# Photographic Analysis of a Low-Current, Vacuum Electric Arc Using an Ultrafast Camera

## TL;DR

This paper uses ultrafast photography to study how low-current electric arcs behave in a vacuum, helping improve the design of vacuum interrupters.

## Contribution

The study introduces time-lapse photographic analysis of low-current vacuum arcs using an ultra-high-speed camera and oscilloscope.

## Key findings

- Vacuum arc voltage remains stable during the stable phase but increases during the unstable phase.
- There is a correlation between arc voltage increases and flash intensity in the interelectrode space.
- Microparticles ejected from contact surfaces were observed moving or adhering to electrodes.

## Abstract

The main component of vacuum interrupters responsible for ensuring the correct flow of current is the contact system. In a vacuum environment, due to the higher values of the mean free path of electrons and particles in the contact gap, the material and condition of the contacts exert the greatest influence on the development of the arc discharge. To accurately analyze the phenomenon of discharge development in vacuum insulating systems, the authors conducted a time-lapse photographic analysis of a vacuum electric arc. For this purpose, they used a test setup comprising a discharge chamber, a vacuum pump set, a power and load assembly, an ultra-high-speed camera, and an oscilloscope with dedicated probes. The measurement process involved connecting the system, determining the power supply, load, and measurement parameters and subsequently performing contact opening operations while simultaneously recording the process using the oscilloscope and ultra-high-speed camera. An analysis of a low-current vacuum arc in a residual helium gas environment, with a pressure of p = 1.00 × 101 Pa was carried out. Different phases of vacuum arc burning between electrodes in the discharge chamber were identified. In the stable phase, the arc voltage remained constant, while in the unstable phase, the arc voltage increased. The results of the time-lapse analysis were compared with the characteristics recorded by the oscilloscope, revealing a correlation between the increase in vacuum arc voltage and the intensity of flashes in the interelectrode space. The movement of microparticles ejected from the surface of the contacts—either reflecting or adhering to one of the electrodes—was observed. This analysis provides a deeper understanding of the processes involved in discharge formation and development under reduced pressure conditions. Understanding these mechanisms can support the design of vacuum interrupters, particularly in the selection of suitable contact materials and shapes.