Research on Electromagnetic Performance Affected by Shielding Enclosure of a Coil Launcher

Shielding enclosure is very important for a coil launcher system. Shielding performance directly determines the electromagnetic performance of a coil launcher. In this paper, the formulation of the eddy current field involving movement is deduced, and the time step transient finite element method calculation is applied to investigate the shielding performance of a coil launcher. The simulation model of a three-stage coaxial induction coil launcher is built based on ANSOFT MAXWELL software. The transient-simulation model, which is involved in moving conductor eddy current, the pulsed power generator, and the power electronic component, is built as a circuit simulation in MAXWELL schematic module. The circuit model is well coupled with the field model in a transient solver. In every time step, the value of current obtained by the circuit simulation in advance is loaded in the field model as an exciting source to the coils. Three-typical shielding materials, iron, steel, and ferrite are used in 2-D field model to study the influence of shielding enclosure on the electromagnetic performance of the coil launcher. Silicon steel (laminated sheets) is taken in the 3-D field model. Different geometric dimensions of shielding enclosure are also taken into consideration. The speed of the armature and the magnetic field are calculated. The current distribution in the armature and shielding enclosing are displayed as well. Effects of shielding enclosure on the electromagnetic performance are then concluded. A ferrite shielding enclosure will increase the speed of armature obviously. The conductive material will induce eddy currents and decrease the leakage magnetic field outside, that shows excellent shielding performance. The silicon steel shielding enclosure has a similar impact on the speed of the armature to the ferrite, whereas it has better shielding effectiveness than the latter. Research results show that the silicon steel is suitable for the coil launcher shielding enc- osure.