Maximum Electric Field Strength Research Articles

Simulation of the electric field strength in the vicinity of metallization edges on dielectric substrates

High electric field strengths at the edge of the metallization of insulated gate bipolar transistor (IGBT) power modules are, besides defects in the substrate or the potting gel, the main reason for partial discharge. These critical electric field strengths occur at the energized contact where it is bordered by the insulating ceramic and the cover (mostly silicone gel). The reduction of high electric field strengths for increasing the threshold voltage for partial discharge has been studied in several publications based on experiments as well as on simulations. Simulations allow the localization of the critical spots and the quantification of the maximum electric field strength. However, a systematic study of the singularities of the electric field strength at the sharp edges is lacking. Such singularities are investigated in this article. The calculation of an absolute electric field strength value is only possible for finite edge radii. For sharp edges, however, the maximum electric field strength returned by simulation depends on the grid size: Through the finite grid size a virtual edge radius is induced that suppresses the singularity at the edge. To get around this problem, a mesh-independent evaluation procedure is introduced. With this procedure it is possible to quantitatively evaluate the electric field strength in the vicinity of the sharp edge. As an example, the influence of the offset between the top and bottom metallization layer on the maximum electric field strength is studied. Moreover, the influence of the thickness of the involved layers and of the shape of the electrodes is discussed. Also, the impact of the material properties of the involved dielectrics is examined. In addition to electrostatic simulations we have carried out electric transient simulations, which show that the ratio of the conductivities of the involved dielectric materials plays a major role for determining the maximum electric field strength.

Pilot Electromagnetic Field Measurements in Certain Areas in Greece

This paper reports preliminary electromagnetic field measurements conducted indoors in selected locations in Greece. The paper focuses on the electromagnetic radiation (EMR) of the extremely low-frequency (ELF) and radiofrequency (RF) frequency bands because these bands are considered as possible human carcinogens according to the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). ELF electric and magnetic fields and RF electric fields were measured indoors in several locations in urban, suburban and rural areas of the Zakynthos and Lesvos islands, suburban houses of Ileia Prefecture (Peloponnisos) and urban dwellings of Attica. A total number of 4816 measurements were taken in Zakynthos (276), Lesvos (964), Ileia (29) and Attica (3547) in the frequency range 50 Hz–2500 MHz. Measurements were conducted with NARDA EMR-300 RF survey meter (3935), Aaronia HF and NF spectrum analyzers (795), HI 3604 Holaday ELF survey meter (48) and ANTENNESSA EME SPY (38). The maximum electric field strengths were in most cases below 5 V/m. Strength of electric fields up to 3000 V/m were addressed near high voltage power transmission lines. Stronger average electric fields were measured in urban areas. The strengths of the magnetic field were in most cases lower than 1000 nTesla (1 μTesla), but values up to 6000 nTesla (6 μTesla) were observed near high voltage power transmission lines. The results indicated that the EMR strength values varied but were all below domestic and international established limits.

Computational study of temporal behavior of incident species impinging on a water surface in dielectric barrier discharge for the understanding of plasma–liquid interface

A lipid bilayer is a basic structure of the cell membrane and is stable in liquid solution. In this study, we analyzed dielectric barrier discharge (DBD) containing water on a quartz substrate using a one-dimensional fluid model. To simulate atmospheric pressure plasma for practical use, a tiny amount of N2 gas (0.5 ppm) was added to He gas ambient as an impure gas. The calculated current–voltage (I–V) characteristics reproduced the measured ones qualitatively. We focused on the behavior of DBD at the plasma–liquid interface and analyzed the temporal behavior of the electric field strength and incident fluxes of charged, excited, and radical species on the water surface. By varying the gap length, it was shown that the maximum electric field strength in an AC cycle saturated at gap lengths ≥0.15 cm. The incident fluxes of N2+ and He2+ on the water surface are almost the same and show strong correlations with the electric field in the vicinity of the water surface.

