Transition Criteria for Critical Current Measurement of High Temperature Superconductor in AC Circumstance

There are a number of AC power devices using high temperature superconductor (HTS) such as Superconducting Fault Current Limiter (SFCL), Superconducting Transformer, AC Superconducting cable and so on. However, the operating current of HTS power devices at alternating current (AC) circumstances is almost decided by critical current which is measured in direct current (DC) circumstances. Applying DC critical current criterion to AC power devices cannot be ideal. So, for AC power devices, a new AC critical current criterion must be needed. Commercial AC frequencies of current grid are 50 and 60 Hz. Therefore, in AC circumstance, the voltage induced by inductance is not negligible. For this paper, AC conducting experiments on variable superconducting tape samples were executed. The voltage induced by inductance is removed by filtering process and the voltage produced by resistance remains and is considered as a parameter (or guideline) of quench. With filtering process, amplitude of voltage generated by resistance can be calculated. As a result of those experiments, the 'Amplitude of input current'-'amplitude of voltage induced by resistance' curve was acquired and alternating critical current criteria were inferred.