Investigations on arc movement in vacuum interrupters by arc rotation measurements with external magnetic field sensors

The primary purpose of an RMF (radial magnetic field) contact system is to force the constricted vacuum arc to rotate on the contact surface, thereby increasing the interruption level and reducing contact erosion. The ability to detect the movement characteristic of the rotating arc inside a vacuum bottle is an important tool to improve performance and lifetime of the contact system. The conventional approach is the use of specially prepared vacuum chambers that allow high speed videos of the rotating arc. Main disadvantage of this approach is that the internal vapor shield has to be modified with viewports or even completely removed, which may have an impact on the movement characteristics. This research project is focused on developing a measuring system to detect the motion of a constricted arc in an RMF contact system inside standard vacuum bottles. The measuring system detects the external magnetic field from the arc using Hall Effect Sensors. This approach allows the investigation of commercially available vacuum interrupters. The possible influence of the original vapor shield, as well as the relatively small vacuum volume, can be observed. The working principle of this measuring system is discussed along with the method to correctly analyze the measured signals. The influence of contact separation and current level on the movement characteristic was investigated.