The behavior of vacuum arcs between spiral contacts with small gaps

The application of small gaps in high-current vacuum interrupters highlights the interdependence of the contact design, the contact gap, and the are behavior. In this investigation, a framing camera was used to record the appearance and motion of drawn vacuum arcs between spiral-petal contacts with final gaps of 2 to 3 mm. After the rupture of the molten metal bridge, a high-pressure are column formed and expanded across the width of the spiral arm. With a single are column for the duration of the half-cycle, an intense anode spot formed if the peak current exceeded similar to 15 kA. Compared to results previously obtained at larger gaps, the are motion was greatly reduced, and severe contact damage was observed at lower currents.