Research on electromagnetic performance affected by shielding enclosure of a coil launcher

Shielding enclosure is very important to designer in a coil launcher system, which directly determines the electromagnetic performance of the coil launcher. The formulation of eddy current field involving movement is deduced, and the time step transient finite element method (FEM) calculation theory is illustrated in the paper. The simulation model of a three stage coaxial induction coil launcher is built based on ANSOFT MAWELL software. In the transient simulation model involved in moving conductor eddy current, the power pulse generator and the power electronic component are modeled as circuit simulation in MAXWELL schematic module. The circuit model is well coupled with field model in transient solver. In every time step, the current values which are obtained in circuit simulation are loaded in field model as exciting source to the coils. Three typical shielding materials, such as, iron, steel and ferrite is set in 2D field model to study the influence of shielding enclosure on the electromagnetic performance of the coil launcher. Silicon steel (laminated sheets) is taken in 3D field model. Different geometric dimensions of shielding enclosure are also taken into consideration. The speed of the armature and the magnetic field are calculated during every calculation case. The current distribution in armature and shielding enclosing are displayed as well. The laws of shielding enclosure on the electromagnetic performance are 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. A silicon steel shielding enclosure has the similar impact on the speed of the armature to the ferrite, but has better shielding effectiveness than the latter. Research results shows that the silicon steel is suitable for the coil launch shielding enclosure.