Measurements of time-resolved spectra of fuse arcs using a new experimental arrangement

A new experimental set-up has been designed to observe spectral studies in fuse arcs. The fuses studied here are high breaking capacity fuses.They consist of a fuse element (in silver or copper) surrounded by silica sand. In this study, the arc dissipates 1200 J, the peak of electric current is about 2000 A and the duration of the arc is 3 ms. The maximum cross section of the squeezed arc is about 0.5 mm × 5 mm. The whole of the visible spectrum has been registered, from 360 nm to 800 nm, in the exploding part of the arc. The spectrum consists of continuous light together with spectral lines. The continuous light intensity is closely correlated with the current intensity. The spectral lines appear mostly when the current decreases. The behaviour of the spectra shows that there is a big gradient of species concentrations in the arc, together with a high gradient of temperature. The temperature is measured from Si II lines in the arc core. The calculation gives about 30 000 K at 1.3 ms. The measured values of electronic densities vary between 10¹⁷ and 10¹⁸ cm^-3.