Spectrum intensity of metal ion and transition boundary to gaseous phase in W break arc

Abstract

The relationship of the spectral intensity for a W break arc to the gaseous phase transition boundary is investigated. The average spectral intensity of tungsten metal ions is small at all arc durations if the closed contact current is below the boundary closed contact current for phase transition, but increases rapidly when the latter current is exceeded, as does the average spectral intensity in the metallic phase. The instantaneous spectrum intensity increases rapidly after the contact gap reaches the value corresponding to the minimum point of the Paschen curve. At currents for which the transition ratio is 100%, the spectrum intensity has a peak just after arc initiation and a minimum when the gap corresponds to the minimum of the Paschen curve; the intensity is also close to the maximum when the arc transits to the gaseous phase.