Arc erosion of AgSnO_2 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.

Equilibrium Composition of a Plasma in the Low Voltage Air Circuit Breaker Contaminated by the Vapor of AgSnO2 Alloy Electrical Contacts

When the circuit breaker cuts the electric current, an electric arc is created between its electrodes. The success or failure of breaking the electric current by the circuit breaker depends strongly on the physico-chemical properties of the electric arc created, such as the composition of which depends on the material of the electrical contacts. In this work, we determine the equilibrium composition of the electric arc in the low voltage air circuit breaker with silver tin dioxide alloy contacts, in a temperature range from 500 K to 15,000 K and at atmospheric pressure. We use the Gibbs free energy minimization method and develop a computer code to determine the equilibrium composition of the created plasma. The analysis of the results obtained shows that O2 particles with a dissociation energy of 5.114 eV, NO with a dissociation energy of 6.503 eV, and N2 dissociation 9.756 eV dissociate around 3500 K, 5000 K, and 7500 K, respectively. We note that the electro-neutrality is established between the electrons and the cations: Ag+ and NO+, for temperatures lower than 6500 K. For temperatures higher than 6500 K, the electro-neutrality is established between the electrons and the cations: N+, O+, and Ag+. The numerical density of the electrons increases when the proportion of the vapor of the electrical contacts increases in the mixture, in particular for temperatures lower than 11,000 K.

THE INVESTIGATION OF CONTACT RESISTANCE CHARACTERISTICS ON ELECTRICAL CONTACTS USED IN COAL MINES

Based on the electrical contact and arc theory, the experiments on contact resistance characteristics of electrical contacts are carried out, by analyzing the experimental results, some conclusions of contact resistance characteristics have been obtained in this paper.

Experiment and finite element method analysis mass erosion and transfer of Ag/La_2NiO_4-based electrical contacts during operation

A uniform transient temperature field model of electrical contacts operation was found by analyzing the process of closing arc constriction resistance Joule heat ~ breaking arc. Essential parameters of Ag/La2NiO4 electrical contact material for transient temperature field calculation were obtained through tests of electrical contact experimental instrument under 18 V DC in different cur- rents, other correlation experiments, and calculation anal- ysis. The finite element method was applied to solve the transient temperature field, and the features and distribution of the transient temperature field were obtained. The condition of material erosion and mass transfer can be forecasted by those calculation results. It is beneficial to research about the lifetime of Ag/La2NiO4 electrical material.

Preparation and Anti⁃arc Erosion Property of Ag Matrix Electrical Contact Material Reinforced by Novel Ti_(2)Cd

Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications.In order to further reduce the Cd content under the premise of meeting the high-performance requirements,in this study,high-purity intermediate Ti_(2)Cd powder of MAX phase(Ti_(2)CdC)was synthesized with a pressureless technique and then applied to reinforce the Ag matrix.The Cd content of the as-prepared Ag/Ti_(2)Cd composites was actually reduced by 38.31%compared with conventional Ag/CdO material.Based on the systematic study of the effect of heat treatment temperature on the physical phase,morphology,interface and comprehensive physical properties of Ag/Ti_(2)Cd composites,the preferred samples(heat treated at 400°C for 1 h)showed high density(97.77%),low resistivity(2.34μΩ·cm),moderate hardness(90.8HV),high tensile strength(189.9 MPa),and exhibited good electrical contact performance after 40000 cycles of arc discharging under severe conditions(DC 28 V/20 A).The results of microscopic morphological evolution,phase change and elemental distribution of the electrical contact surface show that the combination of high stability of Ti_(2)Cd reinforcing phase,good interfacial bonding with Ag matrix and improved melt pool viscosity in the primary stage of arc erosion,results in low and stable contact resistance(average value 13.20 mΩ)and welding force(average value 0.6 N),low fluctuation of static force(2.2-2.5 N).The decomposition and absorption energy of Ti_(2)Cd and the arc extinguishing effect of Cd vapor are the main reasons for the stable arcing energy and arcing time of electric contacts in the late stage of arc erosion.

