Switching device with magnet field-triggered HTS switching units

  • Author: Quoc Hung Pham

Abstract

High-temperature superconducting ReBCO tapes exhibit a dynamic resistance which depends strongly on the transport current in the superconductor, the frequency, and the magnitude of the external magnetic field. Due to the properties of the superconductor, zero on-state resistance can be achieved. The dynamic resistance in off-state has been measured for magnitudes up to 340 mT and frequencies up to 1700 Hz in liquid nitrogen. The experimental results have been compared with different simulation models. The conductivity of the normal conducting layers greatly impacts the resulting off-state resistance. Thus further methods of optimizing the resulting resistance have been investigated by removing normal conducting layers of the superconducting tape while maintaining chemical and electrical stability. The total resistance of the normal conducting layers has been increased from 62 mΩm-1 to 1025 mΩm-1. Multiple switching units were combined into a basic electrical circuit and the function of the circuit was tested experimentally and compared to the simulation in SPICE. In general, a similar behavior compared to semiconductors could be observed. Within this basic electrical circuit, the current distribution and the leakage current of the off-state switching units were measured to estimate the losses and therefore the overall efficiency of the device.