Discharge Current Pulse Research Articles

High rising speed discharge current pulse for EDM generated by inductive boosting voltage circuit

This paper introduces a newly developed EDM pulse generator whose high open voltage for discharge is generated by induced electromotive force using a power supply of only 5 V. The pulse generator can generate short duration and high discharge current pulses. The rising time of discharge current pulses to 5 A can be made shorter than 50 ns with a pulse duration of 200 ns or shorter. The results proved that such discharge current pulse shapes increase material removal volume per discharge and that the higher boosting open voltage facilitates the machining of high resistivity materials.

A Generalized Reverse-Electrodialysis Model Incorporating Both Continuous and Recycle Modes for Energy Harvesting From Salinity Gradient Power

Salinity gradient power (SGP) derived from sea and fresh water through reverse electrodialysis (RED) is an emerging discipline with huge potential for carbon-free energy harvesting. SGP technology is still in an infant stage and there is a need for accurate mathematical tools to study its energy harvesting process. Previous models assume a constant salinity gradient with a continuous flow of sea water with constant salinity. In the case of recycling used sea water, such assumption is no longer valid because the salinity gradient reduces with operating time. This paper presents a generalized RED model that covers both of the continuous and recycle modes. It combines an improved kinetic battery module (KiBaM) with an electrical circuit module (ECM), for capturing the behaviors of both RED stacks operating in continuous mode (C-mode) and those in recycle mode (R-mode). To intuitively describe the compound effects of salinity variation and concentration polarization on electrical performance of the R-mode RED stack, nonlinear capacity effects (i.e., recovery effect and rate capacity effect) and self-consumed effect are introduced into the proposed model. The derivation and extraction procedures of the proposed model are included. An RED stack prototype with 50 pairs of alternating membranes is constructed for model validation. Various pulsed and constant current discharge experimental tests are performed to validate the accuracy of the proposed model.

Using a fiber optic sensor for registration of pulsed plasma discharge current

The problem of increasing the accuracy of recording the pulse shape of a rapidly changing current of a powerful plasma emitter under conditions of powerful electromagnetic interference is considered. To register high-current pulsed discharges, it is proposed to use a polarimetric fiber-optic current sensor based on a Spun-type fiber. Using the indicated current sensor, a technique for recording high-current pulsed discharges of a plasma emitter in the mode of time profiling of the current pulse of two high-voltage capacitive storage devices with a total energy of up to 1800 kJ is realized. The discharge chamber, power supply circuits, and the formation of a plasma discharge are described. The design and principle of operation of a prototype of a two-pass polarimetric fiberoptic sensor with a Spun-type fiber and a Faraday compensator of mutual optical anisotropy are presented. The general scheme of current measurements, the sensor calibration scheme is presented, and the experience of using a prototype sensor for measuring high-power pulse currents is described. The features of the preliminary calibration of the sensor are discussed. The results of measuring the current by optical and traditional recording methods based on the Rogowski coil and Hall sensors are compared with each other, and a noticeable increase in the accuracy of reproducing the current pulse shape by the optical recording method is noted. Possible options for upgrading a fiber-optic sensor to expand the range of current recording are considered.

Rise Time Properties of Partial Discharge Current Pulse Waveforms in SF<sub>6</sub> Gas with Picosecond Order and Its Formation Mechanism

Rise Time Properties of Partial Discharge Current Pulse Waveforms in SF<sub>6</sub> Gas with Picosecond Order and Its Formation Mechanism

Controlling the number of discharge current pulses in an atmospheric dielectric barrier discharge by voltage waveform tailoring

Atmospheric dielectric barrier discharges driven by tailored voltage waveforms are investigated numerically with a one-dimensional fluid model. We use the multi-frequency pulse-type voltage waveform as the control method and the harmonics N as the control parameter to control the number of discharge current pulses. The simulation results show that as N increases from 1 to 11, the number of discharge current pulses in each voltage half cycle (Np) decreases from 5 to 1, representing the transition from the multiple-current-pulse mode to the single-current-pulse (SCP) mode. In this process, both the current amplitude (Jpm) and the gap voltage of the first breakdown moment (Vgb) increase, and the efficiency of the plasma system can be improved by 5.6 times without reducing densities of reactive species. Further analysis reveals that the increase of Jpm is attributed to the variation in discharge current components, and the value of Vgb can be related to Np and the surface charge densities. Finally, an analytical method is proposed to estimate the minimum N to achieve the targeted SCP discharge. The results obtained in this work may contribute to the manipulation of power consumption and discharge stability in industrial applications.

