Decrease In Breakdown Voltage Research Articles

Effect of lateral inhomogeneous AlGaN barrier layer on electronic properties of GaN HEMTs

In this study, an AlGaN/GaN high electron mobility transistor with lateral inhomogeneous AlGaN barrier layer (LI-AlGaN HEMT) is proposed and studied systematically. The LI-AlGaN HEMT comprises three AlGaN regions with varying Al content, connected to the source, gate, and drain, respectively. With the increase of Al content in each region, the saturation current of the LI-AlGaN HEMT increases gradually, while the on-resistance (Ron) and breakdown voltage (BV) decrease. The threshold voltage (Vth) of the LI-AlGaN HEMT depends only on the Al content of AlGaN beneath the gate. By introducing the source field plate (FP), the calculated output current of the conventional FP-HEMT is consistent with the experimental data. After optimizing Al content, the LI-AlGaN FP-HEMT has the same Vth compared with conventional FP-HEMT. However, the saturation current is increased by approximately 20 % and the Ron is decreased by approximately 30 %. Additionally, the BV is increased to 1008 V. So the optimized lateral inhomogeneous AlGaN HEMT has better DC characteristics and is suitable for high power GaN device applications.

Electrical properties evaluation of corn oil biodiesel mixed with lubricant as a potential source of energy

The main aim of this study is to assess the electrical characteristics pertaining to a biodiesel derived from corn oil and lubricant. The first step in the synthesis of biodiesel from corn oil involves the transesterification process. Subsequently, the biodiesel is combined with a base lubricant (20W-40T) in varying proportions, spanning from 5% to 40% of the overall volume. The measurement and analysis of biodiesel blends necessitate consideration of crucial electrical parameters, including breakdown voltage, resistivity, permittivity and electrical conductivity. The decrease in breakdown voltage, permittivity, and electrical conductivity that ensues from an increase in diameter may be attributed to the corresponding increase in diameter. Nevertheless, a positive association exists between the greater quantity of base lubricant and an elevation in resistivity. Despite the positive correlation between resistivity and diameter, this phenomenon persists. The potential cause for the enhancement of the electrical properties might be attributed to the dispersion of the fundamental lubricant.

Effects of the ground-electrode temperature on electrical and optical characteristics of a coaxial dielectric barrier discharge in atmospheric pressure air

The applied power and electron energy are believed to play important roles in plasma applications, which can be significantly altered by controlling the ground-electrode temperature in a coaxial dielectric barrier discharge (DBD). The effects of the ground-electrode temperature on the electrical and optical characteristics of the DBD were investigated in atmospheric pressure air. The results show that the breakdown voltage decreases, and the number of discharge pulses, the transferred charges, and the applied power increase with the electrode temperature, while the peak current tends to decrease when the electrode temperature is below −35 °C and above 25 °C, respectively. When the electrode temperature remains constant, the breakdown voltage increases and the applied power decreases with the gap distance. The applied power increases with the applied voltage. The dielectric capacitance, the total capacitance, and the gap capacitance at the electrode temperature below −35 °C are generally higher than those at the electrode temperature above 25 °C. Moreover, they change in the same trend when the electrode temperature and the applied voltage increase. The dielectric and total capacitances increase while the gap capacitance decreases. The relative intensities of the spectral lines increase with the electrode temperature. The electron, vibrational, and rotational temperatures increase with the electrode temperature above 25 °C. However, the electron and vibrational temperatures increase and decrease with the electrode temperature below −35 °C. The secondary emission coefficients and electron energy distributions with the electrode temperature were discussed.

Spark discharges at the interface of water and heptane: emulsification and effect on discharge probability

Spark discharges in liquid have shown great potential for use in numerous applications, such as pollutant degradation, precision micromachining, and nanomaterials production. Herein, spark discharges are initiated at the interface of two immiscible liquids, heptane and water. This leads to the formation of an emulsion via mechanisms akin to bubble dynamics and instabilities at the gas–liquid. At high discharge number, an additional mechanism contributes to emulsion formation, resulting in an increase in the number of smaller heptane droplets in water. Analyses of the current–voltage characteristics show that high probability of discharge occurrence is obtained when the electrodes are aligned with the interface. This result is correlated with the low erosion rate of the electrodes. In the case of discharges at the interface, we observed that beyond a certain number of discharges, the breakdown voltage drops; far from the interface, it increases with the discharge number. Based on 2D simulation with a Monte Carlo approach to consider various droplet distribution in water, the electric field distribution is determined. The results support the fact that the decrease in breakdown voltage may be attributed to the intensification of the E-field in water close the heptane droplet. Therefore, spark discharges generated at the interface of a heptane/water system produce an emulsion of heptane in water, which facilitates the occurrence of subsequent discharges by intensifying the electric field and reducing the breakdown voltage.

