Contemporary Capacitive Energy Storage Systems

Capacitive energy storage is one of the oldest forms of energy storage for pulsed power requirements. Most energy storage capacitors are made of Kraft paper and aluminum foil and impregnated with castor oil. A typical capacitor stores ~ 3000 joules at voltage ratings of 5 kV - 100 kV. Two types of switches are used for capacitor bank switching, ignitrons and pressurized spark gaps. Ignitrons are commercially available, have a wide voltage operating range and are easy to trigger. However, they are limited to ~ 20 kV for most applications and they will prefire. Spark gaps can be designed for reliable operation at almost any voltage level but they are rarely commercially available. Most spark gaps do not operate satisfactorily below 50% of their design voltage and they require a more complicated trigger system than ignitrons. Low inductance coaxial cable has been developed for capacitor bank transmission systems. It is relatively inexpensive and commercially available. Parallel plate transmission lines can be designed to accumulate large amounts of current and conduct it to a concentrated load but careful attention must be given to the containment of the magnetic forces involved. Large numbers of ignitrons can be triggered with a simple trigger circuit that will be described. A circuit is also given to automatically trigger a crowbar ignitron. A pulse forming network circuit is presented which uses inductive voltage addition to generate an 800 kA pulse rising in 100 nsec with a pulse length of 500 nsec.