Three-dimensional magnetic field analysis of novel asymmetric AMF contacts for vacuum interrupters

An axial magnetic field (AMF) applied to the vacuum arc column in the vacuum tube can make the vacuum arc keeping in diffusion state, even if it is interrupting the short circuit current. In this paper a novel AMF contact with asymmetric structure has been present. In principle, the necessary axial magnetic field would be created by two coils in series behind the static contact plate. The axial magnetic field and eddy field are analyzed based on novel axial magnetic field contact design with finite element method. At zero current, the generation of eddy currents by 31.5kA, 50Hz excitation is also considered. The results of axial magnetic field and eddy field analysis such as distribution of the axial magnetic field are described. It has also studied whether the parameters such as the coil height, the coil thickness and the coil diameter have an effect on the axial magnetic field and to what extent they do.