Numerical studies on the influences of gas temperature on atmospheric-pressure helium dielectric barrier discharge characteristics

A fast-rising gas temperature is due to frequent collisions of the heavy particles in an atmospheric-pressure dielectric barrier discharge. In this paper, a two-dimensional fluid model is applied to investigate the influences of rising gas temperature on an atmospheric-pressure helium dielectric barrier discharge. With the increase in the gas temperature, it is found that: (1) a helium discharge can evolve from the discharge column to a homogeneous discharge; (2) the breakdown time is in advance and the gas breakdown voltage decreases; (3) the spatial distribution evolution of the electron density is similar to that of the helium atom density. The most significant discrepancy between them is that the electron densities are high at some positions where the helium atom densities are nevertheless low. Furthermore, the radial reduced electric fields are obtained under different gas temperatures. The physical reasons for the gas temperature effects are discussed. The simulation results provide a better understanding of the roles of the radial reduced electric field and the heavy particle.

Cumulative Effects in 100 kHz Repetition‐Rate Laser‐Induced Plasma Filaments in Air

Cumulative effects are crucial for applications of laser filaments, such as for the remote transfer of energy and the control of electric discharges. Up to now, studies of cumulative effects in the air of high‐repetition‐rate pulse trains have been performed at lower rates than 10 kHz. Herein, the nonlinear effects associated with short plasma filaments produced by pulses of moderate energy (0.4 mJ per pulse) and repetition rates up to 100 kHz are experimentally characterized. With increasing repetition rate, a decrease in absorption, fluorescence emission, and breakdown voltage and concurrently an increase in peak intensity and third‐harmonic‐generation efficiency are observed. Hydrodynamic simulations of the heated gas show that the observed decreases are directly related to a quasi‐stationary state of reduced gas density in the filament. However, further investigations are required to fully understand the physics underpinning the observed sharp reduction of the breakdown voltage at 100 kHz repetition rates. The results may prove relevant for energy and information delivery applications by laser‐induced air waveguide or electric discharge and lightning control.

Modelling the Effect of Thermal Aging on Transformer Oil Electrical Characteristics Using a Regression Approach

The effect of thermal aging on the electrical properties of the insulating oil used for transformers has been explored in this experimental work. In particular the dielectric dissipation factor, the resistivity and the breakdown voltage have been measured and correlated. The numerical results predicted by mathematical model and those measured in the laboratory have been compared by using a regression analysis. Experiments on thermal aging were performed on insulating oil (Borak 22, Nynas, Austria) during a period of time of 5000-h at three different temperatures. First, the transformer oil’s dielectric dissipation factor, the resistivity and the breakdown voltage are measured after every 500 h of aging. Then, polynomial and exponential regression expressions are proposed for modelling the oil’s electrical parameters variations with thermal ageing at different aging temperatures and periods. The results show that after thermal aging, the resistivity and the breakdown voltage decrease with thermal aging, however, the dielectric dissipation factor which increases. This trend is similar for all different aging temperatures. The numerical results show close agreement with the measured results for all the samples and all studied properties. The regression model presents strong correlation with high coefficients (>94%).

Effect of Acceptor Traps in GaN Buffer Layer on Breakdown Performance of AlGaN/GaN HEMTs.

In this paper, Silvaco TCAD software is used to simulate the buffer traps in AlGaN/GaN high electron mobility transistors (HEMTs), and its effects on the breakdown performance and key parameters of the devices are investigated by changing the position and concentration of the acceptor traps in the buffer layer. The results show that with the increase of trap concentration, the traps capture electrons and reduce the off-state leakage current, which can improve breakdown voltage of the devices. At the same time, as the trap concentration increases, the ionized traps make a high additional electric field near the drain edge, leading to the decrease of breakdown voltage. With the combined two effects above, the breakdown voltage almost ultimately saturates. When the source-to-gate (Access-S) region in the GaN buffer layer is doped alone, the minimum and most linear leakage current for the same trap concentrations are obtained, and the additional electric field has a relatively small effect on the electric field peak near the drain as the ionized traps are furthest from drain. All these factors make the breakdown voltage increase more controllably with the Access-S region doping, and it is a more potential way to improve the breakdown performance.

