DC High-voltage Supply Research Articles

Comparison of Filter with Fuzzy Controlled Three Level DC-DC Converter Fed Drive

A simple Fuzzy logic controller (FLC) applied to buck converter is presented in this paper. This approach uses FLC which performs better when compared with the conventional PI controllers. In proposed buck converters, high voltage dc supply is switched at very high frequency and inductively transferred to dc load via a high frequency transformer and rectifier. In this converter four power switches are connected in series to primary of high frequency transformer for large load currents. To achieve large step-down voltage ratios the power switches are turned ON and OFF alternatively with a time gap. The voltage step-down ratios, Total Harmonic Distortion and angular velocity of drive are the parameters to be analyzed. The comparison with the original FLC and comparison of three level DC-DC converter with capacitor and pi filter is carried out by MATLAB-Simulink simulation and Model is designed to verify the proposed method performance.

Improvement and Red Shift Toward Visible Spectrum of TiO<sub>2 </sub>Nanofibers through Doping by Fe<sub>2</sub>O<sub>3</sub> and Nitrogen

TiO2has many applications as photocatalyst, photo/electrochromic device, solar cell and sensors. It has been activated only by UV light. In this research we have been investigated on the effect of adding Fe2O3nanoparticles and N on the absorption spectrum in order to increase their activity and shift toward visible light for TiO2nanofibers. We used electrospining method to fabricate nanofibers. Sol gel for spinning pure nanofibers contains Titanium tetraisopropoxide (C12H28O4Ti), acetic acid (CH3COOH), ethanol (C2H5OH) and PVP (C6H9NO-12 wt.% ). Then we used Fe2O3nanoparticle (size: 2040 nm, purity: 98%) and HNO3acid for doping. Among Fe2O3-doped samples, the 2.1 wt% Fe2O3indicated the highest activity for visible light, while with HNO3, excellent photo-catalyst activity obtained at 1.5wt% Fe2O3and 5 wt% HNO3(purity :65%). The final solutions were stacked into the syringe and joined to a high voltage DC supply. A piece of glass stacked on aluminum foilwas used as collector. Finally nanofibers calcined at 500°C. FESEM, XRD and Spectrophotometry techniques were employed to deliberation nanofibers. Diameter of the fibers was approximately 100 nm (anatase: 77%). The Fe2O3-TiO2and Fe2O3-N-TiO2nanofibers indicated respectively 50% and 80% growth in absorption intensities under visible light irradiation compared to pure nanofiber and absorption spectrum peak moved towards larger wavelengths (70 and 100nm) when TiO2doped with Fe2O3and Fe2O3-N. Keywords:Fe2O3nanoparticle; nitrogen; red shift; TiO2nanofiber; UV-visible irradiation.

Design and Implementation of Photo Voltaic System with Soft Switched Boost Converter using Analog Fuzzy based MPPT

Environment friendly solutions are becoming more prominent than ever as a result of concern regarding the state of our deteriorating planet. A new system configuration of the front end rectifier stage for a photovoltaic system is used. Further increasing the solar output voltage is achieved by connecting the soft switched boost converter. The soft switched boost converter converts low voltage dc supply to high voltage dc supply .The inherent nature of the soft switched boost converter to reduce the voltage stress and ripple. The input rectifier stage allows the maximum power point tracking to be used to extract maximum power from the sun when it is available. An analog fuzzy based maximum power point tracking (MPPT) will be used for the photovoltaic (PV) system.

Safe and consistent method of spot-welding platinum thermocouple wires and foils for high temperature measurements

A low-voltage (mV) electronically triggered spot welding system for fabricating fine thermocouples and thin sheets used in high-temperature characterization of materials' properties is suggested. The system is based on the capacitance discharge method with a timed trigger for obtaining reliable and consistent welds. In contrast to existing techniques based on employing high voltage DC supplies for charging the capacitor or supplies with positive and negative rails, this method uses a simple, standard dual power supply available at most of the physical laboratories or can be acquired at a low cost. In addition, an efficient and simple method of fabricating non-sticking electrodes that do not contaminate the weld area is suggested and implemented.

Factors that influence the efficiency of a fluidized-bed-type tribo-electrostatic separator for mixed granular plastics

Fluidized bed devices have already been used as tribochargers for various industrial electrostatic separation processes. In the present paper, the authors investigate the behaviour of polyamide – polycarbonate granular plastic mixtures in a parallelepiped bed, the height of which is roughly 2 times its length or width, so that the collisions between granules become the prevailing tribocharging mechanism. Two of the opposite walls of the tribocharging chamber consist of metallic plates connected to two DC high-voltage supplies of opposite polarities, so that the charged particles are attracted to the electrodes and separated while still in the fluidized state. The collecting hoppers are designed as Faraday cups connected to two electrometers, thus allowing the instantaneous measurement of the charge carried by the separated particles. Experimental design methodology was employed for the optimization of the tribo-aero-electrostatic separation process, the input variables being the high-voltage applied to the electrodes and the duration of the tribocharging. Higher voltages applied to the electrode system do not necessarily lead to larger quantities of collected products but improve the purity of the concentrates. The composition of the mixture influences the outcome of the process.

