High current pulse forming by modualized capacitor banks

For use as a driver for a electrothermal-chemical (ETC) gun, a 2.4 MJ pulse power system (PPS) has been developed and built up. The 2.4 MJ PPS consists of 8 modular capacitor banks (CB) with energy of 300 kJ each. The 300 kJ CB modules are designed to operate separately and have a charging voltage of 22 kV and a current capability of 150 kA. Prior to the ETC gun application, various shapes of current pulse have been tried to a dummy resistive load by the multiple CB modules. Investigations on a multimodule operation revealed that the Triggered Vacuum Switch (TVS) in the module are triggered simultaneously when other module fires (sympathetic triggering), and some TVS´s cannot block the reverse current (failure in diode function). The analysis of these malfunctions of the TVS and some countermeasures have been performed. As another problem, an overvoltage surge has been observed during multiple modules operations. The peak of surge voltage can be higher than the charging voltage, and it can cause the breakdown of crowbar circuits in the module. Solutions to protect the crowbar against the surge voltage have been suggested and some modifications of CB module have been carried out. The experiments on a multi-module operation confirmed that our PPS consisting of improved CB modules has a sufficient pulse forming capability required for the ETC gun load.