Improvement of Current Filament Method and Its Application in Performance Analysis of Induction Coil Gun

The performance analysis of induction coil guns is very useful in their experimental research and electromagnetic optimization design. This study improves the current filament method (CFM), which is commonly used in a coil gun's circuit simulation. In the improved CFM, each excitation coil was divided into small subcoils to improve the calculation precision of inductance in the equivalent electric network. In order to check the effect of the improvement and analyze the electromagnetic transient in coil-gun launch, the field-circuit method for induction coil guns was introduced. The field model is built based on the 3-D composite grid method (CGM). CGM uses two sets of mutual independent grids to discretize the solution region, the coarse grids discretize the global region, and the fine grids discretize the moving part. In every time step, instead of remeshing, it is only necessary to change the coordinates of nodes in fine grids. A three-stage coil gun's field-circuit model is built, and the validity of modification is proved by comparing the results of field-circuit model before and after the improvement of CFM.