Showing papers on "Electric discharge published in 1997"

Modeling of DC corona discharge along an electrically conductive flat plate with gas flow

Abstract: The development of a corona discharge was evaluated numerically over a region of a semi-infinite flat plate having small (Ohmic) surface conductivity with a flowing gas. The model simulates a positive corona discharge (ionic wind) generated by two parallel wires mounted flush with the surface of the plate and directed with the free-stream gas flow. The deposition and removal of ions at the surface are permitted. Five coupled partial differential equations govern the gas phase model together with empirical equations for electrical discharge (/spl Phi/-I characteristics). Two voltage bias case studies were considered: first, the two electrodes have the same potential but are of opposite sign, and second, the positive electrode carries the full potential with the remaining electrode grounded. Several interesting effects relating to the voltage and current distributions, surface potential, and free-stream velocity are observed. Boundary layer development and surface shear are also discussed.

Electropulse method of holes boring and boring machine

Abstract: This invention provides an excavator 1 for crushing a matter to be excavated, existing in an excavating hole in which a discharge liquid is fed, by electric discharge between a plurality of electrodes generated by high-voltage pulses. The excavator comprises a high-voltage pulse generator 2; a plurality of electrodes 17, 18, at least one of which is given a high voltage from the high-voltage pulse generator 2; discharge liquid circulating system 3, 4, 5a, 5b; and optimum condition setting devices 13, 14, 15, 16. Also, this invention provides an excavation method in which at least one of the parameters for excavation efficiency of i) load voltage required for crushing the matter to be excavated; ii) single pulse energy; and iii) quantity of discharge liquid, is optimized for minimization of power consumption required for excavation by using the excavator of this invention.

Investigations of double capillary discharge scheme for production of wave guide in plasma

Abstract: Double capillary scheme is proposed for high performance electrical discharge in a capillary. This scheme allows more than 103 shots without significant destruction. It is shown that a thin main capillary can be filled with the plasma formed in a trigger capillary discharge so that the discharge in the main capillary can be excited and a hollow distribution of electron density can be obtained with concentration of up to a few 1019 cm−3. Main properties of this scheme are reported.

Electronic ballast for discharge lamps

Abstract: An electronic ballast for discharge lamps comprises a main resonance circuit for applying a voltage necessary for operating of a discharge lamp having filaments to both ends of the discharge lamp and a filament resonance circuit for supplying a filament current to the filaments, wherein the main resonance circuit and filament resonance circuit have resonance circuits having different resonance characteristics in an output path leading to the discharge lamp and also change their outputs depending on an operating frequency of switching elements. Thereby a filament current and a voltage across the discharge lamp can be set at suitable one of respective operational modes of the discharge lamp according to an operational state of the discharge lamp.

Decomposition of dilute trichloroethylene by nonthermal plasma

Abstract: Decomposition performance of a dilute toxic organic compound, trichloroethylene (TCE), in air by using nonthermal plasma processing was studied extensively. The nonthermal plasma was generated by the high-frequency (2 kHz) or commercial-frequency (50 Hz) barrier discharge in a fused silica tube. Three types of reactors, bolt type, rod type (both are barrier-discharge type), and coil type (surface-discharge type), were tested. Analysis of byproducts, residual materials, and end products generated by the plasma process was performed by a gas chromatography mass spectrometer or gas chromatography. Most organic byproducts decrease with an increase of the electric discharge power, but only toxic phosgene increases with the increase of the discharge power. As a post process, NaOH solution was used to test effluent from the plasma reactor. The solution was found effective in phosgene absorption. Comparison between nonthermal plasma and UV irradiation for TCE decomposition was also made. In regard to the energy efficiency of TCE decomposition, UV irradiation is found much better than discharge plasma.

Plasma display, driving apparatus of plasma display panel and driving system thereof

Abstract: A plasma display panel driving system having common X electrodes arranged on a front glass substrate driven in common, independent Y electrodes arranged parallel to the common X electrodes on the front glass substrate driven independently, address A electrodes arranged perpendicular to the common X electrodes and the independent Y electrodes on the back glass substrate driven independently, and means for performing at least one electric discharge for equalizing electrically charged particles in a cell in which another electrically charged particle is produced beforehand, thereby improving contrast. Erasing and polarization of electrically charged particles are performed by a fine line erasing pulse after a sustaining period, and an equalizing pulse having a high voltage level is supplied to the independent Y electrode to which the last fine line erasing pulse is supplied, and a regulating pulse is supplied to the common X electrode after supplying the equalizing pulse. Further, a field block having plurality of sub-fields are provided, and a full writing electric discharge and a fine line erasing electric discharge are performed in the first sub-field of each field block for reducing the number of electric discharges.

