kV DC Power Supply Research Articles

Performance of an impedance-variable pulsed high-power electron-beam accelerator based on energy efficient transmission.

Versatile high-power pulsed electron-beam accelerators that meet the requirements of pulsed high-power specifications are needed for appropriate applications in medical industry, defense, and other industries. The pulsed electron beam accelerator comprising a Marx generator and Blumlein pulse forming line (PFL) is designed to accelerate the electron beams at the level of 1 MeV when electrostatically discharging. The performance specifications of Marx generators consisting of a 100 kV DC power supply, R-L-C circuit, and high voltage switch are at a maximum 800 kV. At this time, by using the capacitance mismatching principle between the Marx generator and the Blumlein PFL under the law of preserving the amount of charge, it is possible to generate a high voltage in the form of a square pulse up to about 1.1 MV, as much as 1.37 times the charged voltage of the Marx generator. As a result, energy transmission from the Marx generator with a high efficiency of about 85% to the Blumlein PFL is possible. The aim of this study is that the pulsed high-power electron-beam accelerator can be used to change the diode impedance, and the energy of the accelerated electron beam reaches a level of 1 MeV with the square pulse width of about 100 ns at the flat-top in the range of relativistic electron beam generation. Performance tests were securely carried out by installing a dummy load based on CuSO4 solution varying the diode impedance to deter damage to the circuit by preventing reflected waves from being generated in the load.

Corona discharge plasma-based degradation of simulated residual linear alkylbenzene sulphonate and dodecyl benzene sulfonate surfactants

Synthetic surfactants are used in a wide range of products ranging from household cleaning detergents to pesticide formulations. Due to their widespread use, residual surfactants are often released in large quantities into the environment, especially via wastewater and can act as potential toxicants. The present study explored the applicability of a non-thermal plasma, namely corona discharge plasma jet (CDPJ), for the degradation of residual surfactants so as to minimize their harmful effects to aquatic life. The plasma was generated using 20 kV DC power supply, with different input currents (1.00, 1.25 and 1.50 A) and at various electrode-to-sample distances (20, 25 and 30 mm). For degradation treatments, simulated residual surfactants (sodium dodecylbenzene sulfonate [DBS] and sodium linear alkylbenzene sulfonate [LAS]) and DBS-containing dishwashing detergents dispersed on slide glasses were exposed to CDPJ for predetermined periods of time (0–120 min). Results indicated that under optimal treatment conditions of 1.5 A current and 20 mm electrode-to-sample distance, the tested surfactants and surfactants in detergents were maximally degraded to about 57% following the plasma treatment for 120 min. Modeling of degradation kinetics indicated that Weibull distribution was the best-fit model, and decimal degradation times (δ) were calculated for different treatment conditions. The pure surfactants were degraded to a greater extent than surfactants in detergents.

Bipolar high voltage pulse generator without H-bridge based on cascade of positive and negative Marx generators

A parameterized bipolar high-voltage pulse generator without H-bridge based on cascade of positive and negative Marx generators is proposed. In the proposed circuit topology, the positive and negative Marx generators are connected directly without any auxiliary circuits. Each stage of the Marx generators consists of a diode, a storage capacitor, two MOSFETs switches. A 1 kV DC power supply is employed to charge the storage capacitors of the two kinds of Marx generators. The control signals of switches generated by FPGA circuit according to the setting parameters of high-voltage pulses and loads are sent to high-voltage pulse circuit via optical fiber. There are two remarkable features in the developed prototype: (1) the ability to adjust all of the parameters of the high-voltage pulse, especially the variable rising and falling time, (2) the better match properties to different loads. The key parameters of the developed bipolar high-voltage generator show as following: adjustable rising/falling time 50-500 ns, pulse width of top flat 0-1 ms, repetition rate 10 kHz (at ±15 kV and 200 pF), overshoot/undershoot less than 5%, and amplitude 0 to ±15 kV. The shape of waveform can be the rectangle and/or triangle. All the pulse parameters can be programmed arbitrarily.

Analysis of the magnetic properties in hard-magnetic nanofibers composite

The magnetic properties of the strontium hexaferrite nanoparticles were studied as they were embedded at different concentrations in poly(vinyl alcohol) (PVA) nanofibers. These nanoparticles were prepared using the Pechini method and a low frequency sonication process obtaining a 3.4 nm average diameter. The composite consisting of hard magnetic nanoparticles homogeneously dispersed in a polymeric matrix was fabricated using a homemade electrospinning with 25 kV DC power supply. The obtained nanofibers had an average diameter of 110 nm, and nanoparticles were arranged and distributed within the nanofibers under the influence of a strong electric field. The configuration of the magnetic nanoparticles in the PVA nanofibers was such that the interparticle exchange interaction became negligible, while the magnetostatic interaction turned out predominant. The results reveal a considerable improvement in the energy product (BHmax) and in the squareness ratio (Mr/Ms) for nanoparticle concentrations between 15 and 30% per gram of PVA. The nanoparticles arrangement occurred at densities below the percolation concentration enhanced the hard-magnetic properties of the nanofibers, which indicates that the organization of the particles along the fibers induces anisotropy from the magnetostatic interaction among the magnetic nanoparticles. Finally, we close the discussion analyzing the observed effect below the percolation threshold, where the induced anisotropy caused the reduction of the full-width at half-maximum of the switching field distribution curves.

