Precision Capacitor Bank

Summary form only given. High voltage capacitor banks may be required to deliver precise amounts of energy to the load. Various industrial and scientific systems including lasers, magnets and flash lamps may require precise and repeatable energy delivery. This paper discusses the design of capacitor banks to meet these requirements. This includes precise voltage control and stable capacitors. Film capacitors made with nonpolar dielectrics such as polypropylene, when processed in such a way as to maximize mechanical stability, have proven to be quite stable in capacitance and dissipation over a wide range of voltage, temperature, frequency, and lifetime. Energy storage capacitors incorporating self-healing metallized electrodes, are stable, compact, and reliable at voltages of 20kV or more. An example of a 400 kJ bank developed for a commercial application will illustrate these techniques. Special stabilization techniques are used to provide high repeatability of charge voltage extended over days. Techniques include temperature stabilized metering systems, careful control of leakage currents in metering circuits and shielded enclosures. Test results show repeatability over of <0.01% for a 3000 volt 400 kJ capacitor bank over one hour tests. For overnight tests the mean voltages were within 0.025%.