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 [Mu][ohms] during charge intervals of several hundred milliseconds, controlled time to opening, minimal fuse size, and a relatively fast opening of 0.25-0.7ms. 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.