Arc Erosion Research Articles

Experimental Investigation of Arc Plasma in GaInSn Liquid Metal Current-Limiting Device

This paper focuses on an experimental investigation of arc plasma in a liquid metal current-limiting device based on pinch effect. A specially designed experimental setup is employed to observe the dynamic process of arc initiation and arc evolution. From the frames obtained by high-speed photography, the mechanism of arc initiation is revealed. It indicates that the arc ignites due to the self-pinch effect, which starts from the free surface of liquid metal and develops in the form of gas cavities. According to the analysis of the subsequent stage after arc ignition, it can be concluded that the arc plasma should be a mixture of metal vapor and air. With the morphological changes of the arc, the arc evolution can be classified into four stages. The arc erosion on electrodes is observed during the arc process, and its causes are analyzed in detail. Using a liquid metal current-limiting device, the arc characteristics during the current limitation are investigated. It is found that the duration of the prearcing stage and the arc voltage are influenced by the pass-through current. As prospective current increases, the prearcing time reduces because of the acceleration of the pinch process and the arc voltage rise due to the adequate arc burning.

Investigation of the Arc Erosion Behaviour of W-Cu Composites

In practical applications, silver-based composite materials have been used for high load bearing or high class contact materials. However, composites such as CdO-Ag and silver-based SnO2, TiO2 and ZnO are not economically feasible due to toxicity concerns and cost effectiveness. On the other hand, copper matrices are widely used for electrical contact applications in a diverse range of fields. In particular, W-Cu alloys are considered as an alternative for contact materials and arcing resistance electrodes due to the high thermal and electrical conductivity of copper and the high arc erosion resistance and low thermal expansion coefficient of tungsten. However, the contacts are vulnerable to thermal damage due to the high temperature and mass flow on the local surfaces of the contacts during the make-and-break of the contacts. In this study, particle-reinforced copper (W-Cu and TiC-Cu) composite powders were fabricated using a novel electroless copper plating process. Electrical contacts made of pure Cu and the Cu matrix powders were employed for dynamic electrode tests. The specimens were subjected to 1,000 and 10,000 arc breakings to study the effects of arc erosion on the contacts as well as their make-and-break life. Results show that the contacts made of pure Cu had the greatest loss of mass and the shortest life while the W-Cu composites preserved most of their mass; in addition, the W-Cu composites with finer W particles (1 μm) outperformed the rest of the composites.RésuméDans les applications pratiques, on a utilisé les matériaux composites à base d'argent dans les matériaux porteurs de charge élevée ou dans les matériaux de contact de qualité supérieure. Cependant, les composites tels que CdO-Ag ou SnO2, TiO2 et ZnO à base d'argent ne sont pas économiquement réalisables à cause de problèmes de toxicité et de souci d'économie. D'un autre côté, les matrices de cuivre sont largement utilisées dans les contacts électriques dans une grande gamme de champs d'application. En particulier, les alliages de W-Cu sont considérés comme solution de rechange pour les matériaux de contact et pour les électrodes de résistance à la formation d'arc grâce à la conductivité thermique et électrique élevée du cuivre et grâce à la résistance élevée à l'érosion de l'arc et au faible coefficient d'expansion thermique du tungstène. Cependant, les contacts sont vulnérables à l'endommagement thermique à cause de la température élevée et du haut débit sur les surfaces locales des contacts lors de l'enclenchementdéclenchement des contacts. Au cours de cette étude, on a fabriqué des poudres composites de cuivre renforcées de particules (W-Cu et TiC-Cu) en utilisant un nouveau procédé de placage chimique du cuivre. On a utilisé des contacts électriques faits de cuivre pur ou de poudres à matrice de cuivre pour des essais dynamiques d'électrode. On a soumis les échantillons à 1,000 et 10,000 ruptures d'arc pour étudier l'effet d'érosion de l'arc sur les contacts ainsi que leur durée de vie d'enclenchement-déclenchement. Les résultats montrent que les contacts faits de cuivre pur avaient la plus grande perte de masse et la plus courte durée de vie alors que les composites de W-Cu préservaient presque toute leur masse; de plus, les composites de W-Cu avec les particules de W les plus fines (1 μm) surpassaient le reste des composites.

