Study on structures to support AMF electrodes and compensate for AMF loss by itself

Abstract

The AMF(Axial Magnetic Field) electrodes of VI(vacuum interrupters) can be largely classified into two groups; coil type and cup type. While TMF(Transverse Magnetic Field) electrodes do not need structures to support the electrodes, the AMF electrodes should have them inside. In case of separating welded contacts, it is recommended that the structures be brazed with electrodes and contacts. In this case although these structures are generally made of metal of which conductivity is low e.g. stainless steel, the current flows partly through them, which prevents AMF from generating. In this paper, a new structure was proposed to support the AMF electrode and help generate AMF. The structure was made of stainless steel and a form of hollow cylinder with slits like a cup-type AMF electrode. The slits were made on the diagonal to generate AMF in the same direction as the AMF electrodes. The structure can be applied to both coil type and cup type electrodes and preferably to VIs with high breaking capacity, where contact welding occurs sometimes. The AMF distribution and arc appearance of electrodes with the structures were compared with the ones without them. Even though the amplitude of AMF between the electrodes with the structures was lower than the one without them, the former could be increased almost up to the latter depending on the length and direction of the slits. The structures were applied to a 50kA VI and helped pass the ANSI tests.I.