Design of a 500-KJ Capacitor Bank Module for EML Materials Testing

Abstract

The U.S. Navy is considering the development of an electromagnetic launcher (EML) for surface-fire support and other missions[1]. The EML system will need to have fire rates of 6-12 rounds per minute and barrel lifetimes approaching 10,000 rounds. The Naval Research Laboratory has initiated a program to develop and test materials to achieve these fire rates and lifetimes[2]. A facility is being assembled to allow testing of rail and armature materials at the high current density, pressure and sliding velocity of the Navy EML. The test system needs to operate over a large range of charging voltages and test configurations. The system also needs to deliver high reliability and reproducibility to accommodate the testing requirements. A 500-kJ module is being designed as the basic building block of the pulsed power system for the facility. Each module will supply up to 100 kA to the materials test system. The components being considered are similar to those proposed for a 200 MJ EML pulsed power system[3]. The capacitors are new, 125 kJ/can, 11-kV units from General Atomics Electronics Systems. The switching thyristors and crowbar diodes are from ABB. A series inductor of approximately 80 muH is used to limit the peak current to 100 kA and isolate modules from each other and to ensure that the current is delivered to the test system. It is expected that the solid-state components used for switching and crowbarring will provide the reliability and flexibility desired for the pulsed power system. The circuit is analyzed with the dynamic nature of the test system included. The rising inductance of the test must be included in the modeling to accurately reflect the action required from the switching and crowbar elements, and the fuses that are in series with capacitors. The physical layout of the banks is also being designed to provide highly compact modules while providing access for maintenance and repair. Results of the simulations will be presented, along with mechanical layout plans.