Excessive Electric Field Research Articles

Research on methods to increase the flashover voltage of supporting insulators in Tesla transformers.

This paper presents three methods aimed at enhancing the flashover voltage of the supporting insulator in a Tesla transformer. These methods include optimizing the maximum electric field on the insulator surface, adjusting the overall structure of the insulator, and changing the surface structure of the insulator. Ten insulator samples with different structures were designed based on electric field simulation. Subsequent experiments were conducted to validate the effectiveness of these methods in improving flashover voltage. On this basis, the supporting insulator of the Tesla transformer was redesigned, leading to an increased output voltage. The results are summarized in the following. First, optimization of the shielding rings of the cathode and anode reduces the electric field at the triple junction, which significantly increases the flashover voltage. Second, extending the inclination starting position of insulators with the same inclination angle effectively reduces the surface electric field intensity and increases the flashover voltage. Third, increasing the inclination angle within a certain range while keeping the inclination starting position constant extends the creepage distance and enhances the flashover voltage. However, excessively large inclination angles may lead to a decrease in flashover voltage due to excessive normal electric field. Fourth, grooving on the insulator surface at appropriate locations can inhibit the development of the streamer and improve flashover voltage. Finally, the supporting insulator of the Tesla transformer was redesigned based on these results, elevating the output voltage from 750kV to over 1 MV.

Enhanced controllability of droplet evaporation via DC electric field

To enhance the controllability of droplet evaporation, this study introduces a system that integrates an electric field with a temperature field. In addition, lattice Boltzmann method (LBM) simulations were performed to examine the flow field and heat transfer within the droplet, confirming the mechanism of evaporation rate transition. The impacts of the electric field on droplet evaporation and the characteristics of heat and mass transfer were thoroughly investigated through experimental, theoretical and numerical approaches. The findings indicate that elevating the substrate temperature and intensifying the electric field can modify the evaporation rate of droplets via distinct mechanisms: the temperature field governs droplet evaporation by increasing the heat flux and changing droplet surface tension, whereas the electric field predominantly enhances or inhibits droplet evaporation by affecting the droplet’s surface tension and deformation. According to the Rayleigh limit, charge accumulation reduces the droplet’s surface tension, thereby accelerating evaporation. Conversely, greater deformation resulting from a stronger electric field increases the thermal resistance of the droplet, which dampens heat transfer and inhibits droplet evaporation. Furthermore, an excessive electric field may induce oscillation or droplet breakup. Simulations of droplet evaporation under an electric field further revealed that an increased electric field significantly influences the internal flow of the droplet. A low Peclet (Pe) number suggests that internal flow has a negligible effect on the temperature distribution compared to the impact of heat conduction. This research provides critical insights into the precise manipulation of droplet evaporation.

High-tolerance nickel metalized glass gas electron multiplier: development and performance evaluation

Micro-patterned gas detectors (MPGDs) are an important type of gaseous detector that can amplify and detect a small amount of electric charge generated by the interaction between radiation and gas. These detectors have high gain and high spatial resolution, making them useful in various applications ranging from high energy physics to medical instrumentation. However, one of the most widely used MPGDs, Gaseous Electron Multipliers (GEMs), may often experiences electrical discharges due to excessive electric field in the small space, which reduces their durability. To address this issue, we previously have developed a new type of GEM that uses glass as the insulator instead of conventional materials. Our glass GEM demonstrated excellent gas gain and energy resolution characteristics. In this work, we used nickel as the electrode, which has a higher melting point than copper and showed higher durability against arc discharges. Moreover, the nickel glass GEM performed comparably to conventional Cu-based glass GEMs in evaluation using radiation isotopes. Our findings suggest that our new glass GEM with nickel electrodes is a promising solution to the durability problem of conventional GEMs. This could lead to improvements in the performance and longevity of MPGDs, which could have significant implications for various applications in the fields of physics, engineering, and medicine.