Investigation of the Arc Erosion Behaviour of W-Cu Composites

In practical applications, silver-based composite materials have been used for high load bearing or high class contact materials. However, composites such as CdO-Ag and silver-based SnO2, TiO2 and ZnO are not economically feasible due to toxicity concerns and cost effectiveness. On the other hand, copper matrices are widely used for electrical contact applications in a diverse range of fields. In particular, W-Cu alloys are considered as an alternative for contact materials and arcing resistance electrodes due to the high thermal and electrical conductivity of copper and the high arc erosion resistance and low thermal expansion coefficient of tungsten. However, the contacts are vulnerable to thermal damage due to the high temperature and mass flow on the local surfaces of the contacts during the make-and-break of the contacts. In this study, particle-reinforced copper (W-Cu and TiC-Cu) composite powders were fabricated using a novel electroless copper plating process. Electrical contacts made of pure Cu and the Cu matrix powders were employed for dynamic electrode tests. The specimens were subjected to 1,000 and 10,000 arc breakings to study the effects of arc erosion on the contacts as well as their make-and-break life. Results show that the contacts made of pure Cu had the greatest loss of mass and the shortest life while the W-Cu composites preserved most of their mass; in addition, the W-Cu composites with finer W particles (1 μm) outperformed the rest of the composites. Résumé Dans les applications pratiques, on a utilisé les matériaux composites à base d'argent dans les matériaux porteurs de charge élevée ou dans les matériaux de contact de qualité supérieure. Cependant, les composites tels que CdO-Ag ou SnO2, TiO2 et ZnO à base d'argent ne sont pas économiquement réalisables à cause de problèmes de toxicité et de souci d'économie. D'un autre côté, les matrices de cuivre sont largement utilisées dans les contacts électriques dans une grande gamme de champs d'application. En particulier, les alliages de W-Cu sont considérés comme solution de rechange pour les matériaux de contact et pour les électrodes de résistance à la formation d'arc grâce à la conductivité thermique et électrique élevée du cuivre et grâce à la résistance élevée à l'érosion de l'arc et au faible coefficient d'expansion thermique du tungstène. Cependant, les contacts sont vulnérables à l'endommagement thermique à cause de la température élevée et du haut débit sur les surfaces locales des contacts lors de l'enclenchementdéclenchement des contacts. Au cours de cette étude, on a fabriqué des poudres composites de cuivre renforcées de particules (W-Cu et TiC-Cu) en utilisant un nouveau procédé de placage chimique du cuivre. On a utilisé des contacts électriques faits de cuivre pur ou de poudres à matrice de cuivre pour des essais dynamiques d'électrode. On a soumis les échantillons à 1,000 et 10,000 ruptures d'arc pour étudier l'effet d'érosion de l'arc sur les contacts ainsi que leur durée de vie d'enclenchement-déclenchement. Les résultats montrent que les contacts faits de cuivre pur avaient la plus grande perte de masse et la plus courte durée de vie alors que les composites de W-Cu préservaient presque toute leur masse; de plus, les composites de W-Cu avec les particules de W les plus fines (1 μm) surpassaient le reste des composites.

Arc erosion of AgSnO2 electrical contacts at different stages of a break operation

Arc erosion studies are conducted on AgSnO2 contact materials at different stages in the break operation. A resistive load arrangement is used with up to 42 V DC at 24 A and a constant contact opening velocity. The arc current is terminated at different stages as the arc is drawn between the contacts enabling a study of the arcing phenomena up to that point. Surface profiling of the contacts is conducted to determine the extent of erosion at the different stages as the arc is drawn. Spectral analysis is also conducted on the arc and then related to the extent of erosion. The results show that particular features occur at different stages as the arc is drawn. As the arc is initially established, it goes through an “Arc Generation” regime where the arc roots are small and immobile on both the anode and the cathode. Material transfer occurs mainly from anode to cathode. The spectral analysis indicates that Sn and O species dominate the arc followed by the Ag species. As the arc is drawn further and enters the “Arc Degeneration” regime, the anode undergoes significantly larger erosion than the cathode. Also, both contacts indicate that multiple arc roots have formed, which are highly mobile in the later stages of the discharge. The spectral analysis indicates that Ag and N species are in high concentrations compared to other species. The mechanisms of erosion and deposition are discussed in relation to the species within the arc discharge. For the complete break operation, it is found that the anode undergoes major erosion, and it is thought that the gaseous ions species do not dominate the arc under these conditions of short arcs and voltage <42 V to cause cathode erosion.

Electrical breakdown characteristic of a Ce-doped W-Cu contact material

W-Cu composite powder doped with Ce (1.5 wt.%) was prepared by mechanical alloying (MA), and the W-Cu contact material was fabricated by hot pressing sintering in an electrical vacuum furnace. The microstructure, electric conductivity, hardness, and breakdown voltage of the Ce-doped W-Cu alloy were measured and compared with a conventional W-Cu alloy prepared by powder metallurgy. The results show that microstructural refinement and uniformity can improve the breakdown behavior and the electric arc stability of the Ce-doped W-Cu contact material. Also, the Ce-doped W-Cu contact material shows the characteristic of spreading electric arc, which is beneficial to electric arc erosion.

