Muzzle arc control using an inductive shunt

Abstract

Many electromagnetic launcher applications require that no electric arc occurs at the muzzle when the armature exits. Various techniques have been proposed to satisfy this requirement, including a muzzle shorting switch or a resistor connected across the muzzle. This paper examines the prospects for using a fixed inductive short circuit across the muzzle to eliminate muzzle arcing. The design of an inductive muzzle shunt is conceptually simple. During launcher operation, magnetic flux passes through an armature due to its finite resistance. The muzzle shunt traps this flux in the barrel, causing part of the input current to be diverted past the armature to the muzzle shunt. As the armature approaches the muzzle shunt, this flux is compressed into the shunt inductance. If the inductance of the shunt is chosen correctly, then at exit all of the current will be in the shunt and the armature current will be zero. The process of compressing the flux into the shunt can occur quite rapidly as the armature approaches the shunt, resulting in minimal loss of effective launcher length. In addition, the augmentation effect of the shunt reduces the action integral of the armature current, which can result in increased performance. An experimental demonstration of muzzle shunt arc suppression was performed on a 25-mm bore railgun. The shunt design is described and current waveforms are presented that demonstrate armature current interruption at exit.