Power combination of two phase-locked high power microwave beams from a new coaxial microwave source based on dual beams

The new coaxial high power microwave source based on dual beams has demonstrated two phase-locked output microwave beams generated by its two sub-sources. In order to achieve a single higher output power, we present a three-port waveguide-based power combiner to combine the two microwave beams. Particle-in-cell simulation results show that when the diode voltage is 675 kV and the guiding magnetic field is 0.8 T, a combined microwave with an average power of about 4.0 GW and a frequency of 9.74 GHz is generated; the corresponding power conversion efficiency is 29%. The combination effect of the combiner is further validated in the diode voltage range from 675 kV to 755 kV as well as in the pulse regime. The simulations indicate that the maximum surface axial electric field strength of the electrodynamic structure is 720 kV/cm, which is relatively low corresponding to an output power of 4.0 GW. The stable combined output suggests the probability of long-pulse operation for the combined source.

Growth of carbon dendrites on cathode above liquid ethanol using surface plasma

The newly developed method presented in this paper allows growth of carbon dendrites, which exhibit glassy carbon- and pyrocarbon-like structures, using surface plasma on the cathode surface above dehydrated ethanol. The process is based on the polarization of polar organic molecules under the influence of external high electric field strength. Ethanol molecules have a dipole moment, they were aligned in the direction of the electric field, and the process of electronic/dipole-relaxation polarization started to occur in liquid ethanol. The dipole density was maximized in the cathode region located at 7–10mm above the liquid ethanol owing to the non-uniform electric field. The electronic breakdown started in the region experiencing the maximum electric field strength. The decomposition of ethanol molecules changed the condition of the gas phase in the breakdown region a resultant current started to flow in the circuit. The growth of carbon dendrites on the Pt cathode, possible under the stability of surface plasma discharges, was characterized by formation of carbon nuclei on the cathode surface. Another advantage of the plasma surface process is that it enables growth of carbon dendrite on dielectric surfaces without increasing of plasma power generation.

Research on the nonlinear conductivity characteristics of nano-SiC/silicone rubber composites

Nano-silicon carbide/silicone rubber composites with nonlinear conductivity characteristics have been made by mixing nano-sized silicon carbide (SiC) into silicone rubber. In this paper, the nonlinear conductivity characteristics of composites made by mixing 5 wt%, 15 wt%, 30 wt% and 45 wt% of nano-SiC and silicone rubber are investigated. The relationship between conductivity and electric field strength is obtained by experiments. Nonlinear conductivity mechanisms of the composites are analyzed, and their breakdown properties and dielectric spectröscopy characteristics of composites are studied. In order to know the effect of nonlinear SiC/silicone rubber composites on homogenizing electric field, the electric ströss distribution of cables termination and composite insulators are simulated by the COMSOL Multiphysics software. Results show that the maximum electric field strength at cable termination and the end of the composite insulators decreases efficiently when the nano-SiC/silicone rubber composites are used.

Influence of grounded back electrode on AC creepage breakdown

Solid insulation using back electrodes has been adopted in various types of electrical equipment. This paper investigates the impact of back electrode on solid insulation AC creepage discharge characteristics. Breakdown voltages at different gap distances are obtained via experiments, and electric field distribution is calculated using computer software. We compare the results between 'with' and 'without' use of back electrodes, and investigate the internal relationship between breakdown properties and electric field distribution. It is observed that back electrodes result in concentration of the electric field near the high voltage electrode. A larger gap distance results in an increase in the maximum tangential electric field strength. When tangential electric field strength exceeds a certain critical value, partial discharge streamers are generated. Such streamers help to lower the breakdown voltage and make the maximum electric field strength less than expected value.

