Study On AC Loss Of HTS Tapes And Coils Based On Integral Method

Because of the existence of flux pinning,High temperature superconducting(HTS)tapes or coils will generate AC loss while working under the alternating current or magnetic field.If the heat brought by the AC loss can't be taken away in time,the HTS devices will quench or even be burn down.Therefore,fast and accurate measurement of AC loss is very important to the operation state evaluation of HTS devices and the design of superconducting magnet.It is difficult for the traditional measurement methods to take the speed,accuracy and range of measurement into account,so as to realize the real-time measurement of AC loss.In this paper,an electrometric method of AC loss measurement based on integral method is proposed,which is used to measure the AC loss of HTS strips and coils.The main work completed is as follows:(1)Based on the high-precision data acquisition card,Lab VIEW control system and data processing system,a real-time measurement system for AC loss of HTS strips and coils is built.Simultaneously,this system can measure the AC loss under non-sinusoidal or even non-periodic current.(2)A critical current test platform for HTS tapes at 20K-77 K is built.The magnetic field and angle dependence of critical current of HTS tapes are tested and the measuring results are applied to simulate the AC loss of HTS tape.Two measuring systems,respectively based on integral method and lock-in amplifier,are used to measure the AC loss of superconducting tape.The measuring and simulating results show that the measurement system based on integral method has good performance in accuracy,speed and reliability.(3)A small HTS coil is made and its AC loss under sinusoidal and triangular currents are simulated and analyzed.Meanwhile,AC loss of the coil under other different current waveforms are measured by integral method.The results of simulation,integral method and lock-in amplifier are compared and analyzed.It is verified that the AC loss measurement platform of integral method can be used to realize real-time measurement under different working conditions.(4)A small HTS magnet with six coils is made,and its AC loss under sinusoidal current is measured.The results show that the AC loss measurement platform of integral method is also suitable for the real-time measurement of AC loss of HTS magnet.