Electrically assisted stereolithography 3D printing of graded permittivity composites for in-situ encapsulation of insulated gate bipolar transistors (IGBTs)

Insulated gate bipolar transistors (IGBTs) find applications in diverse fields, such as integrated motor drives, controllable power systems, and electric vehicles. However, traditional IGBT encapsulation materials are unsuitable for high-voltage applications due to the excessive electric field stress generated at the triple junction; an insulation-enhanced encapsulation material is therefore necessary. Here, using an electrically assisted stereolithography (SLA) 3D printing strategy, we fabricate an encapsulation material with graded permittivity that can uniform the electric field stress distribution in IGBTs. Compared with pure resin and uniform-dispersed BaTiO3-resin composite encapsulation, the graded BaTiO3-resin composite reduces the generated maximum electric field stress (Emax) from 190.2 to 108.3 kV/mm (nearly a 50% decrease). Regarding the partial discharge inception voltage, the devices packaged with graded BaTiO3-resin composite (4.07 kV) also performed better than devices packaged with resin (1.96 kV) and uniform-dispersed BaTiO3-resin composite (2.51 kV). This novel electrically assisted SLA 3D printing strategy will open a new window for the in-situ encapsulation of IGBTs and other microelectronics.

An Integrated Structure–Material Optimization Strategy for the Packaging of High-Voltage Insulated Gate Bipolar Transistors

High-voltage insulated gate bipolar transistors (IGBTs), such as silicon carbide (SiC)-based ones, are promising as wide bandgap (WBG) power modules. However, current IGBT packaging methods are unsuitable for high-voltage applications due to excessive electric field stress, which increases the risk of partial discharge or electrical breakdown, compromising their insulating property; a new packaging solution is, therefore, needed. In this study, an integrated structure–material optimization strategy through the combination of the finite-element method (FEM) and materials optimization is proposed to reduce the maximum electric field stress ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {max}}$ </tex-math></inline-formula> ) at the triple junction, i.e., the interface of the ceramic substrate, the metal electrode, and the polymer-based encapsulation, of an IGBT. In epoxy resin encapsulation, it was determined that a symmetrical and chamfered electrode structure with a smooth transition at the triple junction reduces <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {max}}$ </tex-math></inline-formula> from near 280 to 40 kV/mm at an operating voltage of 27.5 kV. Furthermore, when the permittivities of the substrate (AlN) and encapsulation materials (BaTiO3–resin composites) satisfy an optimal ratio, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {max}}$ </tex-math></inline-formula> can be further reduced to 34 kV/mm (a 15% decrease). These results indicate that the integrated structure–material optimization strategy effectively enhances the insulating property of the high-voltage IGBTs.

Experiment and simulation on degradation and burnout mechanisms of SiC MOSFET under heavy ion irradiation

Experiments and simulation studies on 283 MeV I ion induced single event effects of silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) were carried out. When the cumulative irradiation fluence of the SiC MOSFET reached 5 × 106 ion⋅cm−2, the drain–gate channel current increased under 200 V drain voltage, the drain–gate channel current and the drain–source channel current increased under 350 V drain voltage. The device occurred single event burnout under 800 V drain voltage, resulting in a complete loss of breakdown voltage. Combined with emission microscope, scanning electron microscope and focused ion beam analysis, the device with increased drain–gate channel current and drain–source channel current was found to have drain–gate channel current leakage point and local source metal melt, and the device with single event burnout was found to have local melting of its gate, source, epitaxial layer and substrate. Combining with Monte Carlo simulation and TCAD electrothermal simulation, it was found that the initial area of single event burnout might occur at the source–gate corner or the substrate–epitaxial interface, electric field and current density both affected the lattice temperature peak. The excessive lattice temperature during the irradiation process appeared at the local source contact, which led to the drain–source channel damage. And the excessive electric field appeared in the gate oxide layer, resulting in drain–gate channel damage.

Adsorption of H2 and C2H2 onto Rh-decorated InN monolayer and the effect of applied electric field

InN monolayer with graphene-like morphology and desirable electronic property is a promising candidate for gas sensing application. In this paper, we study the adsorption and sensing performances of the Rh-decorated InN (Rh–InN) monolayer upon two typical dissolved gases in the transformers oil, namely H2 and C2H2, to explore its potential to evaluate the working condition of the transformers. Rh atom conducts n-doping on the pristine InN surface with E b of −2.01 eV. Also, chemisorption is determined for H2 and C2H2 adsorption on the Rh–InN surface given that the E ad of −0.88 and −2.15 eV, respectively. The opposite changing trend of E g in H2 and C2H2 systems manifests the resistance-based sensing mechanism for selective detection of two gas species. The applied electric field supports the work function analysis that an Rh–InN monolayer possesses a strong potential for field-effect transistor sensor application in terms of H2 and C2H2 detection, wherein the charge-transfer in the gas systems is tunable by altering the voltage. Moreover, the excessive electric field is not considered to be suggestible since it can impact the geometric stability of the Rh–InN monolayer. This theoretical work is meaningful to exploit novel sensing 2D materials to guarantee the good operation of the power system. Highlights Rh-decorating behaviors upon InN monolayer is studied. Expound the potential of Rh-InN monolayer for dissolved gas analysis in transformers. Analyze the effect of applied electric field on gas adsorptions.

