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Articles you may be interested inCurrent sharing between the metallic and superconducting layers of high temperature superconductor coated conductors operated above their critical current

Transport current and n-value of DyBCO−coated conductor pulled in tension were measured experimentally and their relation to crack-induced current shunting was analyzed with the partial crack-current shunting model. The following features were revealed. The shunting current increases with increasing transport current and with increasing crack size. At low voltage where shunting current is low, the transport current of cracked sample normalized with respect to the transport current in non-cracked state is described with the modified ratio of non-cracked area to overall cross-sectional area of superconducting layer. At high voltage where the shunting current is high, the normalized transport current becomes higher than the modified ratio of non-cracked area. The increase in shunting current with transport current (and voltage) leads to a decrease in n-value at high current (voltage). This phenomenon is enhanced by crack extension.

The uniaxial strain dependence of the critical current was examined for YBCO coated conductors with IBAD-CeO 2 /YSZ or ISD-MgO buffer layers on Hastelloy substrates. I c increased with increasing applied strain, reached a maximum and decreased for higher strain values. The reversible strain region of I c variation was observed. The reversible strain limit depends on the buffer layers. For the CeO 2 /YSZ buffered tape, I c recovered the initial value even after the applied strain reached 0.30%. On the other hand, an irreversible degradation of I c was observed at the strain less than 0.22% for the MgO buffered tape. The overall relationship between the I c normalized by the peak value and the intrinsic strain in YBCO obeyed a unified scaling function. Quenching occurred at the strain close to the yield strain of the Hastelloy substrate.