3D finite element simulation and synthetic tests of vacuum interrupters with axial magnetic field contacts

Axial magnetic field improves the interruption ability of vacuum circuit breakers. It is known that the design influences the axial magnetic field (AMF) distribution, current distribution and hence the interruption performance. In this paper, the authors present a numerical and experimental study for several segmented coil geometries. The numerical study involves three-dimensional AMF simulations and the? experimental study evaluates their performance in short-circuit interruption tests. The calculations are analysed for magnetic field distribution. Two empirical models, which relate to the performance design parameters are widely accepted. From this, they deduce several criteria for "effective contact area" depending on the magnetic field strength and position (in time and in space). The first results suggest that the interruption ability of AMF vacuum interrupters could be described by a simple relationship. the interruption ability is proportional to the square of the contact diameter times the "effective area" percentage.