Electrothermal Chemical Guns Capacitance High-power Pulsed Power Supply Passive Protection Method For A Preliminary Study

Six capacitor modules for the electrothermal-chemical (ETC) gun research program have been fabricated. The electrical breakdown of pulse capacitor and the destruction of the crowbar diode took place afterwards. The characteristics and performance of the pulsed power source have been analyzed; and the problems that can occur during these multiple modules operation have been investigated. This paper provides solutions for these problems. The auxiliary facilities are also installed.To prevent the capacitors being recharged by a reverse voltage, a crowbar circuit, which consists of diode-stacks connected in series, is studied mainly. The countermeasures for over-current and over-voltage on the diode-stacks are presented. The causes and characteristics of the surge voltages that generated in the pulsed power source composed of paralleled modules are analyzed and the countermeasures for suppression are presented. To study the causes and characteristics of the surge voltages, designs of voltage dividers are investigated. A design of resistor divider is provided to measure the discharge waveform of the surge voltage on diode-stack accurately. A design of capacitive resistor voltage divider is also provided to measure the discharge waveform of the voltage on the capacitor. Then the Analysis on the causes of the surge voltages is testified.The way to protect pulse capacitors effectively in the event of pulse capacitor faults is put forward. The safety copper fuses have been designed to reduce the current in defective cell; the resistors, which are non-linear, have been desigened to reduce the current in defective module and discharge the cell safely. The effects and the parameter selection of protection elements are also discussed carefully.This paper also presents a novel crowbar circuit, which replaces the expensive crowbar diode-stacks with a triggered vacuum switch. By replacing the crowbar diodes with a TVS, the drawbacks of the diode-stacks, which are very weak in high-voltage surges and are expensive to replace in case of failure, can be overcome. So, the pulsed power source that has the above crowbar circuit will be safer and cheaper.