Research on the Criterion of Transition for Electromagnetic Launching

In this paper, the multiple factors in the transition process is comprehensively analyzed. When the armature is sliding at a very high speed, the velocity skin effect will generate the melt-wave. Then the melt-wave will produce a reversed electromagnetic force, which will leads to the armature separating from the rail. The larger the erosion area, the stronger the separating force. Besides, the mechanical force is much smaller than electromagnetic force. When the contact area cannot meet the conductivity capacity of large current, there will appear transition. The prediction formula of transition is given. The calculation results are almost in consistent with the experimental data. Finally, this paper proposes a key criterion coefficient of j2V, defined as the transition criterion. From the quantitative analysis and experimental data, its value is about 4E20 (A/m/s). When the contact power is greater than this criterion coefficient, there will be transition. It makes the prediction to be more convenient and quickly, which will be very useful for the railgun design.