Excimer emission spectra of rare gas mixtures using either a supersonic expansion or a heavy-ion-beam excitation

Abstract: Results related to the energy transfer in the rare gas mixtures are reported for an electrical discharge excitation with plasma expansion and a heavy-ion-beam excitation. Energy transfer from the lighter rare gases to the heavier ones was observed in a very efficient way for both excitation mechanisms. Strong emission from excited atomic states, which are possible candidates for new lasers, was observed for the electrical discharge case. The broad-band emission of the discharge sources makes them appropriate for strong lamps in the VUV. Some comparisons of the two excitation mechanisms were discussed with respect to the energy deposition, the density of dimers and their vibrational relaxation.

Electrical alternative to pulsed fiber-delivered lasers in microsurgery

Abstract: An electrical system based on a tapered microelectrode has been developed for generation of high voltage sub-microsecond discharge in physiological medium. Different types of the resulting pulses of current are investigated as well as the dynamics of the associated cavitation bubbles. A highly localized zone of power dissipation—about 20 μm in size—results in a low threshold energy of cavitation bubble generation—about 3 μJ—in comparison to laser-based intraocular microsurgical instrumentation with fiber delivery systems. Cavitation bubble dynamics resulting from the electric discharge is similar to that observed with ns-pulsed fiber-delivered lasers in strongly absorbing liquid medium. Efficiency of the pulse energy conversion to the bubble energy is about 12%, which is lower than the best results obtained with lasers. In spite of that, due to the low threshold energy, cavitation bubbles required for effective cutting of soft tissue can be generated at energies lower than that used in laser instrumentati...

Dielectric barrier discharge device

Abstract: A dielectric barrier discharge device in which uniformity of the light irradiation energy density is achieved, even if dielectric barrier discharge lamps have variations with respect to the lamp material and the processing. The dielectric barrier discharge device has at least one dielectric barrier discharge lamps and a feeder device for applying an AC high voltage to the electrodes of the dielectric barrier discharge lamp, the dielectric barrier discharge lamp having a discharge gas-filled discharge gap which produces excimer molecules by a dielectric barrier discharge and one dielectric between at least one of the electrodes and the discharge gap for inducing the discharge phenomenon in the discharge gas. Uniformity of the light irradiation energy density is achieved is achieved in this dielectric barrier discharge device by the feeder device applying the AC high voltage such that an operating state for time interval (Ta) in which in the dielectric barrier discharge lamp produce a discharge emission is repeatedly alternated with an operating state for a time interval (Tb) in which essentially no discharge is produced, or in which a lower voltage is applied within a range that is only sufficient to maintain discharge in the dielectric barrier discharge lamps.

Influence of insulating barrier on the creepage discharge in transformer oil

Abstract: The propagation aspects of a creepage discharge in transformer oil are observed simultaneously and in detail under a positive impulse voltage condition, by means of a high-speed Schlieren optical system, an LED current measurement system and a charge measurement system using a capacitor. In the present paper, the influence of the material type and the thickness of insulating barriers on the propagation of the impulse creepage discharge are discussed for a point to plane electrode geometry. In addition, the influence of a barrier surface to the electric field direction on the propagation of the impulse creepage discharge is discussed for a parallel plane electrode gap with a protruding point.

A high pressure series arc discharge lamp construction with simplified starting aid

Abstract: A high pressure gas discharge lamp includes first and second discharge devices electrically connected in series within an outer envelope. The discharge devices each include a discharge vessel enclosing a discharge space with an ionizable fill and first and second discharge electrode assemblies. The first discharge electrode assemblies of the discharge devices are connected so as to receive a starting pulse and lamp operating voltage. Each discharge vessel includes a first wall portion spaced from the first discharge electrode assembly and defining an ionizable gap therebetween. A conductive element bridges the discharge devices at the first wall portions and capacitively couples the first discharge electrode assemblies to induce ionization in one of the discharge devices in the ionizable gap between the first wall portion and first discharge electrode assembly.

