Investigation on the Influence of Different External Magnetic Field Strength on the Dynamic Voltage Distribution of Double-Break Vacuum Gaps in Series

Previous researches show that grading capacitors truly improve the dynamic voltage distribution uniformity of multibreak vacuum circuit breakers (VCBs). However, large capacitors can reduce the breaking capacity. In order to obtain balanced voltage distribution with small capacitors, nonsynchronous external magnetic field was adopted. The Helmholtz coil was designed to generate a stable magnetic, and nonsynchronous magnetic field control system was designed to realize double-break nonsynchronous control. The 3-D models of Helmholtz coil and axial magnetic field (AMF) contact were simulated and analyzed in Maxwell. The external magnetic field (EMF) experiment platform for double-break vacuum gaps was set up. In the experiment, the strength of EMF on each break can be adjusted by the nonsynchronous magnetic field control system. The experimental results show that different EMF strengths on two vacuum breaks in series can improve the voltage distribution uniformity. Meanwhile, the magnetic field strength has the best matching parameters. The works in this article provide references for magnetic field regulation and interruption performance of VCBs.