Factors That Influence the Decay Rate of the Potential at the Surface of Nonwoven Fabrics After Negative Corona Discharge Deposition

Surface potential decay (SPD) measurements are considered as the most appropriate technique for the investigation of the corona charging of dielectric surfaces. The aim of the experiments reported in the present paper was to point out the peculiarities of SPD in the case of nonhomogeneous dielectrics, such as the nonwoven fabrics employed for heat, ventilation, and air conditioning. This paper reports experimental data collected on two types of polypropylene (PP) media, characterized by different fiber diameters. The experiments were performed on 60 mm × 50 mm samples of nonweaved sheets of PP (sheet thickness: 400 μm; average fiber diameter: 20 μm), in ambient air (temperature: 18°C to 22°C; relative humidity: 25% to 60%). The samples were charged for 10 s by exposing them to the negative corona discharge, using a triode-type electrode arrangement, energized from a dc high-voltage supply. Their surface potential was then measured with an electrostatic voltmeter. The measured data indicate that the charge of the filter is limited by the local discharges that occur inside the fibrous dielectric.

Experimental Study of Corona Discharge Generated in a Modified Wire–Plate Electrode Configuration for Electrostatic Process Applications

Parallel wire-plate electrode arrangements are widely used to generate corona discharges in various electrostatic processes. This paper analyzes the characteristic features of a slight modification of such an electrode configuration. In all the experiments, a stainless steel wire of diameter 0.18 or 0.57 mm was used as the corona electrode, energized from a reversible dc high-voltage supply. The modified two-level grounded electrode consisted of three metallic plate segments, which are parallel to the wire and located at 20, 15 (or 10), and 20 mm from it, respectively. In a first set of experiments, the current-voltage characteristics of this electrode arrangement were obtained for both polarities of the high-voltage supply and compared to those of a standard wire-plate electrode system. In a second set of experiments, two of the plate segments were made of several aluminum strips insulated from each other and successively connected to a microammeter, in order to characterize the distribution of the corona current at the surface of the modified grounded electrode. The third set of experiments described in this paper was performed with the corona electrode energized from a rotary spark gap connected at the output of the dc high-voltage supply. Finally, the possibility of applying this modified electrode configuration for the precipitation of dust contained in flue gases is briefly discussed.

Factors that influence the corona charging of fibrous dielectric materials

Corona discharge has a wide range of industry applications, such as charging the photosensitive layer and the toner particles in photocopying machines, modifying the wet-ability of plastic films, and conditioning the electrets for air filters. In all these situations, it is important to evaluate the surface charge density and compare it to the dielectric rigidity of atmospheric air. Experiments were carried out on 0.3 mm and 0.8 mm thick non-woven polypropylene fibrous media (average diameter of the fibres: 20 μm) that were exposed to positive corona discharges from a wire–grid–plate electrode system. The electrode system was powered from a continuously-adjustable DC high-voltage supply, employed as constant current generator. The monitored variable was the surface potential detected by the probe of an electrostatic voltmeter. The controlled variables were the potential of the grid electrode and the pre-conditioning temperature of the samples. The results of the experiments enabled a crude evaluation of each factor effect. Research should continue, using the experimental design methodology, in order to establish the optimum operating conditions.

Numerical simulation of conductive particle behaviour at the surface of a plate electrode affected by a DC corona field

The electric field in certain electrostatic devices can be modeled by a grounded plate electrode affected by a corona discharge generated by a series of parallel wires connected to a DC high-voltage supply. The system of differential equations that describe the behaviour (i.e., charging and motion) of the conductive particle in such an electric field has been numerically solved, using several simplifying assumptions. Thus, it was possible to investigate the effect of various electrical and mechanical factors on the trajectories of conductive particles. This model has been employed to study the behaviour of coal particles in fly-ash corona separators.

