Voltage Spark Research Articles

Analysis of the Possibility of Using Drill-Type Electrodes for Air Ionization

In this article, the authors present the results of the analysis of the ionization efficiency of drill-type needle electrodes in air. The analysis was carried out on the basis of experimental laboratory measurements, examined at alternating voltages. Drill-type electrode systems of different diameters were adopted for the tests. The ionization efficiency for this type of electrode has been characterized by values of characteristic voltages, such as the initial voltage of the corona voltage and the sparking voltage. The obtained results were compared with the results of classical conical needle electrodes. The ionization efficiency of drill-type electrodes has been shown to be higher than that of classical conical needle electrodes.

Effect of Spark Plasma Sintering Current and Voltage on the Microstructure and Electrical Properties of Borosilicate Glass–Indium Tin Oxide Composites

Borosilicate glass–indium tin oxide (ITO) composites made from glass microspheres and ITO nanoparticles provide a unique model system to monitor the effect of spark plasma sintering (SPS) parameters on the resultant electrical properties of the composites. Composite sets containing different ITO content (up to 10 phr), fabricated under the same SPS conditions, are used as the starting point for the equivalent circuit analysis. The effect of changing the various SPS parameters such as heating rate, hold temperature, and applied pressure on the current and voltage profiles experienced by samples containing 2.5 phr (2.44 wt%) ITO, and their resultant electrical response are reported. Experiments are carried out varying a single SPS parameter at a time while keeping others constant. The applied pressures used range from 5 to 40 MPa; the hold temperature is varied from 610 to 680 °C; and the heating rate is tested between 2 and 200 °C min−1. It is demonstrated that not only do the current and voltage profiles change in all of these instances but also the microstructure and resultant electrical properties of the composite samples being fabricated. Results indicate that all of these parameters are interdependent and can affect the electrical properties of the fabricated samples by many orders of magnitude in some cases.

A Fuzzy Modelling for Selection of Machining Parameters in Wire Electrical Discharge Machining of D2 Steel

Wire Electrical Discharge Machining (WEDM) is a widely used non-traditional machining process used for machining of hard and difficult-to-machine materials. Proper selection of machining parameters in WEDM is required for better output performance, such as Material Removal Rate (MRR), Wire Wear Rate (WWR) and Surface Roughness (SR) etc. In the present paper, Pulse ON time, Pulse OFF time, Peak Current, Spark Voltage, Wire Feed and Wire Tension were taken as the input parameters to optimize MRR, WWR and SR. A set of 27 experiments were performed as per Taguchi Design. A Fuzzy model has been proposed to select the optimum values of machining parameters. The proposed fuzzy model was found to predict the experimental values with more than 90 percent accuracy.

Optimization of Electro-Discharge Diamond Drilling of Inconel 718 using Taguchi Method

In this paper Taguchi method has been applied for optimization of electric discharge diamond drilling of Inconel 718 super alloy. Electrical discharge diamond drilling (hybrid process) process has been carried out on Inconel 718 using Taguchi L9 orthogonal array (OA). The effects of process parameters such as peak current (I), pulse-on time (Ton), pulse-off time (Toff) and drill speed (DS) on average surface roughness (ASR) have been studied to optimize and improve the process capabilities. Taguchi’s orthogonal array L9 (34) with three level of each four control factor were peak current, pulse-on-time, pulse-off-time and the rotational speed of tool electrode has been used in this study. In this study, the effect of varying process parameter with fixed machining time and constant spark voltage been investigated on average surface roughness of Inconel 718. Pulse-on time and peak current found the most influencing parameters for average surface roughness during electric discharge diamond drilling of Inconel 718. The optimum value of average surface roughness was found 1.88 μm. The percentage error between experimental and predicted values of average surface roughness was found 6.844%.

