Application and simulation of liquid-quenched fuses in hybrid opening switches

For the experimental investigation of high current high voltage fuses (HVF), a two-stage opening switch was designed and tested. It comprises of a vacuum circuit breaker serving as a first stage and an HVF in series with an SCR as a second stage. The switch offers a low resistance of 20 /spl mu//spl Omega/ during charge intervals of several hundred milliseconds, controlled time to opening and a relatively fast opening of 0.25-0.7 ms. In a series of experiments, the current of 30-40 kA was commutated routinely from a 130 /spl mu/H inductor into the resistive load at a voltage of 3 kV. Liquid quenching media were examined and found to yield a high transfer efficiency, with fuse losses as low as 5-8% of the stored energy. A strong correlation existing between these parameters and the pressure generated in the fuse is discussed. A semi-analytical engineering fuse model based on an electron-ion recombination mechanism of the fuse resistance change is developed. This model is integrated into a PSpice circuit simulation. The calculations are in fairly good qualitative and quantitative agreement with experimental results.