High Voltage Capacitor Research Articles

Study on Dielectric Properties of (Ba<sub>0.90</sub>Sr<sub>0.10</sub>) TiO<sub>3</sub> Based Ceramic Capacitors for Energy Storage Applications

The development of energy storage capacitors with high dielectric constant and good stability has been focused on by researchers due to many issues regarding environmental protection and energy conservation. Barium-Strontium Titanate based ceramic capacitors are widely used for energy storage applications due to their attractive dielectric properties. In this study, (Ba0.90Sr0.10) TiO3 based capacitors were produced, and the influence of additives i.e. CaZrO3, MnCO3, CeO2, ZnO, and Nb2O5 was investigated. The parameters of all the fabrication processes have been optimized to get defect-free green and sintered samples. The defect-free green parts were sintered at 1380°C for 2 h and perovskite structure was confirmed by XRD profiles. The grain size was refined from 25 μm to 08 μm analyzed by scanning electron microscopy (SEM). The capacitor was tested at 40 KV successfully and capacitance of 2.0 nF was measured at this high voltage. The results showed that high-voltage capacitors can be fabricated with enhanced energy storage.

Accurate Technique for the Calibration of High-Voltage Capacitance and Dissipation Factor Bridges up to 1 kHz

This paper presents a comprehensive methodology for the precise calibration of high-voltage capacitance and dissipation factor (DF) bridges. The technique involves meticulous adjustments using a digital high-precision phase and ratio-measuring system to determine correction factors for DF and capacitance measurements. Unlike other methods that are limited to a narrow range, this approach allows calibration across the entire operational working spectrum of any bridge. While the method has been developed up to 1 kHz, its adaptability for future requirements is facilitated by the developed software. This method has been carried out by calibrating a highly accurate bridge for a capacitor ratio of up to 100, with DFs ranging from −0.01 to 0.01 and currents ranging from 0.1 mA to 1 A. Linear correction factors are established, with their accuracies being rigorously quantified. This methodology achieves expanded uncertainties as low as 3.5 µF/F (3.5 ppm) for capacitance and 2.2 × 10−⁶ for DFs, significantly enhancing measurement reliability across diverse high-voltage capacitor applications.

Sandwich-structured polymer dielectrics exhibiting significantly improved capacitive performance at high temperatures by roll-to-roll physical vapor deposition

Electrostatic capacitors with ultrahigh power density are the key components in modern electrical and electronic systems. Polymers are preferred dielectrics for high-voltage electrostatic capacitors, however, unable to meet the ever-growing high-temperature requirements in emerging applications, such as electric vehicles, and photovoltaic power generation. In this work, sandwich-structured Polyphenylene sulfide (PPS) films with Al2O3 as the coating layer have been prepared by using roll-to-roll magnetron sputtering. The incorporation of Al2O3 coating layers enhances the potential barrier height at the electrode/dielectric interface, thereby impeding charge injection from electrodes and suppressing high-temperature electrical conduction. Consequently, the sandwich-structured PPS films demonstrate significantly improved breakdown strengths and enhanced capacitive performance at elevated temperatures compared to neat PPS films. The roll-to-roll magnetron sputtering process employed in fabricating these sandwich-structured dielectric films is highly compatible with large-scale capacitor film production. Thus, sandwich-structured PPS films hold promise in addressing the challenge of scalable fabrication of high-performance, high-quality polymer films required for high-temperature capacitive energy storage.

A Review of Polyolefin-Insulation Materials in High Voltage Transmission; From Electronic Structures to Final Products.

This review focuses on the use of polyolefins in high-voltage direct-current (HVDC) cables and capacitors. A short description of the latest evolution and current use in HVDC cables and capacitors is first provided, followed by the basics of electric insulation and capacitor functions. Methods to determine dielectric properties are then described, including charge transport, space charge, resistivity, dielectric loss, and breakdown strength. The semicrystalline structure of polyethylene and isotactic polypropylene is described, and the way it relates to the dielectric properties is discussed. A significant part of the review is devoted to describing the state of art of the modeling and prediction of electric or dielectric properties of polyolefins with consideration of both atomistic and continuum approaches. Furthermore, the effects of the purity of the materials and the presence of nanoparticles are presented, and the review ends with the sustainability aspects of these materials. In summary, the effective use of modeling in combination with experimental work is described as an important route toward understanding and designing the next generations of materials for electrical insulation in high-voltage transmission. This article is protected by copyright. All rights reserved.

