100 kA test results of the 1 MA resonant series counterpulse opening switch system

At the Pulse Physics Laboratory, research is being performed to develop a counterpulse technique for the controlled interruption of very high currents in inductive storage pulsed power systems. Presently, a repetitive mechanical high current opening switch is applied to commutate current to an inductive load (e.g. a rail accelerator) from a storage inductor charged by a homopolar generator. To increase the current level the mechanical switch is able to interrupt, the application of a counterpulse technique looks promising. Otherwise, the arc that would occur between the contacts of the switch during opening and closing at high currents, would severely damage the contacts. To prevent the damage caused by arcing, the current must be reduced to zero or a low level before opening the switch. To be able to achieve this, the resonant series counterpulse circuit is proposed. The circuit incorporates units consisting of a capacitor bank of electrolytic capacitors with parallel connected diodes and a thyristor connected in series. Upon command, these units will create a resonant counterpulse current through the opening switch. The net current through the switch reduces to zero and the switch is opened without damaging the contacts. The units have been designed to generate a current of up to 50 kA. By placing several units in parallel, higher counterpulse currents can be generated. This paper discusses the construction of a unit and demonstrates the operation of one unit and the parallel operation of two units.