Eddy Brake Reaction at Bus Structures of Medium-Large Caliber Electromagnetic Launchers

An important application for large-scale pulse power supplies (PPS) is electromagnetic launchers (EMLs). These devices turn stored electrochemical energy, measured in megajoules (MJ), into linear mechanical energy. Simulations play a vital role in EML research due to the presence of challenging physical conditions. As the level of operational risk increases, the addition of more energy to the system enhances the accuracy of the model. We encountered an unforeseen surge in rail current during our recent 8 MJ launch experiments. Underestimating peak current can be dangerous due to the potential risks it poses, such as armature stall leading to contact meltdown and overheating of cables. This phenomenon did not occur with small and medium calibre EMLs, specifically the EMFY-l and EMFY-2. A comprehensive analysis is performed to reveal the fundamental physical root-cause for the current overshoot. It has been found that the bus structure acts as a shield against eddy currents, leading to a decrease in the machine's inductance. This reduction is crucial as it has an impact on the dynamics of the start-up launch. The hypothesis is tested using a combi-nation of simulations and experimental results. Electromagnetic calculations are investigated by measuring rail currents, breech voltages, and muzzle voltages. The results demonstrated a strong correlation with the experimental data, particularly when the bus structure was explicitly modelled.