Kerr Electro-Optic Effect-Based Methodology for Measuring and Analyzing Electric Field Distribution in Oil-Immersed Capacitors

In the current design and verification processes of insulation structures for high-voltage oil-immersed capacitors, there is a heavy reliance on electric field simulation calculations using idealized models that lack empirical validation of spatial electric fields. This study employs the Kerr electro-optic effect to establish a non-contact optical remote sensing system for measuring the spatial electric field distribution in the insulating liquid dielectric (benzyltoluene) between the capacitor’s element and the case under various temperatures and main insulation distances. The findings reveal that the measured spatial electric field stress can be up to 15% higher than the simulated values. The electric field stress measured in the Y1 direction (up toward the capacitor top) is comparable to that measured in the Y2 direction (down toward the capacitor end). Furthermore, when varying the main insulation distance, the electric field stress consistently shows a negative correlation with increasing measurement distance. Specifically, at a main insulation distance of 1.5 mm, the electric field stress is 1.81 times that at 5.5 mm. As the temperature rises, the spatial electric field stress increases gradually, and the electric field distribution becomes more uneven at higher temperatures. At 80 °C, the field stress is approximately 1.57 times that at 20 °C, with the measured field stress at 80 °C being 19% higher than the simulated value. Finally, this paper undertakes a comprehensive theoretical analysis and experimental validation to elucidate the discrepancies between simulated and measured spatial electric fields. Leveraging these insights, it proposes advanced optimization strategies for the insulation structures of capacitor elements. The outcomes of this study furnish substantial technical and theoretical support, significantly enhancing the design, verification, and optimization processes for insulation in oil-immersed capacitors.

High dielectric breakdown strength of antipolar CaTiGeO5 ceramics sintered at optimized temperature

Titanite CaTiSiO5 (CTS) is considered to be a promising dielectric material for preparing high-voltage multilayer ceramic capacitors because it exhibits a positive bias dependence of the dielectric permittivity due to its antipolar crystal structure. In this study, we investigated the dielectric response and breakdown strength of CaTiGeO5 (CTG), a structural analog of CTS, inspired by its higher low-field dielectric permittivity. Particular attention was paid to the sintering temperature to reveal the effect of the microstructure and loss of volatile Ge on the electrical properties of CTG. Dense CTG ceramics with relative densities above 97 % and grain sizes between 1.3 and 3.4 μm were obtained through a conventional solid-state reaction route at sintering temperatures between 1150 and 1250 °C. A secondary phase of CaTiO3 was formed in the ceramics sintered at 1200 and 1250 °C due to Ge loss, but this phase was easily removed by surface polishing alone. The sintering temperature largely affected the dielectric breakdown strength through microstructural development, resulting in the highest breakdown strength of 1190 kV cm−1 for a sample sintered at 1200 °C, while it did not change the low-field dielectric properties of the samples. Furthermore, the sample retained high breakdown strength of >900 kV cm−1 at elevated temperatures up to 150 °C and exhibited a nonlinear polarization response, resulting in the positive electric field dependence of the dielectric permittivity.

Optimization Design of Temperature Field Distribution for AC High Voltage Parallel Capacitors

Abstract With the change in the overall harmonic working background of the system, the harmonic current spectrum borne by high-voltage AC shunt capacitors becomes increasingly complex, particularly with a gradual increase in high-frequency harmonic content. The wide frequency band, large value range, and long duration of harmonic current lead to increased heating of the capacitor. In this paper, a thermal field physical model is established for an AC parallel filter capacitor based on the skin effect, and trends are analysed in the current distribution of the capacitor plate under the skin effect. Furthermore, based on this established model, it is analysed how harmonic order and capacitor placement mode affect temperature field distribution within the capacitor, and it is concluded that these factors impact temperature rise release. This research lays a theoretical foundation for designing capacitor unit structures.

Utilization of Capacitor Bank for Electromagnetic Pulse Crimping

Capacitors play an important role in an electrical system. They have numerous applications in the field of lasers, fast X-ray, neutron sources, electromagnetic pulse generators, electron beam accelerators, plasma generation and electromagnetic welding of materials. One of the applications of high voltage capacitors as energy storage and discharge devices is in the crimping of cables using the electromagnetic pulse forming technique. This research paper investigates the use of a high-voltage energy storage capacitor with a capacitance of 208 microfarads and rated voltage of 44 kV to perform Electromagnetic Pulse Crimping (EMPC) of lugs for 70 mm2 and 120 mm2 cables. The capacitor operates at 12 kV and is discharged to produce a high current that generates a strong magnetic field of up to 20 Tesla, which is utilized for joining the cable conductor and the lug. The study examines the performance of the capacitor under different operating values such as voltage, capacitance, and discharge time and investigates the effect of these parameters on the termination quality. The paper presents the experimental results of the crimping, which include the contact resistance, weld strength, microstructure, and defects of the welded joints. The results indicate that the capacitor-based electromagnetic pulse crimping produces welds with high strength and minimal defects. Additionally, the paper discusses the future scope of research in this area and the potential applications of such capacitors in other welding techniques. The findings of this research paper provide valuable insights for engineers and researchers working in the field of energy storage, high-voltage applications and welding.

