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We analyzed the fault current limiting characteristics of a flux-lock type high-Tc superconducting fault current limiter (HTSC-FCL) using series resonance between capacitor for series resonance and magnetic field coil which was installed in coil 3. The capacitor for the series resonance in the flux-lock type HTSC-FCL was inserted in series with the magnetic field coil to apply enough magnetic field into HTSC element, which resulted in higher resistance of HTSC element.However, the impedance of the flux-lock type HTSC-FCL has started to decrease since the current of coil 3 exceeded one of coil 2 after a fault accident. The decrease in the impedance of the FCL causes the line current to increase and, if continues, the capacitor for the series resonance to be destructed. To avoid this operation, the flux-lock type HTSC-FCL requires an additional device such as fault current interrupter or control circuit for magnetic field.This paper investigated the parameter range where the operation as mentioned above for the designed flux-lock type HTSC-FCL using series resonance occurred from the experimental results. In the design of the flux-lock type HTSC-FCL, the some methods to avoid the continuous increase of the line current were suggested and confirmed by the experiments that the suggested methods were available to prevent the continuous increase of the line current after a fault happened. [Copyright &y& Elsevier]

We investigated the time dependence of the resistance of superconducting fault current limiters (SFCLs) based on YBa2Cu3O7 thin films after quench completion. The 0.3 μm thick film was coated with a gold layer of 0.2 μm thickness and patterned into pairs of 1 mm wide and 26 cm long meander lines by photolithography. The SFCL was subjected to simulated AC fault currents of various peak values. The resistance of the SFCL consisted of an oscillatory component and a slow varying one. The slow varying component of the resistance increased exponentially with time after the initial rapid increase due to phase transition. The magnitude of the oscillatory component was small compared with the slow varying one. These results could be explained quantitatively with the concept of heat transfer within the film and to the surroundings. [Copyright &y& Elsevier]