Analysis of Triangular WEDM Cut Corner Inaccuracy of Aluminium Composite Mold Material

Aluminium Composite mold has been used exclusively in industries such as Aerospace, Automobile, Medical Equipment, Transportation, and Marine. They are preferred due to efficient heat transfer and strength. These molds are used to produce seat foams, urethane panels, silicone patterns, MRI instrument covers. Leakage in any of the products due to machining inaccuracy in corners will lead to serious problems. Therefore, the corner inaccuracy has been investigated. Composite mold material is made of Al-TiB2. Wire EDM can be used for machining Al-TiB2 composite efficiently and the optimization of the parameters in WEDM such as MRR, surface roughness, and corner inaccuracy. Triangular profile of 60° angle with sides 30 mm was cut from the composites. Composites machining done with wire electric discharge technique by varying control factors wire tension, spark voltage, pulse on duration, and pulse off duration. Machining experimentation was done using a brass tool electrode wire and size of 0.25 mm in diameter. The surface roughness (Ra) of the cut was evaluated through a surf-tester with a sampling length of 0.8 mm. To examine a corner inaccuracy of the machined surface, OM pictures were taken on the machined surface of Al-TiB2 composites. Calculation of inaccuracy in the corner was done using ImageJ software. The corner inaccuracy can be estimated by subtracting a machined area from actual area. By calculating the inaccuracies of machined composites, it was found that the minimum deviation in corner area was observed in the machining conditions of maximum wire tension (WT) and maximum Pulse on time (Ton). Wire Tension provided less deflection during the machining. The less deflection in wire provided stable sparks and constant inter-electrode gap providing the least corner inaccuracy during machining. In order to increase corner accuracy, the wire tension can be increased to a certain limit and above that which the wire tends to break due to the presence of non-conductive ceramic particles in the aluminium matrix.

Об оценке коммутационной способности тяговых двигателей грузовых электровозов

An important direction in the development of JSC Railways is increasing the volume of freight traffic over the railway network. A number of measures are being taken to achieve the predicted strategic indicators in the locomotive complex. The most large-scale activities include research and experimental works aimed at improving the traction properties of electric locomotives in the Eastern polygon, which is one of the most heavily loaded sections of the Russian railway network. This is an important link connecting Southeast Asia and Europe. The conditions under which the railway transport operates require, among the priority tasks, efficient use of the locomotive fleet with high operational reliability to ensure safe train traffic. The Eastern polygon uses a system of electric traction powered by the 25 kV, 50 Hz AC voltage. Freight trains are driven by 2ES5K and 3ES5K electric locomotives equipped with pulsating current commutator traction machines. In implementing the required traction forces, the traction electric drive of such locomotives has a number of limitations. One of them is the quality of switching on the traction motor commutator. Achieving better reliability of traction motors, which are regarded as the weak link of electric locomotives, is a topical problem. The number of their failures due to faults of direct and pulsating current traction motors is at the level of 20--22%. The greatest difficulty is to increase the switching reliability. A switching quality criterion for traction electric motors of electric locomotives is proposed, which takes into account the degree to which the armature reaction magnetomotive force is compensated in the switching zone. The width of the sparkless operation region cannot fully characterize the traction electric motor switching capacity. Its calculation takes into account the spark voltage under the brush, the effect of electromagnetic factors on the switching, the design of additional poles, and the kind of load current. The accomplished calculations have shown that the proposed switching reliability quality criterion objectively characterizes the switching quality in the limiting mode and is consistent with the long-term experience of their operation in AC electric locomotives.

Measurement of sparking voltage in electric machines based on their transient functions

The article proposes a method for measuring the sparking voltage in DC electric machines based on the transient functions of these machines connected to bipolar brushes. Knowing the resulting response of the system to an impact in the form of a series of pulses obtained experimentally, it is possible to determine the response of the system to an arbitrary input action from a real spark in the sliding electrical contact of an electric machine. Using real transitional parameters of the anchor circuit of an electric machine will eliminate the systematic error of the method for estimating the level of switching sparking using a signal with bipolar brushes of this machine.