Effect of Al2O3 Content on Electrical Breakdown Properties of Al2O3/Cu Composite

Al2O3/Cu composites were prepared by external addition of Al2O3, and the effect of Al2O3 content on microstructure, density, hardness, electrical conductivity and vacuum electrical breakdown properties was studied. The results show that with increasing Al2O3 addition, the density of Al2O3/Cu composite significantly decreases, the hardness sharply increases and then slowly decreases, but the electrical conductivity invariably decreases. The vacuum breakdown test shows that with increasing Al2O3 addition, the breakdown strength first sharply increases and then decreases when the Al2O3 content exceeds 1.2 wt.%; the chopping current always exhibits a decreasing trend and the arc life first increases and then decreases. According to the morphology of arc erosion and analysis, the arc erosion resistance increases and then decreases sharply. In the range of experiments, the optimal arc erosion resistance of Al2O3/Cu composite can be obtained with the addition of 1.2 wt.% Al2O3.

Arc Erosion of Polarised Contacts Ag-W by High Current

The paper presents the state of knowledge about thermal-erosion processes in contacts of low-voltage switching devices for power engineering on switching currents under short-circuit conditions. The graphical models of the short arc and the distribution of arc power introduced into contacts are shown. The method for measurements of a contact temperature during an electric discharge has been elaborated. The obtained test results are presented, i.e. changes of a contact temperature as a function of arc parameters such as current, energy, and integral ∫ idt. The tests have shown that a break exists on the curve expressing the relationship between a temperature rise and arc parameters in the range of high currents. The location of this point is dependent on a diameter of contacts and a value of current, and is associated with thermal energy delivered to electrodes. It has been observed that for each diameter of contacts there exists such value of an energetic quantity of arc (current, ∫ idt, energy), at which diameters of arc roots are the same as a contact diameter. Above this value, the shape of a curve is changed. The obtained results explain and confirm the discontinuity of a curve expressing a contact arc erosion as a function of current, which was observed earlier by the other research workers.

A Study on Wear of Brush and Carbon Flat Commutator of DC Motor for Automotive Fuel Pump

In an automotive fuel pump system, a small DC motor is widely used to drive the pump and driven by a automotive battery. Recently a bio-fuel, usually a mixture of gasoline and ethanol has been used due to shortage of gasoline and environmental aspect. It affects strongly the performances of a DC motor, especially commutation phenomena, what kind of fuel is used. Therefore the authors have started to investigate the influence of ethanol on the commutation phenomena. They have been reporting the wear of brush and carbon flat commutator in gasoline and ethanol so far. In this paper commutation period, arc duration, brush and commutator wear are examined in ethanol 50-gasoline 50%. Brush wears are very small compared with the previous results. Namely in the present test a mechanical sliding wear is predominant rather than erosion by arc due to short arc duration. Further, an area eroded by arc is observed to re-appear as a sliding surface. From these results a threshold arc energy between arc erosion and mechanical sliding wear is obtained, and a wear model is proposed to explain the above wear pattern on the sliding surface.

CHARACTERISTICS OF ARC EROSION FOR Cu-C COMPOSITE MATERIALS IN AIR

Arc erosion of Cu - C composites was investigated in air. The eroded zones on the cathode surface were observed by a scanning electron microscope, and the cathode erosion rates were measured. It can be found that the main mass loss results from ejection of copper and oxidization of carbon during discharges. The degree of erosion increases with the copper content. Meanwhile, the arc erosion rate is larger for the Cu - C materials with higher copper content. A large number of bubble-like particles appear on the electrode surface. The formation of those particles is closely related to the melting and ejection of copper and material transfer between the electrodes.

Effect of Milling Time on Electrical Breakdown Behavior of Al2O3/Cu Composite

In order to clarify the relationship between the microstructure and the arc erosion behavior of metal-matrix composite, Al2O3/Cu composites with different distributions of Al2O3 particles were prepared by high energy ball milling and powder metallurgy. The effect of milling time on microstructure, properties, and arc erosion behavior of Al2O3/Cu composite was investigated. The results show that the distribution of Al2O3 particles improves significantly with increase of milling time, but Al2O3 particles will be aggregated if milling time is too long. The optimal milling time is 24 h in the range of experiments. A uniform distribution of Al2O3 particles in copper matrix can improve the hardness, electrical conductivity, average breakdown strength, chopping level, and arc life. With improvement in the distribution of Al2O3 particles, the erosion area becomes larger, and the erosion pits become shallower and are dispersed more uniformly.

