Arc Power Research Articles

Novel Approach for the Monitoring of Single Phase-to-Ground Fault Associated with Power Arc

This paper presents a general theoretical overview of a novel approach for the monitoring of the single phase-to-ground fault associated with power arc. Although several existing fault protection methods have been employed in order to resolve the power arcing faults associated with the single phase-to-ground faults, still ongoing research is trying to develop efficient methods that could help to suppress completely these dangerous power arcs from the systems. The operation of the protective relays and fuse systems is quite often questionable during recurrent failures in detecting the electric arcs as expected, especially during these arcs earlier events of formation. The most relevant reason causing these traditional faults protective switchgears seldom failures, limitations and drawbacks include essentially the varying amounts of resistance associated with these previously mentioned power arcs. Subsequently, the electric arcs related impedance and that of the power system tend to limit the arcing fault currents and voltages quantities at very low rates. Hence preventing the existing fault protective devices and switchgears to detect these arcs hazards, as long as the arcing fault related currents and voltages quantities are kept for a relatively long period of time below the nominal setting values of both the relays and the fuses systems. Subsequently, the entire power distribution system experiences the devastating effects of theses dangerous parasitic electric arcs hazards. However, in order to overcome the limitations, the disadvantages and the drawbacks of the above mentioned conventional fault protective devices, this paper divorces completely with the traditional practices in order to propose a radio measurement method.

Development of optimal deposition strategies for cladding of Inconel 625 on carbon steel using wire arc additive manufacturing

The use of nickel alloys for cladding and repair has a high scientific and industrial interest in surface engineering. The use of smart processes for surface modification, such as additive manufacturing, particularly wire arc additive manufacturing (WAAM), is relevant due to its high deposition rate and capacity for customisation and deposition over complex geometries and paths. The present research is focused on strategies for cladding Inconel 625 on low-carbon steel using WAAM, investigating the effect of different welding parameters to control and optimize the penetration, geometry, dilution, and overall quality. Parameters such as the torch/table travel angle, welding technique, contact-tip-to-work distance, current/wire feed speed (WFS), welding travel speed and heat input were analysed. Three deposition strategies were developed: the deposition with a shorter contact-tip-to-work distance to increase penetration resulting in the least iron-containing clad; the welding with a higher WFS but with a proportional increase in the travel speed to maintain the heat input allowing faster welding and adequate iron content; and the welding with higher WFS and lower travel speed resulting in a thicker clad and the second least iron-containing deposition. It was found that the arc power showed a more direct relationship with the penetration and dilution in the clad than the heat input. The results suggest that for cladding evaluation, it is important to analyse the heat input together with the arc power and travel speed.

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources

In this work, the procedure for direct atomic emission spectrometry (AES) determination of fluorine impurities in carbon materials was proposed. Two types of simple radiation sources with direct solid (powdered) sample introduction were studied: direct current arc (25A) and high-power low voltage spark (300 V, of 2348 μF). For each source, standard graphite extra high purity electrodes and argon discharge atmosphere were used. Red spectral region approach to non-metal AES determination was employed with analytical line F I 685.603 nm. The spectra were registered by compact tunable fiber-optic spectrometer with linear complementary metal oxide semiconductor array (CMOS) sensor and short-focus lens. Special measures were taken to counter red spectral region interferences, such as CN molecular bands and thermal radiation. The excitation of F in both types of radiation source was studied. A set of artificial graphite and NaF based standards was prepared for calibration and evaluated by two independent approaches: indirect dc arc AES and water extraction photometry. Limit of detection was determined for dc arc source was 5 μg/g, and for spark 20 μg/g of F. The whole cycle of measurement with each type of radiation source takes 10 min. As the power of dc arc is limited by generator capabilities, it is possible that even lower limit of detection is achievable with higher discharge current.

