Two-stage opening switch for inductive energy storage systems

A two-stage opening switch comprising of a vacuum switch as the first stage and a high voltage fuse in series with a silicon controlled rectifier (SCR) as the second stage is presented. The switch offers low resistance of 20 μΩ during charge intervals of several hundred milliseconds, controlled time to opening, minimal fuse size, and a relatively fast opening of 0.25-0.7 ms. It serves as a closing switch as well. In a series of experiments, the current of 30-40 kA was commutated routinely from a 0.13 mH inductor into a resistive load at a voltage of 3000 V. Various quenching media were examined. The liquids were found to yield maximum inductively generated voltage and transfer efficiency. A strong correlation exists between the fuse performance and the pressure generated in the fuse. This dependence is used as a guideline in fuse design. It was found that a 2-3 ms fuse conduction time suffices for the recovery of the vacuum switch. A PSpice circuit simulation using an action-dependent fuse model is in good agreement with experimental results. A semi-empirical fuse model based on electron-ion recombination mechanism of the fuse resistance change is proposed. This model is integrated into PSpice circuit simulation. The calculations are in fairly good agreement with experimental results