Comparative study on discharge conditions in micro-hole electrical discharge machining of tungsten carbide (WC-Co) material

WC-Co is used widely in die and mold industries due to its unique combination of hardness, strength and wear-resistance. For machining difficult-to-cut materials, such as tungsten carbide, micro-electrical discharge machining(EDM) is one of the most effective methods for making holes because the hardness is not a dominant parameter in EDM. This paper describes the characteristics of the discharge conditions for micro-hole EDM of tungsten carbide with a WC grain size of 0.5 μm and Co content of 12%. The EDM process was conducted by varying the condenser and resistance values. A R— C discharge EDM device using arc erosion for micro-hole machining was suggested. Furthermore, the characteristics of the developed micro-EDM were analyzed in terms of the electro-optical observation using an oscilloscope and field emission scanning electron microscope.

Wear behavior of Cu–La 2O 3 composite with or without electrical current

A new type Cu–La 2O 3 composite was fabricated by internal oxidation method using powder metallurgy. Sliding wear behavior of the Cu–La 2O 3 composites was studied by using a pin-on-disk wear tester under dry sliding conditions with or without electrical current, rubbing against GCr15 type bearing steel disk at a constant sliding speed of 20 m/s. The influence of varying applied load and electrical current was investigated. The worn surfaces were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to determine the wear mechanisms. The results showed the Cu–La 2O 3 composites had an electrical conductivity of 81.9% IACS (International Annealed Copper Standard, 100% IACS = 58 MS/m) and a hardness of HV105. The wear rate of the Cu–La 2O 3 composite pins increased with the increase in the electrical current at high sliding speed. The main wear mechanisms of the Cu–La 2O 3 composites were found to be adhesive wear, abrasive wear and arc erosion.

Effect of Al 2O 3 particle size on vacuum breakdown behavior of Al 2O 3/Cu composite

In order to clarify the effect of Al 2O 3 particle size on the arc erosion behavior of the ceramic-reinforced Al 2O 3/Cu composite, Al 2O 3/Cu composites with different sizes of Al 2O 3 particles were prepared by powder metallurgy, the effect of Al 2O 3 particle size on the characteristics of arc motion was studied, and the mechanism of arc erosion of Al 2O 3/Cu composites was discussed as well. The results show that with decrease in the size of Al 2O 3 particles, the erosion area increases significantly and the erosion pits become shallower. The vacuum breakdown is preferred to appear in the area between Al 2O 3 particle and the copper matrix. Based on the experimental results and theoretical analysis, a particle partition arc model is proposed.

Effect of sintering temperature on morphology and arc erosion properties of La-Ni-O ceramic and its composites

Ceramic LaNiO 3 samples were prepared by solid state reaction method at different sintering temperatures. It was found that the resultant was not ABO 3 perovskite single phase but dual phase La 2NiO 4 and NiO, and the percentage of the two phases varied with sintering temperature. Ceramics sintered at 1400 °C were well crystallized and the phase ratio of La 2NiO 4 was the maximum. The surface morphology observed by scanning electron microscopy (SEM) indicated that the grains of the ceramics sintered at 1400 °C were uniform and compact, which were in agreement with the properties of high density and low electrical resistivity of the samples. X-ray diffraction (XRD) patterns of ceramics before and after arc erosion indicated their high structural stability, which resulted in the good arc erosion resistance properties for silver-based electrical contact materials. The contact materials prepared with the ceramic sintered at 1400 °C exhibited better mass transition and arc erosion resisting properties.

What can we learn from HF signal scattered from a discrete arc?

Abstract. We present observations of a discrete southward propagating arc which appeared in the mid-night sector at latitudes equatorward of main substorm activity. The arc observations were made simultaneously by the ALFA (Auroral Light Fine Analysis) optical camera, the SuperDARN-CUTLASS HF radar and the Demeter satellite during a coordinated multi-instrumental campaign conducted at the KEOPS/ESRANGE site in December 2006. The SuperDARN HF signal which is often lost in the regions of strong electron precipitation yields in our case clear backscatter from an isolated arc of weak intensity. Consequently we are able to study arc dynamics, the formation of meso-scale irregularities of the electron density along the arc, compare the arc motion with the convection of surrounding plasma and discuss the contribution of ionospheric ions in the arc erosion and its propagation.

