Basal Research On Electromagnetic Characteristics Of High-Temperature Superconductor Applied In Pulsed Power

Pulsed power is attached importance to the application for the future launch vehicles and new concept weapons. Superconducting technology applied in pulsed power apparatuses such as energy storage magnet, pulsed transformer, switch, inductive device and coils would be very promising. In this dissertation, the electromagnetic characteristics of Bi-2223/Ag high temperature superconductor (HTS) under pulsed currents, and the pulse forming technology based on HTS magnet energy storage systems (SMES) are researched. The over-loading characteristics of HTS under pulsed over-currents and keys to the pulse forming technology based on SMES are identified. The results are also important for HTS applied in power systems.Lots of experimental researching on the quench and recovery characteristics of HTS tapes under DC, AC, oscillating current, and pulsed current are carried out respectively. Meanwhile, using heat transfer and a finite difference method to analyze and simulate the quench propagation properties of HTS tapes under different kinds of over-currents, the simulation results resemble experimental results. Through analyzing normal resistance voltage developing and recovery characteristics of HTS tapes under different over-currents, the relations between the quench recovery characteristics and amplitudes, frequencies, durations of over-currents are identified. A theory model about quench developing in HTS is proposed, which thinks that quench developing is influenced by heat varying ration caused by normal resistance dQr dt and heat loss ration caused by liquid nitrogen cooling dQl dt . And experimental results show that HTS tapes have a range of over-loading under sinusoidal or pulsed over-currents.It is important to detect a quench for superconducting equipments under AC over-currents. However, the inductance voltage induced by AC is much larger than resistance voltage when a quench takes place, which results in judging difficultly for a quench. Through a lot of experimental researching on the quench processes of HTS coil under AC over-currents with different amplitudes, it is identified that the phase angle between the voltage and the current of the coil has changed as a quench taking place in the coil, and the phase angle decreases as the amplitude of over-current increases. The result would be very important application for detecting a quench and protecting superconducting equipments applied in power systems.Based on the electromagnetic characteristics studies of HTS tapes and coils, a pulsed HTS magnet applied in experiment is designed and manufactured. And a series of electromagnetic characteristics experiments on the magnet have been carried out.A kind of pulsed power technology is researched. Firstly, Using Matlab simulation, the pulse forming network is designed, according to the characteristics of SMES and superconducting switch, the ideal structure of superconducting magnet and switch is presented, and some important questions are identified. Then, experimental researching on pulse forming technology based on HTS magnet is carried out, the pulsed power is acquired under resistance load. A solution which changes the structure of the circuit and the magnet parameter in the circuit to realize pulse forming is proposed.