Twenty-Stage Toroidal XRAM Generator Switched by Countercurrent Thyristors

Abstract

As inductive energy-storage technology presents-at the same power-output capability-energy densities that are one order of magnitude higher than those of capacitive storage, its use is very interesting for pulsed-power applications. An additional advantage is the capability of inductors to generate any voltage required for discharge. In other words, if a high-voltage discharge is necessary, the inductors can still be charged at a low voltage-in contrast to capacitors. An XRAM generator is an inductive energy-storage device capable of multiplying the charging current by its number of stages. The obstacle to be overcome when operating XRAM generators is the need for opening switches capable of interrupting the charging current. Here, an improved version of a countercurrent-commutation circuit developed at and patented for the ISL allows charging currents of at least 28 kA per XRAM stage to be switched off safely. A 20-stage XRAM generator could thus deliver 20 × 28 kA = 560 kA to a low-impedance load, e.g., a railgun. We report on the design and first tests of a 20-stage countercurrent switched toroidal XRAM generator demonstrator model, designed for charging currents of up to 3 kA, i.e., 60 kA in the load. The compact demonstrator has a circular ground plate with a diameter of 100 cm, and the height of the installation is 25 cm. The toroidal-coil arrangement provides a very good containment of the magnetic field and, consequently, a high efficiency.