Research The Characteristic Of YBCO Superconducting Switch

The superconducting switch uses zero-resistance characteristics of superconductor for closed loop operation and quench to generate resistance for breaking circuits. As a key component of superconducting magnetic energy storage system, the superconducting switch not only can constitute a near-zero-loss closed loop with a superconducting magnet, but also achieve rapidly release of energy.In present research and applications, the majority of superconducting switches are made of Low Temperature Superconducting (LTS) materials or Bi High Temperature Superconducting (HTS) tapes. The critical temperature of LTS is relatively low. It usually works in the liquid helium circumstance, which makes the operation costly. On the other hand, the strong anisotropy of Bi HTS tape makes its critical current vulnerable to the magnetic field and thus limits its application. Therefore, this article uses the YBCO HTS tape to make superconducting switch because of its ability to work in liquid nitrogen circumstance, good performance in the strong magnetic field and better current carrying capacity. The characteristics of superconducting switch were analyzed as well.First, the superconductor quench propagation theory was summarized. Experiments were carried out to analyze the quench propagation property of YBCO and Bi-2223/Ag HTS tapes and verified the theories, this property is related to the Normal Zone Propagation Velocity (NZPV). Then, the paper studied the quench characteristics of YBCO tape under large current pulse. The effect of different bending strain on YBCO performance was studied as well. The results showed that YBCO tapes had a minimum bending radius, and the critical current of YBCO tapes decreased with the decrease of the bending radius.Based on the experimental study of YBCO tapes, we used the YBCO tapes to fabricate superconducting switches, which can be triggered by heat pulse or current pulse. The experiment results showed that when constituting a near-zero-loss closed loop with a superconducting magnet, the heat-pulse-triggered YBCO superconducting switch not only can achieve a relatively high stable magnetic field, but also release the energy rapidly. Finally, the experiments researched the characteristic of current-pulse-triggered YBCO superconducting switch circuit, in which the capacitance works as the trigger source, and the thyristor works as the trigger switch. The experimental results showed that the current-pulse-triggered YBCO superconducting switch cannot be used as an effective circuit breaker. The method to improve the performance of the superconducting switch was put forward, through theoretical calculation analyzed the feasibility of the improved method as well.