Magnetic field triggered switching of High-Temperature Superconductors - Basic Experiments

High-temperature superconductors have a wide range of applications due to their high availability and excellent performance. One attractive technology is using superconductors as switches. In general, a change of resistance can be achieved by temperature, current or magnetic field. In the latter case, a dynamic resistance can be obtained by an alternating magnetic field and has been investigated in this work. These properties enable zero on-state resistance and fast switching times. The magnetic field has been generated by an iron magnet with an air gap of 1 mm and penetrated the superconductor perpendicular to the ab-plane. The dynamic resistance of one superconducting HTS tape has been measured for magnetic flux densities up to 340 mT and frequencies up to 500 Hz in liquid nitrogen at 77 K. The experimental results have been compared with simulation models. In addition, a parallel circuit of two superconducting switching units was set up where each magnet was controlled individually and switched in an alternating mode. The commutation time, dependent on the magnetic field's amplitude and frequency, was measured. With this setup, a resistance of 13.14 mΩm-1 has been achieved. Commutation times below 5 ms could be achieved with ReBCO tapes.