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.

Arc erosion behavior of a nanocomposite W-Cu electrical contact material

The erosion behavior of a nanocomposite W-Cu material under arc breakdown was investigated. The arc erosion rates of the material were determined, and the eroded surfaces and arc erosion mechanisms were studied by scanning eleclion microscopy. It is concluded that the nanocomposite W-Cu electrical contact material shows a characteristic of spreading arcs. The arc breakdown of a commercially used W-Cu alloy was limited in a few areas, and its average arc erosion rate is twice as large as that of the former. Furthermore, it is also proved that the arc extinction ability and arc stability of the nanocomposite W-Cu material are excellent, and melting is the major failure modality in the make-and-break operation of arcs.

Preparation and Arc Erosion Resistance of C_f/Cu Composite by Vacuum Melting Infiltration

Cf/Cu composite was prepared by vacuum melting infiltration. Ti and Cr were doped to the Cu alloy to improve the wettability between Cu and carbon. The microstrueture was investigated by XRD, SEM and EDS. The arc erosion rate of Cf/Cu composite was investigated in vacuum. The results showed that the Ti and Cr could improve the wettability between Cu and C/C preform and the infiltration ability of Cu into C/ C preform greatly. A TiC interface formed between the fibers and matrix. The good bonding between the fiber and matrix guaranteed that part of the Cu matrix can still be bonded on the fibers even when the material was exposed to the plasma. Consequently, the carbon fibers were protected from the erosion. In comparison, Cu was completely consumed by the arc erosion. Hence, the graphite was eroded and presented a cauliflower-like morphology. Therefore, the prepared C/Cu bad better ability to resist the arc erosion, compared with common Cu-C material.

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

Ceramic LaNiO3 samples were prepared by solid state reaction method at different sintering temperatures. It was found that the resultant was not ABO3 perovskite single phase but dual phase La2NiO4 and NiO, and the percentage of the two phases varied with sintering temperature. Ceramics sintered at 1400 ℃ were well crystallized and the phase ratio of La2NiO4 was the maximum. The surface morphology observed by scanning electron microscopy （SEM） indicated that the grains of the ceramics sintered at 1400 ℃ 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 ℃ exhibited better mass transition and arc erosion resisting properties.

Research on arc erosion of silver-based alloy contact materials under low voltage,resistive load and small current at 400 Hz and 50 Hz

By using a self-developed IF power and a ASTM contact material experimental system of small-capacity and variable frequency,the value of arcing characteristics and the welding force of the silver-based contact material are acquired under low voltage,resistive load and small current at 400 Hz and 50 Hz. By means of an electricity-ray analytical balance,SEM and EDAX,the weighing values of the contact materials and the changes of AgCdO,AgNi,AgC and AgW contact material surface profile and micro-area constituent are obtained and analyzed. The arc erosion causes of silver-based alloy contact materials at 400 Hz and 50 Hz are also discussed.

Study of the Material Transfer Characteristics and Surface Morphology Due to Arc Erosion of PtIr Contact Materials

By means of breaking tests on PtIr contact materials via a JF04C contact material testing machine, it was attempted to elucidate the characteristics of the various surface morphology and material transfer after the arc erosion process caused by break arc. The material transfer characteristics appeared in the experiments were concluded and analyzed. Meanwhile, the morphology of the anode and cathode surface were observed and analyzed by SEM.

Preparation and Arc Erosion Characteristics of Ultrafine Crystalline CuCr50 Alloy by MA-SPS

The ultrafine crystalline CuCr50（Cr 50 wt%） alloys were fabricated by a combination of mechanical alloying and spark plasma sintering process. The effects of milling time on crystallite size and solid solubility of the CuCr50 composite powders were investigated. The results showed that crystallite size of powders decreases gradually and solid solubility of Cr in Cu was extended with increasing milling time. The minimal crystallite size about 10 nm and the maximum solid solubility about 8.4 at%（i e, 7 wt%） were obtained at 60 h. The microstructure of ultrafine crystalline CuCr50 alloy was analyzed by SEM and TEM, which contains two kinds of size scale Cr particles of 2 μm and 50-150 nm, distributing homogeneously in matrix, respectively. The arc erosion characteristics of ultrafine crystalline CuCr50 alloy were investigated by the vacuum contact simulation test device in low D.C. voltage and low current（24 V/10 A）. A commercial microcrystalline CuCr50 alloy was also investigated for comparison. Experiments indicate that the cathode mass loss of ultrafine crystalline CuCr50 contact material is higher than that of microcrystalline CuCr50 material, but its eroded surface morphology by the arc is uniform without obvious erosion pits. While the surface of microcrystalline CuCr50 contact is seriously eroded in local area by the arc, an obvious erosion pit occurred in the core part. Therefore, the ability of arc erosion resistance of ultrafine crystalline CuCr50 alloy is improved compared to that of microcrystalline CuCr50 material.

