Investigations Into the Design of a Compact Battery-Powered Rep-Rate Capacitor Charger

The U.S. Naval Research Laboratory is developing a battery-powered rep-rate charger for a 60-kJ capacitor bank. The goal is to charge a 4800-mu F capacitor to 5 kV in < 5 s for a 50-shot burst at 10 shots/min. A bank of LiFePO4 batteries is used with a full H-bridge converter, a transformer, and a rectifier to transform the 600 V battery voltage to 5-kV secondary voltage. There are two major aspects to the charger design: battery energy store and the dc-dc converter. A stable battery pack requires active cooling, management, and feedback for proper and safe operation. A design study has been performed to identify an appropriate dc-dc converter that can minimize the weight and volume of the system while maintaining high electrical efficiency. An LLC is being evaluated, as it has the possibility of eliminating a discrete inductor using the magnetizing inductance of the transformer in the resonant circuit. Work has also been performed in the design and evaluation of a battery pack, specifically on characterizing the operational parameters of the pack as applied to the desired load. This paper will present simulation data and results from the experiments.