An energy optimization study of the electric arc furnace from the steelmaking process with hot metal charging

A study of energy optimization derived from simulation software has been done for the high-intensity energy of an Electric Arc Furnace (EAF), hot metal charging within the cooler duct dedusting system. The present work aims to develop a dynamic model of the EAF operation based on mass and energy balances integrated with simulation of the dedusting system with hot metal charging system using MATLAB® and Computational Fluid Dynamics (CFD). The effect of various percentages of hot metal charging on EAF performance and the dedusting system was simulated and validated from the real EAF data plant from one of the steel manufacturer companies in Indonesia. Three cases for the EAF with various hot metal (HM), sponge iron, and scrap iron charging compositions and four cases for the EAF with post-combustion CO have been developed. Careful observation shows that the electric arc power consumption can be reduced down to 72.9 MWh from 87.4 MWh (ca. 16% more efficient) while at the same time increasing the HM charging temperature at the endpoint of the duct dedusting system up to 900°C from 540°C (app. 65% higher). Additionally, advanced simulation of an EAF with post-combustion CO shows that power consumption can be decreased to 59.9 MWh (ca. 30% more efficient).

Slag mode regulation in electric arc furnace based on electrical parameters control during melting oxidation period

The results of observation of steelmaking oxidation stage at EAF-135 were analyzed with automated control system of the electrical characteristics. There are three main zones in the furnace working space, which differ by the aggregate state of the materials in them: arc discharge, melt and foamed slag. The distribution data of electric power over the furnace zones is given. There is active powers asymmetry of the arcs under single electrodes affected by asymmetry of the short network. It is shown that the main factors impacting the melt and slag resistances are oxygen blow and electrode movement. The authors studied the influence of magnesia flux feeds on the melt resistance. These feeds correspond to a sharp increase and a subsequent gradual decrease in resistance, and the time for assimilation of additives does not exceed one minute. The average electrical parameters of the working space zones are given for the EAF-135 at single heats. A comparison was made of the nature of change in the arc discharge power and the change in the melt temperature. The profiles match of changes in these characteristics to an increase in the arc power corresponds to increase in the melt temperature. An attempt to correlate FeO content in the slag with the arc power did not give a positive result. However, this methodology should be tested under conditions of steel refining in a ladle-furnace unit. It is noted that the parameter control at changing of the electrical parameters of the arc and slag zones due to the overwhelming influence of intense oxygen blast, melt mixing and electrode displacement does not meet the reliability criterion.

Cathode-arc-anode behavior in cooling-induced cathode-focusing GTA system: A unified numerical model

A gas tungsten arc (GTA) is an important heat source for manufacturing, cooling to the tungsten electrode has a critical influence on the cathode-arc-anode behavior because cooling-induced cathode-focusing (CICF) effect forms. In this research, a unified arc-electrode model is established to predict the influence of tungsten electrode cooling degree on heat transfer behavior in the cathode-arc-anode system. The results show that enhancing the cooling degree of the tungsten electrode can: (1) increase the arc voltage and arc power; (2) increase the arc pressure and the heat transferred to the anode and improve the arc penetration ability; (3) but slightly increase the heat transfer to the cathode tungsten rod at a given arc current. The developed model is validated by available experimental data. The research results deepen the understanding to the CICF effect and provide guidance for increasing optimizing the GTA torch structure to improve the arc penetration ability.

High power arc ion plating of thick Cr2N hard coating on Ti-based alloys: Oxidation and wear behaviors

Thick Cr2N hard coating was obtained at a high rate of around 15 μm/h by high power arc ion plating to improve the oxidation and wear resistance of Ti6Al4V at medium high temperatures. The coating grew only about 1 μm thick Cr2O3 scale after oxidation for 500 h at 600 °C accompanied by a slight interfacial diffusion, whereas a non-protective TiO2-based scale of around 8 μm in thickness was formed on the Ti6Al4V after oxidation at the same condition. The wear rate of Cr2N-coated Ti6Al4V was significantly reduced by about 99.6 % and 86 % at 25 °C and 600 °C, respectively. In addition, the Cr2N coating maintained excellent structural integrity after oxidation and wear, demonstrating that the Cr2N coating is a promising candidate for protecting Ti-based alloys against oxidation and wear.