Methodology to study the resistance of spark discharges

Abstract: Spark discharges are normally associated with real-event electrostatic discharges (ESDs). The electrical characteristics of the spark channel can influence the nature of the discharge current which can cause both direct and indirect damage in semiconductor devices and electronic systems. In this paper, a method is described to determine the resistance of spark discharges. Discharge currents are measured for underdamped and forced overdamped cases; an analysis of the resulting waveforms is used to calculate the effective resistance of the discharge. The technique is applied to measure the resistance of a spark discharge between two spherical electrodes.

Surface treating method by electric discharge

Abstract: A surface treating method uses an electric discharge machining to form a coating layer having strong adhesion and excellent characteristics on a metal surface such as a hard metal. A discharge electrode is formed by powders containing metal hydride. Electric discharge is generated in a working fluid containing carbon between the discharge electrode and a workpiece. Thus, a coating layer of the metal hydride is formed on a surface of the workpiece.

Coupled Electron and Molecular Vibrational Kinetics in a 1D Particle-in- Cell Model of a Low Pressure, High Frequency Electric Discharge in Nitrogen

Abstract: The interaction between state-to-state vibrational and charged particle kinetics in a low-pressure, high frequency electric discharge in N 2 is investigated by using a PIC-MCC (Particle-in-Cell with Monte-Carlo collisions) model assuming a one-dimensional bounded system, while the vibrational kinetics is introduced by solving a set of reaction and diffusion equations. The catalytic activity of the electrode surfaces is considered in the boundary conditions. The coupling of the two kinetics has an effect on the Electron Energy Distribution Function (EEDF) and consequently on the rate of vibrational and electronic excitation of N 2 molecules, the charged particle distribution and the electric field.

Formation of Composite Layer Containing TiC Precipitates by Electrical Discharge Alloying

Abstract: In order to improve friction and wear characteristics, surface modification of aluminum matrix composites was carried out by applying a new method named Electrical Discharge Alloying, in which a conventional electrical discharge machine can be utilized. Titanium contained in a green compact electrode, and also carbon and silicon decomposed from a working fluid are transferred to the substrate surface through a single discharged arc. An increase in the gap voltage widens the gap distance. Since the pressure due to the evaporation of working fluid in the vicinity of a discharged arc decreases with a gap distance widened, it is hard to blow off the top layer of discharged craters with enriched titanium and carbon if the gap voltage is high. Consequently, the volume fraction of TiC in the modified surface increases with increasing gap voltage, and then the hardness of modified surfaces becomes high. The process, electrical discharge alloying, makes it possible not only to coat a composite layer containing TiC precipitates with a thickness of nearly 80 μm within a few minutes, but also to get different volume fractions of TiC by changing the gap voltage, which is one of the process parameters. Hardness of the modified surface can be controlled to have any value of 7-14 GPa by varying the volume fraction of TiC. It is also recognized that the process improves wear resistance of the modified surfaces.

Ozone production and de-NO x modeling in dry air electrical discharges

Abstract: Numerical simulations are performed to assess the possibility of using different kinds of electrical discharges operating in dry air under normal conditions as ozone generators. The ozone production and NOx destruction efficiency are investigated as a function of discharge parameters such as the reduced electric field, the energy deposition, and the electron density. The specific energy deposition becomes a key parameter to compare the different classes of ozonators. During the operative phase the electric discharge produces an appreciable amount of nitrogen oxides. Taking into consideration both the active phase of flue gas processing and the post-discharge phase it is possible to achieve a good NOx-removal efficiency even for initial concentrations as high as 1000 ppm. The main processes and characteristic times are discussed.

Electrical breakdown of small gaps in vacuum

Abstract: The comparison of the characteristics of an electric arc breakdown in vacuum between two silver or silver-nickel alloy convex electrodes, enabled us to show experimentally that the process initiating discharge in vacuum is the electronic emission at the micrometer scale. Increased content of nickel in the alloy improves the insulation and achieves high resistance to erosion for low power arcs. Heating in vacuum demonstrates the multiple layer structure of studied alloys. Secondary electron microscopy and energy dispersing spectroscopy of the electrode surfaces after breakdown, as well as the measurements of fall and delay times, enabled us to evidence the origin of the electric arc.

