An Experimental Study on Manipulation of Individual Coil Current in Parallel-Connected HTS Pancake Coils

This paper reports experimental results of individual coil current manipulation by heater operation in parallel-connected three no-insulation (NI) high-temperature superconductor (HTS) pancake coils. The resistive heater was installed at the coil terminal of the lowermost pancake coil. During magnet operation with a power supply current held constant in a bath of liquid nitrogen at 77 K, the heater was operated to reduce the coil current of the lowermost pancake coil. Due to the heater operation, the coil currents of the uppermost and the middle pancake coil increased as a result of the coil-to-coil current sharing mechanism. The result demonstrates the potential of handling the unstable magnet operation in a parallel-connected magnet by taking action to each coil individually such as coil current reduction without significant degradation of the magnetic field intensity.