Critical parameters of the cathode region of a vacuum arc

Rakhovsky, V. I.

doi:10.1109/27.55943

Cited by 16 publications

(11 citation statements)

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“…been assumed in the present model. As has been established with a high-speed optic-electronic registration system, the real arc spot has a complex structure, with a number of microspots existing inside the integrated one [29,30]. These microspots can aggregate or disaggregate, depending on the surface temperature and the current.…”

Section: Discussionmentioning

confidence: 99%

A theoretical and experimental investigation of copper electrode erosion in electric arc heaters: I. The thermophysical model

Marotta

Sharakhovsky

1996

J. Phys. D: Appl. Phys.

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A simple model is reported for copper electrode erosion in electric arc heaters as a result of electrode surface fusion by the action of the arc spot. In the analysis we substitute the real arc spot by an intensive moving surface heat source. The time evolution and the distribution of the electrode surface temperature within the arc spot is studied in coordinates coupled with the moving heat source. The electrode erosion is attributed in the model to the unbalance between the heat supply and the heat removal due to the development of an arc spot fusion zone. An erosion effective enthalpy is applied in the analysis, including all physical processes for the material transformation from the solid state into the plasma state under the action of the intensive heat flux. Formulae were obtained that enable one to calculate the electrode erosion as a function of arc velocity, electrode temperature, current, near-electrode thermal volt-equivalent, current density and electrode material properties. We show briefly that the theory agrees reasonably well with experimental results. The present model enables us to reveal the relative significance of the different parameters in the erosion process and to predict the erosion behaviour in copper electrode electric arc heaters.

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Section: Discussionmentioning

confidence: 99%

A theoretical and experimental investigation of copper electrode erosion in electric arc heaters: I. The thermophysical model

Marotta

Sharakhovsky

1996

J. Phys. D: Appl. Phys.

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“…Therefore, basic cathode spot processes in vacuum arcs, such as evaporation and current transfer, might be expected to be observed in gas arcs. 8 Extending this assumption to the spot structure, as described by Rakhovsky, 3 it can be suggested for atmospheric arcs that type I spots might also be found in the micro-erosion regime, and type II in the macro-erosion regime, the transition to type II occurring when the temperature under the spot reaches T f .…”

Section: Resultsmentioning

confidence: 91%

“…Many authors have shown that the arc spot in a cold cathode is composed of many, high current density (10 10 -10 12 A m Ϫ2 ) micro-spots ͑see, e.g., Jüttner, 8 and references therein͒. Studying the internal structure of arc spots in vacuum, Rakhovsky 3 observed that, for one type of arc spots, which he called the ''type I cathode spots,'' the microspots inside the larger spot act practically independently one of the other. Type I micro-spots are typical of low currents and low cathode temperatures, and are not followed by visible erosion traces on the electrode surface.…”

Section: Resultsmentioning

confidence: 99%

“…Many researchers ͑see Marotta 1 and references therein͒ have investigated cold cathode erosion under different operating conditions. Empirical power formulas of the type g ϰI a have been proposed 2,3 in the literature, with the exponent a between 2.24 and 4.5, depending on electrode surface conditions. An analysis of the erosion dependence on current was also attempted for a copper cathode.…”

Section: Introductionmentioning

confidence: 99%

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The influence of the arc current on the cold electrode erosion

2003

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A study of copper cathode erosion in a magnetically driven arc setup, as a function of arc current, is reported. The experiments showed the presence of two different erosion regimes. In the low current micro-erosion regime, erosion slowly rises with arc current. Then, at a certain critical current, macro-erosion begins, and has a strong dependence of erosion on current. It was shown that the critical current for transition from micro- to macro-erosion is a linearly decreasing function of the applied magnetic field. The erosion versus current behavior is shown to be explained by a recently published thermal model.

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“…We can consider two stages in the development of a cathode spot: namely, the stage of ignition and the stage of the remaining arc lifetime (regular stage) which consist of arc spot operation until it is ultimately extinguished [21]. For spot ignition by plasma heating, a high power density should be imposed on the cathode surface by plasma particles (ions and electrons).…”

Section: Introductionmentioning

confidence: 99%

The heating sources of spots on the vacuum arc cathodes

Askari¹,

Minoo²

2009

J. Phys. D: Appl. Phys.

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We have considered two stages in the development of a spot on the surface of a vacuum arc cathode: the stage of ignition and the stage of the remaining arc lifetime which consists of arc spot operation until ultimately it is extinguished. A model for the near cathode region of electric arc has been applied to obtain different parameters involved in the cathode spot region during the spot ignition stage. This model is based on the construction of a thin sheath near the cathode wall and electron emission upon the thermo-field theory of electron emission. The model is time-dependent and hence the different parameters of the cathode, plasma and sheath can be derived as a function of time. In particular, we determine the required values of the plasma and sheath parameters for spot ignition on the smooth cathode surface. Based on these calculations and taking into consideration the fluctuation in plasma and sheath parameters, the contribution of different heating mechanisms at the spot initiation stage is evaluated. After spot ignition, some spot parameters such as temperature and mass density of spot material, electron current density and vapour pressure considerably increase. High values of the electron current density and low values of the electrical conductivity of the dense plasma in the spot region significantly increase Joule heating during the evolution stage of spot operation.

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Critical parameters of the cathode region of a vacuum arc

Cited by 16 publications

References 0 publications

A theoretical and experimental investigation of copper electrode erosion in electric arc heaters: I. The thermophysical model

A theoretical and experimental investigation of copper electrode erosion in electric arc heaters: I. The thermophysical model

The influence of the arc current on the cold electrode erosion

The heating sources of spots on the vacuum arc cathodes

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