Search

Inductive fault current limiters (FCLs) have several advantages, such as significant current limitation, immediate triggering and relatively low losses. Despite these advantages, saturated core FCLs have not been commercialized due to its large size and associated high costs. A major remaining challenge is to reduce the footprint of the device. In this paper, a solution to reduce the overall footprint is proposed and discussed. In arrangements of windings on a core in reactors such as FCLs, the core is conventionally grounded. The electrical insulation distance between high voltage winding and core can be reduced if the core is left at floating potential. This paper shows the results of the investigation carried out on the insulation of such a coil-core assembly. Two experiments were conducted. In the first, the behavior of the apparatus under high voltage conditions was assessed by performing power frequency and lightning impulse tests. In the second experiment, a low voltage test was conducted during which voltages of different frequencies and pulses with varying rise times were applied. A finite element simulation was also carried out for comparison and further investigation. [ABSTRACT FROM AUTHOR]

This paper explores the technique of ozone injection to induce reactions leading to NO conversion in a diesel engine exhaust and subsequent adsorption by lignite ash, an industrial waste from lignite coal fired power plants. Experimental investigations were carried out using a diesel engine fuelled by biodiesel, prepared from pongamia pinnata, a native Indian plant. Ozone is produced from dry air in a Dielectric Barrier Discharge (DBD) reactor by the application of high voltage. The choice of the high voltage was made after a comparative study between high frequency AC and unipolar repetitive pulse source, with the latter consuming lesser power for given ozone production. By injecting ozone, the higher composition of NO in biodiesel exhaust gets oxidized to higher oxides of nitrogen in general and NO2 in particular. This NO2 can be adsorbed in the lignite fly ash pellets as successfully demonstrated in this paper. This combined ozone injection-lignite ash adsorption technique has resulted in an overall removal efficiency of oxides of nitrogen (NOx) as high as 95% even under loaded conditions. A comparison has also been made between the ozone injection technique and direct plasma treatment of exhaust for NOx removal. [ABSTRACT FROM AUTHOR]

Studies were carried out to estimate the power input to Dielectric Barrier Discharge (DBD) reactors powered by AC high voltage in the context of their application in nonthermal plasma cleaning of exhaust gases. Power input to the reactors was determined both theoretically and experimentally. Four different reactor geometries energized with 50 Hz and 1.5 kHz AC excitation were considered for the study. The theoretically estimated power using Manley?s equation was found to agree with the experimental results. Results show that the analytically computed capacitance, without including the electrode edge effects, gives sufficiently good results that are matching with the measured values. For complex geometries where analytical calculation of capacitance is often difficult, a novel method of estimating the reactor capacitance, and hence the power input to the reactor, was introduced in this paper. The predicted results were validated with experiments. [ABSTRACT FROM AUTHOR]

Seven hundred fifty kilovolt extra-high voltage (EHV) shunt reactors are important power equipment that stabilize the normal operation of an entire 750 kV power grid. Internal winding faults of a reactor could be a difficult issue when the reactor is in service, and result in sudden equipment failure and significant economic losses. To prevent sudden catastrophic failure of equipment, online detection should be implemented to evaluate the state of the reactor properties when requested. In this paper, a noninvasive method based on online impulse frequency analysis was proposed and developed to detect internal winding faults of a 750 kV EHV shunt reactor. Initially, the safe implementation of the online detecting device was verified before field installation. Unlike in previous work, the online detecting device was modified and improved according to the specific situation of shunt reactors. Original fingerprints of 750 kV EHV shunt reactors were obtained and analyzed after site installation and normal operation of the detecting device. A fault simulation test was implemented to validate the method. This paper provides guidance on actual implementation of online impulse frequency response analysis on power equipment. [ABSTRACT FROM AUTHOR]