Discharge characteristics under non-uniform electric field in He, Ar and air at low pressures

Abstract: We measured dc discharge inception voltage V/sub i/ for various electrode configurations in He, Ar and air in vacuum range from 10/sup 5/ to 10/sup -1/ Pa to determine discharge characteristics under a space vacuum environment. By quantitative consideration of the E/sub i//p distribution in the gap space at the discharge inception, the discharge inception mechanism under non-uniform electric field was investigated in vacuum. At the same time, we observed the discharge profile variation with residual gas pressure and quantitatively analyzed its characteristics, using an image processing technique. Based on the analysis, we found that the dependency of the discharge inception voltage and the length of the discharge path on the residual gas pressure under non-uniform field conditions agreed well with that previously obtained for uniform field conditions.

Creeping discharge performance of oil-paper insulation with streaming electrification

Abstract: In this paper, the influence of streaming electrification on the creeping discharge of an oil-paper insulation system has been investigated, using experimental models. Experimental results indicate that the initial creeping discharge voltage of the oil-paper insulation system decreases with oil flow rate. The creeping discharge path develops toward the oil entrance, and there are polarity and position effects on the creeping discharge under oil flowing conditions. Reasons for failure due to dendritic discharge on the surface of barrier boards in power transformers have been revealed in these experiments.

Non-electrode discharge lamp apparatus and liquid treatment apparatus using such lamp apparatus

Abstract: A non-electrode discharge lamp apparatus comprises a discharge tube, exciting coils wound on an outer periphery of the discharge tube, a vessel, having liquid-tightness, containing the discharge tube and the exciting coil means, and lead line guiding means for guiding lead lines connected to the exciting coils to the outside of the vessel, thereby supplying high frequency electric power to the exciting coils through the lead lines. Liquid is prevented from directly contacting the discharge tube and the exciting coils, temperature of the discharge tube can be suitably maintained, and an irradiation efficiency of ultraviolet rays can be prevented from being reduced.

Glow discharge plasma processing method and device thereof

Abstract: PROBLEM TO BE SOLVED: To continuously generate uniform glow discharge plasma under pressure in the vicinity of atmospheric pressure regardless of a gas atmosphere in processing, and perform stable glow discharge plasma processing by setting voltage rising time not more than a specific valve, and setting electric field strength to a specific range in a device where an impressing electric field is converted into a pulse. SOLUTION: In glow discharge plasma processing, a pulse electric field on which electric field strength is 1 to 100kV/cm and rising time is not more than 100μs, is applied. In this device, a solid dielectric 16 is arranged on a lower electrode 15, and discharge plasma is generated in a space between the solid dielectric 16 and an upper electrode 14. Processing gas is supplied to a discharge plasma generating space 13 from a gas introducing pipe 18, and an upper surface of a base material 17 contacting with generating discharge plasma is processed. When both surfaces of the base material 17 are wished to be processed, the base material 17 is floatingly arranged in the discharge plasma generating space 13.

Influence of ultraviolet illumination on microdischarge behavior in dry and humid N2, O2, air, and Ar/O2: The Joshi effect

Abstract: The influence of UV illumination on the behavior of silent electrical discharge streamers (microdischarges) in dry and humid gases (nitrogen, oxygen, air, and Ar/O2 mixtures) is presented. A commercial low-pressure mercury lamp, which was spectrally calibrated, provides UV light. The UV irradiance power coupled into the discharge cell is also calculated. The transferred charge per mean microdischarge (in a voltage half-cycle) was measured for a pin electrode assembly, configured to deliver either M−G+ transitions (electrons going from metal towards dielectric) or M+G− transitions (electrons going from dielectric to metal). The total transferred charge is recorded by monitoring a charge versus voltage plot (Lissajous figure). When illumination is restricted to the gas alone, both the total transferred charge and the individual-microdischarge transferred charge remain constant for either transition (M−G+ or M+G−). However, when the dielectric is illuminated, a marked decrease in the individual-microdischarg...

Method and device for controlling discharging current slope of wire cut electrical discharge machine

Abstract: It is a main object of the present invention to improve the drawback of a conventional wire cut EDM which controls the pulse width of discharging current to supply discharge energy under the state of constant current slope. The discharging current slope control method and device of the wire cut electrical discharge machine of the present invention comprises an electrical discharge detecting circuit, a timing controller circuit, a normal discharge driver circuit, an arc discharge driver circuit, normal discharge switch elements and arc discharge switch elements. The slopes of the output triangle waveform currents shall be variable due to the different results of detecting by the electrical discharge detecting circuit, depending on normal discharge or arc discharge condition, to render the current slope of the arc discharge smaller than the current slope of the normal discharge, so as to achieve the effect of keeping a high machining speed without easily breaking of the wire electrode.