Analysis of Projectile Motion in Bore and Transfer Efficiency for Electromagnetic Railgun
Electromagnetic railgun (EMG) use a high-current, high-energy electrical pulse to accelerate projectiles to hypersonic velocities. A pulsed power supply (PPS) that employ capacitors as the energy store are typically used to shape the required electrical pulse. In this paper, the differential equations of projectile moving in the bore has been given and solved. The general pattern of projectile moving in the bore has been studied. Considering the influence of current fluctuation on velocity, the stability of armature has been discussed. In order to improving system performance, the efficiency of main energy transfer process has been calculated. The influence of current shape consists of several electrical pulse on muzzle velocity and efficiency has been studied. And some important conclusions have been reached, which provide theoretical references for guiding railgun design and choosing waveform of discharging current.
A compact pulse forming network, based on semiconducting switches, for electric gun applications
At ISL a highly modular pulse forming network (PFN) for electric guns (railguns, electrothermal-chemical guns) has been developed and built up. The PFN consists of pulse forming units (PFU), which are composed of a capacitor (E=50 kJ), semiconducting switches (thyristor, crowbar diode), an inductor and a coaxial cable connecting the PFU to the electric gun. The inductor is required in order to limit the maximum current capability of the SCR switch. Due to novel SCR with a higher current rate (dI/dt) and current capability (I>150 kA) a PFU without the above mentioned inductor could be designed. The new PFU has a smaller size and less weight than the former. Based on this PFU, a PFN consisting of 24 units has been investigated. The features of the novel PFN are presented in the paper and are compared to the former PFN including an inductor. The lower inductance makes the novel PFN more flexible due to the ability of generating arbitrary waveforms and the current shape can be adjusted to the load in a very sophisticated manner. Additionally the current in the load decreases more rapidly (I(t)/spl sim/e/sup -(R/L)(t)/). So the electrical energy stored in the electrical gun at projectile exit is strongly reduced and the efficiency of the electric accelerators is enhanced.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).