Molecular dynamics simulation of behaviours of W/Gr enhanced Cu-Cr anode in vacuum arc

Adding tiny amounts of tungsten (W) and graphene (Gr) in traditional Cu-Cr contact efficiently enhances the mechanical strength and breakdown strength of vacuum circuit breakers (VCBs). However, anodes made of W or W-alloy are acknowledged to harm the interruption performance of VCBs through impeding the post-arc recovery of vacuum gap by stronger surface emission. To investigate into the influence of W/Gr addition with a small mass ratio in Cu-Cr contact, this study employs molecular dynamics method to simulate anode behaviours during arcing and post-arc processes. Through the simulations, surface temperature and surface atom emission of the anode, which are perceived as the key phenomena affecting the post-arc recovery of vacuum, are used to assess the influence of material modifications on the interruption performance of VCBs. As a result, the existence of additional phases and the resulted interfaces are shown inevitably affecting the thermal processes of anode. Furthermore, this influence relates to the position, thickness, and orientation of the additional phases, and could be mitigated by limiting the size of the additional phases. Simulation results are validated by experiences of W usage in VCBs, as well as theoretical analysis of thermal processes of anode. Based on the simulation, suggestions on the material preparation of material modifications are provided to mitigate their influences on the interruption performance of VCBs.