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Investigation of Magnetic Field Arrangement on Launching Performance of Multistage Synchronous Induction Coilgun

For the multistage induction coilgun, many researchers pay great attention to improving the system efficiency. The directions of magnetic field generated by the driving coils are consistent for conventional coilgun, because it is convenient to analyze acceleration characteristic and stress status for the armature in the barrel. In this paper, the launching performance of multistage induction coilgun is investigated in terms of different directions of magnetic field in order to improve the system efficiency. A field-circuit coupled model for a 6-stage coilgun is built. The simulation for the consistent direction of magnetic field is calculated. For the same parameter setup, the directions of magnetic field generated by the last three stages current are changed. The simulation results show that the armature endures a large braking force when going through the last three stages, and the velocity drop is obvious. Meanwhile, the currents in the last three stages are very large. The distribution of the current density and the magnetic field during the transition process of magnetic field are analyzed. The reason for velocity drop when changing the direction of magnetic field is discussed. A method that the trigger position is adjusted for the armature is proposed. The simulation results show that the armature can be accelerated to a higher speed on condition of inconsistent direction of magnetic field with adjusting the trigger position. It is feasible to improve the system launching performance through changing the direction of magnetic field. A 15-stage coilgun is built to validate the method. The experimental results show that the velocity and system efficiency are increased dramatically through changing the direction of magnetic field. It provides valuable reference for multistage induction design.