Effect of impedance distributions on current imbalance in insulated multi-stranded superconducting conductor

We have been investigating a current imbalance in multi-strand cable conductor using several types of solenoid coils wound by insulated multi-stranded copper cable, and obtained a result that the current distribution in the multi-stranded conductor is strongly affected by the magnetic coupling coefficient between strands. This time, we have carried out an experiment to investigate the current imbalance problem using a superconducting cable conductor. The main purpose of this investigation is to make clear the relation between the current imbalance and the impedance distributions among the strands. The experiment was carried out on (1) DC test, and (2) AC test. The calculation results show that the resistance component becomes dominant in the frequency region lower than 0.1 Hz. On the other hand, inductance component becomes dominant in the frequency region higher than 1 Hz. For the experimental results lower than 1 Hz, the amplitude and the phase characteristics of the current in each strand coincide well with the calculated results based on the measured resistance and impedance distribution. From these results, it can be concluded that a precise impedance measurement utilizing high accuracy LCR meter can estimate the current imbalance in insulated multi-stranded superconducting cable conductor before actual superconducting operation.