Magnetic blow-off in armature transition

Magnetic blow-off forces play an important role in arcing and failure of electrical joints and contacts in electrical systems under high current fault conditions. Magnetic blow-off forces arise from concentration of current in the contact interface and tend to blow the contacts apart, causing separation and arcing. Simple models have been developed to predict the magnitude of these forces and permit the design of joints and contacts that can successfully resist the forces. In this paper, the role of magnetic blow-off in railgun armature contacts is explored. It is shown that magnetic blow-off forces are important and may be the final step in a series of events that ultimately leads to transition. Models that predict the conditions under which blow-off will occur are developed, and supporting experimental data is described.