Physical arc appearance and electrode phenomena of vacuum arcs in axial magnetic fields

An experimental study of high current vacuum interrupters with axial magnetic field contact geometries is presented. Arc visualisation shows a progressive constriction of the arc, the temperature of the contacts is very homogeneous and in excess of the melting temperature, and shadowgraphy shows the presence of an agitated liquid. From this we deduce that it is by the flow of liquid contact material that the heat of the arc is distributed across the contact surface. This knowledge stimulates the conception of a new type of Liquid Metal Flow (LMF) vacuum interrupter with a 30 % improvement in interrupting capability.