High Voltage Source Research Articles

다중 필터를 이용한 고품질 전압원 인버터에 관한 연구

다중 필터를 이용한 고품질 전압원 인버터에 관한 연구

(Sub)nanosecond transient plasma for atmospheric plasma processing experiments: application to ozone generation and NO removal

In this paper we use a (sub)nanosecond high-voltage pulse source (2–9 ns pulses with 0.4 ns rise time) to generate streamer plasma in a wire-cylinder reactor and apply it to two atmospheric plasma processing applications: ozone generation and NO removal. We will investigate what pulse parameters result in the highest plasma processing yields.The results show that for ozone generation, secondary-streamer effects appear to have a slight influence on the ozone yield: if the pulse duration increases and/or the voltage increases in such a way that streamers can start to cross the gap in the reactor, the ozone yields decrease. Furthermore, for NO removal, we see a similar effect of pulse duration and applied voltage as for the ozone generation, but the effect of the pulse duration is slightly different: long pulses result in the highest NO-removal yield. However, the NO-removal process is fundamentally different: besides removing NO, the plasma also produces NO and this production is more pronounced in the primary-streamer phase, which is why the pulse polarity has almost no influence on the NO-removal yield (only on the by-product formation). Moreover, the rise time of the pulses has a much more significant effect on ozone generation and NO removal than the pulse duration: a long rise time results in a lower enhanced electric field at the streamer heads, which consequently reduces the production of radicals required for ozone generation and NO removal, and decreases the streamer volume. Consequently, the resulting ozone yields and NO-removal yields are lower. Finally, the main conclusion is that the plasma generated with our nanosecond pulses is very efficient for ozone generation and NO removal, achieving yields as high as 175 g · for ozone generation and 2.5 mol · (or 14.9 eV per NO molecule) for NO removal.

Initial Results From an In-Orbit High-Voltage Experimental Platform: HORYU-IV

HORYU-IV is a nanosatellite developed to conduct experiments on electrostatic discharges (ESDs) in real space environments. Testing in space is very important to confirm ground testing results, because it is difficult to fully simulate the comprehensive environment of space on the ground, to evaluate the effects of such things as satellite movements, plasma conditions, sunlight, and chamber walls. Conventionally, occurrence counters have been used for such in-orbit experiments to find threshold voltages. However, they cannot provide detailed information for example magnitudes and the location of each ESD. We became highly aware of this limitation through our HORYU-II experience (which only had an occurrence counter) and we designed HORYU-IV in order to overcome this limited data issue. The main challenge with HORYU-IV is the carrying of standard laboratory equipment, such as oscilloscopes and event-capture cameras, which have never been successfully used in space before. Such measurement instruments, with solar array sample coupons and a high-voltage source, were launched on this satellite and have successfully provided current waveforms and images of spark of light from ESDs from space. This experimental method has been commonly used in ground-based spacecraft charging experiments, but has never been used in orbit. Hence, our satellite became the world’s first operational platform equipped with an oscilloscope and event-capture camera for high-voltage experiments in space. Three different shapes of current waveforms were observed, and the arcing locations from images captured in orbit were identified. We have proved the concept of the remote laboratory in orbit. The observed discharge conditions will be replicated on the ground and the feedback will improve the ground testing methodology.

The protective effect of melatonin and Ganoderma lucidum against the negative effects of extremely low frequency electric and magnetic fields on pulp structure in rat teeth

