PULSED ROTATING MACHINE POWER-SUPPLIES FOR ELECTRO-THERMAL-CHEMICAL GUNS

With the recent successes in the development of electro-thermal-chemic al cartridge technology, the need for an advanced repetitive fire powe r supply has become a more near-term problem. While capacitor banks ha ve provided the single-shot capability necessary for optimizing charge design and the required electrical pulse shape, it is not clear that it is the best power supply for a gelded system. The primary disadvant age of the capacitor approach is the requirement for recharging the ba nk between shots. Conceptually, the required charging is accomplished with either a high voltage alternator and rectifier, or a battery bank which requires power conditioning (D-D converters, etc.) to achieve t he required 15 to 20 kV charging voltage. In the case of the alternato r-rectifier system, energy storage for multiple shots can be built int o the alternator rotor (or by adding an energy storage flywheel). Sinc e battery charging system design is typically driven by power consider ations, the battery needed to perform the charging will generally stor e-sufficient energy for several shots. In either case, the pulsed powe r system is composed of two distinct components: a capacitor based pul se forming network (PFN) and an energy storage/charging power supply. Rotating machines provide the advantage of combining the two functions described above into a single smaller package. Under Us. and Marine C orps funding, the Center for Electromechanics has been developing comp act, lightweight pulsed rotating machines (compensated pulsed alternat ors, or compulsators) for electromagnetic guns for the past 10 years. Air-core and iron-core variants of these machines have demonstrated an ability to efficiently drive low impedance pulsed loads. Other advant ages of these machines over PFNs include lower operating voltages, hig her burst firing rates, and the ability to store a substantial number of shots in rotor energy. In addition, a wide variety of pulse shapes are possible and the current profile can be varied from shot to shot i f needed. This paper describes the important rotating machine power su pply design considerations for two operational ETC missions. Aspects o f energy storage for burst bring and prime power averaging, pulse shap ing capabilities, and switching requirements are also discussed.