Charge-Decay Characteristics of Granular Materials Forming Monolayers at the Surface of Grounded Electrodes

Laboratory studies and in-field observations have shown that the charge-decay characteristics of the granular materials at the surface of the grounded roll electrode significantly influence the outcome of the electrostatic separation process. This paper validates an indirect method of charge-decay characterization, based on the measurement of the electrical potential at the surface of a monolayer of granular insulating material. The study was performed on three materials - polyvinyl chloride, polyethylene, and rubber - extracted from chopped electric wire wastes. The granules (characteristic size in the range 1-4 mm) were disposed on the surface of a grounded plate electrode (layer area: 100 mm times 100 mm; electrode area: 200 mm times 200 mm). A wire-type corona electrode, energized from a dc high-voltage supply, was employed for charging the granules. The potential due to the charge at the surface of the granular layer was measured with the capacitive probe of an electrostatic voltmeter connected to a personal computer. Data acquisition and processing were done using the LabView environment. The influence of particles characteristics and of ambient factors was studied. The findings enabled a more accurate modeling of discharging phenomena that affect the performances of electrostatic separators. The method can be easily adopted in electrostatic discharge studies for material characterization.

Modelling of corona discharge in cylinder-wire-plate electrode configuration

Numerical computation of the electric field strength and ionic space charge density in electrode systems consisting of ionizing wire and non-ionizing cylinder, connected to the same DC high-voltage supply and facing a grounded plate, is a difficult problem, which is of interest to several electrostatic processes applications. In a previous study a simple numerical method has been proposed to calculate the spatial distributions of electric field and ionic space charge in a case of a continuum and uniform corona discharge originating at the surface of the wire. The aim of the present paper is to improve the physical model of the corona discharge in this particular electrode configuration, by assuming a more realistic law of charge injection on the wire circumference. The computations were carried out for an ionizing wire of radius r=0.1 mm, located at different distances h from a metallic tubular support of radius R=13.4 mm.The initial conditions of the corona discharge took into account the non-uniformity of the charge injection around the ionizing wire electrode. The computational results were compared with those obtained under the assumption of uniform corona discharge. The comparison pointed out that neither the non-uniformity of the electric field nor that of the charge injection can be neglected. They depend on the geometry of the electrode system and affect the distribution of the electric field and of the space charge density in the inter-electrode gap.

Computational and Experimental Study of Ionic Space Charge Generated by Combined Corona–Electrostatic Electrode Systems

Numerical computation of the electric field intensity and space charge density in electrode systems consisting of ionizing and nonionizing elements, connected at the same direct current (dc) high-voltage supply and facing a grounded plate, is a difficult problem, which is of interest to several electrostatic processes applications. The aim of the present paper is to demonstrate the effectiveness of an original method of field computation in the analysis of the factors that influence the distribution of the ionic space charge in such combined corona–electrostatic electrode systems. The computations and the experiments were carried out for an ionizing wire of diameter 0.3 mm, located at different distances <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$h$</tex> (10–30 mm) from a tubular support of diameter 25 mm. Several interelectrode distances (20–45 mm) were simulated. The extension of the zone at the surface of the grounded electrode, which is affected by the space charge, diminishes when reducing the intervals between these elements of the electrode system, and, at similar applied voltage, the density of the corresponding corona current increases. The experimental data were in good agreement with the computed results, validating the accuracy of the numerical method of space-charge calculation in this special electrode configuration.

Robust Design of Electrostatic Separation Processes

The aim of this paper is to analyze the robustness of the electrostatic separation process control. The objective was to reduce variation in the process outcome by finding operating conditions (high-voltage level, roll speed), under which uncontrollable variation in the noise factors (granule size, composition of the material to be separated) has minimal impact on the quantity (and the quality) of the recovered products. The experiments were carried out on a laboratory roll-type electrostatic separator, provided with a corona electrode and a tubular electrode, both connected to a dc high-voltage supply. The samples of processed material were prepared from genuine chopped electric wire wastes (granule size >1 mm and <5 mm) containing various proportions of copper and PVC. The design and noise factors were combined into one single experimental design, based on Taguchi's approach, and a regression model of the process was fitted. The impact of the noise factors could be estimated, as well as the interactions between the design and noise factors. The conditions of industry application of Taguchi's methodology are discussed, as well as the possibility of adapting it to other electrostatic processes.

Corrugated copper membranes for use in reconfigurable ground plane antenna

Thin-film copper membranes on silicon substrates were constructed using micromachining techniques. Membranes possessed surface corrugations 10 µm deep and ranged in size from 1.04 mm to 10.0 mm in diameter. Membranes were released using a combination of both KOH and xenon difluoride (XeF ) backside etching. Surface corrugations were made using KOH etching on the frontside of the wafer. The membranes were electrostatically actuated using a high-voltage dc supply, and flexibility was studied as a function of diameter. Measured data were compared to simulations of flat and corrugated membranes. Copper membranes were used as a reconfigurable ground plane under a microstrip transmission line. Actuation of the membranes induced phase shift in the transmitted signal. An array of five 4.3 mm diameter membranes was tested, as was a single 10.0 mm membrane, over frequencies ranging from 9.95 GHz to 35 GHz. A phase shift of 55.63° at 34.42 GHz was achieved for the array of five 4.3 mm membranes, and a phase shift of 57.93° at 35.0 GHz was achieved for the 10.0 mm membrane.

