A two-stage opening switch for inductive energy storage systems

A two-stage opening switch comprises of a vacuum circuit breaker (VS) as a first stage and a high voltage fuse (HVF) in series with an SCR as a second stage. The switch offers low resistance of 20 mu Omega 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 30-40kA was commutated routinely from a 130 mu H inductor into the resistive load at a voltage of 3kV. 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. It was found that a two-three millisecond HVF conduction time suffices for the recovery of the VS. A PSpice circuit simulation using an action-dependent fuse model gave good agreement with the experimental results.