ABSTRACTBackground/aim: The aim of this study was to determine whether Extremely low frequency electric and magnetic field (ELF-EMF) had any harmful effects on dental pulp tissue and examine histologically whether melatonin (MLT) and Ganoderma lucidum (GL) play a protective role against these harmful effects.Material and method: A total of 56 adult, male Wistar Albino rats were used in the study. The rats were separated into 8 equal groups and were exposed to ELF-EMF, generated by high voltage source, for 8 hours/day for 26 days – Groups I, II and III and for 52 days-Groups V, VI and VII. For sham-control groups (Groups IV and VIII for 26 and 52 days), rats were placed into same experimental set-up as exposure groups and same procedure was applied except ELF-EMF exposure. GL (20 mg/kg/day) and MLT (10 mg/kg/day) were administered by oral gavage and the intraperitoneal route respectively. At the end of the study, the rats anterior teeth were examined immunohistochemicaly using vimentin and vascular endothelial growth factor (VEGF).Results: Degeneration in the odontoblast cells, inflammatory cell infiltration, dilatation of the blood vessels and haemorrhagic changes were determined in the pulp of the rats in Groups I and V. A statistically significant difference was determined in the groups treated with MLT and GL (p < 0.05).Conclusion: It was determined that exposure to ELF-EMF induced histological changes in the dental pulp of rats, the using of MLT and GL could have a protective effect against these effects.

Two-stage electrostatic precipitator with co- and counter-flow particle prechargers

Lab-scale, two-stage electrostatic precipitation system comprising of precharging stage, in which PM2.5 particles are electrically charged, and collection stage, in which the charged particles are removed from the flowing gas by electric field, was investigated in this paper. Two types of electrostatic particle prechargers were compared with respect to the collection efficiency of the system: (1) co-flow precharger, in which ionic current was generated co-currently with the gas conveying the particles, and (2) counter-flow precharger, in which ionic current was generated oppositely to the flowing gas. In each case, the electrodes of precharger were supplied with DC or AC high-voltage in order to compare the effect of discharge mode on the collection efficiency of two-stage electrostatic precipitator. The collection stage was formed by two parallel-plate electrodes connected to DC high voltage source. Plate electrodes without discharge points (spikes) are corona-free electrodes, which prevent the collection stage from electrical discharges, and reduce the probability of back discharge ignition. The back discharge decreases collection efficiency of conventional electrostatic precipitators.It was concluded that the co-flow electrode configuration of the precharger, supplied with DC high voltage, has the highest total number collection efficiency for PM2.5 particles, higher than 95% and the mass collection efficiency larger than 99%. The counter-flow precharger provided only about 90% number collection efficiency of two-stage electrostatic precipitator. It was also shown that by AC electrode excitation, the collection efficiency of the system is lower than for DC supply. The two-stage electrostatic precipitators allowed obtaining higher fractional collection efficiency for PM2.5 particles than other conventional systems and can be recommended as highly effective devices for gas cleaning in power plants or cement industry.

High-voltage power sources for powerful SHF devices with pulse-periodic output voltage

Problems in the development of high-voltage power sources (HVPSs), magnetrons and gyrotrons, providing powerful SHF devices of two types with a continuous generating mode of SHF and periodic-pulse radiation have been considered in this paper. High-voltage power sources (HVPS) are made on the basis of a transistor–capacitor direct-voltage converter. It ensures parametric stability and safety of the HVPS–powerful SHF device system in standard operating conditions and the emergency-operation mode due to HVPS’s negative external characteristic of this type. Mathematical models of an HVPS–powerful SHF device loop describing processes at the various output-voltage pulse-forming stages of HVPS’ have been proposed and checked. An HVPS–powerful SHF device system using the control-current injection method has been analyzed. A feedforward compensator the parameters of which are determined by confinement conditions in the given ranges of output regulation limits and dynamic parameters of forming pulses has been constructed using the asymptotic-expansion method of log-magnitude curves. Taking into account the results that have been obtained, a number of HVPS devices have been produced for technological and research SHF complexes. Basic technical specifications of two developed HVPS devices have been provided as an example in this paper. The first HVPS, which has a medium-voltage power of 60 kW (25 kV/2.4 A), enables generation by an SHF radiation gyrotron of up to 20 kW of capacity in both continuous- and periodic- pulse modes with a maximum frequency of 10 Hz. The second HVPS, which has a medium-voltage power of 20 kW (5 kV/4 A), is intended for supplying power to an M-168 magnetron in the periodic-pulse generation mode of SHF radiation with a maximum frequency of 500 Hz.

Effect of electromagnetic fields and antioxidants on the trace element content of rat teeth.

