Investigation in Forced Shifts of Current on the Dynamic Armature and Rail Interface

The armature and rail (A/R) interface in railgun is considered a dynamic electrical contact involving contact pressure and area variations, and the extreme working conditions lead to distinct electromagnetic properties from the bulk and perfect contact. This article investigates the mechanical and electromagnetic properties of the dynamic A/R interface based on imperfect contact boundary conditions. The contact area expands as the driving current increases, which increases the current distributed area and enhances uniformity. The current redistribution patterns are identified as forced shifts of current, with currents on the previous contact area boundaries decreasing and those on the existing boundaries increasing sharply. The analysis results indicate that the electric scalar potential difference and contact conductivity dominate the current variations on previous and existing boundaries, respectively. In other words, the conduction current and the contact state are the primary factors causing forced shifts of current rather than the induction current. Furthermore, the influences of dynamic contact conditions on the electric scalar potential difference are studied, and the results indicate that contact area variation has a more significant impact on the electric scalar potential difference. As the contact area changes, the conduction current paths shift with contact area boundaries, which causes variations in electric scalar potential differences, consequently, leading to the phenomenon of forced current shifts.