In this paper, we propose and design a novel generator for the high voltage square pulses with the changeable polarities in order to reach the requirements and the needs for the intended experiments on sterilization of microorganism. The major component of our circuits is a non-trivial combination between a half bridge Marx generator and an H bridge in series, combining with the DSP control unit, which can adjust the voltages, frequencies, pulse widths and polarities, and also tolerate various loads. More precisely, we illustrate the design and operation principles for each module in the constructed circuit and analyze the system performance with various loads. The effectiveness and correctness of our proposed circuit and methodologies have been verified and demonstrated by both PSIM simulation results and our own prototype. In this paper, we also show the stability and reliability of the pulse generator we proposed in terms of various load conditions and operation safety respectively. Furthermore, we also observe that the key parameters based on our constructed pulse generator can be easily adjusted which include voltages, frequencies, pulse widths and polarities. We hope that our work will stimulate the further investigations on design and analysis of pulse generators with a focus on modularization and miniaturization. [ABSTRACT FROM PUBLISHER]

The research work in this paper is based on generation of high voltage pulses using compact power supply sources for abatement of NOX from the diesel engine exhaust. The high voltage source is made up of zero voltage switch cascaded with flyback converter to produce high voltage AC, a Cockroft-Walton voltage multiplier to generate high voltage DC and a rotary spark gap for the production of high voltage pulses of rise time in the range of nano seconds. The rectifier based power supply is validated by a 12 V battery supply. To corroborate the feasibility of proposed methodology in diesel operated vehicles, the experiments are conducted with a 12 V battery. Performance of various shapes of electrodes (cylindrical 5mm diameter, square 5 mm diagonal and hexagonal with vertex to vertex diameter of 5 mm) at different flow rates of 2 l/min, 4 l/min and 6 l/min are also examined. [ABSTRACT FROM PUBLISHER]

An electroporation reactor comprises a treatment area for the application of pulsed electric fields to biological tissue. A homogeneous opening of cells within the whole treatment area can be achieved by applying a homogeneously distributed electric field of sufficient field strength and also sufficient total energy to the tissue. However, such an ideal homogeneous electric field can be achieved in a closed volume only. Inlet and outlet of an electroporation reactor designed for a continuous flow of material involve inhomogeneities of the electric field. Such inhomogeneities cause additional losses due to current flowing also in low-field regions, which are ineffective for electroporation. Depending on the design of the electrode system also the electric field in the center of the electroporation area might be to some extend inhomogeneous. So the specific energy required for the treatment of a defined volume of material depends on the electrode design. When comparing this specific energy to the specific energy required in the ideal case of a treatment area with a homogeneous field, a factor describing the energy efficiency of the electrode design can be defined. The paper describes this approach in more detail. [ABSTRACT FROM AUTHOR]

Biodiesel run engines are gaining popularity since the last few years as a viable alternative to conventional petro-diesel based engines. In biodiesel exhaust the content of volatile organic compounds, oil mist, and mass of particulate matter is considerably lower. However, the concentration of oxides of nitrogen (NOx) is relatively higher. In this paper the biodiesel exhaust from a stationary engine is treated under controlled laboratory conditions for removal of NOx using dielectric barrier discharge plasma in cascade with adsorbents prepared from abundantly available industrial waste byproducts like red mud and copper slag. Results were compared with gammaalumina, a commercial adsorbent. Two different dielectric barrier discharge (DBD) reactors were tested for their effectiveness under Repetitive pulses /AC energization. NOx removal as high as 80% was achieved with pulse energized reactors when cascaded with red mud as adsorbent. [ABSTRACT FROM PUBLISHER]

The application of non-thermal plasma excited by strong electric fields is becoming a key technology for water treatment because of the efficient generation of oxidants, such as hydroxyl radicals, and no secondary pollution. In this paper, a water treatment system mainly consisting of a pulsed power generator and a dielectric barrier discharge reactor was constructed. The reactor consists of five rows of staggered positive and negative electrodes and separating plates. Wastewater dropped into the discharge area from the tiny holes in the separating plates. Degradation of indigo carmine solution was attempted by this system. The effects of discharge time, discharge voltage, frequency, initial pH value, and H2O2 were studied. The degradation rate came to 100% in 8 minutes at the voltage of 30 kV and frequency of 200 Hz under the initial concentration of 450 mg/L. The energy cost of the degradation of indigo carmine reached 80 g/kWh. [ABSTRACT FROM PUBLISHER]

