Demonstration of a 1 MJ XRAM Generator Supplying a Medium Caliber Railgun

The electric power supply for an electromagnetic launcher has to provide energy in the mega-joule range within an acceleration time which only lasts for milliseconds. Today's giga-watt pulsed power generators are based on large capacitor banks and are therefore unsuitable for most mobile applications. Thus, power supply research focuses on size reduction by means of alternative technologies like inductive storage. The XRAM topology, where several inductors are charged in a series and discharged in a parallel connection, is a concept for inductive current multiplication. This technique requires simultaneous switching of closing and opening switches and was realized by using thyristors turned off by a counter-current pulse (inverse current commutation with semiconductor devices - ICCOS). At the French-German Research Institute of Saint-Louis (ISL), several aspects of this technology have been investigated and several demonstrators for different energies have been developed. Nowadays, the development of inductive pulsed power generators advances towards energy levels relevant for future applications. This paper presents the development of a 1 MJ XRAM generator which demonstrates the suitability of this technology by supplying the medium-caliber ISL railgun RAFIRA during dynamic experiments. The results of the latest experiment are reported, where the XRAM generator was charged to 842 kJ. A current of 40 kA was successfully interrupted by the ICCOS opening switches and an 80 g brush projectile was accelerated to 1120 m/s. The railgun current was switched off at the time of the projectile's bore-exit, thus approximating a rectangular current pulse shape. Experimental results are compared to outcomes achieved with capacitor banks as railgun power supply.