SiC Fin-Shaped Gate Trench MOSFET with Integrated Schottky Diode.

A silicon carbide (SiC) trench MOSFET featuring fin-shaped gate and integrated Schottky barrier diode under split P type shield (SPS) protection (FS-TMOS) is proposed by finite element modeling. The physical mechanism of FS-TMOS is studied comprehensively in terms of fundamental (blocking, conduction, and dynamic) performance and transient extreme stress reliability. The fin-shaped gate on the sidewall of the trench and integrated Schottky diode at the bottom of trench aim to the reduction of gate charge and improvement on the third quadrant performance, respectively. The SPS region is fully utilized to suppress excessive electric field both at trench oxide and Schottky contact when OFF-state. Compared with conventional trench MOSFET (C-TMOS), the gate charge, Miller charge, Von at third quadrant, Ron,sp·Qgd, and Ron,sp·Qg of FS-TMOS are significantly reduced by 34%, 20%, 65%, 0.1%, and 14%, respectively. Furthermore, short-circuit and avalanche capabilities are discussed, verifying the FS-TMOS is more robust than C-TMOS. It suggests that the proposed FS-TMOS is a promising candidate for next-generation high efficiency and high-power density applications.

Nanoscale Fiber Deposition via Surface Charge Migration at Air-to-Polymer Liquid Interface in Near-Field Electrospinning

In electrospinning, a liquid polymer meniscus deforms into a conical structure called the Taylor cone when an excessive electric field is applied to the air-to-polymer interface. This Taylor cone i...

Study on FAIMS ion source control and optimization using over-electric field

Ion source provides sample ions for FAIMS. The key technology is ionization method. Efficient ionization of analytes is the core technology for data acquisition in high quality FAIMS systems. In order to long-distance detect and analyze harmful and toxic substances such as explosives, drugs, chemical reagents and environmental pollutants in an open environment, without pretreatment, real-time and on-line, the ion source control and its technical device using excessive electric field were designed and developed. The disadvantages of high flow rate of APCI and low flow rate of ESI are integrated, based on the chemical analysis principle of FAIMS, an experimental platform of ionization technology based on excessive electric field is proposed and designed, which mainly includes: ion focusing system, flat-panel migration zone with focusing structure, sample integration, etc. The experimental results show that the ion source based on excessive electric field can be widely used in biochemical weapon warning, drug tablet detection, environmental monitoring, food and drug detection and clinical medicine, and the detection limit can reach 0.1 ppm.

Failure Mechanism of Avalanche Condition for 1200-V Double Trench SiC MOSFET

Due to superior properties of silicon carbide (SiC), the unipolar conduction mechanism of metal-oxide-semiconductor-field-effect transistor (MOSFET), and the structural feature, double trench SiC MOSFETs have great potential to be one of the next-generation power switches. In this article, an avalanche safe operation area (SOA) is established, and a new failure behavior of 1200-V double trench SiC MOSFET is revealed timely through unclamped inductive switching (UIS) test (300 K of initial temperature). With comprehensive analyses involving terminal impedance measurement, monitoring of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> and I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gss</sub> before and after each avalanche test, inner electric field comparison by physics-based device modeling, maximum die temperature estimation, and decapsulation validation, the predominant failure mechanism (fracture of trench gate oxide) is identified for double trench SiC MOSFET under UIS test. Before the maximum die temperature approaches the melting point of source metal, the fracture of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer located at gate trench bottom and corner occurs, which is degraded by duration, excessive electric field, and elevated temperature. Accordingly, we propose I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gss</sub> as a predicting indicator of avalanche failure, which should be a key monitoring scheme in particular for trench type SiC MOSFET.

Different JFET Designs on Conduction and Short-Circuit Capability for 3.3 kV Planar-Gate Silicon Carbide MOSFETs

Both large current capability and strong short-circuit (SC) ruggedness are necessary for 3.3 kV SiC MOSFETs to improve system efficiency and reduce costs in industrial and traction applications. In this paper, the effects of Junction Field Effect Transistor (JFET) region width and JFET doping (JD) on conduction and SC capability of the 3.3 kV planar-gate SiC MOSFETs are systematically investigated by experiments and simulations. When the JFET width (WJFET) of device without JD is smaller, the positive temperature coefficient of the special on-resistance (Ron,SP) is larger. The JD is effective to improve the Ron,SP, but excessive electric field in gate oxide induced by JD should be paid more attention. The optimization of WJFET can be used to improve both Ron,SP and short circuit withstanding time (SCWT) at the same time. The drain-source current (Ids) and SCWT of the optimized devices are 50 A and more than $20~{\mu }\text{s}$ , respectively, which is state-of-the-art for 3.3 kV SiC MOSFETs.

