Research on the Interruption Characteristics of Wan-type Transverse Magnetic Field Contacts

With the outstanding advantages of short current path, small on-resistance and low cost, the transverse magnetic field (TMF) contacts have been widely applied in medium voltage power systems. In this paper, the vacuum arc experimental system was established using the inductor-capacitor (LC) oscillation circuit, wan-type transverse magnetic field contacts were installed in the demountable vacuum chamber, and the vacuum arc behavior was recorded by the high-speed video camera to research arc characteristics during the arcing process, which including the initial ignition stage, the expansion stage, the arc motion stage and the diffuse stage. In addition, the impact of opening moments was analyzed, and the relationship between arc voltage and arc appearances was summarized. It was found that the change of arc column number in the expansion stage would cause sudden fluctuations of the arc voltage, and unstable arc motion and plasma splash would give rise to arc voltage noise. Then tested contacts were installed into the vacuum interrupters with the same structure and size, the interrupting characteristic experiments of vacuum interrupters with TMF contacts and vacuum interrupters with axial magnetic field (AMF) contacts were completed, and the power frequency withstand tests and the lightning impulse tests of the vacuum interrupters were carried out. The results showed that the wan-type TMF contacts used in this paper had equivalent interruption characteristics as the six-slot cup-shaped AMF contacts.