Contact Resistance and Arc Erosion of Tungsten-copper Contacts in Direct Currents

The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to study the microstructure of the W-Cu powders and compacts. The contact resistance, arcing energy, and arcing time were continuously measured by JF04C contact materials test system. Changes in tungsten-copper contact surface were observed by SEM. The test results showed that the arcing time and arcing energy all increase with current and voltage, but the changes of average contact resistance are more complicated. For a short arcing time, the average contact resistance decreases with increasing current due to the vaporization of Cu. However, for a longer arcing time, it slightly increases due to the formation of high resistant films, compound copper tungsten. The formation of compound copper tungsten was confirmed by the increased Rc kept in the range from 1.1 to 1.6 mΩ. The compound copper tungsten is first exposed with a tungsten and copper-rich surface, and then totally exposed due to evaporation of copper from the surface. At last a stabilized surface is created and the crystals decrease from 8 μm to 2 μm caused by the arc erosion.

Effects of different atmospheres on the arc erosion behaviors of Ti_(3)SiC_(2)cathodes

The effects of ambient atmospheres on the arc erosion behaviors of Ti_(3)SiC_(2)cathodes were investigated at 5.5 kV in argon,nitrogen,air,and oxygen.The mass loss of the cathodes increased in the order of argon,nitrogen,air,and oxygen and the morphologies were measured by 3D laser scanning confocal microscope with a gradual blooming phenomenon.Raman spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy were employed to detect the components of erosion regions.The erosion-chemical products mainly consisted of TiNx in nitrogen,TiN_(x),TiO_(2)and SiO_(2)in air,TiO_(2)and SiO_(2)in oxygen.The arc energy was responsible for the arc erosion characteristics in different atmospheres.

Arc Erosion Behavior of Cu–0.23Be–0.84Co Alloy after Heat Treatment: An Experimental Study

The arc erosion behavior of Cu-0.23Be-0.84Co alloy after heat treatment was investigated experimentally by a JF04C electric contact test system. The arc duration, arc energy, contact resistance and contact pressure of Cu-0.23Be- 0.84Co alloy after solution treatment and aging treatment were analyzed. The arc erosion morphologies were contrastively observed by a three-dimensional measuring system and scanning electron microscopy. For the Cu-0.23Be-0.84Co alloy in solution state and aging state, the maximum values of arc duration are 90 and 110 ms, and the arc energies are 15,000 and 18,000 mJ, respectively. The maximum value of the contact resistance of Cu-0.23Be-0.84Co alloy in different states is about 33 mΩ The contact pressure of Cu-0.23Be-0.84Co alloy in solution state generally changes between 50 and 60 cN during whole make-and-break contacts, while in aging state, it has a larger fluctuation range. Moreover, the quality of moving contact （anode） decreases, while static contact （cathode） increases. The materials transfer from anode to cathode during make-and-break contacts. The total mass losses of Cu-0.23Be-0.84Co alloy in solution state and aging state are 3 and 1.2 mg, respectively. In addition, a number of discrete corrosion pits, molten droplet, porosity and cavity distribute on the surface of moving contact and static contact. The arc erosion model of Cu-0.23Be-0.84Co alloy in make-and-break contact was built. The arc erosion resistance of Cu-0.23Be-0.84Co alloy after heat treatment is closely related to the microstructure and the properties of contact materials. This experimental study is important to evaluate the anode or cathode electrocorrosion fatigue life.

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.