A review of tribological properties and deposition methods for selected hard protective coatings

Surface modification is widely adopted as a viable solution for surface damage under sliding or impacting conditions. Various coatings can be manufactured using different techniques and it has been applied on various substrates in previous studies which results in different characteristics. This review presents the anti-wear techniques with a focus on the most recent coatings of superior properties. Hard protective coatings may consist of various compositions; however, based on the hardness and the resistance to wear, some of the frequently used elements are Titanium (Ti), Nickel (Ni), carbides, Zirconium (Zr), Boron (B) and the Diamond Like Carbon (DLC). The deposition methods such as Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD) as well as the cutting-edge coating hybrid-deposition methods such as Pulsed DC Magnetron Sputtering (PDCMS), High Power impulse (HiPIMS) and Arc Ion Plating (AIP) are reviewed and the resulted significant differences in the coating properties are discussed. In this review, listing the most important findings from previous studies in a table for each group of coatings make it easy to compare between various techniques and coatings. Some of the listed factors affecting the coating properties, such as the substrate, and others affecting the coefficient of friction, such as the counter body, were not been sufficiently highlighted before despite their importance in analyzing the tribological behavior for the coatings investigated. Although the focus was on the most recent studies, a wide range of studies was covered in order to accumulate and integrate the knowledge toward a complete analysis and discussion. Coating hardness is essential for better wear resistance; however, coating bonding, thickness and roughness may be equally important. Various techniques are used to improve the bonding. For some coatings, the Coefficient of Friction (CoF) increases with increasing the wear resistance where the counter body plays a major role. For most of the deposition techniques, the controlling parameters are the cleaning treatment, arc current, pressure, time, and gas supply. It was found that diamond-like carbon coatings are among the hardest coatings and the Plasma-Assisted Chemical Vapor Deposition (PACVD) is frequently reported as one of the most promising deposition techniques. Many coatings including the diamond-like carbon coating were not been investigated for their erosion wear resistance by solid particles despite the importance of such investigations for many applications.

Radiation Power of a Short High-Current Vacuum Arc at High Current Densities

The radiation of a vacuum arc was measured in the spectral region <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~\text {nm} \le \lambda \le 1100$ </tex-math></inline-formula> nm. The arc was initiated in the center of the cathode by breaking the current in the auxiliary circuit and was fed by the rectangular current pulse with a duration of 10 ms. The interelectrode gap was fixed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$h = 4$ </tex-math></inline-formula> mm, and the butt <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2r =30$ </tex-math></inline-formula> -mm CuCr30 electrodes were used. The arc was stabilized by an external uniform axial magnetic field (AMF). The radiation was coming out of the vacuum chamber through quartz ultraviolet (KU)-1 quartz window. The radiation detector was a silicon photodiode with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d =1.2$ </tex-math></inline-formula> mm. It was located on an axis intersecting the axis of symmetry of the discharge in the center of the interelectrode gap. The distance from the diode to the axis of symmetry was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L =1340$ </tex-math></inline-formula> mm. After amplification, the signal from the diode was recorded on an oscilloscope. The measurements were made in a range of currents from 10 to 25 kA in order to cover the modes with the anodic activity. It was found that under the conditions of these experiments, the anode activity begins to manifest itself at the end of the pulse, starting with currents exceeding 15 kA. As the current increases, the activity begins closer to the beginning of the pulse. Considering the type of the spectral sensitivity of the diode, two series of measurements were made—measurements without a filter and through a yellow filter ZhS-10 that cuts off radiation with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \le400$ </tex-math></inline-formula> nm. The results obtained made it possible to analyze the dependence of the radiation power on the arc current. The results showed that at high current densities in the developed vacuum arc with anodic activity, a significant part of the power is transferred by radiation. At the end of a pulse with a current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 25$ </tex-math></inline-formula> kA, the radiation power is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {uv}}~\approx ~150$ </tex-math></inline-formula> kW, while in the discharge, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{a} ~\approx ~800$ </tex-math></inline-formula> kW is released. That is, at high current densities at the end of the pulse, the radiation power reaches almost 20% of the power released in the arc at this time. Estimates of lateral losses due to radiation are made.

Lightning Protection of Electric Power Overhead Distribution Lines by Long-Flashover Arresters in Russia