Analytical Model and Experimental Study of a Cylindrical DBD Discharge Operating in the Filamentary Mode

In this work, we present an experimental and theoretical study of a cylindrical atmospheric pressure dielectric barrier discharge (DBD) operating in the filamentary mode. An analytical model that takes into account the nonuniformity of the charge distributions on the dielectrics was developed. Using the model, it is possible to estimate important characteristics of a DBD device, like breakdown voltage, mean power consumption, and circuital parameters, directly from the geometry and physical characteristics of the device. The model also helps to understand and quantify some aspects of the behavior of the DBD discharge, like the decrease of breakdown voltage as the amplitude of the applied voltage increases, and how the fraction of area of dielectric covered with deposited charge determines the device performance. The theory was tested with experiments performed with a DBD operated in atmospheric air, with voltages from 14 to 22 kV peak to peak, and a frequency of 10 kHz.

Analysis of Oil Dielectric Strength Insulation on Oil Circuit Breakers Based on Service Life and Operating Frequency

The electricity distribution breakdown can be caused the service life and operating frequency of Oil Dielectric Strength (ODS). Hence, it requires a study due to the spare part is difficult to find. This paper aims to test the ODS on Oil Circuit Breaker (OCB) of 13.8 kV aged between 29 to 43 years. The test used the ASTM D1816 standard to analyze the effect of oil life and circuit breaker operating frequency on the physical, color and strength of ODS. For the visual test used the ASTM D1524 standard. The color test based on the ASTM D1500 standard. From the test results, it can be seen that 6DN F1 was yellow-black in colors. The color level was from 0.5 to 6, which was a striking color difference. This happens because it had been operating for 3 years with a frequency of 2 manual open times and 11 trips with a large normal load of 206A. In the 8D F7 feeder, there was also a decrease in breakdown voltage, which was far from 45.6 kV to 9.7 kV. Therefore, the oil was declared failed due to below the minimum standard of 27 kV. Based the validity test, the six samples were still within the allowable limits based on ASTM D1816 with the range value being below 92%. This means that the six samples were valid.

Breakdown Behaviour of Polyesterimide Enamelled Wire Subjected to Thermal Aging

This work concerns the effect of thermal aging on breakdown voltage of polyesterimide enamelled copper wire. Samples are aged in ovens at different temperatures. After aging, a large population of samples were taken and submitted to dielectric breakdown under AC and DC voltages. The material was characterized by TGA and DSC. The values of failure were treated statistically using Weibull model. The study shows a decrease in breakdown voltage with respect to aging time. DC breakdown voltage is greater than AC breakdown voltage. Under DC stress, breakdown voltage is related to the polarity. TGA thermograms exhibit one decomposition stage. The beginning temperature of the mass loss and the residue are greater in the case of pure samples. The glass transition temperature decreases as a function of aging time resulting to a plasticization in the material. In long-term, the decomposition occurs by a scission reaction of imide - bond and ester – bond at interface of polyesterimide-copper. A through discuss of the obtained results is given as well.

Influence of Space Charge on Dielectric Property and Breakdown Strength of Polypropylene Dielectrics under Strong Electric Field

Space charge accumulation in polypropylene (PP) affect the dielectric properties and breakdown strength of the material. The pre-injected charge in PP under the action of different polarity voltage is quantitatively characterized, and the effects of the pre-injected charge inside the dielectric on the dielectric properties and breakdown strength are measured and analyzed. Based on the molecular simulations, the influence mechanism of the temperature on dielectric properties and breakdown are discussed. The experimental results show that the injected charges in PP under the negative polarity voltage is significantly larger than that of the positive polarity. These charges have a great influence on the dielectric constant and breakdown performance of PP, and the effect is different for different charge polarity. The effect of negative polarity pre-voltage conditions on the dielectric constant is much greater than that of positive polarity, and the dielectric constant of PP decreases from 2.2 to 1.3, decreasing about 41% under the negative polarity pre-voltage. By contrast, the dielectric constant slightly increases under the effect of the homopolar preload. Furthermore, the breakdown strength of the dielectric after the heteropolar preload is 249 kV/mm, which is 36% lower than that of PP without pre-voltage, and it slightly increases after the positive polarity pre-voltage. As the temperature increases, the increase in free volume favors the development of electron collision ionization and electron collapse processes, leading to a decrease in breakdown voltage at high temperatures. This work has a good guiding significance for the comprehensive evaluation of energy storage parameters.