Some geometrical and electrical aspects on the wire-to-cylinder corona discharge

Corona discharge is a gas discharge that can be applied in a vast number of industrial applications. In all of them, knowing the current-voltage curves (CVCs) is of high importance because they determine the corona discharge operation range, from the inception voltage to the breakdown voltage. The CVCs are influenced by geometrical factors, ambient conditions and electrical parameters so the one only way to increase operation range without achieving spark voltage is lowering the inception voltage. Regarding geometrical parameters, it is widely known that reducing the distance between electrodes decreases the inception voltage, however two behaviours are found for the emitter radius in the literature. One of them establishes that there is a limit to the emitter size from which there is no change in the CVCs, while the another theory states that by reducing the emitter radius there is always an increase in the corona current. A series of measurements were carried-out for wire-to-cylinder corona discharge in parallel arrangement to study the influence of geometrical and electrical parameters over the current-voltage curves, mainly focusing in the wire radius. The results show that reducing the emitter radius always produces an increase in the corona discharge current. Although the inception voltage is generally higher for positive than for negative polarity, the experimental data suggest that there is an emitter radius from which this trend changes, being the negative inception voltage larger than for positive i.e. the inception voltage depends on the polarity of the discharge and the wire radius. Furthermore, the determination of the inception voltage by using four formulae is compared with the experimental data due to its importance to establish the operation range of corona devices. The influence of geometrical parameters is especially relevant to design and manufacture corona discharge devices e.g. low noise and without moving parts flying systems.

Large amplitude stationary solutions of the Morrow model of gas ionization

We consider the steady states of a gas between two parallel plates that is ionized by a strong electric field so as to create a plasma. We use global bifurcation theory to prove that there is a curve \begin{document}$ \mathcal{K} $\end{document} of such states with the following property. The curve begins at the sparking voltage and either the particle density becomes unbounded or the curve ends at the anti-sparking voltage.

Digital Triggering Device and Generator of Starting Pulses for Ignition of Spark Gaps of REB Accelerator “TEMP”

To ensure the controllability and high noise immunity while measuring the characteristics of the accelerators of relativistic electron beams (REB) “TEMP”, and parameters of the processes in them, triggering devices with galvanic isolation of input and output circuits, allowing to set up the pulse delays in the range from 1 μs to tens of milliseconds, have been developed. When they are used, the effect of loop currents, which flow in the common ground circuits and affect the operation of the measuring equipment, is eliminated. To synchronize the operation of the REB accelerator “TEMP” a triggering device was developed and assembled. It was assembled from blocks produced on the up-to-date elemental base and is a complete functional product. The triggering device comprises a trigger block and delay units. The trigger block is developed on the basis of an AND - NOT chip and a multivibrator. The delay units are built on single-shot vibrators K155AG1 and differ in the value of adjustable delays, which are determined by the external elements R and C, connected to the multivibrator. Unfortunately, in case the millisecond delays are set up, the pulse drop on the multivibrator is not stable. Therefore, a digital triggering device was developed. The digital triggering device is built on the basis of digital microcircuits and consists of the following blocks: binary-decimal counters, decoders, and one oscillator with quartz frequency stabilization, which is common to all four channels. It contains four identical channels with delay adjustment from one microsecond to one hundred milliseconds. Such a pattern of the circuit allows, if necessary, adding channels for starting other units. Pulse signals of the triggering device are fed to the ignitor unit of the spark-gaps. A pulse generator for igniting the spark-gaps of the REB accelerator “TEMP” has been developed. A generator, designed to control the spark gaps ignition in the High Voltage Pulse Generator (HVPG) and spark gaps ignition in the magnetic systems, which are used in switching systems of the capacitor banks with the energy of 60 ¸ 150 kJ, has been described. The generator provides voltage pulses with the amplitude of up to 20 kV, at the current in the short circuit mode of 5 A, the pulse duration of the first half wave of 12 μs, and the pulse repetition frequency (PRF) of not more than 10 Hz.

Inner-wall modification of a commercial polymeric microfluidic chip using pulsed He/O2 and Ar/O2 µplasmas

Pulsed He/O2 and Ar/O2 µplasmas were used to modify the postbonded microchannels of a commercial cyclic olefin copolymer microfluidic chip. The µplasmas were generated throughout a 60-mm-long microchannel with a cross section of 340 × 86 µm2 at atmospheric pressure using Pt wire electrodes under discharge conditions of spark voltages of 6–8 kV and a pulse repetition frequency of 50 Hz with a duty ratio of 0.2%. From optical emission spectroscopy results, the electronic excitation temperature was estimated to be approximately 2.1 × 104 K for both He and Ar µplasmas, and atomic oxygen radicals were increasingly produced with increasing O2 gas concentration. The plasma-treated microchannel inner wall was analyzed by X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. The wettability of the microchannel inner walls treated with both He/O2 and Ar/O2 shows the following tendencies; the wettability increased by about 4 times that of a raw microchannel at O2 gas concentrations of 5–10% and then the wettability decreased with increasing O2 gas concentration over 10%. It is found that the wetting property of the microchannels depends on both the oxygen polar groups, such as –C–O–, C=O, and COOH, introduced onto the inner walls and the surface roughness due to plasma etching.