Investigation of tail pipe breakdown incident for 110 kV cable termination and proposal of fault prevention

For cable termination, which is regarded as a key segment of power grid connecting cable lines with other electrical equipments, its insulation parts withstand much higher electric field strength than the average electric field strength of overall cable line. The excessive local electric field strength may result in the appearance of cable termination breakdown fault which can cause serious harm to the power supply reliability of whole transmission line. Historical statistics show that the breakdown location of cable termination is not confined to the vicinity of stress cone. However, the existing researches have not attached enough importance to the breakdown faults at the tail pipe of cable termination. Thus, it is of considerable significance to study the mechanism of breakdown fault at the tail pipe of cable termination. In this paper, a breakdown fault case of cable termination tail pipe on a 110 kV transmission line is investigated. Firstly, the disassembly inspection is applied to cable terminations of this fault line, and the possible breakdown reasons are preliminarily inferred. Then, a three-dimensional electric field simulation model of intact cable termination is established, and the mechanism of creeping discharge and air discharge inside the tail pipe occurred at the initial stage of breakdown fault is explained by this model. Subsequently, by setting defects on cable insulation surface in the simulation model of intact cable termination and varying the size of defects, the process of cable insulation damage inside the tail pipe formed in the initial stage developing into a penetrating cable insulation damage is simulated. Finally, the mechanism of breakdown fault case of cable termination tail pipe is concluded, and some improvement measures for the installation of cable terminations are proposed to reduce the incidence probability of such breakdown fault at the tail pipe of cable termination. The method for analyzing the breakdown fault case of cable termination tail pipe presented in this paper, which combines the disassembly inspection and simulation analysis, can provide reference and suggestions for the investigation and solution in similar cases.

Enhancing spray drying tolerance of Lactobacillus bulgaricus by intracellular trehalose delivery via electroporation.

Spray-drying is an efficient drying technique for preparing probiotic powders, but the high temperatures employed during the process results in low survival rates of lactic acid bacteria. This study aimed to enhance spray-drying tolerance of lactic acid bacteria by intracellular delivery of trehalose via electroporation. Diverse electroporation conditions were applied to Lactobacillus delbrueckii ssp. bulgaricus sp1.1 cells exposed to 10% trehalose prior to spray drying with 30% re-constituted skimmed milk. Survival rates of spray-dried bacteria increased with an intracellular trehalose content of ≥3.5 µg/107 colony-forming units (CFU) and reached 100% with intracellular trehalose content of 10.1 µg/107 CFU. The application of two electroporation pulses at 2.5 kV/cm helped increase the survival rate of L. bulgaricus from 38% to 61% after spray drying. Membrane damage and pore formation caused by excessive pulsed electric field treatment resulted in cell death after spray drying. Sufficient intracellular trehalose protected cell walls and membranes from further damage by spray drying. Multi-pulse electroporation of trehalose into lactic acid bacteria prior to spray drying can potentially increase cell viability.

Compact asymmetric cross‐shaped rectangular dielectric resonator antenna for wideband circular polarization

AbstractA compact asymmetric cross‐shaped dielectric resonator (DR) antenna with broadside wideband circularly polarized has been investigated by using the coaxial probe feeding technique. The presented antenna consists of the asymmetric cross‐shaped DR, a metal strip, and a coaxial feed. Here, the metal strip is used at the corner of the cross‐shaped DR to reduce the excessive tangential electric field and acts as a mirror for the normal filed components. Therefore, the orthogonal modes TExδ11 and TEy1δ1 are excited at resonance frequencies of 4.55 GHz and 5.55 GHz in this antenna structure, and because of these modes, the proposed antenna is able to produce CP fields. The antenna with −10 dB impedance bandwidth provides the measured results of 43.84%, whereas the measured 3‐dB axial ratio bandwidth is found to be 11.23%. Moreover, the proposed antenna shows low profile geometry, that is, 0.175λ0, where λ0 is the wavelength at the central frequency.