Dielectrophoresis-Magnetophoresis Force Driven Magnetic Nanoparticle Movement in Transformer Oil Based Magnetic Fluids

Magnetic fluid is a stable colloidal mixture contained magnetic nanoparticles coated with a surfactant. Recently, it was found that the fluid has properties to increase heat transfer and dielectric characteristics due to the added magnetic nanoparticles in transformer oils. The magnetic nanoparticles in the fluid experience an electrical force directed toward the place of maximum electric field strength when the electric field is applied. And when the external magnetic field is applied, the magnetic nanoparticles form long chains oriented along the direction of the field. The behaviors of magnetic nanoparticles in both the fields must play an important role in changing the heat transfer and dielectric characteristics of the fluids. In this study, we visualized the movement of magnetic nanoparticles influenced by both the fields applied in-situ. It was found that the magnetic nanoparticles travel in the region near the electrode by the electric field and form long chains along the field direction by the magnetic field. It can be inferred that the movement of magnetic nanoparticles appears by both the fields, and the breakdown voltage of transformer oil based magnetic fluids might be influenced according to the dispersion of magnetic nanoparticles.

Applying Bionic Intelligent Algorithm Combined with Finite Element Method to Optimize Cable

The paper adopts bionic intelligent algorithm including particle swarm optimization and differential evolution algorithm combined with finite element method to optimize cable on the platform of ANSYS finite element soft. Parametric programming of a single-phase cable and a three-phase cable is accomplished to optimize the maximum electric field strength of cable insulation layer by using particle swarm optimization and differential evolution algorithm combined with finite element method, that provides enlightenment for optimizing high-voltage equipment in other aspects of electromagnetic field.

Electro-Mechanical Coupled Characteristics of Piezostack Actuator under the Combined Loads

In the present paper, a finite element model is developed to investigate the static analysis of the piezostack with two hundred layers, in which the polarization directions are opposite between two adjacent layers in axial one. The distributions of the stress and voltage are simultaneously taken into account under both the constant electric and mechanical loads. The results show that the maximum Von Mises stress locates in the corner of the structure near the constrained surface, and the maximum electric field strength locates over the end of the internal electrode that has zero potential. In addition the effect of strip electrodes is considered for the above computation, the numerical simulation indicates that its influence is insignificant and can be ignored in practice analysis.

A compact hexapole state-selector for NO radicals

Focusing of molecular beams using an electrostatic hexapole is a mature technique to produce samples of state-selected molecules. The ability to efficiently focus molecules depends on the properties of the molecular species of interest, the length of the hexapole state selector, as well as on the maximum electric field strength that can be achieved in these devices. In particular for species with a small effective dipole moment such as nitric oxide (NO), hexapole state selectors of several meters in length are required to focus the beam. We report on a novel design for an electrostatic hexapole state-selector that allows for a maximum electric field strength of 260 kV/cm, reducing significantly the length of the hexapole that is required to focus the beam. We demonstrate the focusing of a molecular beam of NO radicals (X (2)Π1∕2, v = 0, J = 1∕2, f) using a hexapole of only 30 cm length. A beamstop is integrated inside the hexapole at the geometric center of the device where the molecular trajectories have the largest deviation from the beam axis, effectively blocking the carrier gas of the molecular beam at minimum loss of NO density. The performance of the hexapole state-selector is investigated by state-selective laser induced fluorescence detection, as well as by two-dimensional imaging of the focused packet of NO radicals. The resulting packet of NO radicals has a density of 9 ± 3 × 10(10) cm(-3) and a state purity of 99%.

Single step combustion synthesis of β-NiAl-coated γ-TiAl by microwave ignition and subsequent annealing

β-NiAl-coated γ-TiAl-based alloys were synthesised following a single combustion synthesis step in a mono mode microwave applicator operating at 2.45GHz under a moderate pressure of 0.15MPa, allowing the simultaneous synthesis and forming of the required shape. Two reactive cylindrical specimens composed respectively of substrate (Ti+Al, 50:50at.%) and coating (Ni+Al, 50:50at.%) powder mixtures were positioned in the region of maximum electric field strength of the microwave applicator. The high exothermicity of the reactions involved, together with the application of pressure, allowed synthesising in a self-propagating regime the new intermetallic phases and to promote a good adhesion between them, due to the formation of complex reaction interface belonging to the Ni–Al–Ti system. A subsequent isothermal annealing treatment at 1230°C led to the obtainment of the desired homogeneous γ-TiAl structure into the substrate without affecting the single β-NiAl phase constituting the coating. The anomalous presence of annealing twins was observed and explained considering the different states in which combustion synthesis of aluminides in the Ni+Al, Ti+Al and Ni+Al+Ti systems occurs.

