A Novel Technique to Arrest the Armature Capture Effect in an Induction Coilgun

In an induction coilgun, the exit velocity of the projectile (or armature) differs from its theoretical maximum velocity that can be achieved. This difference significantly depends on the pulsed power source (PPS) parameters and the armature (sleeve or solenoid) structures. It has been reported that the "armature capture effect" phenomenon is the cause of this velocity reduction. The armature capture effect must be nullified to achieve the maximum possible exit velocity or to increase the efficiency of the induction coilgun to its maximum possible extent. However, not much attention has been given to this issue so far. This article shows through computer simulation that the reduction in the projectile velocity can be arrested successfully if the drive coil current is commutated at the right instant. An SCR-based switching circuit for the drive coil current has been implemented in the induction coilgun under development in the laboratory. This article describes the SCR commutation circuit topology to commutate the drive coil current for an induction coilgun operating at high voltage and high current and compares the simulation results obtained with and without the current commutation for four different sleeve armatures of varying lengths but of fixed mass.