A resonant series counterpulse technique for high current opening switches

Abstract

A bstract-A counterpulse technique for the controlled interruption of very high currents in inductive storage pulsed power systems i s described and analysed, and some simulation results of its performance are presented. The accompanying circuit comprises a pre-charged capacitor bank, connected in series with the inductive load, which has to be provided with a current pulse. Upon actuation, a resonant counterpulse current is created in the opening switch, connected in parallel with the current source and the load. In this way, the opening switch is opened at low current. A separate closing switch prevents closing of the opening switch at high voltage. Operation of the opening switch, often a mechanical switch, at low current and low voltage prevents arc erosion of the contacts.The advantage of this circuit compared to other counterpulse circuits is that the capacitor bank does not experience a voltage reversal. Electrolytic capacitors, which have a high energy density, are applied. The remaining energy of the capacitor bank after opening the opening switch, is transferred to the load. The required initial voltage of the capacitor bank is only a few hundred volts, whereas it may be above B kilovolt in other circuits.Another advantage of the method described here is that the load does not experience a pre-current, causing unwanted preheating of the load, before the resonant current is activated.At the moment, work is being performed at the Pulse Physics Laboratory to develop the resonant series counterpulse circuit for use with rail accelerators, which must be supplied with current pulses in the millisecond range up to the mega-ampere level.

Demonstration of a 1 MJ XRAM Generator Supplying a Medium Caliber Railgun

“…The ICCOS is basically a fast switching thyristor with an additional circuit for the generation of a counter current in order to return them into the blocking state. The same technique was previously used at the TNO in Delft, the Netherlands, with a mechanical opening switch in the megaampere level [40]- [42]. In case of semiconductor switches, such current levels require devices in a parallel connection which is critical in terms of a reliable operation.…”

Review of Inductive Pulsed Power Generators for Railguns

“…Three kinds of opening switches are basically available: mechanical switches, fuses, turn-off controlled semiconducting switches and hybrids of all of them [15]- [17]. For inductively powered railgun systems, heavy duty contactors [18], explosively driven switches [19]- [21] and counter-current switchoff techniques [22]- [25] were used. Today, considerations go toward semiconducting switches like GTOs or IGBTs which are now capable to operate for short time in the MW range [26], [27].…”

Non-US electrodynamic launchers research and development

“…This may not be an attractive solution for a future fieldable weapon system. Counterpulse techniques for high-current (up to megampere) opening switches have been discussed by van Dijk and van Gelder (1994). Such techniques utilize an auxiliary capacitor to provide a rapid counterpulse that lowers the current in the switch to near zero immediately before it is opened, thereby greatly reducing the arc damage that would otherwise occur when a high-current switch is opened in the high-current circuit of, for example, a homopolar-powered inductor for a railgun.…”