Analysis of electrode heating processes in the switching contacts of vacuum circuit breakers

Vacuum interrupters are widely applied for the protection of medium-voltage electric circuits. For stabilization of the arc behaviour the spiral contacts producing the axial magnetic field (AMF) are typically used. The properties of AMF are strongly affected by eddy currents which inevitably appear in the contact system due to variation of the magnetic field. Furthermore, those currents are responsible for the local heating of the contact material and can lead to its degradation. Optimization of the contact system geometry requires, therefore, the knowledge about the spatial distribution of eddy currents. Electro-magnetic simulations have been used for the visualization of distribution of current flow, magnetic field and eddy currents in a sample AMF contact. A simplified model of the arc column has been used. The cases of the symmetric and asymmetric current flow through the electrode gap have been considered. The contribution focuses on the analysis of the eddy currents and discusses the ways for influencing the distribution and the magnitude of eddy currents inside the contact system.