Current Concentration of Large-Caliber C-Shaped Armature 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 is more severe due to high energy density and large current. For a large-caliber armature (LCA) that has the same muzzle speed as small-caliber armatures (SCAs), 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 LCA (90 mm x 90 mm) and SCA (20 mm x 20 mm) are studied and compared. The current distribution coefficients of these two armatures are obtained, and it is 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 x 90 mm and 20 mm x 20 mm armatures are obtained, which indicate that the induced current is the main reason for current concentration in LCA. At last, measures to improve current distribution in LCAs are discussed.