Study on current concentration of large-caliber C-shaped armature at current ramp-up stage in square railgun

Compared with small and medium caliber railguns, large caliber railguns (LCRs) could be applied in more occasions. Armatures for LCRs could be designed according to studies on small and medium caliber railguns, yet there are some unique features of the design. Current concentration is a special phenomenon in LCR systems, where it's more severe due to high energy density and large current. For a large-caliber armature that has the same muzzle speed as small-caliber armatures, which guarantees the identical velocity skin effect, the skin effect and the induced current are studied and have to be considered as the main influence factors. In this paper, the current distribution and concentration between large caliber armature (90 mm × 90 mm) and small caliber armature (20 mm × 20 mm) are studied and compared. The current distribution coefficients of these two armatures are obtained, it's shown that current density in large armature is more concentrated than the small one. The proportions of induced current to the total current for 90 mm × 90 mm and 20 mm × 20 mm armatures are obtained, which indicate that the induced current is the main reason for current concentration in large-caliber armature. At last, measures to improve current distribution in large-caliber armatures are discussed.