Time lag characteristics of spark discharge in humid air with increased voltage

This study investigates experimentally the time lag (τ) characteristics of lightning impulse spark discharges in air with relative humidity (RH) over the range 20 to 80%. The experiment was conducted using a wire-plate electrode system with a 30 mm gap and with overvoltage of 30 to 50% of the DC sparking voltage. The statistical and formative time lags (τs and τf) are discussed relative to the effects of RH and overvoltage on electron attachment and detachment mechanisims.

Experimental study on electrostatic removal of high-carbon particle in high temperature coal pyrolysis gas

A high-temperature electrostatic precipitator (ESP) presents a good solution for hot gas cleaning, which can remove fly ash from pyrolysis gas at temperatures higher than the tar dew point. In this paper, the characteristics of negative DC corona discharge in air and simulated coal pyrolysis gas were studied. The removal of coal pyrolysis furnace fly ash (ash A) was investigated and compared with that of coal-fired power plant fly ash (ash B) in ESP with a temperature ranging from 300 K to 900 K. The current density of simulated gas was higher than that of air under the same discharge voltage and at different temperatures. The simulated gas also had a higher spark voltage and a lower onset voltage compared with air. The fractional collection efficiency of ash A was lower for particles with diameters of larger than 0.1 µm at high temperature, compared with ash B. A lower collection efficiency in simulated gas was obtained for particles with diameters of less than 0.1 µm compared with air. The collection efficiency of submicron particles in simulated gas was usually higher than it in air, especially for particles with diameters of less than 0.04 µm. In simulated gas, the overall collection efficiency of ash A was obviously lower than that of ash B, especially at high temperature. From 300 K to 700 K, the collection efficiencies of both ash samples were as high as above 93%, but the collection efficiency of ash A in simulated gas decreased to 78.7% at 900 K.

Study of the H2O/Al2O3 Interface and the Acting Mechanism of Water in the Working Electrolyte

Using a working electrolyte containing mixed solvents of ethylene glycol and N,N-dimethylformamide, this paper presents a study of the reactions on the H2O/Al2O3 interface with sum frequency vibrational spectroscopy and the effects of different water content on the performance of the working electrolyte and an aluminum electrolytic capacitor and summarizes the rules of the variations in the performance parameters of the working electrolyte and aluminum electrolytic capacitor with respect to the water content. The results demonstrate that, when the water content is increased from 2.5 to 15%, the conductivity of the working electrolyte increased by 930 μS/cm, and the sparking voltage decreased by 27 V. Also, the increased water content causes lower oxidation efficiency and lower thermal stability. The leakage current of the aluminum electrolytic capacitor after high-temperature storage increases with an increase in the water content, and the attenuation rate of capacitor’s the low-temperature capacitance decreases with an increase in the water content.

A Novel Discharge Status Inspection Method for EDM of Thermal-barrier-Coated Nickel-based Superalloys

The aircraft-engine hot end components were generally made of thermal-barrier-coated nickel-based superalloys(TBCs) that consist of insulating ceramic coating, electrical conductive coating and metal superalloy substrate. The discharge status of insulating ceramics is significantly different from that of metal materials, especially for the spark voltage. Existing discharge status inspection approaches have been focusing on the machining of metal materials, and cannot effectively identify the discharge status of insulating ceramics. Hence, aim to the EDM of TBCs, a novel inspection method, utilizing the prominent difference of the spark voltage and ignition delay of discharging pulse, is proposed to distinguish the discharge status for both ceramic coating and metal substrate. In this paper, the discharge status both ceramic coating and substrate material were analyzed and distinguished. A specialized inspection circuit based on field programmable gate array (FPGA) is developed to realize the inspection of 15 typical discharge statuses. Finally, a confirmation experiment is employed to demonstrate the validity and feasibility of this approach.