Recently, water treatment using pulsed streamer discharge in water is studied, because the pulsed streamer discharge generates active species that decompose organic compounds in water. We have studied the method spraying water droplets into discharge space as one of the water treatment methods. In this paper, improvement of a treatment rate by changing structure of reactor has been investigated. At first, the influence by changing an electrode and packing pellets was investigated. The indigo carmine solution was decomposed as sample water. As the result, the treatment efficiency for the discharge energy was decreased by using the reactor of longer electrode and using the reactor with the pellets. The reason of the decrease of the treatment efficiency is that water droplets become water film and that the voltage falls due to the increase of capacitance components of the electrode. To solve these problems, the reactor setting the insulation grids was investigated. This reactor improved the treatment efficiency because setting the insulation grids prevented the fall of energy efficiency by the long electrode and quickened the decomposition of the organic compounds. [ABSTRACT FROM PUBLISHER]

In this paper, a different type of cross flow dielectric barrier discharge (DBD) reactor was designed and tested. Here the gas flow is perpendicular to the barrier discharge electrode. Discharge plasma was utilized to oxidize NO contained in the exhaust gas to NO2 and subsequent NO2 removal can be improved using an adsorbent system. A detailed study of DeNOX in a stationary diesel engine exhaust was carried out using pulsed electrical discharges/adsorbent processes. Activated alumina (Al2O3) and MS-13x were used as adsorbents at room temperature. The main emphasis is laid on the removal of NOX from the filtered diesel engine exhaust. In filtered exhaust environment, the cross flow reactor along with adsorbent exhibits a superior performance with regard to NOX removal when compared to that with axial flow of gas. In this paper we bring out a relative comparison of discharge plasma and plasmaadsorbent process at various gas flow rates, ranging from 2 l/min to 25 l/min. The discharge plasma-adsorbent assisted barrier discharge reactor has shown promising results in NOX removal at high flow rates. [ABSTRACT FROM PUBLISHER]

This paper describes a novel MOSFET gate driver circuit design for pulsed power application. It is shown that MOSFET switching speed can be enhanced by using an energised inductor as a high current source in series with the gate terminal of a power MOSFET. This topology demonstrates switching speeds of less than 10ns for MOSFETs with high input gate capacitance. It is also shown that by increasing the current in the gate drive and with an optimised layout, a single gate driver can be used to drive multiple parallel connected MOSFETs synchronously without compromising their performance. The circuit design is analysed and experimental results presented when operating at an instantaneous power of 25 kW. [ABSTRACT FROM AUTHOR]

In pulsed power system, mechanical characteristic means the structure of the plasma reactor, and impedance matching between the pulse generator and the plasma reactor means the electrical characteristics. It is a very important issue in the industry because impedance matching is closely related to the efficiency and reliability of the pulsed power system. In this paper, the design and implementation for improving the energy density of the wire-plate plasma reactor are presented. The system configuration, impedance characteristics and structures of the plasma reactor are described, and the output characteristic of the plasma reactor according to the structure of the wires and plates is analyzed. The plasma reactor model is realized on the simulation tool, and the simulation results are compared with the experiment data. Based on the theoretical analysis and the simulated model, impedance matching between the wire-plate plasma reactor and the pulsed power generator can be more fully achieved. [ABSTRACT FROM AUTHOR]

Capacitor charging power supply (CCPS) is a developed technology that utilizes resonant converters topology for high power applications. This paper proposes new a capacitor charging power supply using leg-rotation control method within a phase-shifted PWM full-bridge dc/dc converter. The capacitor charging power supply was connected in series to increase output voltage. Also, the proposed system is designed with soft switching techniques in order to achieve high efficiency, and a leg-rotation control method was used to reduce the heat generated from the IGBTs. The operation of the converter and design methodology will be described. A simplified model of a high-voltage high-frequency transformer is given and the structure is designed to decrease high-voltage stress. The validity of the proposed system is then verified by experimental results. The performance test of the capacitor charging power supply was carried out with a 2 μF capacitive load with a 20 kV output voltage. [ABSTRACT FROM AUTHOR]