Preparation and tribological investigation of resin–matrix contact strip with variable current

The resin–matrix contact strip (RMCS) with high friction reducing function and good wear resistance under current has been studied to improve the performance of the traditional contact strips, such as high maintenance cost, high wear rate under current and severe damage to contact wire. The tribological behaviours of RMCS against copper were investigated under laboratory conditions with a wear tester which simulated the train motion. The results showed that the current played a major role in determining the wear behaviour and wear rate of RMCS increased with current density and sliding velocity. The wear rate of RMCS was 21·75 × 10−4 mm3 m−1 under the conditions of a sliding velocity of 41·7 m s−1 for 30 min with the current density of 285 A cm−2. The dominant wear mechanisms and arc erosion processes of the worn surface were discussed based on the microscopic observation of the worn surface and wear debris, which indicated that arc erosion wear, oxidative wear and adhesive wear were the dominant mechanisms of RMCS against copper during the electrical sliding processes, while mild adhesive wear and low stress abrasive grains wear are the main mechanisms during the sliding process without current.

Thermal wear and electrical sliding wear behaviors of the polyimide modified polymer-matrix pantograph contact strip

In the present study, the polyimide resin (PI)/cashew-modified resin (YM) polymer-matrix pantograph contact strip (PMPCS) was prepared by using hot repressing, hydro-solidification and dipping treatment processes. The thermal properties of cured resins were studied by thermogravimetry analyzer and differential scanning calorimetry. The thermal wear and electrical sliding wear behaviors of PMPCS against copper were evaluated by a ring block wear tester at elevated temperature under dry sliding conditions and a wear tester which simulated the train motion under laboratory conditions, respectively. Worn surfaces and wear debris of PMPCS were analyzed by scanning electron microscopy and energy dispersive spectrometer, and the wear mechanism was discussed. It has been found that the thermal stability of the PI/YM is superior to that of the YM under the same testing conditions. The results also showed that PI/YM-PMPCS had superior wear resistance than that of YM-PMPCS at elevated temperature and with electrical current. At elevated temperature, the wear mechanism of tribological pair evolved from adhesive wear to oxidative wear with mild delamination wear. Arc erosion wear, oxidative wear, and adhesive wear were the dominant mechanisms of tribological pair during the electrical wearing process.

Experimental Research of Arc Behavior in Liquid Metal for Current Limiting Application

The liquid metal current limiter (LMCL) is a possible alternative to limit the short current of power system due to its special merits. This paper is devoted to the investigation of the arc behavior in liquid metal GaInSn for current limiting application. Firstly, the arc evolution including arc initiation, arc expansion and arc extinguish is observed through an experimental device. The resistance of arc and the self healing property of liquid metal are described. Subsequently, the arc erosion on electrodes is presented with its causes analyzed. Finally, the arc characteristics with the influence of rise rate of prospective current and channel diameter are discussed in details.

359829 ELECTRICAL SLIDING WEAR OF COPPER-BASED CONTACT WIRE MATERIALS FOR ELECTRIC RAILWAY(Catenary,Technical Session)

In the present study, the electrical sliding wear behavior of eight copper-based alloys was investigated by a pin-on-disc tribometer. Various copper-based alloys in the form of cylindrical rod were forced to slide against a counterface stainless steel disc in air under unlubricated condition at a sliding velocity of 31.2 km/h under normal load up to 20 N with and without electric current. The worn surface and wear debris of the specimens were studied by scanning-electron microscopy. Mechanical wear and electrical arc erosion were the dominant wear mechanisms for the alloys worn at 50 A. Considering both electrical conductivity and wear resistance, CuCrZr is a promising candidate as the contact wire material for electric railway systems.

Effect of Cathode Microstructure on Arc Velocity and Erosion Rate of Cold-Sprayed Copper Cathodes in a Magnetically Rotated Atmospheric Pressure Arc

Atmospheric pressure arc velocity and erosion measurements were performed on cold-sprayed cathodes in a continuously running arc system. Ultrahigh purity (99.99% pure) argon was used as plasma forming gas. An external magnetic field of 0.10 T was used to rotate the arc, which was operated at a constant power of 6 kW (40 V). Cathodes having microstructures with mean grain sizes, ranging from 1.12 to 3.06 μm, were produced using cold spraying (CS) and annealing methods. CS cathodes were tested in their as-sprayed state and annealed state. Annealed CS coatings with near equi-axed grains of 2.29 μm average size gave 60% higher steady-state arc velocities and up to 50% lower erosion rates than massive copper cathodes having 20-23 μm average grain size. An effect of cathode microstructure on arc velocity and on arc erosion rates was observed.