A new mechanism for efficient hydrocarbon electro-extraction from Botryococcus braunii

BackgroundRecent understanding that specific algae have high hydrocarbon production potential has attracted considerable attention. Botryococcus braunii is a microalga with an extracellular hydrocarbon matrix, which makes it an appropriate green energy source.ResultsThis study focuses on extracting oil from the microalgae matrix rather than the cells, eliminating the need for an excessive electric field to create electro-permeabilization. In such a way, technical limitations due to high extraction energy and cost can be overcome. Here, nanosecond pulsed electric fields (nsPEF) with 80 ns duration and 20–65 kV/cm electric fields were applied. To understand the extraction mechanism, the structure of the algae was accurately studied under fluorescence microscope; extraction was quantified using image analysis; quality of extraction was examined by thin-layer chromatography (TLC); and the cell/matrix separation was observed real-time under a microscope during nsPEF application. Furthermore, optimization was carried out by screening values of electric fields, pulse repetition frequencies, and energy spent.ConclusionsThe results offer a novel method applicable for fast and continues hydrocarbon extraction process at low energy cost.

Case study to assess the safety of irreversible electroporation near the heart.

IntroductionIrreversible electroporation (IRE) is a promising technique for the focal treatment of soft tissue tumors. Even though the local application of an excessive electric field is a potential cause of cardiac arrhythmias, initial clinical studies have shown that IRE is generally safe when cardiac gating is employed.Case descriptionIn this case report, we observed an episode of ventricular extrasystoles without hemodynamic changes during which time the synchronization device failed to operate properly, with pulses delivered not in the absolute refractory period but in the relative refractory period.Discussion and evaluationAt present, persons performing IRE must keep in mind that there is a small but real risk of synchronization failure even when a cardiac synchronization device is used.ConclusionIt is advisable to err on the side of caution when treating lesions near the heart.

Quality testing methods of foil-based capacitors

Foil-based capacitors are widely used passive elements and therefore should be cheap and reliable. The contemporarily applied methods of their testing are time-consuming and energy-intensive. Additionally, these methods cannot select capacitors that should be very durable due to specific consumers demands (e.g. mining industry, medical equipment). Therefore, new and more efficient methods should be proposed. This manuscript presents in depth the mechanisms of capacitor failures which result from their construction and production methods. Theoretical consideration of possible capacitor failures due to an excessive electric field within the dielectric foil are enclosed. Results of correlation between the selected electrical parameters and capacitance drop due to excessive aging is presented and new methods of capacitor quality prediction are proposed and discussed in detail.

A detailed analysis of hotspots and insulation breakdown phenomena in power inductor windings at high frequency regimes: overcurrents and overvoltages

AbstractThis research paper is the last of a group of three papers dedicated to the analysis and computation of the high‐frequency electromagnetic behaviour of inductor windings where a multiconductor transmission line approach is used. The present work is essentially concerned with application aspects linked up with the important engineering problem of windings insulation damage, which can occur either because of excessive temperature (winding hotspots) or because of excessive electric field strength (dielectric breakdown). For single and multilayer windings we present here a wealth of information in graphical and tabular form concerning the distribution of voltages, currents, electric charges, charge densities, electric field components and power losses along the inductor winding turns, operating at the critical resonance frequencies characteristic of the structure (which is the worst possible scenario). This information is analysed and processed in order to allow for a detection of the winding zones where breakdown phenomena and hotspots could most probably occur. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Heterostructure transistor with tunable gate bias

Excessive electric field at the end of the channel of a Field Effect Transistor (FET) causes mobility degradation, leads to hot electrons and impact ionization events, and generates gate leakage. To minimize the negative influence of non-uniform and strong electric fields in the second half of the channel, a variety of techniques were used in the past, namely a lightly doped drain and delta doping of the channel, or a field plate positioned behind the gate. All mentioned methods succeeded to some extent in reducing field strength, but demonstrated a lack of flexibility when operational voltages at FET terminals were changing. In the current study, we demonstrated a novel heterostructure FET, namely a pHEMT with a 0.5 μm gate, and a second, longer gate positioned above the first one at a distance of 100 A. The gates are biased separately in the manner V g1 > V g2 . Variable combinations of voltages V g1 and V g2 makes tuning (tailoring) of the field extremely flexible for a wide range of HEMT operations. As a result, the first design iteration demonstrated a maximum gain of 15 dB and f T of about 5 GHz. The transistor carries almost constant transconductance of about 225 mS/mm.