In this paper studies were carried out on two compact electric discharge plasma sources for controlling nitrogen oxides (NOX) emission in diesel engine exhaust. The plasma sources consist of an old television flyback transformer to generate high frequency high voltage ac (HVAC) and an automobile ignition coil to generate the high voltage pulses (HV Pulse). The compact plasma sources are aimed at retrofitting the existing catalytic converters with electric discharge assisted cleaning technique. To enhance NOX removal efficiency cascaded plasma-adsorbent technique has been used. Studies were reported at different flow rates and load conditions of the diesel engine. [ABSTRACT FROM PUBLISHER]

This paper is aimed at investigating the nitric oxide (NO) removal using dielectric barrier discharges (DBD) in a multi-rod reactor stressed by ac and pulse high voltages. The effects of various parameters (the voltage amplitude, frequency, gas flow rate, use of the γ-alumina pellets and the voltage type) on the discharge power and NO removal rate have been studied experimentally in the multi-rod DBD reactor. When the reactor was filled with γ-alumina pellets, improvement in NO removal rate was observed. The pulse voltage gives higher NO removal rate in comparison with ac voltage at the same energy density. Records of the discharge photograph and the emission intensity have been made at varying voltage amplitude, frequency, and gas flow rate. The records confirm the dependency of the discharge power on these parameters. [ABSTRACT FROM AUTHOR]

This paper presents a novel topology for the generation of high voltage pulses that uses both slow and fast solid-state power switches. This topology includes diode-capacitor units in parallel with commutation circuits connected to a positive buck-boost converter. This enables the generation of a range of high output voltages with a given number of capacitors. The advantages of this topology are the use of slow switches and a reduced number of diodes in comparison with conventional Marx generator. Simulations performed for single and repetitive pulse generation and experimental tests of a prototype hardware verify the proposed topology. [ABSTRACT FROM AUTHOR]

Improving efficiency and flexibility in pulsed power supply technologies is the most substantial concern of pulsed power systems specifically with regard to plasma generation. Recently, the improvement of pulsed power supply has become of greater concern due to the extension of pulsed power applications to environmental and industrial areas. With this respect, a current source based topology is proposed in this paper as a pulsed power supply which gives the possibility of power flow control during load supplying mode. The main contribution in this configuration is utilization of lowmedium voltage semiconductor switches for high voltage generation. A number of switch-diode-capacitor units are designated at the output of topology to exchange the current source energy into voltage form and generate a pulsed power with sufficient voltage magnitude and stress. Simulations carried out in Matlab/SIMULINK platform as well as experimental tests on a prototype setup have verified the capability of this topology in performing desired duties. Being efficient and flexible are the main advantages of this topology. [ABSTRACT FROM AUTHOR]

The saturated reactor is used in the DC converter valve to protect thyristors. A fluid-solid coupling heat dissipation model was established for the saturated reactor in this study, which included water cooling, heat conduction, heat convection and heat radiation. By the means of finite element method, the temperature and flow field distribution were calculated, which indicated that the low thermal conductivity of epoxy resin hinders the heat dissipation of the saturated reactor. To research effects of thermal conductivity on heat dissipation, the heat dissipation performance of saturated reactor with different epoxy resins was numerical simulated by using this model. The results showed that the heat dissipation performance of the saturated reactor can be effectively improved by the rise of the thermal conductivity of epoxy resin, but the marginal benefit of increasing the thermal conductivity of epoxy resin is gradually reduced. Meanwhile, high-thermal conductivity epoxy resin could have the longer service life under the same operation conditions. [ABSTRACT FROM AUTHOR]

