Switching Overview--Fundamental Issues

Good afternoon. It is a pleasure to be here and an honor to be asked to overview and chair this switching session. I feel unprepared for the task, because I have much less experience than those on the program in designing, building, and operating switching systems, and I am sure the same is true with respect to almost everyone in the audience as well. Nevertheless, I have an active interest in switching, and I am involved technically with a group working on switching problems. These have led me to think about fundamental problems of switching. I wil share with you briefly my thoughts on a few of what I consider to be the most fundamental and difficult issues in switching. I hope that these thoughts will be useful to you as you continue your efforts to improve your switching systems. As we all know, switching is the process by which a branch in an electric circuit changes from being a very good conductor (ideally a short circuit) to being a very poor conductor (ideally an open circuit), or vice versa. There are applications that require both closing and opening switches, and each has its own set of fundamental issues. The interest here is almost entirely in opening switches, so I wil confine my remarks to those. The switching system envisioned here for a discussion of fundamental issues is one which carries current for a relatively long time, typical of charging a storage inductor from a homopolar generator, and then transfers the current to a load in such a short time that circuit inductance dominates the current transfer. After current transfer; the switch must withstand the voltage of the load.