Effects of interfacial wettability on arc erosion behavior of Zn_(2)SnO_(4)/Cu electrical contacts

Interface wettability is a vital role in directly impacting the electrical contact characteristics of oxides/Cubased composites under arc erosion.Exploring its influence mechanism,especially at atomic/electronic scales,is significant but challenging for the rational design of oxides/Cu contacts.Here,we designed Zn_(2)SnO_(4)/Cu electrical contacts aiming to solve the poor wettability of SnO_(2)/Cu composites.It was found that Zn_(2)SnO_(4)could remarkably improve the arc resistance of Cu-based electrical contacts,which was benefited by the excellent interface wettability of Zn_(2)SnO_(4)/Cu.The characterization of eroded surface indicated that Zn_(2)SnO_(4)particles distributed uniformly on the contact surface,leading to stable electrical contact characteristic.Nevertheless,SnO_(2)considerably deteriorated the arc resistance of SnO_(2)/Cu composite by agglomerating on the surface.The effect mechanism of wettability on arc resistance was investigated through density function theory(DFT)study.It revealed that strong polar covalent bonds across the Zn_(2)SnO_(4)/Cu interface contributed to improving the interfacial adhesion strength/wettability and thus significantly enhanced the arc resistance.For binary SnO_(2)/Cu interface,ionic bonds resulted in weak interface adhesion,giving rise to deterioration of electrical contact characteristic.This work discloses the bonding mechanism of oxide/Cu interfaces and paves an avenue for the rational design of ternary oxide/Cu-based electrical contact materials.

Field-effect at electrical contacts to two-dimensional materials

The inferior electrical contact to two-dimensional(2D)materials is a critical challenge for their application in post-silicon very large-scale integrated circuits.Electrical contacts were generally related to their resistive effect,quantified as contact resistance.With a systematic investigation,this work demonstrates a capacitive metal-insulator-semiconductor(MIS)field-effect at the electrical contacts to 2D materials:The field-effect depletes or accumulates charge carriers,redistributes the voltage potential,and gives rise to abnormal current saturation and nonlinearity.On one hand,the current saturation hinders the devices’driving ability,which can be eliminated with carefully engineered contact configurations.On the other hand,by introducing the nonlinearity to monolithic analog artificial neural network circuits,the circuits’perception ability can be significantly enhanced,as evidenced using a coronavirus disease 2019(COVID-19)critical illness prediction model.This work provides a comprehension of the field-effect at the electrical contacts to 2D materials,which is fundamental to the design,simulation,and fabrication of electronics based on 2D materials.

Influence of alloy components on arc erosion morphology of Ag/MeO electrical contact materials

Arc erosion morphologies of Ag/MeO（10） electrical contact materials after 50000 operations under direct current of 19 V and 20 A and resistive load conditions were investigated using scanning electron microscope（SEM） and a 3D optical profiler（3DOP）. The results indicated that 3DOP could supply clearer and more detailed arc erosion morphology information. Arc erosion resistance of Ag/SnO_2（10） electrical contact material was the best and that of Ag/CuO（10） was the worst. Arc erosion morphology of Ag/MeO（10） electrical contact materials mainly included three different types. Arc erosion morphologies of Ag/ZnO（10） and Ag/SnO_2（10） electrical contact materials were mainly liquid splash and evaporation, and those of Ag/CuO（10） and Ag/CdO（10） were mainly material transfer from anode to cathode. Arc erosion morphology of Ag/SnO_2（6）In_2O_3（4） electrical contact materials included both liquid splash, evaporation and material transfer. In addition, the formation process and mechanism on arc erosion morphology of Ag/MeO（10） electrical contact materials were discussed.

Sliding electrical contact behavior of AuAgCu brush on Au plating

The sliding electrical contact behavior of AuAgCu brush on Au plating was investigated at various normal loads and sliding speeds.The contact voltage drop and electrical noise between the two brushes were measured and the resistance waveforms were recorded.The morphologies of the worn surfaces and wear debris of the brush and plating were observed.The results show that the contact voltage drop and electrical noise decrease with the addition of load whereas increase drastically with increasing sliding speed.With the electrical current in vacuum,the wear process of AuAgCu brush on Au plating involves adhesion,transfer of gold from the plating to the brush,rolling of wear debris between contact surfaces and arc-induced melt at the contact edge,and this gold-on-gold sliding electrical contact system is reliable within experiment period.

