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

We have been investigating a current imbalance in multi-strand cable conduc tor using several types of solenoid coils wound by insulated multi-stranded copper cable, and obtained a result that the current distribution in the m ulti-stranded conductor is strongly affected by the magnetic coupling coeff icient between strands. This time, we have carried out an experiment to inv estigate the current imbalance problem using a superconducting cable conduc tor. The main purpose of this investigation is to make clear the relation b etween the current imbalance and the impedance distributions among the stra nds. The experiment was carried out on (1) DC test, and (2) AC test. The ca lculation results show that the resistance component becomes dominant in th e frequency region lower than 0.1 Hz. On the other hand, inductance compone nt becomes dominant in the frequency region higher than 1Hz. For the experi mental results lower than 1Hz, the amplitude and the phase characteristics of the current in each strand coincide well with the calculated results bas ed on the measured resistance and impedance distribution. From these result s, it can be concluded that a precise impedance measurement utilizing high accuracy LCR meter can estimate the current imbalance in insulated multi-st randed superconducting cable conductor before actual superconducting operat ion.