Calculation of eddy-current-induced magnetic fields in vacuum interrupters with axial magnetic field contacts

The variation of the nonsteady magnetic-induction field of axially symmetric contact arrangements in space and time is calculated by using a finite-element program system. The influence of individual design elements on the induction field is analyzed and the effectiveness of measures for suppressing eddy current is represented. The delaying and damping effect of the eddy currents on the magnetic field increases from the outside towards the axis of symmetry. This changes the radial field distribution for the duration of the arc and the zone of maximum induction travels towards the inside. When the contacts are open, the radial component predominates over the axial induction field in the vicinity of the contact edge. The azimuthal inherent magnetic field of the arc is free of eddy currents and dominates in the outer arc region, particularly in the phase of current increase