Preparation and microstructure characterization of a nano-sized Ti^(4+)-doped AgSnO_2 electrical contact material

A Ti^4＋-doped nano-structured AgSnO2 material was prepared using sol-gel method and characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and scanning electron microscopy （SEM）. The results show that Ti^4＋ cations are successfully doped into the crystal lattice of SnO2, and thus significantly improve the electrical conductivity of the sample. Furthermore, the coating of Ag on Ti^4＋-doped SnO2 nano-sized particles enhances the surface wettability and enables the resulting AgSnO2 material to have better mechanical properties.

Effects of silver powder particle size on the microstructure and properties of Ag-Yb_2O_3 electrical contact materials prepared by spark plasma sintering

mg-Yb203 electrical contact materials were fabricated by spark plasma sintefing （SPS）. The effects of silver powder particle size on the microstructure and properties of the samples were investigated. The surface morphologies of the sintered samples were examined by optical microscope （OM）, and the fracture morphologies were observed by scanning electron microscopy （SEM）. The physical and mechanical properties such as density, electrical resistivity, microhardness, and tensile strength were also tested. The results show that the silver powder particle size has evident effects on the sintered materials. Comparing with coarse silver powder （5 ktm）, homogeneous and fme microstmcture was obtained by fine silver powder （_〈0.5-1am）. At the same time, the electrical conductivity, microhardness, and tensile strength of the sin- tered samples with fine silver powder were higher than those of the samples with coarse silver powder. However, silver powder particle size has little influence on the relative densities, which of all samples （both by free and coarse silver powders） is more than 95%. The fracture characteristics are ductile.

Evolution of the electrical contact of dynamic pantograph–catenary system

A good contact between the pantograph and catenary is critically important for the working reliability of electric trains, while the basic understanding on the electrical contact evolution during the pantograph--catenary system working is still ambiguous so far. In this paper, the evolution of electric contact was studied in respects of the contact resistance, temperature rise, and microstructure variation, based on a home-made pantograph-catenary simulation system. Pure carbon strips and copper alloy contact wires were used, and the experimental electrical current, sliding speed, and normal force were set as 80 A, 30 km/h, and 80 N, respectively. The contact resistance presented a fluctuation without obvious regularity, concentrating in the region of 25 and 50 mf~. Temperature rise of the contact point experienced a fast increase at the first several minutes and finally reached a steady state. The surface damage of carbon trips in microstructure analysis revealed a complicated interaction of the sliding friction, joule heating, and arc erosion.

Testing results analysis of contact materials’electrical contact performance

Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages: smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished.

Morphology and electrical contact properties of electrical connection materials in corrosive atmosphere

The impact mechanism of environmental fac tors, such as corrosive atmosphere, on connector materials was investigated, and the porosity of gold plating was tested. Series of inspections and analytical research meth ods were introduced in this article. The surface morphology of specimens after corrosion was observed by stereoscopic microscope and scanning electron microscope. Chemical constitution was examined by Xray energy spectrum. The contact resistances were measured by fourpoint method. The experiment results show that after exposure to certain environment, the corrosion products, such as Cu20, Cu（NO3）2.3H20, and NiO, are observed on the surface of the specimens without gold coatings, whereas the corrosion products appear to have circleshaped spots on goldplating surface after corrosion test, which indicate that the gold plating has good corrosion protection. The porosity is increased with the increase of corrosion time for every kind of specimens gold plated, and the corrosion degree of gold plating specimens is decreased with the increase of the thickness of gold coatings. The static contact resistances of circleshaped spots appear higher contact resistance than normal value, which can reach to 2,000 mr2 nearly. It is found that the high and unstable contact resistance of the pore and products is more likely to cause contact failure.

Influence of operation number on arc erosion behavior of Ag/Ni electrical contact materials

Arc erosion behavior of Ag/Ni materials with different operation numbers was investigated by OM,3DOP and SEM.The results indicated that the arc erosion of Ag/10Ni electrical contact material fabricated by sintering−extrusion technology was more and more serious with the operation numbers increasing from 1000 to 40000.With the same operation numbers,the arc erosion on anode was more serious than that on cathode.Besides,the pores preferred to emerge around the arc effect spot during the first 10000 operations.And the morphology of the molten silver on cathode and anode was different due to the action of gravity and arc erosion.Furthermore,the relationships among arc energy,arc time,welding force,electric resistivity,temperature and mass change on contacts were discussed,which indicated that the mass loss on cathode was mainly caused by the fracture of molten bridge.

