dependent on the nature of the matrix, Leff is the effective penetration depth into the normal metal or alloy. Increasing ξeff can be achieved by increasing the matrix resistivity, generally using Cu-Ni alloy, or by destroying electron pairs using magnetic elements Ni, Mn etc.^1,2 The addition of 0.9wt%Mn to Cu has the same effect as the addition of 31wt%Ni to Cu in reducing the proximity effect. ³