A 540 kJ modular capacitive pulsed power supply system for basic investigations on ETC-performance

The investigations of the electrothermal control of the combustion of solid propellants to be applied in electrothermochemical (ETC) guns requires pulsed power supply systems which provide a high flexibility in pulse shape adjustment. In order to support the ETC gun investigations to be performed within the German ETC-programme at TZN a modular capacitive pulsed power supply system was designed, set-up and tested by TZN and has been in operation since May 1997. The paper describes the design of the system in detail and reports about the results of the checkout tests. The system consists of 540 kJ capacitive discharge modules with a maximum charge voltage of 30 kV each. The modules are crowbared by 33 kV semiconducting diodes. Triggered vacuum switches are installed at each module in order to provide sequential firing capability. The pulse shape of each module can be adjusted by the selection of its capacitance in four steps as well as by the selection of six different inductance values which are provided by the pulse shaping inductors. Up to now about 300 experimental shots have been performed with the system supplying different closed vessel set-ups with charge chamber volumes from 45 ml to up to 6.51. By making use of the high degree of pulse shape flexibility of the pulsed power supply a large amount of scientific information has been obtained so far in order to understand the physical relations between electrical energy conversion and propellant combustion.