Case study of stationary energy storage device in a 3 kV DC traction system

The paper presents the results of economic study of energy storage system (ESS) implemented in 3 kV DC power supply system. Two conceptions of ESS have been investigated: ESS with supercapacitor (SC) and hybrid ESS (HESS) with SC and LFP battery. The investigated locations of energy storage systems are considered among existing traction substations in two railway lines with different density of train operation. The considered aims of energy storage system implementation are decreasing of energy consumption by maximum regenerative energy utilization and reduction of peak 15- min power demand of traction substation. The paper presents a method of regenerative power estimation depending on the location of the considered ESS implementation point. Also the method of optimal location selection of ESS in terms of minimization of Simple Payback Time (SPBT) of investment is presented. Besides the influence of initial cost value as well as energy price on the SPBT value are investigated. The results are compared between two railway lines with different number of trains operating.

Intermittent corona discharge plasma jet for improving tomato quality

The effectiveness of intermittent corona discharge plasma jet (ICDPJ) treatment over continuous mode for the decontamination of cherry tomatoes was evaluated. Microbial contaminants, namely aerobic bacteria, yeasts and molds and coliform bacteria, were detected in tomatoes in the range of 2.49–3.05 log CFU/g. Tomatoes were treated with corona plasmas generated using 8 kV DC power supply and at 2.0–4.0 A currents. A distance of 60 mm was maintained between the discharge electrode and the sample surface during plasma treatment, with a maximum treatment time of 2 min. In contrast to CDPJ-treated tomatoes in continuous mode, a maximum surface temperature of 33.7 °C and no plasma-induced alterations in tomato color and firmness were observed in ICDPJ-treated tomatoes. The ICDPJ treatment decreased the contaminants loads by 0.68–1.02 log CFU/g at 2.0 A, by 1.42–1.71 log CFU/g at 3.0 A, and by 2.00 log CFU/g to non-detectable level at 4.0 A. There were no significant differences in terms of taste, flavor, color, texture, and total acceptance scores between the untreated and ICDPJ-treated samples for 2 min at 2.0, 3.0, and 4.0 A. During storage at 25 °C for 15 days, the samples treated using the ICDPJ at 3.0 and 4.0 A currents exhibited significant extension of shelf life for up to 10–15 days, in contrast to untreated controls (6 days).

Improving the quality of voltage in the system of traction power supply of direct current

Purpose of the work is improved approaches to ensure the required quality parameters of voltage in the traction network based on modern technologies and equipment in the application of power distribution system. Actuality. The introduction of high-speed traffic, increase weight standards Train necessitates increasing the carrying capacity of railways. Often the carrying capacity of existing sections electrified at 3.0 kV DC power supply unit limits. Such limitations include voltage decrease on the electric current collector below the allowable value for the normal operation of 2700 (2900 for high-speed V) and heating the contact wires, thereby losing their mechanical strength. Existing power supply system of RS, which have considerable installed traction substations, can not provide the required level of power density traction network for high-speed movement within 1.5 - 2 MW / km and, respectively, the required voltage quality. At the same time, the daily loading of a powerful traction substations in providing intensive schedule of trains does not exceed 20-25%, while the energy loss in traction network peak load increases and reaches 10-15% of the energy consumed. Thus, the existing system of power traction networks is not sufficiently effective and economical, even with the application of existing methods to strengthen them. In our view, the main limiting factor for a given quality of voltage in the traction network is the use of centralized power. From this, the development of measures to improve the quality of voltage in the traction network in the implementation of high-speed traffic in a growing scarcity of energy resources is an urgent task. Scientific novelty. Using distributed power supply system with adjustable supply points combined into intelligent power supply, which enables adaptive change the characteristics of the transfer, conversion and consumption and optimize the mode of functioning of the traction power supply is suggested for improving the quality of voltage in the traction network in the implementation of high-speed and heavy traffic. Practical significance. Improving the quality of voltage in the traction network by using the proposed circuit design traction power supply will ensure the desired mode voltage and power characteristics of the traction network in the implementation of high-speed and heavy traffic while reducing electricity losses by 20-30%.

Relationship of Pressure and Plasma Temperature in Plasma DC Glow Discharge

The DC glow discharge of nitrogen gas was carried out by 5 kV DC power supply, which was used to bias voltage between two parallel plate electrodes in the cylindrical glass tube chamber. The distance between two parallel plate electrodes was about 37.5 cm. The voltage was applied on these electrodes between 800 V to 1400 V. The nitrogen pressure in the cylindrical glass tube chamber was controlled by rotary pump and vacuum value. Optical Emission Spectroscopy (OES) was used to investigate the local emissivity of nitrogen glow discharge in the range between 200 and 1,100 nm. The spatial distribution of reactive species was measured at different nitrogen pressures from 0.15-1.90 mbar. These measurements were obtained to analyze the electron temperature. The effect of different nitrogen pressures was studied on the electron temperature and the configuration of nitrogen plasma. In the result, it was found that the plasma column increased with increasing the nitrogen pressure. The electron temperature was less than 0.8 eV.

