A Comparison of Velocity Skin Effect Modeling with 2-D Transient and 3-D Quasi-Transient Finite Element Methods

Analysis of the velocity skin effect in electromagnetic launchers requires a 3-D transient finite element method, unlike magnetic skin and proximity effects. However, large speeds with velocity skin effect dominance cause convergence problems when moving or deformed mesh physics are used in a transient FEM in the 3-D analysis. Commercial finite element codes are unable to solve the electromagnetic aspects of a launch using a transient solver in 3-D due to the aforementioned challenges. However, 2-D approximation suits well to model VSE even with commercial software. Such approximation overestimates VSE resistance due to the error comes from the assumption of infinitely high rail height. In this study, we used a quasi- transient 3-D FEM model where the conductivity of the air- armature region is varied to emulate the movement of the armature to invest the accuracy of the 2-D approximation. Results have shown that using 2-D approximation, the VSE resistance is overestimated by nearly 40%. The proposed VSE calculation model has been included in the EML model, and simulation results compared for experimental results with different electromagnetic launchers, EMFY-l and EMFY-2, and showed good agreement.