Current distributions at steady-state of superconducting cable conductors for AC use

In order to obtain information towards achieving uniformity of current distribution in superconducting cable conductors for AC use, the authors have developed a compact measuring system that enables them to quantitatively evaluate the current distribution. In this system, current distribution is found from the observed results of the self-field measured by a group of coils, each of which is composed of six small pick-up coils, located around the sample conductor. It is confirmed that the accuracy and the sensitivity of this system are good enough to measure the current distributions for the superconducting cable conductors for AC use by adopting it to a dummy conductor composed of insulated copper wires. Using this system, they experimentally investigated how the localized transport current, in the steady-not quenched state, is made uniform in the superconducting cable conductor composed of strands without insulation for AC use. By this experiment, they observed how the localized current transfers among the noninsulated strands. At the same time, the frequency dependence of the change of the current distribution can also be observed as well. These measured results are discussed using approximate analysis relating to the inter-strand coupling effect.