Electrostatic Separation of Flower Parts from Onion Seeds

ABSTRACT THE purpose of this research was to study the application of electrostatic principles in removing flower parts from onion seeds. The optimal machine and environmental factors that would cause separation of flower parts from an onion seed/flower part mixture were determined. The electrostatic separator had a beam type electrode, conducting type conveyor belt, and a 25 kVDC power supply. The chemical contents of the seeds and the flower parts were determined. The germination percentages and the densities of the seeds in the different separated fractions were determined. The electrostatic separator, at 17 kV in the pinning position, was effective in separating flower parts from onion seeds. Humidities less than 40% and temperatures less than 24 C were found to be essential for effective separation of flower parts from onion seeds. The onion seeds had higher protein dry weight, crude fat, acid detergent fiber content but lower ash and nitrogen-free extract than the flower parts. The electrostatic separator was capable of separating seeds based on density. Seeds having higher density had higher germination.

EFFECT OF THERMIONIC CATHODES EVAPORATION PRODUCTS ON HIGH VOLTAGE VACUUM BREAKDOWN

We have studied electrical conduction and electrical breakdown in a vacuum gap between molybdenum electrodes in the presence of the evaporation products of a dispenser cathode and a thoria coated tungsten filament. The field enhancement factor was determined and the work function and the emitting area were determined before and after the Mo electrodes were exposed to the vapors. The surface damage on the electrodes due to arcing was examined in a scanning electron microscope. We have studied the phenomenon of electrical conduction and breakdown in a vacuum gap between molybdenum electrodes in the presence of the evaporation products of a dispenser cathode and a thoria coated tungsten filament. The Fowler-Nordheim equation was used to determine the field enhancement factor. The work function of the molybdenum cathode and the emitting area of the field emission sites were measured before and after the Mo electrodes were exposed to the vapors. We have also examined in a scanning electron microscope the surface damage on the electrodes due to arcing. The critical voltages and local fields for breakdown have been measured. Experiments were performed in a stainless steel base bell jar systeml.Varian model Vl-221. It is equipped with a sorption pump, a 140 -g ion pump and a titanium sublimation pump. The flanged ports on the chamber were used with various feedthroughs. During experiments, the pressure in the system was =2xl09 torr. The molybdenum electrodes were cut from h inch diameter rod with a purity of 99.99%. The edges were rounded to provide a smooth profile so that a high electric field would not be produced due to sharp edge. The electrodes were screwed on supporting molybdenum rods in the vacuum chamber. The front surfaces of the electrodes were mechanically polished using finally a 0.05 um AI2O3 abrasive powder in water suspension. The high voltage electrode was mounted on a stationary high voltage ceramic insulated feedthrough and the ground potential electrode was mounted on a linear motion feedthrough. Both the electrodes could be simultaneously outgassed at =1300K by electron bombardment heating. Electrodes temperature was measured with an optical pyrometer. A 2 HI resistor was used in the voltage-current measurement circuit to protect the power supply. The high voltage was applied by a Sorensen 0-30 KV dc power supply and measured by an electrostatic voltmeter. A Keithley picoammeter was used for measuring the current. During breakdown experiments the ammeter was removed and the voltage was increased until a spark occurred between the electrodes. The electrode surfaces were examined in a JEOL model JSM-35 scanning electron microscope (SEM). Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984951 C9-304 JOURNAL DE PHYSIQUE The Mo e l e c t r o d e s were outgassed s e v e r a l t imes between 1250-1350 K till s t a b l e va lues of t h e f i e l d enhancement factor ,B and t h e emi t t ing a r e a were obta ined. The d i spense r cathode used was Semicon type-S i n which a porous tungsten ma t r ix i s impregnated wi th a mixture of BaO, CaO and A1203 i n t h e mole r a t i o 4 : l : l . The d i s penser cathode was brought t o f a c e t h e s u r f a c e of t h e Mo cathode and then heated t o 10500C br igh tness . The Table 1 g ives t h e work func t ion and t h e e l e c t r o n emi t t ing a r e a of t h e molybdenum e l e c t r o d e f o r d i f f e r e n t exposure t imes t o t h e vapors which c o n s i s t of Ba, BaO and some calcium2. The work func t ion decreased a s t h e exposure time was increased. The minimum va lue obta ined was 1.OleV. From t h e known evaporat ion r a t e 2 of t h e impregnants we es t ima te t h a t one monolayer (1015 %!ZE cm2 ) of t h e vapor atoms i s depos i t ed i n approximately 15 minutes.

A protective circuit for a 60 kV dc power supply

A description is given of the surge protection of a 60 kV dc power supply used in the centre terminal of a 30 MV Van de Graaff machine. The surge voltage encountered can be very fast (of the order of 10 ns) and can have amplitudes of many hundreds of kilo-volts.