Influence of frequency on the surface discharge characteristics of PEEK under positive repetitive square voltage

In this study, the surface discharge current pulses of polyetheretherketone (PEEK) material under positive repetitive square voltage in a nitrogen atmosphere are measured. The influences of different voltage amplitudes and frequencies on the detail parameters of forward discharge and backward discharge current pulses are statistically analysed. The results show that as the square voltage amplitude increases, the current pulse amplitude, fall time and pulse width of both forward and backward discharge current increase, and the rise time does not change significantly. As the voltage frequency increases, current pulse amplitude, fall time and pulse width of both forward and backward discharge current decrease, and the rise time does not change significantly. Due to the independence of the discharge at different repetitive cycles, the specific discharge process in one cycle is analysed in detail to explain the influence mechanism of the voltage amplitude and frequency on the discharge current. By mean of the Richardson–Schottky and the Cavallini relaxation model, the relationship between discharge voltage ratio and surface charge, and the decay process of surface discharge are analysed. Furthermore, the influences of amplitude and frequency of the positive repetitive square voltage on the PEEK surface current pulses are explained qualitatively.

Design of Transmission Line and Electromagnetic Field Sensors for DC Partial Discharge Analysis

In this paper, a testbed is designed and constructed for the investigation of DC PD pulses. The testbed is equipped with a 50 Ω transmission line (TL) that terminate to an oscilloscope for measuring the charge displacement current generated by PD pulses. Besides the oscilloscope measurements, two types of electromagnetic field sensors (D-dot and B-dot) were developed to capture the EM fields of the PD pulses propagating through the TL. The main goal of this paper is to investigate the DC PD pulses through the EM fields and the corresponding discharge current pulses that are considered as calibrating signals for the developed D-dot and B-dot sensors. The results of DC cavity discharge measured by the constructed testbed and the EM field sensors demonstrate close agreement with the reference PD pulses measured via oscilloscope.

Theoretical basis for the movement of a pulsed current discharge through a plant organism

The article presents the current state of the problem of contamination of cultivated areas with weeds. A tribute to the analysis of scientific and technical information on weed control, their advantages and disadvantages are described. Theoretically substantiated processes are the destructive effects of electric discharges of current on plant tissue.

Physics of chromatic focusing, post-acceleration and bunching of laser-driven proton beams in helical coil targets

To increase the fluence and maximum energy of laser-driven proton beams in view of potential applications such as isochoric heating of dense material or isotope production, it has been proposed to attach a helical coil normally to the rear side of the irradiated target. By driving the target discharge current pulse through the coil, this scheme allows a fraction of the proton beam to be selected in energy and to be focused and further accelerated. The previously published results are extended to higher laser pulse energies and longer coils. This leads to an increased number of guided protons and the generation of several proton bunches. Large scale particle-in-cell simulations with realistic boundary conditions reproduce well the experimental results. A detailed analysis of the numerical simulations and an analytical model demonstrate that the current propagation along a helical wire differs from the one of a linear or folded wire. In a helical wire, the current pulse is subject to velocity dispersion, which results in progressive modification of its spatial profile, and so in proton bunch trapping and focusing.

XAD-2 resin modified by nanosecond pulsed discharge to improve the adsorption capacity of polycyclic aromatic hydrocarbons

In this study, nanosecond pulsed discharge plasma is employed to treat the XAD-2 resins in the purpose of improving its adsorption capacity of polycyclic aromatic hydrocarbons. The discharge images, waveforms of pulse voltage and discharge current, and optical emission spectra are measured to investigate the plasma characteristics. The scanning electron microscopy, N2 adsorption-desorption analysis, Fourier transform infrared spectrum, and x-ray photoelectron spectroscopy are employed to characterize the physical and chemical properties of raw and modified XAD-2 resins. It is found that the adsorption capacity of modified XAD-2 resins for polycyclic aromatic hydrocarbons is obviously improved. The adsorption capacity of XAD-2 resins modified by plasma increased by 70% in 10 min adsorption time under the optimal conditions of 20 min treatment time and artificial air. The reason for the improved adsorption capacity is attributed to the increase of specific surface area, the number of 28–33 nm micro-mesopores, and relative intensity of oxygen-containing functional groups (C=O, C–O, and COOH). The possible mechanism of plasma modification of XAD-2 resin is also proposed.

