Numerical analysis of brush commutation in helical coil electromagnetic launchers

Helical launchers have become attractive for launching large masses to intermediate velocities because of their high inductance gradient. At these velocities the commutation of the brushes assumes great importance and it is supposed to be the main limiting factor of their performance. The possible presence of destructive arcs and the dissipation of the commutation energy in the brush material are serious problems that affect these launchers. A numerical model based on an equivalent circuit approach is adopted here to investigate the commutation process and to address the dissipation of the commutation energy in the brush material owing to the presence of arcs. A comparison with the performance predicted by neglecting the arcs has been carried out. This comparative analysis has clearly evidenced the need to consider the presence of the arcs also in the preliminary design of the device. Both the integrity of the brushes and the final velocity of the armature may be heavily affected.