Final results from the high-current, high-action closing switch test program at Sandia National Laboratories

Abstract

We tested a variety of high-current closing switches for lifetime and reliability on a dedicated 2 MJ, 500 kA capacitor bank facility at Sandia National Laboratories. Our interest was a switch capable of one shot every few minutes, switching a critically damped, DC-charged 6.2 mF bank at 24 kV, with a peak current of 500 kA. The desired lifetime is 24 thousand shots. Typical of high-energy systems, particularly multi-module systems, the primary parameters of interest related to the switch are: (1) reliability, meaning absence of both pre-fires and no-fires, (2) total switch lifetime or number of shots between maintenance, and (3) cost. Cost was given lower priority at this evaluation stage because there are great uncertainties in estimating higher-quantity prices of these devices, most of which have been supplied before in only small quantities. The categories of switches tested are vacuum discharge, high-pressure discharge, and solid-state. Each group varies in terms of triggering ease, ease of maintenance, and tolerance to faults such as excess current and current reversal. We tested at least two variations of each technology group. The total number of shots on the switch test facility is about 50 thousand. We present the results from the switch testing. The observed lifetime of different switches varied greatly: the shortest life was one shot; one device was still operating after six thousand shots. On several switches we measured the voltage drop during conduction and calculated energy dissipated in the switch; we show these data.