Influence of the ambient air temperature on the electrical contact reliability of electromagnetic relay

The dynamic contact resistances of HH52P electromagnetic relays are measured under different ambient air tem- perature. Their diagnostic parameters are extracted and determined. It is found that the ambient air temperature obviously influ- ences some parameters. In order to research its influence on the electrical contact reliability of electromagnetic relay, the statistic analysis is applied to study the static contact resistance, the max of the dynamic contact resistance and the bounce time. It is found that the ambient air temperature regularly influences the three parameters. Thoroughly, the phenomenon is studied and analyzed in the point of material science so as to probe into the essential matter of it.

Study on the failure mechanism of Ag-Ce contacts in DC level

Nominal contact resistance, minimum erosion and material transfer are required with low cost materials working in a wide currents range for DC relays. Ag-Ni contact materials have low contact resistance, but the erosion and material transfer are large at high current level. Ag-SnO2 contact materials have good anti-welding properties and resistance to arc erosion, but they have large contact resistance during working and are easily block SnO2 from flocking together on the surface at low current level. In this paper, the failure mechanisms of Ag-Ce contact material were studied. The surface morphologies of the contacts after electrical endurance test for Ag-Ce contact material were compared with that of Ag-Ni and Ag-SnO2 contact materials. The effect of Ce on the surface morphologies of the contacts after electrical endurance test was analyzed.

Effects of Rare Earths on Electrical Conductivity, Melting-Welding and Corrosion Resistance by Electric Arc of Copper-Based Alloys

The effects of rare earths on electric conductivity fusion welding-resistance and erosion-resistance by electric arc of copper-based compound material by adding different amount of rare earths to copper base to get copper based compound materials were studied. Rare earths improve active ability among interfaces and optimize organizational structures. The conductivity of samples with rare earths is obviously better than that of materials without them. Moreover, wear ability and oxidization resistance of materials with rare earths can be improved greatly. For copper contact head with rare earths, electric arc corrosion resistance and welding-melting resistance are improved. Such alloys also decrease resistance change with increasing temperature. But the adding quantity of rare earths should be appropriate and formed handicraft should be properly regulated.

Electrical Conductivity of Spark Plasma Sintered W-Cu and Mo-Cu Composites for Electrical Contact Applications

Tungsten copper and molybdenum copper composites, with weight percent copper in the range of 20% - 40%, have been produced using the spark plasma sintering (SPS) technique. Other specimens having similar compositions were also developed using the conventional techniques of Liquid Phase Sintering (LPS) and Infiltration. Electrical conductivity measurements showed that the specimens produced by the SPS process had substantially higher levels of electrical conductivity than those produced by the other methods. Relative density measurements showed that the SPS specimens achieved very high densification, with relative densities in the range of 99.1% - 100%. On the other hand, the specimens produced by LPS and infiltration had relative densities in the range of 88% - 92% and 96% - 98% respectively. The superior conductivity of the SPS specimens has been attributed to the virtually full densification achieved by the process. The effect of porosity on electrical conductivity has been discussed and three standard models were assessed using results from porous sintered skeletons of pure tungsten and pure molybdenum.

Improving the Electrical Contact Property of Single-Walled Carbon Nanotube Arrays by Electrodeposition

A parallel method for the fabrication of metal contacts on single-walled carbon nanotube(SWNT)arrays was presented and the electrical contact property was evaluated by a SWNT-field effect transistor structure. Copper and gold contacts were fabricated on both semiconducting SWNTs and metallic SWNTs by using a maskless electrodeposition process. The SWNT array remained a p-type semiconductor after the electrodeposition. The contact resistance between SWNT array and microelectrodes was reduced more than 50% by the established copper contacts. The source-drain current of the carbon nanotube field-effect transistor(CNT-FET)structure can be further increased from 7.9 μA to 9.2 μA when the copper contacts were replaced by gold ones,which is probably due to the better contact property to SWNT of gold contacts with fine grain size.