Effect of La_(2)Sn_(2)O_(7)content on Ag-La_(2)Sn_(2)O_(7)/SnO_(2)arc erosion behavior and mechanism

La_(2)Sn_(2)O_(7)/SnO_(2)powder was synthesized by chemical co-precipitation method,and Ag-La_(2)Sn_(2)O_(7)/SnO_(2)composites were prepared by hot-pressing sintering.The electrical resistivity,density,Brinell hardness and flexural strength of Ag-La_(2)Sn_(2)O_(7)/SnO_(2)composites were measured.Moreover,the effect of La_(2)Sn_(2)O_(7)content on the arc erosion behavior of Ag-La_(2)Sn_(2)O_(7)/SnO_(2)composites at 7 kV voltage was studied.With the increase of La_(2)Sn_(2)O_(7)content,the arc duration and arc energy decrease,and the breakdown strength increases.The surface morphology of Ag-La_(2)Sn_(2)O_(2)/SnO_(2)composites after arc erosion was investigated using scanning electron microscopy and three-dimensio nal laser confocal scanning microscopy.With the increase of La_(2)Sn_(2)O_(7)content,the smaller the erosion damage,the better the anti-arc erosion performance.However,too much La_(2)Sn_(2)O_(7)results in the decrease of Ag-La_(2)Sn_(2)O_(7)/SnO_(2)properties and severe arc erosion.X-ray photoelectron spectroscopy was used to determine the composition of the erosion region.The effect of La_(2)Sn_(2)O_(7)on wettability between Ag and SnO_(2)was investigated,and the erosion mechanism of Ag-La_(2)Sn_(2)O_(7)/SnO_(2)composites was discussed systematically.This study can provide a reference for the application of Ag matrix electrical contact materials in high-voltage electrical appliances.

Erosion Characteristics of Oil-immersed On-load Tap Changer Contacts Under Varying Contact Speeds and Pressures

With the growing demand for precise voltage adjustment and reactive regulation,the frequent operation of on-load tap changers(OLTCs)in oil-immersed systems has led to increased erosion of switch contacts by arcs during the switching process.This erosion causes significant wear on the contacts,thereby reducing their lifespan.Therefore,the present study aims to investigate the behavior and mechanism of arc erosion on contact surfaces in oil-immersed OLTCs.To achieve this,a self-designed friction and wear test device for OLTC contacts was utilized to conduct experiments at various sliding speeds and contact pressures.Additionally,finite element analysis was employed to validate the experimental results regarding the influence of sliding speed on arc energy.The surface morphology of the contacts was observed using an optical microscope.The findings revealed that as the sliding speed increased,the arc energy,arc initiation rate,and contact resistance initially exhibited an upward trend,then decreased,and eventually increased again.The minimum values were observed at a sliding speed of 90 mm/s.Moreover,the arc energy,arc initiation rate,and contact resistance decreased gradually as the contact pressure increased.After reaching a contact pressure of 1.5 N,the variation in the arc energy stabilized.At lower contact pressures,arc erosion dominated the wear on the contact surface.However,at higher contact pressures,the wear transitioned from predominantly arc erosion to a combination of mechanical wear and arc erosion.In summary,experimental and analytical investigations provided insights into the effects of sliding speed and contact pressure on the behavior of arc erosion,contact resistance,and surface damage of OLTC contacts in oil-immersed systems.

Modeling of flow and debris ejection in blasting erosion arc machining in end milling mode

Blasting erosion arc machining(BEAM)is a typical arc discharge machining technology that was developed around 2012 to improve the machinability of difficult-to-cut materials.End milling BEAM has been successfully developed and preliminarily applied in industry.However,owing to the high complexity of the flow field and the difficulty of observing debris in the discharge gap,studies of the flow and debris in end milling BEAM are limited.In this study,fluid dynamics simulations and particle tracking are used to investigate the flow characteristics and debris ejection processes in end milling BEAM.Firstly,the end milling BEAM m o d e is introduced.Then the numerical modeling parameters,geometric models,and simulation methods are presented in detail.Next,the flow distribution and debris ejection are described,analyzed,and discussed.The velocity and pressure distributions of the axial feed and radial feed are observed;the rotation speed and milling depth are found to have almost no effect on the flow velocity magnitude.Further,debris is ejected more rapidly in the radial feed than in the axial feed.The particle kinetic energy tends to increase with increasing milling depth,and smaller particles are more easily expelled from the flushing gap.This study attempts to reveal the flow field properties and debris ejection mechanism of end milling BEAM,which will be helpful in gaining a better understanding of BEAM.