Cosmic rays and thunderstorms at the Tien-Shan mountain station

Experimental work of the past few years has shown that runaway breakdown determines the maximum electric field strength in thunderclouds and is behind a variety of phenomena newly observed in thunderstorm atmosphere, such as TGFs, TLEs, etc. The necessary condition for the occurrence of runaway avalanche is the existence of high-energy electrons. In the atmosphere, these are the cosmic ray secondary electrons. Therefore the observed effects reflect close relationship between cosmic rays and electrodynamic processes in a thunderstorm atmosphere. The Tien-Shan high-altitude cosmic ray station is a unique site for investigations effects of cosmic rays and thunderstorm discharge. "Thunderstorm" detector complex is designed especially for a systematical study of atmospheric discharges by the means of simultaneous recording of the different kinds of radiation. The presence of a widespread extensive air shower trigger set-up at the Tien-Shan station permits to study the role of energetic cosmic ray particles in lightning development. Overview of main results, obtain during last several years at the Tien-Shan are presented. A phenomenological description and theoretical vision of the cosmic rays role in atmosphere processes during thunderstorm are discussed.

Reproducibility of Microsecond Self-Breakdown Water Switch With Negative Field Enhancement

Based on the “QiangGuang-I” facility, three negatively enhanced microsecond water switches are experimentally studied, and their self-breakdown reproducibilities are particularly investigated and compared. Experimental results show that the annular-cathode-plate switch has a lower jitter (about 110 ns) and its lifespan can be up to 100 shots. Moreover, it is found that the close jitter decreases with the increase of negative field-enhancement factor f (the ratio of the maximum electric-field strength to the mean one of the anode-cathode gap). Finally, the experimental phenomena mentioned previously are particularly discussed according to the results of optical (3-5 ns gated charge-coupled device) and electrical diagnostics.

4H-SiC Trench MOSFET with Thick Bottom Oxide

A 4H-SiC trench MOSFET has been developed that features trench gates with a thick oxide layer on the bottoms of the trenches. The maximum electric field strength and gate-drain charge of this device are 46% and 38%, respectively lower than that of a conventional MOSFET. The drain-source breakdown voltage is 1400V and the specific on-resistance is 4.4mΩcm2 at a gate bias of 20V and a drain voltage of 2V.

Transfer of electrolyte ions and water dissociation in anion-exchange membranes under intense current conditions

Polarization characteristics of electromembrane systems (EMS) based on the Russian commercial heterogeneous membranes MA-40 and MA-41, the anion-exchange heterogeneous membrane AMH (Mega, Czech Republic), and the modified membrane MA-40M are studied by the method of rotating membrane disk in dilute sodium chloride solutions. The effective transport numbers of ions are found; the partial voltammetric characteristics (VAC) with respect to chloride and hydroxyl ions are measured; the limiting current densities are calculated as a function of the membrane disk rotation rate. In terms of the theory of the overlimiting state of EMS, based on experimental VAC and the dependences of the effective transport numbers on the current density, the following internal parameters of systems under study are calculated: the space charge and electric field strength distribution over the diffusion layer and the membrane. It is shown that water dissociation can be virtually completely eliminated by substituting chemically stable quaternary ammonium groups inert with respect to water dissociation in the surface layer of a heterogeneous anion-exchange membrane MA-40 for the active ternary and secondary functional amino groups. The maximum electric field strength values at the membrane/solution interface, which were found in the framework of the theory of over-limiting state, turned out to be close for all anion-exchange membranes studied, namely, (7–9) × 106 V/cm. This suggests that it is the nature of ionogenic groups in the surface layer rather than the field effect that plays the decisive role in the membrane ability to accelerate the water dissociation reaction. It is proved experimentally that in highly intense current modes of the electrodialysis process, the thermal hydrolysis of quaternary ammonium bases occurs in strongly basic MA-41 and AMH membranes by the Hofmann reaction to form ternary amino groups catalytically active in water dissociation reaction. Based on the concept on the catalytic mechanism of water dissociation, the fraction of ternary amino groups formed by thermal hydrolysis in the surface layer (the space charge region) of monopolar anion-exchange membranes MA-41 and AMH is assessed quantitatively as 0.7 and 6.5%, respectively.

