Influence of contacts’ orientation on the AMF distribution in inter‐contact gaps of VCBs

Abstract

An axial magnetic field (AMF) plays an important role in the process of vacuum arc stabilisation during the current breaking process in the vacuum circuit breakers (VCBs) of the AMF type. To minimise the contacts erosion special attention should be paid to reach a possibly high value of the AMF density (between contact plates), especially in the outer electrode region. Various contact geometries are patented all over the world to improve the AMF distribution. Nevertheless, there is an issue which is not raised in the literature as yet. It is the mutual orientation (rotation) of the moving and fixed contacts. This orientation can have an influence on the AMF distribution. The above problem is analysed here numerically using Maxwell (ANSYS) software package based on the finite element method. The own (patented) contact design is considered in the analysis mentioned. However, the beneficial influence of AMF on the arc behaviour is well known for VCB designers, the explanation of this phenomenon is described (in the literature) rather seldom and very cursorily. Therefore, a simplified model accounting for the role of AMF in vacuum arc diffusion is shortly presented at the beginning of this study.