The purpose of this study was to examine the possible effect of extremely low-frequency electromagnetic fields (ELF-EMFs), from a high-voltage source, on rat teeth in terms of changes in trace elements (TEs) and the effect of antioxidants (melatonin [MLT] and Ganoderma lucidum [GL]) in counteracting these effects. We used adult male Wistar albino rats with a mean weight of 250–300 g and divided the rats into eight groups. The groups were subjected to an ELF-EMF that was applied with a high-voltage line for 8 hours/day for 26 days (Groups I, II, and III) or 52 days (Groups V, VI, and VII). Groups IV and VIII were the 26- and 52-day control/sham groups, respectively. Groups II and VI were treated with GL, and Groups III and VII were treated with MLT. MLT and GL were administered daily based on the weight of the animals and appropriate standards. At the end of the study, the rats were euthanized, and their anterior teeth were extracted. The teeth were preserved in pure water before evaluating the major TEs. At the end of the study, TE concentrations (in mg/kg) were assessed in the control and test groups. Compared with Group V, statistically significant differences in the concentrations of zinc (Zn) and strontium (Sr) were found for Group VII (ELF-EMF + MLT) (P<0.05). Therefore, ELF-EMF exposure can change the content of certain TEs in teeth and, after administering MLT and GL, the values of some of the TEs return to normal.

A high-voltage system of a differential spectrometer for measuring the neutron electric dipole moment

A system of hardware and software for supplying a bipolar high voltage of up to 200 kV to a differential spectrometer that measures the neutron electric dipole moment is described. The high-voltage source is based on two 10-cascade voltage multipliers using quasi-resonant technology. The hardware and application software allow operation of the system in the manual, semi-automatic, and automatic modes.

Active-Forced-Commutated Bridge Using Hybrid Devices for High Efficiency Voltage Source Converters

In high power converters, the on-state characteristics of semiconductor devices dictate its efficiency performance even if the optimized topologies are adopted. This letter proposes an active-forced-commutated (AFC) bridge that employs the hybrid power devices of thyristor and insulated-gate bipolar transistor (IGBT) to operate as a voltage source converter (VSC) or the building blocks of complex multi-stage high-voltage high-power converters. In this scheme, the thyristors are placed in the main power path that conducts for most of the fundamental period to lower the on-state losses; while the IGBT based full-bridge chainlink (FB-CL) is used for controlled (soft) transition and forced commutation of the main thyristor bridge, operating in short period. This stepped transition voltage also leads to minimized dv/dt exerted on the interfacing transformer. To coordinate the operation of these two parts, the FB stack is designed to operate in a concave polygon stepped transition (CPST) mode for the ordered turn-on and turn-off of thyristors according to different categories of commutation events. Detailed commutation analysis for the AFC-bridge is provided in this letter; also, high level discussions and simulation results are presented to demonstrate its potential technical merits.

Research on generation of micro-plasma arc and its power intensity

In order to realize practical application of micro-plasma arc welding, the generation method of submillimetre-sized plasma arc was developed through controlling the DC electrical discharge in the range from glow to arc discharge with use of an experimental torch device and a newly designed high-voltage power source. The electrical discharge was established between the cathode of a tungsten electrode and the anode of stainless steel sheet through a plasma constriction nozzle made from heat-resistant material of boron nitride. It is shown that the micro-plasma arc with use of a submillimetre diameter nozzle is stabilized as the size of the plasma beam corresponds to the nozzle diameter and decrease in the nozzle diameter increases the power density of micro-plasma arc at the anode surface. A submillimetre-sized melt spot can be obtained with the current of 1 A and discharge time of 5 ms.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.

