A compact pulse forming network, based on semiconducting switches, for electric gun applications

At ISL a highly modular pulse forming network (PFN) for electric guns (railguns, electrothermal-chemical guns) has been developed and built up. The PFN consists of pulse forming units (PFU), which are composed of a capacitor (E=50 kJ), semiconducting switches (thyristor, crowbar diode), an inductor and a coaxial cable connecting the PFU to the electric gun. The inductor is required in order to limit the maximum current capability of the SCR switch. Due to novel SCR with a higher current rate (dI/dt) and current capability (I>150 kA) a PFU without the above mentioned inductor could be designed. The new PFU has a smaller size and less weight than the former. Based on this PFU, a PFN consisting of 24 units has been investigated. The features of the novel PFN are presented in the paper and are compared to the former PFN including an inductor. The lower inductance makes the novel PFN more flexible due to the ability of generating arbitrary waveforms and the current shape can be adjusted to the load in a very sophisticated manner. Additionally the current in the load decreases more rapidly (I(t)~e^-(R/L)(t)). So the electrical energy stored in the electrical gun at projectile exit is strongly reduced and the efficiency of the electric accelerators is enhanced