Design and Implementation of a Linear Induction Launcher with a New Excitation System Utilizing Multi-Stage Inverters

Abstract

Linear induction launchers (LILs) are a specific subtype of linear motors. However, LILs are air-core machines that consistently operate in a transient rather than a steady state. Moreover, their operating currents and voltages exceed those of traditional machines. The execution time of LILs often remains within a few milliseconds, and it is essential to manage extremely high-power levels quickly. The control methods for LILs differ from those used for regular machines due to the differences from conventional linear motors. In this respect, there are still challenges to be overcome in power systems designed for LILs in the literature. This study has developed a novel power energization system to address these challenges, particularly in terms of inadequate V/f control and the unnecessary energization of regions along the barrel where no projectile is present. It focuses on the system’s design using multi-stage H-bridge inverters to produce a sinusoidal current for section-by-section polyphase excitation. An FPGA-based electronics control system generates bipolar PWM fiber-optical signals for IGBT switches for scalar V/f control of the inverters. Distributed multi-inverters power each stage of the launcher’s barrel and are controlled by the FPGA to create the travelling electromagnetic wave package. Three-dimensional FEM analysis is used for observation of the trigger timing to ensure positive force along the barrel. By driving each inverter independently, the coils on the barrel are excited sequentially based on the position of the projectile. This study also explains the implementation of a laboratory-scale barrel prototype, a 40 mm aluminum projectile, its power electronics, and the control part of the multi-stage inverters. In this study, 3300 V–1200 A IGBTs and 8.8 mF–2000 V DC-Link capacitors were used in the H-bridge inverter modules. Experimental studies have been conducted on the launcher, and the results obtained, including achieving a velocity of 30 m/s, are consistent with the electromagnetic simulations. It has been observed that the launcher, powered by the proposed system, is approximately 57.14% more efficient compared to the version energized by a single inverter.