Research on the current-zero period of vacuum arc interruption and equivalent model of post-arc gap

Abstract

In this paper, the current breaking experiments of vacuum interrupter are conducted and the waveforms of voltage and current are obtained. The results show that there is current instability phenomenon when the value of is low and the value of instability-initiation current decreases as the value of increases. The number of voltage spikes will also decrease and irregular oscillation will weaken. According to the experimental results and theoretical analysis, the ‘memory characteristic’ of plasma is proposed and a new mathematical model of post-arc initial plasma density is estabilished which will provides a new method for the calculation of the sheath growth. The equivalent circuit model of post-arc gap is established to analyze the transient recovery voltage. The equivalent parameters in the circuit are obtained by the calculation of sheath growth and plasma density and verified by comparison with measurements. Through the comparison of experimental results between the axial magnetic field (AMF) contact and the butt contact, the effects of AMF on post-arc plasma density and sheath growth are analyzed. The results show that AMF can make the post-arc plasma density higher and the sheath growth slower.