Examining the formation and properties of TiO2 oxide coatings with metals of iron triad

We proposed a composition of citrate-pyrophosphate electrolytes with the addition of sulfates of iron triad metals for the formation of mixed oxide systems with the varied content of dopants. The introduction of an additional ligand contributes to an increase in the stability, operation period of working solutions and to the more uniform distribution of metals-dopants. The range of voltages for the single-stage plasma-electrolytic oxidizing of titanium alloys BT1-0 and OT4-1 is 120–160 V. As a result of oxidizing, we obtained metal-oxide systems TiO x ·MO y (M=Fe, Co, Ni), which, depending on the nature of a dopant, have different types of surface structures. The largest content of dopant and the minimum size of the grain are characteristic of the cobalt-containing coatings. A potential possibility of obtaining the mixed oxide systems TiO x ·(FeCoNi)O y on the alloy OT4-1 is shown. We examined the dependences of spark voltage and the rate of change in the interelectrode voltage on the concentration of dopants in electrolyte. It was established that the formed mixed oxide coatings of titanium with the iron triad metals possess significant corrosion resistance; the highest value is inherent to the systems based on cobalt. It is shown that the incorporation of iron triad metals into the composition of oxide layers leads to an increase in the degree of surface development. This ensures an increase in the catalytic activity in the reactions of carbon mono-oxide oxidation. The obtained materials of varied thickness and morphology might be used in the technological systems of catalytic purification of natural and technogenic toxicants.

Mathematical modeling and analysis of WEDM machining parameters of nickel-based super alloy using response surface methodology

Inconel 625 is one of the most versatile nickel-based super alloy used in the aerospace, automobile, chemical processing, oil refining, marine, waste treatment, pulp and paper, and power industries. Wire electrical discharge machining (WEDM) is the process considered in the present text for machining of Inconel 625 as it can provide an effective solution for machining ultra-hard, high-strength and temperature-resistant materials and alloys, overcoming the constraints of the conventional processes. The present work is mainly focused on the analysis and optimization of the WEDM process parameters of Inconel 625. The four machining parameters, that is, pulse on time, pulse off time, spark gap voltage and wire feed have been varied to investigate their effects on three output responses, such as cutting speed, gap current, and surface roughness. Response surface methodology was used to develop the experimental models. The parametric analysis-based results revealed that pulse on time and pulse off time were significant, spark gap voltage is the least significant, and wire feed as a single factor is insignificant. Multi-objective optimization technique was employed using desirability approach to obtain the optimal parameters setting. Furthermore, surface topography in terms of machining parameters revealed that pulse on time and pulse off time significantly deteriorate the surface of the machined samples, which produce the deeper, wider overlapping craters and globules of debris.

Evaluation of the Influence of Wire Electrical Discharge Machining Parameters on Material Removal Rate and Surface Characteristics in Cutting of Inconel 825

Wire electrical discharge machining (WEDM) is a significant and broadly applicable non-conventional machining process due to its capability to produce parts with higher precision, accuracy and tolerance and complex profiles involving considerable surface characteristics. In this research, practical attempt has been made for cutting Inconel 825 material by WEDM process. Taguchi method and regression analysis have been adopted in order to optimize machining variables and developed equation to correlate the input variables and output variables. Input variables such as spark voltage, wire tension, flushing pressure and pulse on time have been taken for analysis and used orthogonal arrays to design experiments. Enumeration of output variables, material removal rate and surface roughness, has been carried out as they are of crucial importance in machining processes. The surface morphology of machined samples has also been examined by scanning electron microscopy (SEM).

平行円板電極におけるマイクロギャップ間の火花放電に伴う放電電流の測定と火花抵抗則に基づく実験検証

Measurements of discharge currents caused by the sparks between parallel disc electrodes with a micro-gap were conducted at a charge voltage of 500 V in order to estimate the corresponding spark voltages and spark currents, which were verified by using a spark resistance formula.

Parametric optimization of electrical discharge machining process on α–β brass using grey relational analysis

Abstract