I. Introduction
The coilgun is a device used to launch a projectile using electromagnetic energy. It uses the magnetic field generated by the coil current to accelerate the projectile in the barrel. In fact, coilguns are electromagnetic guns that use the Lorentzforce to accelerate a projectile with a conducting armature [1] and [2]. In theory coilguns can be divided in two categories, asynchronous and synchronous [3]. In recent years, coilguns have been used by armed forces [4]. The design of coilgun depends on the magnetic flux density in the air gap, maximum current density over a coil cross section and repulsive force acting on the coil. In a practical case very high magnitude and short duration of current pulse is applied to the coil. In order to gain a quantitative understanding of these parameters it is desirable to calculate these parameters well in advance.