Enhanced discharge and surface properties of TiSiCN coatings deposited by pulse-enhanced vacuum arc evaporation

Pulse-enhanced vacuum arc evaporation (PEVAE), an advanced version of conventional DC vacuum arc evaporation, generates a high flux of electrons to ionize more gaseous and metallic atoms in the deposition system to facilitate coating deposition. Compared to the conventional DC mode, the highly ionized plasma improves the structure and properties of the coatings deposited by the PEVAE mode. To obtain a better understanding and evaluate the advantages and limitations of this technique, we conduct a comparative study on TiSiCN coatings deposited by the traditional DC mode and PEVAE mode for different target-to-substrate distances (Dt-s) in the reactive environment of HMDSN. The substrate current is determined by an oscilloscope and optical emission is monitored by a miniature fiber-optics spectrometer. The microstructure and properties of the coatings are characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, indentation test, nanoindentation, electrochemical measurement, and ball-on-disk wear test. The results demonstrate that the average substrate current increases by 53.8% as Dt-s increases from 200 mm to 300 mm. The pulsed current discharge in the HMDSN atmosphere increases the deposition rates by up to 36.4% and Ebi increases by 29% reflecting a denser microstructure. The PEVAE mode improves the microstructure of the TiSiCN coatings as well as resistance to corrosion and wear. Furthermore, it has good processing adaptability for different target-to-substrate distances.

Time-Frequency Analysis of Partial Discharge Current Pulses in Different Gas Environment under Lightning Impulse

Abstract This paper deals with a time-frequency analysis of the measured partial discharge (PD) currents in different insulation gases. These gas environments consist of a pure SF6 (sulphur-hexafluoride) and sulphur-hexafluoride and nitrogen (1 % SF6 + 99 % N2) mixture, under both positive and negative lightning impulse (LI) voltage stresses. In this study, the short time Fourier transform was used to extract the time-frequency information of PDs for different gases at different pressures, and these results were compared to each other. Thus, the relationship between the time, amplitude, and frequency of PD currents was studied. Moreover, some statistical formulas, such as mean, standard deviation, kurtosis, and skewness were applied to the time-dependent PD current data. As a result, a correlation between obtained statistical results and PD frequencies was examined. In most cases, the frequency of partial discharge decreased when the pressure increased. The amplitude of the partial discharges for negative polarity was more than that for positive polarity gas insulations. The partial discharge amplitudes of the pressure of 2 bar were mostly high compared to other pressures. This case demonstrated that SF6 had a maximum minimum character in terms of breakdown. The partial discharge frequency of a 1 % SF6 mixture was higher than that of pure SF6. It is thought that SF6 suppresses the discharge frequency, and statistical evaluations support the experimental results.

Application of Glow Discharge Mass Spectrometry for the Monitoring of Dopant Distribution in Optical Crystals Grown by TSSG Method

Direct analysis of matrix and admixture elements in non-conducting crystals is a relevant analytical task in terms of quality assurance of optical materials. The current study aimed to develop a method capable to assess the inhomogeneity of optical crystals with sufficient sensitivity. K1−xRbxTiOPO4 (x = 0.002 and 0.05) and KGd1−yNdy(WO4)2 (y = 0.05) were grown using the top-seeded solution growth method (TSSG). The samples were analyzed by microsecond direct current pulsed glow discharge time-of-flight mass spectrometry (µs-PDC TOF GDMS). The data were compared with the results obtained by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM EDX) and spectrophotometry and validated by the analysis of certified reference material. Sample glow discharge sputtering and analysis were optimized and implemented in real samples. Sample coating with a silver layer and sample pressing in the metallic matrix were proposed to ensure effective sputtering for K1−xRbxTiOPO4 and KGd1−yNdy(WO4)2, respectively. Using the designed method, the inhomogeneity of the dopant’s distribution was demonstrated along the growth axis and in the case of K1−xRbxTiOPO4, also in the growth sectors of different faces. The designed method is applicable for the direct analysis of optical crystal and may be implemented in quality assurance in the manufacturing of optical materials.

Gas desorption induced discharge in vacuum and its polarity effect

The objective of this paper is to propose mechanisms of gas desorption induced discharge and their polarity effect. Three electrode pair types were combined in the in-situ experimental apparatus with high vacuum; air-exposed cathode and anode, airexposed cathode and conditioned anode, conditioned cathode and air-exposed anode. Electrode pairs were subjected to repetitive impulse voltage breakdowns till conditioning saturation. The results showed two gas desorption induced discharge mechanisms; namely, pulsed current discharge (PCD) and pulsed current induced breakdown (PB). Many gas desorption induced discharge (PCD and PB) occurred in air-exposed cathode and anode pair and air-exposed cathode and conditioned anode pairs. While only a few discharges occurred in the conditioned cathode and air-exposed anode pair. The gas desorption induced discharge in vacuum showed a polarity effect; Only when the cathode electrode of the pair was the original air-exposed electrode, no matter the anode electrode was or not, gas desorption induced discharge (PCD and PB) could occur in the beginning stage of the conditioning. The physical evolution of gas desorption induced discharge is explained.