Research on Calibration Method of 7kV Single Voltage Pulse for IGBT Models Test System

Power IGBT module is widely used in high power conversion applications in various fields because of the advantages of high voltage and high current applications. In order to avoid the influence of temperature rise to the device measurement, pulse test method is widely used to test its static and dynamic parameters, So there are single high pulse voltage source and single pulse high current source in power IGBT modules test instruments. For now in the metrology field, how to calibrate its Single High Pulse Voltage source is a difficult problem. Now the amplitude of single high pulse voltage source is above 7kV with the pulse width as 50 microseconds. Based on detailed research on the test principles of the power IGBT modules test instruments, the pulse high voltage divider and the data acquisition unit are used to setup a calibration device for Single High Pulse Voltage source to calibrate the amplitude of Single High Pulse Voltage source. Resistors are usedto develop the pulse high voltage divider, and did carefully research on the pulse response time, voltage dispersion, voltage regulation of the pulse high voltage divider. Also the data acquisition unit with 20MHz bandwidth and 100MS/s acquisition rate is evaluated through tests including vertical accuracy test, bandwidth test, rise time test, comparison test and etc.. Through above relevant test results, with the comprehensive consideration of the influence of each measurement uncertainty component, It have finished that the evaluation of the uncertainties of the amplitude measurement for Single High Pulse Voltage source. The uncertainty of measurement is better than 2% with the coverage factor as 2.

Design and Development of a Series-configuration Mazzilli Zero Voltage Switching Flyback Converter as a High-voltage Power Supply for Needleless Electrospinning

Nanofiber is one-dimensional material that has broad application. It can be formed by applying a high-voltage source to a polymer solution so that the polymer solution becomes charged. Usingthe high electric field, the charged polymer solution is formed as a Taylor cone and then drawn to the collector to form long, nanoscale fibers. This method is known as electrospinning. There are two types of electrospinning method; they are needle and needleless electrospinning. The latter is intended for mass production nanofibers because it can make tens to hundreds ofjets at a time. Therefore, the high-voltage source required for the needleless electrospinning process must have a higher voltage and current compared to those for the needle one. Accordingly, the high voltage power supply using a series-configuration Mazzilli ZVS flyback converter was designed and developed. The Mazzilli flyback converter was able to generate a high voltage with relatively high power. Two converters were connected in series to achieve more output voltage. The output voltage was adjusted by changing the input voltage. The single converter could generate a high voltage up to 34kV whereas the series-configuration converter could increase the voltage by 98.41% to be 67kV. The output voltage of converter was relatively stable and good enough to perform nanofibers synthesis using the needleless electrospinning. Visual observation confirmed that the nanofibers were formed well on the collector.

Experimental analysis of direct current corona discharge

This paper presents the experimental analysis of current-voltage characteristic of DC corona discharge. In experiments were used an electrostatic discharge system, consists of an active brass electrode, and a passive copper electrode (plane). A high-voltage source has been used to produce the positive or negative DC discharge. To analyse the influence of active electrode surface were used a conical and a spherical electrode, with small radius of curvature. The gap between the electrodes was varied by moving the passive electrode. Current-voltage characteristics of DC corona discharge were obtained at a constant distance between the discharge electrodes, by changing the amplitude of supply voltage. Corona current and voltage were acquired using a digital oscilloscope. Experiments allowed the study of the effects due to the active electrode and the air gap between the electrodes, on the onset voltage and the current of corona discharge.

Intelligent control system for the high-voltage pulse power source of the complex for electrofiltration and destruction of gas emissions

Intelligent control system for the high-voltage pulse power source of the complex for electrofiltration and destruction of gas emissions

New diagnostic method of electrical insulation properties based on current integration

We developed a compact system for evaluating the deterioration of insulating materials used in high-voltage dc power apparatuses. The developed system can be used for simultaneous determination of three basic parameters important for evaluating the deterioration of high-voltage insulation materials, i.e., conductivity, dielectric constant, and charge accumulation. Charge accumulation, which is detrimental to high-voltage dc electrical apparatuses, such as power devices, transformers, and power cables, can be evaluated using this system. With this system, the charges accumulated are measured by integrating the current through a capacitor inserted between the highvoltage power source and the high-voltage apparatus to be tested. The obtained information is transmitted to the unit placed at ground potential. The evaluation is carried out by comparing the amount of initial charges in the insulating material with that of charges accumulated at a certain time after application of a high voltage. When the ratio of the charges accumulated at time (t) to that of the initial charge is 1, it is assumed that there was no charge accumulation; thus, no deterioration of the insulating material is assumed. However, when the ratio is greater than 1, the insulating material is considered to have deteriorated. Using the evaluation system, we developed, we examined the deterioration of insulating materials used in coaxial cables by exposure to 1) γ-rays and 2) high-temperature conditions. From these two experiments using the developed system, the deterioration of insulating materials was found to have advanced substantially when the charge accumulation ratio exceeded approximately over 2.0.

