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

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.