A simple and effective method for lightning protection of power overhead distribution lines by long flashover arresters (LFAs) is presented. Even large lightning currents do not pose any threat to these arresters because the discharge develops in the air and not inside the device. LFAs, which are based on the creeping discharge effect, increase the lightning flashover length significantly and thus eliminate Power Arc Follow (PAF). To protect a line against induced overvoltages, a single arrester should be mounted on a pole. To protect a line against direct lightning strokes, LFA-M arresters should be mounted in parallel with each insulator. For covered-conductor overhead lines (CCL) using conductors with three-layer insulation a new lightning protection approach is suggested, involving use of antenna-type long flashover arresters whose essential component is the protected conductor itself. The essence of antennatype long flashover arresters (LFA-A) is that the arrester which is connected to the antenna gets flashed over well before the lightning leader comes in immediate contact with the line. The toroid-shaped antenna made of a metal tube is mounted on the covered conductor’s surface midway between the protector’s edge and the piercing clamp with the help of the toroid fixation unit. As the lightning leader progresses from a thunderstorm cloud to the CCL a high potential gets induced on the LFA antenna. A voltage drop that develops between the electrode and the zero-potential conductor core gives rise to development of a creeping discharge. Even before the lightning leader hits the line the creeping discharge channel flashes over the covered conductor’s surface Thereby the conductor insulation get bypassed by the discharge channel and thus protected against puncture. LFA’s main applications and field experience are presented.

Influence of the Secondary Arc on the Operation of Single Phase Autoreclosure of the 400 kV interconnection between Hungary and Croatia

&#x0D; &#x0D; Sažetak: Faults on EHV lines are generally single-phase-to-ground ones and not permanent in the majority of cases. Thus single phase auto reclosure (SPAR), at which the faulty phases are tripped for a short time, eliminates the predominant part of the faults [1,2]. The secondary arc, which follows the high power arc after tripping the faulty phases at both side of the line may endanger the successfulness of reclosing if the duration of the switched off interval (dead time) is not long enough to ensure the extinction of the arc. The secondary arcing times recorded on different EHV lines or measured in laboratory tests show significant spread, consequently, to select a dead time according to the longest experimental secondary arc extinction time is not feasible. During commissioning of the double circuit 420 kV interconnection between Hungary and Croatia several staged faults were initiated to analyze the arc extinction performance. Initially the line was in operation by connecting the two circuits in parallel along the 1/3rd of the full length. In this configuration the longest secondary arc extinction time was 4 seconds and the secondary arc has not extinguished in 27s in one of the tests, so the line had to be tripped out to clear the staged fault. Later on, the length of the Croatian section of the line has been significantly shortened after putting a new substation into service. The increased performance of SPAR of the new arrangement has been proved with field tests. A realistic representation of the secondary arcs is essential in determining the auto-reclosure performance of EHV transmission lines. As shown in the paper, the random variation of the arc parameters influences significantly the arc extinction time. The results of the field tests confirmed the importance of the distributed nature of the transmission line and the nonlinear characteristic of the arc resistance in the intermittent region of arcing, where temporary extinctions and sudden re-ignitions in the arc channel produce transient wave processes along the line.

ელექტრული ღუმლის ელექტროდების გადაადგილების მართვის სისტემის ოპტიმიზაცია

It’s known that the efficient operation of electrical appliances used in production significantly improves the quality and quantity of products. Competent control of technological processes is especially important for such a heavy industry as metallurgical production, where one of the most important issues is the optimal control system for electric motors of moving electrodes, which in turn ensures the required dynamics of arc power control and high productivity. The existing arc power control systems do not fully meet the basic requirements, such as insufficient sensitivity of the regulating parameter, speed and reliability of the electrode movement motor control system. The study of electric motor control systems is an important scientific and technical task in this regard. The optimization of the electric motor control system for moving the electrodes of an electric arc furnace based on the use of logic in control is discussed.

Real-time monitoring of temperature field, metal transfer and cooling rate during gas metal arc-directed energy deposition

Gas metal arc-directed energy deposition is a metal additive manufacturing technique that involves the melting of a filler wire under an electric arc resulting in a high rate of deposition of molten metal and fast building of large scale parts in a layer-by-layer manner. A novel attempt is presented here for real-time simultaneous monitoring of the arc current, voltage and power, and the nature of surface temperature field and filler wire deposition during the process. The recorded temperature fields are analysed to trace the layer-wise variation in melt pool dimensions and solidification cooling rates. Together these process signatures demonstrated a synchronised assessment and potential to support an integrated feedback control system for gas metal arc-directed energy deposition.