A six cavity inductive voltage adder with pulsed power incorporated into a single assembly, linear transformer driver (LTD), has been developed. Each LTD cavity is driven by a single pulse forming network and spark gap switch. The output pulse is approximately square in shape due to the pulse forming networks (PFNs) used for the drivers. In some cases, when unreliable switch firing occurred, multiple output pulses were observed. The pulses stem from each cavity firing at a different time. A circuit model which explains the multi-pulse behavior and details the current path is developed. This observation shows the potential for an LTD to discharge each cavity individually to the load thus providing extremely high repetition rates on a common cathode stalk. [ABSTRACT FROM AUTHOR]

High-Voltage pulse generators are commonly used in biotechnology, medicine, industrial applications, food processing and drinking water purification. The dc-dc boost converter has been used before in pulsed applications for its ability to amplify a relatively low input dc voltage to a high-voltage output. A high-voltage solid-state chopping switch is then used to chop the generated high output voltage. In this work, a boost-converter based ringing circuit with high voltage gain is proposed for water treatment applications. The basic concept of the proposed approach depends on operating the boost converter under discontinuous current conduction. With the proposed approach, the chopping high-voltage switch at the output stage is eliminated, which positively affects the system cost and efficiency. A full-design of the circuit and passive components is presented to ensure that the desired pulse specifications are achieved. The proposed approach has been validated using simulation and experimental results. [ABSTRACT FROM AUTHOR]

A nonlinear lumped element transmission line (NLETL) that consists of a nonlinear LC ladder network whose capacitors are nonlinear and inductors are linear can be used to produce oscillating pulses. This article describes the implementation of an oscillating pulse generator based on such high voltage nonlinear capacitive lines (NLCL) using commercial-off-the-shelf (COTS) components. Instead of using complex pulse forming networks or pulse forming lines, a storage capacitor and a fast semiconductor switch are used to provide an input pulse onto the cascading LC-elements of the NLCL with good approximation of a rectangular pulse-shape. The design of the NLCL is based on the NLETL circuit model that was developed earlier in-house. Experimental results are compared with simulations predicted by this NLETL model. The voltage modulation and the frequency content of the output pulses are analyzed. The conventional single NLCL produces a signal with a DC offset and a decoupling capacitor is needed at the end of the line to extract the AC component before injecting onto a load such as an antenna. A novel method of directly extracting the AC component without the use of a decoupling capacitor is proposed and investigated. Results of this direct AC extraction, which show the possibility of better performance, are discussed. The frequency tunability of this nonlinear line was also demonstrated. [ABSTRACT FROM AUTHOR]

Red mud is a waste by-product generated during the processing of bauxite, the most common ore of aluminium. With the presence of ferric oxide, high surface area, resistance to poisoning and low cost, red mud made itself a good alternative to the existing commercial automobile catalyst. The cascading of dielectric barrier discharge plasma with red mud improved the NOX removal from diesel engine exhaust significantly. The DeNOX efficiency with discharge plasma was 74% and that with red mud was 31%. The efficiency increased to 92% when plasma was cascaded with red mud catalyst operating at a temperature of 400°C. The NOX removal was dominated by NO2 removal. The studies were conducted at different temperatures and the results were discussed. [ABSTRACT FROM AUTHOR]

The pulsed power is one of technologies to solve the problem of water pollution. Since the pulsed streamer discharge can generate not only ozone but also OH radical, ultraviolet rays and shockwaves, it is expected to have high efficiency for the treatment and decompose the pollutants that cannot be easily decomposed by even ozone oxidation. Therefore, we have been studying the method that uses the pulsed streamer discharge generated in air with water droplets as the method with highest energy efficiency in the water treatment method by the discharge. In this study, in order to get higher efficiency in this method, we have investigated a pulse circuit design and pulse conditions in which the energy is transferred efficiently from a pulsed power generator to the discharge and the treatment efficiency is higher. The output power from the pulsed power generator is limited by switching time of the high voltage FET switches in it. In the experiment, optimum output time of pulsed voltage and resistance value in the pulsed power generator for higher energy efficiency was investigated. The results show that high resistance value and the output time of pulsed voltage of 100ns give highest efficiency for the generator and the treatment, because the discharging power increased at high resistance value and until the output time of 100 ns. The maximum energy transfer ratio is approximately 40 %. [ABSTRACT FROM AUTHOR]