Effect of rail/armature geometry on current density distribution and inductance gradient

The distribution of current in the conductors which is affected by the geom etry of the armature and velocity of the armature plays an important role i n the performance of an electromagnetic launcher. In the early launching st age the current tends to flow on the outer surfaces of the conductors, resu lting in high local current densities. Later in the launch, the tendency fo r current to concentrate on the surface is driven by the velocity skin effe ct. High current densities produce high local heating and, consequently, in creased armature wear. This paper investigates the effects of rail/armature geometry on current density distribution and launcher inductance gradient (L'). Three geometrical parameters are used to characterize the railgun sys tems. These are the ratio of contact length to root length, relative positi on of contact leading edge to root trailing edge, and the ratio of rail ove rhang to the rail height. The distribution of current density and L' for va rious configurations are compared.