Підвищення ефективності запалювання вакуумно-дугового розряду в джерелах плазми

The analysis of the existing vacuum-arc discharge ignition systems showed the following ways to improve their efficiency: development of new design solutions for both individual units and the entire ignition system as a whole; the use of composite materials to fill the discharge gaps of starting devices; creation of new circuit solutions for power supplies of starting discharges; the use of non-traditional methods of ignition of a vacuum-arc discharge - the transition of a glow discharge into an arc one; using laser radiation to ignite the arc. Criteria for evaluating the reliability and durability of vacuum-arc discharge initiation systems in technological plasma sources are proposed, based on which complex studies of contact-type arc excitation systems with spark surface breakdown and two-stage launch systems with an autonomous plasma injector. Based on the performed studies, designs of vacuum-arc plasma sources with contact-type systems have been developed that ensure their performance in a certain range of technological parameters; The design of the ignition system turned out to be the most effective, in which the ignition electrode and the auxiliary anode are made as a single structural element in the form of a cut cone-shaped spiral. These design features, firstly, do not prevent the condensation on the surface of the starting discharge gap of a part of the metal evaporated by the cathode spot (CS) of the arc during the operation of the device, and secondly, they greatly facilitate the output of the CS from the place of initiation to the working end of the cathode. Here, the magnetic field, under the action of the CS moves, created by the current of the starting discharge itself, flows along with the turns of the cone-shaped spiral. This ignition system does not require a separate power supply and can operate in an automatic mode from the arc power source. To implement a non-contact method of arc excitation using a plasma injector, various designs of it were studied, when the discharge gap was filled with different materials; it was found that the resource of starting injectors when filling the discharge gap with M-7 ceramics does not exceed 104 operations, with 22XC ceramics at the level of 105 operations, and when using a composite material (CM), it exceeds 106 operations at ignition energy of 5 J, an operating pulse frequency of 1 Hz and arc duration 2 s. The developed composite materials are distinguished by increasing resistance to electric discharges and low surface breakdown voltage (up to 100…200 V/mm). Such characteristics are provided by the features of the CM structure, which is a dielectric glassy matrix filled with finely dispersed conductive particles and semiconductor components. The theoretical and experimental dependence of the arc ignition probability on the ignition energy during the operation of the injector in the electric film explosion mode are compared, showing satisfactory agreement between the results.

The distribution pattern of the electron density and the electron temperature in a weakly compressible argon plasma jet measured by a Langmuir triple probe

High-speed plasma plays an important role in diverse areas. Plasma flow with a sufficiently high speed to arouse compression is usually not in thermal equilibrium, and the plasma characteristics are closely coupled with the flow field. The relation between the flow and the plasma parameters, especially the distributions of electron density, i.e. n e, and the electron temperature, i.e. T e, are of ultimate importance; however, this is not yet completely understood. In this work, a weakly compressible plasma jet produced by an arc torch is diagnosed using a Langmuir triple probe. The two-dimensional distributions of n e and T e are obtained consisting of 80 spatial points under arc currents of 70–100 A. The spatial patterns of the distributions demonstrate alternative expansion–compression wave structures. As the arc power increases, the wave structures remain almost unchanged, while n e increases monotonically. Moreover, in some regions T e decreases with the arc power, which has seldom been reported in the literature. In addition, the peaks of the radial distributions of T e always deviate from the central axis. These results are compared with previous works of strongly compressible plasma flows. The phenomena are then analyzed and explained from the perspective of fluid wave-plasma interactions and the actions of the ambipolar field in the electrons.

A research on rigid polyurethane foam resistibility to ignition from an electric arc welding spark

Introduction. A fire investigation assumes that electric arc welding sparks (hereinafter referred to as “sparks”) are effective sources of ignition. However, the spark ignition of a combustible material depends on the contact time. This work has experimentally proven that a smooth vertical wall, made of combustible rigid polyurethane foam (PUF), is not subjected to spark ignition. To explain this fact, the author calculated the time of contact between the spark and the wall τint, and compared it with the minimal estimated contact time τmin required to ignite the wall.The sample and the testing procedure. Sparks (the arc power up to 6 kW, the current up to 160 A) reached the PUF wall located at a distance of 0.1–0.15 m from the arc. An everyone experiment was continued until the electrode was burned down.Research results and discussion. Neither attempt to inflame the PUF sample by a spark was successful. Sparks bounced off the PUF sample and fell down. The characteristic dimensions of cooled iron droplets ranged from 0.2 to 3 mm.An evaluation of τint. The authors applied a model of elastic interaction between a drop of molten iron and a rigid wall, assuming that the sum of the potential energy of the drop, associated with its surface, and the kine­tic energy of a spreading drop, if flattened, is conserved. The longest contact time is achieved for drops, featuring the maximum diameter of 3 mm: τint ≈ 0.004 s.Estimation τmin. The authors applied the experimental modeling of the process, whereby the effect of an iron drop on PUF was replaced by the time-controlled effect, produced by a wooden cylinder (6 mm in diameter), inflamed at one edge. τmin ≈ 0.3 s. The ratio τint &lt;&lt; τmin explains the inability of electric arc welding sparks to ignite the PUF wall.Conclusions. Electric arc welding sparks, having a diameter of up to 3 mm, cannot ignite a vertical wall, made of rigid combustible polyurethane foam, in case of a side impact. The lack of ignition is explained by the short-term contact between the spark and the surface of the polyurethane foam.