Calculation and Analysis of Electrical Field in Valve Side Winding of Converter Transformer

The numerical calculation model with compound insulation of transient electrical field is established. The types of voltage applied on the valve side winding of the converter transformer are complicated and the insulation is more prominent. So the simplied calculation model of the valve side winding of the converter transformer is established. The distribution characteristics of electrical field of the valve side winding of the converter transformer is analyzed and electric field in different electrical conductivity and permittivity are calculated under AC high voltage, DC high voltage, AC superimposed DC voltage, polarity reversal voltage. Under all kinds of high voltages, the maximum electric field strength is calculated and analyzed. Some important influence factors for electrical field distribution are also discussed in this paper.

Pilot 채널을 이용한 WCDMA 기지국의 최대 전기장 강도 예측

In this paper, we predict a maximum electric field strength of WCDMA base station using a pilot channel in a code domain. In order to verify the feasibility of our method, we compare our predicted value on a self-designed test base station with a general electric field strength measurement value at a full-traffic load condition and with a calculated value by a ray-tracing technique. Predicted results show above 90 % agreement with the general measurement and calculation values. We also show that our prediction method can be applied to electric field measurement on a real operating base station. Therefore, it is concluded that our prediction method be an effective method to measure a maximum electric field strength in a base station inspection test.

Simulation of space charge dynamics in low-density polyethylene under external electric field and injection barrier heights using discontinuous galerkin method

In this paper, a novel high-order accurate numerical method was proposed to simulate the space charge transport in solid dielectrics. It is based on a unified framework, discontinuous Galerkin (DG) method, to solve both charge concentration and electric field. It is easier to implement and more efficient than the combined DG and boundary element method (BEM) with equivalent numerical accuracy. With this new method and symmetric model parameters for low-density polyethylene (LDPE), space charge concentration and electric field distribution under different external electric field and injection barrier heights were obtained. The simulation shows that above an electric field threshold, large oscillations appear in the time-dependent maximum electric field strength and the total charge quantity. This phenomenon can be considered as a sign of a relatively larger quantity of charge injection compared to the low field regime. When the Schottky injection barrier height in the simulation is raised, this electric field threshold also increases in order to maintain a certain amount of carrier injection.

Occupational exposure to electric fields and induced currents associated with 400 kV substation tasks from different service platforms

The aim of the study was to investigate the occupational exposure to electric fields, average current densities, and average total contact currents at 400 kV substation tasks from different service platforms (main transformer inspection, maintenance of operating device of disconnector, maintenance of operating device of circuit breaker). The average values are calculated over measured periods (about 2.5 min). In many work tasks, the maximum electric field strengths exceeded the action values proposed in the EU Directive 2004/40/EC, but the average electric fields (0.2-24.5 kV/m) were at least 40% lower than the maximum values. The average current densities were 0.1-2.3 mA/m² and the average total contact currents 2.0-143.2 µA, that is, clearly less than the limit values of the EU Directive. The average values of the currents in head and contact currents were 16-68% lower than the maximum values when we compared the average value from all cases in the same substation. In the future it is important to pay attention to the fact that the action and limit values of the EU Directive differ significantly. It is also important to take into account that generally, the workers' exposure to the electric fields, current densities, and total contact currents are obviously lower if we use the average values from a certain measured time period (e.g., 2.5 min) than in the case where exposure is defined with only the help of the maximum values.