Abstract: Armature transition of railgun causes rails erosion and change of launching parameters, which is one of the key problems restricting the performance of railgun. The formation mechanism of armature transition at the down-slope of driving current is analyzed. The armature transition estimation model and electromagnetic parameters calculation model are given. The formation process of armature transition at the down-slope of driving current is simulated by AYNSYS Workbench. The current and magnetic field distribution are simulated, so as the armature deformation caused by the armature electromagnetic force. The effect of current dropping rate on armature transition is analyzed. The simulation and analysis result show that, the eddy current at current down-slope may lead to change the direction of electromagnetic force in armature tail, even the deformation of armature tail, which leads to the armature transition. The reverse electromagnetic force in armature tail increases with the increasing of the driving current dropping rate. As a result, the armature transition occurs more easily.

Key words: railgun, armature transition, current down-slope, arc contact, sliding electric contact