Parameters and properties of a pulsed planar vacuum magnetron discharge

We have developed a vacuum (gasless) magnetron discharge initiated by a vacuum arc plasma. The discharge operating conditions for different magnetron target materials have been determined. The mass-to-charge plasma composition and its evolution during a discharge current pulse were measured. It is shown that, after transient processes of cathode outgassing and purification, the plasma ion component consists mainly of singly-charged ions of the magnetron target material. The measured total ion current from the vacuum magnetron discharge plasma is up to 7.5% of the discharge current.

The polarity effect of nanosecond voltage pulses on the propagation of streamers in a point-to-plane gap filled with air

The results of experimental studies of the effect of polarity on the streamer velocity at various voltage amplitudes are presented. In the experiments, nanosecond voltage pulses were applied across an 8.5 mm point-to-plane gap filled with air at a pressure of 100 kPa. The formation of positive and negative streamers has been experimentally studied using a HSFC-PRO four-channel ICCD camera and a Hamamatsu C10910-05 streak camera. Waveforms of voltage and discharge current pulses were also recorded. The propagation velocity of streamers was estimated by streak images. It was found that a negative streamer crosses the gap faster than a positive one. This is most likely due to the presence of runaway electrons with the negative polarity of a pointed electrode. The experiment showed that runaway electrons are generated before the formation of a negative streamer. Runaway electrons can preionize the gas in the gap.

Analysis of the Machinability of Copper Alloy Ampcoloy by WEDM

The unconventional technology of wire electrical discharge machining is widely used in all areas of industry. For this reason, there is always an effort for efficient machining at the lowest possible cost. For this purpose, the following comprehensive study has been carried out to optimize the machining of the copper alloy Ampcoloy 35, which is particularly useful in plastic injection moulds. Within the study, a half-factor experiment of 25-1 with 10 axial points and seven central points of a total of 33 rounds was carried out, which was focused on the response monitoring of the input factors in the form of the machine parameters setup: gap voltage, pulse on time, pulse off time, discharge current, and wire speed. Based on the study of the response in the form of cutting speed and surface topography, their statistical models were created, while the optimal setting of machine parameters was determined to maximize the cutting speed and minimize the topography parameters. Further, a detailed cross-sectional analysis of surface and subsurface layer morphology was performed using electron microscopy including chemical composition analysis. In order to study microstructural changes in the material at the atomic level, a lamella was created, which was then studied using a transmission electron microscope.

Effect of Accelerated Electrons on the Glow Structure of Nanosecond Diffuse Discharge in the Rod–Plane Air Gap

A diffuse discharge in a rod (cathode)–plane gap with an interelectrode spacing of 10 cm is studied in air at atmospheric pressure. The cathode voltage is 370–390 kV at a pulse FWHM of about 70 ns. It is shown that a pulse-to-pulse variation in delay time of the discharge formation in an interval of 3–15 ns leads to variations in the discharge current and X-ray pulse amplitude in intervals of 100–200 A and 20–250 relative units, respectively. A relationship of the amplitude of the X-ray pulse and structural parameters of the discharge glow is obtained. It is shown that fast electrons with energies of less 30 keV that are accelerated by strong electric field in the vicinity of the cathode play the key role in the formation of the longitudinal structure of glow at relatively large delay times of the discharge formation. Fast electrons ionize peripheral regions of the discharge, increase its cross section, and, hence, provide a decrease in the current density, specific energy deposition, and radiation intensity at a distance from the cathode that corresponds to electron path in air.

Propagation Characteristics of Partial Discharge Current Pulse for Branched Line

Propagation Characteristics of Partial Discharge Current Pulse for Branched Line

Verification of Fuzzy Inference System for Cutting Speed while WEDM for the Abrasion-Resistant Steel Creusabro by Conventional Statistical Methods

Wire electrical discharge machining is an unconventional machining method for the production of complex-shaped and very precise parts. Because of the high energy consumption of this machining process, it is necessary to maximize the cutting speed for its appropriate implementation. The abrasion-resistant steel Creusabro 4800 was chosen as the test material for this experiment, which is widely used especially for machines working in mines and quarries. In order to maximize the cutting speed, a fuzzy inference system (FIS) has been built, which uses 18 expert propositions to “model” the cutting speed based on five selected input parameters: gap voltage, pulse on time, pulse off time, discharge current, and wire feed. The obtained results were further verified by a design of experiment consisting of 33 tests for five selected input factors. Using the fuzzy inference system, the optimum machine parameters setup was found to maximize the cutting speed, in which the gap voltage = 60 V, pulse on time = 10 µs, pulse off time = 30 µs, wire feed = 10 m∙min−1 and discharge current = 35 A. The predicted value of the cutting speed using the fuzzy inference system is 6.471 mm∙min−1.