Honeywell develops new technology for production of green hydrogen

Composites of high density polyethylene, HDPE, filled with submicrometric particles of BaTiO3, BT, have been prepared. Uniform dispersion of the particles was achieved by high energy ball milling and subsequent hot pressing. Using SEM, FTIR, TGA-DTA and stress-strain tests, studies of the structural, morphological and mechanical features of the composites have been carried out. Frequency response analysis, dielectric strength and resistivity measurements were also performed to evaluate the final electrical properties as a function of the processing and the amount of BaTiO3 particles. From the analysis of the microscopic structure, it can be deduced that any change in the properties of the materials must be solely ascribed to the presence of the BT particles. A balance between an enhancement of space charge polarization with the presence of BT and the existence of permanent dipoles associated to them might explain an initial increase in the dielectric losses with the BT content, and its later decrease at higher BT content. The observed decrease in resistivity and breakdown voltage when increasing the amount of BaTiO3 can be explained by the lower resistivity of BT particles at room temperature and the growing accumulation of space charge.

Interaction of Transformer Oil Parameters on Each Other and on Transformer Health Index Using Curve Estimation Regression Method

Power transformers are one of the most significant and expensive equipment in power systems that are exposed to electrical, thermal, and chemical tensions. The transformer health index is a measure that uses test data and field inspections to assess the condition and determine the remaining life of the transformer. The purpose of this article as a new idea is to determine the relationships between electrical, physical, and chemical parameters of transformer oil, dissolved gases, and the transformer health index. One of the advantages of using the regression method in analyzing transformer data compared to the other methods to evaluate the transformer health index is determining the influence of the parameters that have the most impact on each other. Some achievements of this article are as follows: (1) introducing moisture content as the parameter that plays an effective role in reducing dielectric oil breakdown voltage and improving the transformer health index; (2) determining the inverse relationship between acidity and furfural components; (3) determining furfural as a parameter with the greatest role in reducing the Interfacial tension (IFT) of oil (molecular interconnection); (4) determining CO gas as the parameter with the most role in the production of furfural component; (5) determining C2H2 gas as the parameter with the most role in producing the acid component. For example, with a 1 ppm increase in the moisture component, the oil breakdown voltage decreases by 0.583 kV in the compound, growth, exponential, and logistic regressions, or with a 1 ppm increase in the furfural component, the oil interfacial tension decreases by 0.644 mN/m in power regression. In this article, the curve estimation regression method is used and the results are plotted by SPSS statistical software to analyze the interaction between different transformer parameters. To perform the simulations, test data related to 120 transformers have been considered.

Application of SiGe layer for reinforcing conductivity modulation in trench insulated gate bipolar transistor

In this work, an investigation for inserting a SiGe layer in an insulated-gate bipolar transistor (IGBT) has been performed to analyze the relation between on-state property and breakdown voltage (BV) with the help of technology computer-aided design simulation. For a carrier storage (CS) IGBT, which is widely studied for enhancing conductivity modulation by increasing hole density, the BV decreases by increased conductivity in the CS layer. However, by using the SiGe layer instead of the CS layer, the on-state property is improved with lower BV reduction than a CS IGBT due to the absence of impurity doping. Finally, an optimization for a Ge mole fraction is performed. Based on the results, it is found that the SiGe with 0.3 mole fraction shows the best performance because over 0.3 Ge mole fraction, the excessive energy band bending induced by over-accumulated holes makes low carrier velocity in the n-drift layer.

Effect of Environmental Parameters on Streamer Discharge in Short Air Gap between Rod and Plate

Environmental meteorological parameters (temperature, humidity, air pressure, etc.) have an important impact on short gap streamer discharge. Based on the streamer theory and particle continuity equation of gas discharge, a short gap streamer discharge simulation model is established, and the influence of environmental parameters on the dynamic development process of streamer discharge is simulated and analyzed. The short gap air gap discharge characteristics were tested in a self-made gas discharge chamber. The results show that at low humidity (relative humidity <80%), with the increase of humidity, the electron density of the streamer channel increases, the field strength of the streamer head increases, the streamer development speed speeds up, and the gap breakdown voltage decrease; At higher humidity (relative humidity >80%), with the increase of humidity, the electron density of the streamer channel decreases, the field strength of the streamer head decreases, the development speed of the streamer slows down, and the gap breakdown voltage increase. With a decrease of gas pressure, the electron density of the streamer channel decreases, the field strength of the streamer head decreases, the development speed of the streamer increases, and the gap breakdown voltage decreases; The temperature change has little effect on the streamer development process.

Electric strength of dielectrics under influence of bipolar voltage pulses of submicrosecond duration

The development of electric pulse technologies for the destruction of solids states (rocks) --- drilling, cutting and crushing requires reduction of high pulse voltages. In this work, for the first time, studies are proposed and carried out to determine the breakdown voltages of various dielectric media (air, water, rocks) while simultaneously supplying two pulses to the electrode system by two high voltage generators of different polarity --- positive and negative, which halves the operating impulse voltage each generator. In addition, experiments have shown that for all media there is a decrease in breakdown voltage in comparison with a monopolar voltage pulse, which reaches 28% --- for the breakdown of sandstone, 23% --- granite, 24% --- water, 25% --- air. A physical explanation of the discovered effect is given. Keywords: monopolar and bipolar pulse voltage, breakdown voltage, discharge channel.

