Effect of Rail's Material on Railgun Inductance Gradient and Losses

Abstract

Inductance Gradient is one of the most important and effective factors in the efficiency of a railgun. This factor is, in turn, a function of various parameters such as railgun geometry, dimensions and materials. In this paper, we will discuss the effects of rail's material conductivity (sigma) and permeability (mu) on the inductance gradient (L') and the ohmic losses of railgun. By simulation of the railgun using two dimensional Finite Element Method (2D-FEM), for different values of sigma and mu, the stored magnetic energy and ohmic losses are calculated and then L' obtained and tabulated. Increasing the material conductivity (sigma) of rails, or choosing a good conductors for rails fabrication, will decrease inductance gradient. However, in this case, we can reduce ohmic losses. High value of permeability (mu) results the increasing of L' and decreasing of losses. In this paper, we will present two dimensional finite element models for railgun, electromagnetic equations and the boundary conditions, field and current distributions, L' and losses tables for different materials of the rail and some useful graphs.