On velocity skin effect — Part II: Restraining method analysis and optimal design simulation

Velocity skin effect (VSE) is a kind of current clustering phenomenon, which occurs in the sliding contact interfaces between the hypervelocity armature and the stationary rails for electromagnetic railgun, disadvantageous to launchers performance. The physical principle of VSE is Skin Effect of pulsed current in rails, and Clustering Near Small Source and Clustering Along Short Path of steady current in armature. The corresponding methods to restrain VSE was deduced and classified in this paper as the followings: 1) to lengthen the contact surface according to the velocity skin depth expression, 2) to add a hard and resistive cladding on the rail´s sliding surface and 3) to narrow the interface considering the Clustering Near Small Source, 4) to adopt U-shaped armature instead of cuboid armature and 5) to control the armature legs´ thickness distribution owing to Clustering Along Short Path. The equivalent 3-D models for VSE were adopted and the contrastive simulations were carried out for three kinds of armature´s legs. The most uniformed distribution of current in three interfaces was accomplished, with which the typical uniform index is about 66%. The conclusion reached was that the general use of five methods and reasonable design could effectively restrain velocity skin effect.