Investigation of welding parameters effects on temperature field and structure field during laser-arc hybrid welding

Thermo-structural weak coupling model was adopted in numerical simulation of laser-arc hybrid T-joint welding. Gauss surface heat source and Rotary-Gauss body heat source were used to form a combined heat source in the temperature field analysis and simulate the arc and laser heat source. The laser-arc hybrid overlaying welding test of 304 stainless steel was carried out, and the weld molten pool morphology was obtained by metallographic corrosion test. The test results of a molten pool morphology show that the combination heat source can better simulate the laser-arc hybrid welding process. The effects of laser power, arc power and welding speed on residual stress and deformation of T-joint in laser-arc hybrid welding were studied by orthogonal experiments. Experimental results show that the arc power has great influence on the depth-width ratio, the laser power has great influence on the welding residual stress, and the welding speed has great influence on the thermal deformation. Through quantitative analysis and comparison, the optimal parameters were found during laser-arc hybrid welding.

Research on Residual Stress Distribution in Different Areas of Laser-MAG Arc Hybrid Welding by Numerical Simulation

In this research, through experiments and numerical simulations, the residual stress distribution of the top and bottom surfaces of the laser (TruDisk16002)-arc (MAG) hybrid welding seam and the weld cross-section are studied. The results show that when the arc power is 6.5KW and the laser power is 7.5KW, the weld is formed well. The residual stress on the bottom surface near the weld is higher than that on the top surface. The laser zone in the center of the weld has the largest residual stress, the arc zone is smaller, and the mixed zone is the smallest. The laser zone has the largest residual stress at the fusion line and the heat-affected zone, followed by the mixed zone, and the arc zone is the smallest. followed by the mixed zone, and the arc zone has the smallest.

Inaccuracy in arc power calculation through a product of voltage and current averages

Power is an indirect measurand, determined by processing voltage and current analogue signals through calculations. Using arc welding as a case study, the objective of this work was to bring up subsidies for power calculation. Based on the definitions of correlation and covariance in statistics, a mathematical demonstration was developed to point out the difference between the product of two averages (e.g. P = overline{U} x overline{I}) and the average of the products (e.g. P = (overline{UxI}). Complementarily, a brief on U and I waveform distortion sources were discussed, emphasising the difference between signal standard deviations and measurement errors. It was demonstrated that the product of two averages is not the same as the average of the products, unless in specific conditions (when the variables are fully correlated). It was concluded that the statistical correlation can easily flag the interrelation, but if assisted by covariance, these statistics quantify the inaccuracy between approaches. Finally, although the statistics' determination is easy to implement, it is proposed that power should always be calculated as the average of the instantaneous U and I products. It is also proposed that measurement error sources should be observed and mitigated, since they predictably interfere in power calculation accuracy.

Stabilization Methods in the Submerged Arc Discharge Synthesis of Carbon Nanostructures

Many papers, in which the submerged arc discharge (SAD) method in nanoparticle synthesis was used, reported similar operating parameters, but different electrode erosion rate values, different yields and purities of the obtained nanostructures, and a different sort of contaminants present in the synthesis. Analyzing these articles, we found insufficient attention to ensure the arc power stability, which is a key factor guaranteeing the product homogeneity and quality. This paper presents an analysis of different control strategies, remarks their advantages and drawbacks, and proposes the most appropriate technique to be used in SAD. The most appropriate technique is proposed from the SAD stabilization method analysis.