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When armature passes through the central plane of a driving coil in the process of reluctance coil launching, the magnetic force will reverse and slow down the armature speed. To overcome this problem, the principle of reluctance coil launcher is analyzed. Meanwhile, this paper establishes a finite element analysis model to calculate the electromagnetic force, velocity, displacement and other parameters of the armature while the reluctance coil launcher works. Based on the simulation results, dynamic characteristics of the reluctance coil launcher are summarized and two methods for reverse force suppression are discussed. Furthermore, an experiment system is established and some experiments are carried out. This research concludes that resistor consumption method can effectively restrain the generation of reverse force, with no obvious bad impact on other performance, which provides a practical approach to achieving higher speed and efficiency for reluctance electromagnetic launcher.

A railgun is a kind of new-concept kinetic energy weapon. To overcome the local aggregation of the high pulse current on the surface of the railgun conductor, a method was introduced to abate the skin effect. On the basis of theoretical analysis, three kinds of methods were adopted to increase the current uniformity coefficient. Then, the copper strips, whose thicknesses were 40, 20, 15, and 10 mm, respectively, were simulated with a typical half-period sine waveform that had a 10-ms pulsewidth and a 2-MA peak current. The best current uniformity coefficient in the copper strips is more than 83%. Three conclusions are drawn in this paper. First, under the same conditions, the current distribution will become more uniform as the copper strips become thinner. Second, the current distribution can be improved to a certain extent by rounding strip edges. Third, the added tungsten sheaths or iron sheaths on both sides of the copper strips can further improve the current distribution. The results of this paper have great significance for improving the pulse current-carrying capability of the railgun conductors.Index Terms-Current distribution, finite-element simulation, railguns, skin effect, uniformity coefficient.

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