Analysis of the force characteristic on the armature of inductive coil launcher and trigger strategy

The inductive coil launcher utilizes the theory of magnetic coupling between the driving coil and the armature. The armature is accelerated when the direction of induced current in it is opposite to the current direction in the driving coil, or else it will be slowed down. By the finite element analysis, the relationship between the induced current, the velocity of armature, and the waveform of current in the driving coil, is obtained, especially the moment and the position when the armature current reverses its direction or passes zero. The reverse position will be brought forward as the increase of the armature velocity, even the passing zero position of induced armature current will be ahead of the peak point of driving coil current. Thus, it is very important to cut off the current of driving coil at this moment, to avoid slowing down of the armature. Based on the movement and the reverse point of armature current for multiple driving coils system, the trigger strategy of multiple coils can be designed.