Experimental study of electrode erosion and aging process of a specially designed gas switch under repetitive arc discharge

In this paper, a study concerning self-breakdown voltage characteristics, electrode erosion, and degradation of the insulator, of a two-electrode spark-gap switch has been presented based on experiments. A 6 μF pulse capacitor and a DC high voltage source (set at −40 kV) were utilized to achieve ∼0.1 pulses per second repetitive arc discharge between two fixed Cu-W (Cu30/W70) alloy electrodes in the 1.2 L airtight chamber of the switch. With average transfer charge of 2.2 C per shot, this switch was tested for 5800 shots altogether. The results demonstrated the electrode erosion rate of the cathode was 6.3434×10−6 cm3/C whereas that of anode was 5.4691×10−6 cm3/C. Besides, by analyzing electrode surfaces' morphology and PTFE insulator surfaces' compositions after 5800 shots with the help of a scanning electron microscope, a dynamic 3D aspheric metrology instrument, an X-ray photoelectron spectrometer, a metallographic microscope, and a Mettler-Toledo analytical balance, some evidence of physical processes and chemical reactions between plasma channel, electrode materials, and insulation materials could be observed. Moreover, the chamber was opened and inspected for 10 times during the whole procedure, thus providing an overall description of the variation of the switch. It should also be pointed out that owing to complex mechanisms during the aging process, the self-breakdown voltage followed a mixed Normal distribution other than any other simple distributions.

High voltage source control on FODS

The implementation of the high voltage power supply control system (HVPSCS) for experimental setup FODS (FOcusing Doublearmed Spectrometer) at accelerator U-70 of the Federal State Budgetary Institution State Research Center Of Russia Institute for High Energy Physics of the National Research Centre “Kurchatov Institute” (hereinafter referred to as IHEP) or for the test bench of the detector components is considered. The required set of hardware is defined and the appropriate software to operate HVPSCS is written in C/C++ codes. The date acquisition (DAQ) system [1] makes automatic control on HVPSCS for data taking run. It allows to get the dependence of appropriate detector parameters on the high voltage supply values and choose its optimal values for FODS detectors. The test run results of HVPSCS are presented.

A sectioned high-voltage rectifier for a compact tandem accelerator with vacuum insulation

A prototype of a compact sectioned high-voltage source for the modernization of a tandem accelerator with vacuum insulation has been created at the Budker Institute of Nuclear Physics. In contrast to the existing voltage source, it is possible to specify the potential at the accelerating electrodes directly from the rectifier sections, as well as to decrease the accelerator height. This paper presents a new source design and the test results.

Experimental setup for temporally and spatially resolved ICCD imaging of (sub)nanosecond streamer plasma.

Streamer discharges are efficient non-thermal plasmas for air purification and can be generated in wire-cylinder electrode structures (the plasma reactor). When (sub)nanosecond high-voltage pulses are used to generate the plasma, components like a plasma reactor behave as transmission lines, where transmission times and reflections become important. We want to visually study the influence of these transmission-line effects on the streamer development in the reactor. Therefore, we need a unique experimental setup, which allows us to image the streamers with nanosecond time resolution over the entire length of the plasma reactor. This paper describes the setup we developed for this purpose. The setup consists of a large frame in which a specially designed plasma reactor can be mounted and imaged from below by an intensified charge-coupled device (ICCD) camera. This camera is mounted on a platform which can be moved by a stepper motor. A computer automates all the experiments and controls the camera movement, camera settings, and the nanosecond high-voltage pulse source we use for the experiments. With the automated setup, we can make ICCD images of the entire plasma reactor at different instances of time with nanosecond resolution (with a jitter of less than several hundreds of picoseconds). Consequently, parameters such as the streamer length and width can be calculated automatically.