Critical current density and dissipation in sintered YBCO filaments

Critical current density and dissipation of four sintered YBCO filaments were measured with a continuous DC power supply. Each sample exhibited somewhat different characteristics from the others even though three of the four samples were from the same batch. The data suggest that it is possible for the YBCO filament to be in a state of stable equilibrium when part of the filament is in the flux-flow state and part is in the normal state due to local hot spots. This behavior may be advantageous for resistive fault current limiters because the intermediate state (partly flux-flow and partly normal) has an overall resistance that is much higher than that of the flux-flow state but does not lead to thermal runaway (burnout) or excessive heating, unlike a YBCO filament driven into the normal state over its entire length. Two of the samples were broken as a result of local burnout.