Improved performance of linear induction launchers

Abstract

This paper deals with the effect of parallel (rather than series) connection of the drive coils on the input voltage requirements, as well as on the energy utilization, of hypervelocity linear induction coil launchers fed by flywheel motor/generator sets. All of our previously published studies, 1987 to date, have dealt with series (rather than parallel) connected drive coils, which led to high input phase voltages and relatively low phase currents. In practice, the phase voltage per coil length should be kept below 30 kV/cm, the breakdown voltage of air. Furthermore, at any given time during the acceleration, the moving projectile (surrounded by a cylindrical sleeve) occupies only a portion of a barrel section length. When a parallel connection is used, the currents in the drive coils around the sleeve will be higher than the currents in the other coils in that section. That results in a greater accelerating force than in the series case, which leads to improved energy utilization. The simulation code used in our previously published work to predict the performance of a sectionalized, 3 kg projectile machine, was modified to obtain parallel-connection results for a similar machine. The paper describes the new drive-coil/pulse-generator configuration, explains the mathematical model, and provides graphs to compare the new results with those obtained previously with the series configuration.