Электрическая прочность диэлектриков при воздействии двуполярных импульсов напряжения субмикросекундной длительности

The development of electric pulse technologies for the destruction of solids states (rocks) - drilling, cutting and crushing requires reduction of high pulse voltages. In this work, for the first time, studies are proposed and carried out to determine the breakdown voltages of various dielectric media (air, water, rocks) while simultaneously supplying two pulses to the electrode system by two high voltage generators of different polarity - positive and negative, which halves the operating impulse voltage each generator. In addition, experiments have shown that for all media there is a decrease in breakdown voltage in comparison with a monopolar voltage pulse, which reaches 28% - for the breakdown of sandstone, 23% - granite, 24% - water, 25% - air. A physical explanation of the discovered effect is given.

In English

Boron carbide (BC, B15-xCx B4C) has a unique combination of properties. This makes it a material for priority applications for a wide range of engineering solutions. The high melting point and heat resistance of the compound contribute to its use in refractory conditions. Due to its extreme abrasion resistance, B4C is used as an abrasive powder and coating. Due to its high hardness and low density, B15-xCx has ballistic characteristics. It is usually used in nuclear programs as an absorbent of neutron radiation Boron carbide ceramics (B15-xCx or BC) may lose strength and toughness due to the amorphization effect under high shear stresses. Aluminum dodecaboride AlB12 or B12Al, as well as boron carbide B12 [(CCC) x (CBC) 1-x] have common structural units B12 family of boron-icosahedral structures. The bond between icosahedrons is mainly due to atoms (Al, Si, O) or chains (CMC), where M is Al, Si, B, C. Doping BC powder with a small amount of AlB12, in cases of shock-shear stress, triggers the mechanism of "micro-cracking". Micro cracks and pores are formed in ceramics. The breakdown voltage decreases. AlB12 synthesis is associated with known difficulties. On the other hand. The production of metal-ceramic materials for several decades is associated with the interaction of liquid aluminum and boron nitride. The calculation of this reaction shows that it is exothermic. Avoiding oxidation in vacuum, the reaction occurs through the formation of aluminum nitride and aluminum dodeca-boride. In contrast to the liquid state, the process continues until the end, at conditional temperatures of evaporation of aluminum with slight changes in vacuum. The reaction product is a mixture of nanosized AlN/AlB12 powders with a weight ratio of 3/1 ready for baking without grinding. The acid-base properties of the nanosized powder mixture AlN + AlB12, the products of the interaction BN + Al in vacuum, which are used optionally, emit separate in pure phases of aluminum nitride and aluminum dodeca-boride. The yield of AlB12 is ~ 25%, boron reaches ~ 100%. The average particle size of the AlB12 powders according to TEM and ACS X-rays (area of coherent X-rays scattering), L (nm) is LTEM=110-150nm, LACS=51-70nm. The average specific surface area of the powder according to BET, TEM and ACS, SBET.m2/g=21,0-15,0; STEM.m2/g=21,4-15,4; SACS.m2/g=46,1-33,6; (at 1460 and 1640K, respectively).

Morphology evolution and breakdown mechanism of cross‐linked polyethylene (XLPE)–silicone rubber (SiR) interface induced by silicone grease diffusion

Silicone grease (SG) is used for lubrication during cable accessory installation and can penetrate into the silicone rubber (SiR), leading to properties deterioration of the SiR. In this study, the effects of SG on the breakdown characteristics of the cross-linked polyethylene (XLPE)–SiR interface are investigated. First, the variation of the XLPE–SiR interface breakdown voltage with SG coating time is experimentally explored. The interface breakdown voltage significantly increases after SG is applied, remains stable for coating times of up to approximately 144 h and then rapidly decreases; the minimum interface breakdown voltage is lower than that without the SG coating. Next, the effects of SG on the chemical composition and surface topography of the SiR are examined by infrared spectroscopy and optical profilometry, respectively. The SG penetration does not change the functional groups of the SiR but significantly increases its surface roughness. Finally, the interface electric-field distribution after coating with SG is analysed by finite-element simulation, revealing that the residual SG at the interface distorts the interface electric field after a long coating time. The increase in the SiR surface roughness caused by SG diffusion and the interface electric-field distortion caused by the residual SG together lead to the decrease of the interface breakdown voltage.