Model of contact transitioning with 'realistic' armature-rail interface

摘要

Arcing transition of metal-to-metal contacts is a key technical challenge in the development of railgun launchers. Theoretical understanding of the process remains poor and controversial. Several authors have explained transitioning by a velocity skin effect driven "melt wave" Others have shown experimentally, that arcing transition even occurs for static contacts subject to high current pulses, and have proposed a "contact resistance" model, with the contact resistance due to A-spots. This model explained the available experimental data reasonably well for armatures with relatively short lengths of the contact zone. The velocity skin effect model assumes a perfect, resistance free contact, while the contact resistance model neglects any velocity related effects. In this paper we combine the two approaches to obtain a more realistic picture of the velocity skin effect and its role in transitioning of armature contacts. We show that when realistic properties of the contact interface are taken into account, the structure of the velocity skin effect and the speed of a wave of local transitioning may significantly differ from the "ideal" theory.