Behaviour of granular starches in low-pressure glow plasma

Granular starches of nine botanical origins were exposed to low-pressure glow plasma generated in the air from either a high voltage DC supply or an AC inductor. Experiments with low energy air-plasma (10 −2 Torr) and starches provided insight into some details of their surface structure. Starches were partly oxidized to carboxylic starches and partly depolymerized. Their affinity to plasma depended on their botanical origin. The structure of starch granules seemed to be a crucial factor, which determined the behaviour of starches in plasma. Lipids and/or proteins stabilized polysaccharides to plasma being preferentially decomposed.

Corona inception in typical electrode configurations for electrostatic processes applications

The corona inception electric field at the surface of a wire electrode is usually evaluated by an empirical formula established by Peek. That formula was found to be valid in several simple electrode configurations (wire cylinder, wire plate), which are typical to electrostatic precipitators. The aim of this paper is to extend the study to other situations encountered in electrostatic applications. The experimental setup specifically modeled the several electrode arrangements which are commonly used with roll-type electrostatic separators. It consisted of wire-type corona electrodes, connected to a regulated DC high-voltage supply, and a rotating roll electrode, connected to the ground. The effect of associating the corona wire to one or several tubular electrodes of various shapes and sizes was investigated. The experimentally determined corona inception voltage was used as input data of a boundary-element-method program for the electric field computation. The computed values of the electric field were compared with those given by Peek's formula for wire electrodes of the same radius. The derived conclusions can be of help in the custom design of the corona electrode arrangements for various electrostatic applications.

The behaviour of conductive particles in pulsed corona fields

The efficiency of certain electrostatic technologies (precipitation of dust, removal of gaseous pollutants from flue gases and separation of mixed granular solids) can be improved by using pulsed instead of DC corona discharges. In this work, the behaviour of millimetre-sized conductive spheres and cylinders either in DC or in pulsed corona fields was studied with a three-electrode arrangement, which had the advantage that the space charge density and the electric field strength could be independently controlled. By energizing the upper corona electrode from a square-wave high-voltage generator (30 kV; 250 pulses per second), a space charge density of periodical variation in time was produced in the air gap of 10 to 25 mm between the earthed median metallic grid and the lower static electrode, connected to a DC high-voltage supply. It was found that particle movements in pulsed fields (small-amplitude vertical oscillations on the surface of the lower electrode) were less affected by the space charge than in the case of a DC corona. The results of numerical simulation of particle behaviour in ionized fields were in good agreement with the experimental findings. The observed phenomena can be explained in connection with the process of particle charging in corona fields.

Bipolar high voltage dc supply for deflecting charged particle beams

We report on the design of a regulated bipolar power supply with a continuously variable output range of ±2.4 kV. A simple 0–9 V control circuit allows the simultaneous operation of two ±5 kV regulated power supply modules coupled to a passive resistive adder. This arrangement eliminates the need of polarity inversion. Excellent linearity, very low ripple, and high regulation over the whole range were obtained.

Electrical Characteristics of the Short-Lived Decay Products of Thoron in Underground Uranium Mines

The thoron progeny charged fraction has been determined in underground uranium mines. Use has been made of a long hollow aluminum tube (108 cm long, 5.92 cm internal diameter, and 0.42 mm wall thickness) equipped with a coaxial conductor and a DC high voltage (HV) supply. One end of the tube was open-face for air intake; the other end was terminated with a filter holder, housing an appropriate filter where the activity not collected by the tube walls and coaxial conductor was deposited and measured when an HV was supplied. The charged fraction was calculated from the activity collected on the filter with and without an applied voltage. A value for the charged fraction of about 60% was obtained.

Electrical Characteristics of the Short-Lived Decay Products of Thoron in Underground Uranium Mines

The thoron progeny charged fraction has been determined in underground uranium mines. Use has been made of a long hollow aluminum tube (108 cm long, 5.92 cm internal diameter, and 0.42 mm wall thickness) equipped with a coaxial conductor and a DC high voltage (HV) supply. One end of the tube was open-face for air intake; the other end was terminated with a filter holder, housing an appropriate filter where the activity not collected by the tube walls and coaxial conductor was deposited and measured when an HV was supplied. The charged fraction was calculated from the activity collected on the filter with and without an applied voltage. A value for the charged fraction of about 60% was obtained.