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The distribution and dissipation of neutral atoms are crucial for understanding the dielectric recovery process after interrupting direct current (DC) vacuum arcs. This article aims to investigate the dissipation of copper atoms after a forced extinction of the vacuum arc experimentally, adopting the plane laser-induced fluorescence method. The change in the 2-D distribution of copper atoms with time is presented. The results show that the magnetic fields, the axial magnetic field (AMF), and the transverse magnetic field (TMF) have a limited effect on the initial density of copper atoms. For both the AMF and the TMF, the copper atom densities at current zero (CZ) vary in the range (6– $8) \times 10^{17}\,\,\text{m}^{-3}$ when 3-kA vacuum arcs are forced to 0 in 0.2 ms. Contrary to the TMF case, in the AMF case, the evaporation on the anode after the CZ results in long-existing atoms near it. Consequently, the atom density of the TMF decays faster than that of the AMF, which indicates that a vacuum interrupter with the TMF contacts has a better performance when interrupting a DC load. The difference between the two magnetic fields originates from the arc control patterns. Namely, the AMF tends to keep vacuum arcs in a stable mode, which is unfavorable for a DC interruption; on the contrary, the TMF drives the vacuum arcs to move at high velocities resulting in faster dissipation of copper atoms after the CZ. In addition, the composition proportion of CuCr contacts has a limited effect on the diffusion of copper atoms when a low-vacuum arc is interrupted. [ABSTRACT FROM AUTHOR]

Anode surface temperature has a significant impact on the interruption capacity of a vacuum circuit breaker. The objective of this paper is to experimentally understand the decay process of anode surface temperature after extinguishing a high-vacuum arc with a large contact gap. The anode surface temperature after current zero was measured by a two-color pyrometer and arc modes observation was recorded by a highspeed charge-coupled device. A pair of asymmetric butt type contacts (contact materials: CuCr25 and CuCr50) was subjected to an axial magnetic field in a demountable vacuum chamber. The experimental result shows that there are two modes in decay processes of anode surface temperature: Mode I and Mode II. Mode I describes the anode surface decay process after diffuse low-current extinction and Mode II corresponds to high current extinction. In addition, the decay time of anode surface temperature will last longer, if the proportion of chromium rises from 25% to 50% in anode material. [ABSTRACT FROM PUBLISHER]

We report our measurements of anode current density distributions for different modes in vacuum arc discharge using a split-anode and a cup-shaped axial magnetic field cathode configuration system. The modes investigated included the diffuse arc and anode spot. The anode surface was divided into four regions: one central region and three symmetrical-disposed peripheral annular-arc regions. Three different-sized central regions were selected with diameters of 12, 18, and 20 mm. The contact material was CuCr25 (25% Cr). The arc current in the tests ranged from 6 to 14 kA (rms) at 50 Hz. The opening velocities were 1.8 and 2.4 m/s, respectively. The currents of the four areas on the anode contact were measured by four Rogowski coils situated outside the vacuum chamber. The experimental results show the current density distribution in different arc modes. For the diffuse arc mode with arc currents of 6 and 8 kA (rms), the average current density in the central region at current peak ranged from 8.5 to 15.9 A/mm ^2 . The anode spot current density ranged from 31.9 to 37.7 A/mm ^2 , estimated from the current density in the eroded region caused by the anode spots covering the entire central region of diameters 12 and 18 mm, at currents of 12 and 14 kA, respectively, regarded as the lower limit current density of the anode spot. Moreover, the dependence of the current density distribution on opening velocity in diffuse arcs was slight. For the anode spots, the current density distribution with higher opening velocity was more concentrated. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to investigate the anode erosion pattern caused by the blowing effect in constricted vacuum arcs under an axial magnetic field (AMF). The blowing effect was reflected from the microstructure of the melt layer on the anode. A pair of 42-mm-diameter AMF contacts were installed inside a detachable vacuum chamber. The contact material was CuCr25 (25% Cr). The arc modes were observed with a high-speed charge-coupled device video camera. The anode surface temperature after current zero was measured with a two-color pyrometer. The microstructure of the cross section of the anode surface melt layer was observed by scanning electron microscopy. The experimental arc currents increased from 10.5 to 17.8 kA (rms) with an interval of 2 kA. The results show that the anode erosion pattern in constricted arcs is caused by an interactive process of thermal and mechanical effects. The constricted arc columns melted the anode surface material and blew the molten material from the center to the peripheral region. The redistribution of the anode molten layer caused by this blowing effect formed two erosion regions on the anode surface. The depth of the melt layer in the central region was less than 100 \mu \textm , but in the peripheral region it was in the range of 100–400 \mu \textm . In these different erosion regions of the anode melt layer, there was considerable variation in both size and shape of the Cr sphere. Moreover, the thermal and mechanical effects of the constricted arc redistributed the Cr content of the molten layer on the anode surface. The Cr content in the central region (Erosion Region I) increased to 31% and in the periphery region (Erosion Region II) it decreased to 18%, respectively, from 25% before the experiments. [ABSTRACT FROM PUBLISHER]