Novel DC current interruption technology based on the instability of vacuum arc under composite transverse magnetic fields

Abstract

The objective of this work intends to propose a novel current interruption technology in vacuum for LVDC power systems, based on the instability of vacuum arc under composite transverse magnetic fields (TMFs). The interruption characteristics were experimentally determined in an overdamping C-L-R circuit. The experimental results indicated that the DC current of 800 V/500 A could be successfully interrupted within 5 ms by the proposed technology. Moreover, the interruption process could be divided into two stages, the Stable and Unstable stages. In the Stable stage, the arc voltage linearly increased from 20 to 35 V, where the arc current was limited slightly. In the Unstable stage, the arc voltage would rapidly increase and exceed the supply voltage, where the current would be forced to zero. Finally, the double-break LVDC vacuum switches, no matter in series or parallel, were difficult to improve the interruption capability, because of the asynchronous occurrence of the Unstable stage in series vacuum interrupters and the fast current-commutation between parallel vacuum interrupters. This technology takes advantages of high interruption capability, short arcing time and low complexity, which is a promising solution to expand the application of vacuum switch to the LVDC power systems.