Decoupling electrolyte strategy for a high-voltage Na-ion hybrid capacitor based on NaFeO2 and activated carbon

Sodium iron dioxide (NaFeO2) with high specific capacity, has been widely used as a kind of electrode materials for Na-ion batteries. When NaFeO2 is used as the battery-type electrode for aqueous Na-ion hybrid capacitors, there are a lot of technical challenges to meet, especially the narrow voltage window limited by the thermodynamic decomposition of water. We propose a novel decoupling electrolyte strategy to suppress the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) on the NaFeO2 anode and the activated carbon (AC) cathode respectively, in order to expand the voltage window of the aqueous AC//NaFeO2 Na-ion hybrid capacitor. The alkaline anolyte (2 M NaOH) and the neutral catholyte (1 M Na2SO4) can be decoupled by the cation exchange membrane, which selectively allows the Na+ ions through the membrane to carry the electric currents in the charge/discharge process. The NaFeO2 sample with the stable crystal structure and oxygen vacancy defects, can provide a gravimetric specific capacitance of 101.1 F g−1 at 1 A g−1. Electrochemical kinetic analysis indicates that the capacitor-type behaviour is predominant in the electrochemical energy storage process of the AC//NaFeO2 Na-ion capacitor at the scan rates higher than 40 mV s−1. The AC//NaFeO2 Na-ion capacitor with the stable voltage window of 2 V, can provide an energy density of 12.6 Wh kg−1 at 1 kW kg−1. Due to its inhibiting effects on HER and OER, this decoupling electrolyte strategy holds great potential for constructing high-voltage aqueous energy storage devices.

Tuning of Ionic Liquid–Solvent Electrolytes for High-Voltage Electrochemical Double Layer Capacitors: A Review

Electrochemical double-layer capacitors (EDLCs) possess extremely high-power density and a long cycle lifespan, but they have been long constrained by a low energy density. Since the electrochemical stability of electrolytes is essential to the operating voltage of EDLCs, and thus to their energy density, the tuning of electrolyte components towards a high-voltage window has been a research focus for a long time. Organic electrolytes based on ionic liquids (ILs) are recognized as the most commercially promising owing to their moderate operating voltage and excellent conductivity. Despite impressive progress, the working voltage of IL–solvent electrolytes needs to be improved to meet the growing demand. In this review, the recent progress in the tuning of IL- based organic electrolyte components for higher-voltage EDLCs is comprehensively summarized and the advantages and limitations of these innovative components are outlined. Furthermore, future trends of IL–solvent electrolytes in this field are highlighted.

Improving the electric energy storage performance of multilayer ceramic capacitors by refining grains through a two-step sintering process

Dielectric materials for multilayer ceramic capacitors (MLCCs) have been widely used in the field of pulse power supply due to their high-power density, high-temperature resistance and fatigue resistance. However, the low energy storage density is one of most critical issues hindering their miniaturization and integration development in cutting-edge technologies. In this manuscript, Na0.5Bi0.5TiO3-based MLCCs with improved energy storage properties were fabricated via composition modification and sintering process improvement. The introduction of BiMg0.5Hf0.5O3 weakens the ferroelectricity of 0.94Na0.5Bi0.5TiO3-0.06BaTiO3, while ensures high saturation polarization, delays polarization saturation, and low residual polarization, improving energy storage efficiency. Specifically, we adopted a two-step sintering process, by which the grain size of MLCCs sintered reduces by 60 %, the dielectric breakdown field strength increases by 33 %. The energy storage density reaches 7.8 J cm−3, 77 % higher than the MLCCs fabricated by traditional one-step sintering method. Moreover, the energy storage density changes by less than 10 % in a wide temperature range of 10 ∼ 180 °C. This study confirms that two-step sintering can also be applied to the preparation of Na0.5Bi0.5TiO3-based MLCCs and provides a way to improve the energy storage performance of lead-free MLCCs, and benefits to the application of MLCCs as high voltage capacitors.

Boosting energy storage performance in Na0.5Bi0.5TiO3-based lead-free ceramics modified by a synergistic design

Na0.5Bi0.5TiO3-based relaxor ferroelectric ceramics have attracted widespread attention due to their potential applications in energy storage capacitors for pulse power system. We herein propose a synergistic strategy of introduction of 6s2 lone pair electrons, breaking the long-range ferroelectric order, and band structure engineering for high performance energy storage by introducing Bi(Mg0.5Sn0.5)O3 (BMS) with weak ferroelectric active cations into 0.7Na0.5Bi0.5TiO3-0.3SrTiO3 (BNT-ST) to form BNT-ST-BMS ceramics. The doped ceramics display the excellent dielectric stability versus temperature and frequency. The suitable BMS doping can increase the band gap of the BNT-ST ceramic and effectively avoids early dielectric breakdown and polarization saturation. The BNT-ST-BMS ceramic in the composition of x = 0.08 exhibits an outstanding recoverable energy storage density (Wrec) of 5.99 J/cm3, together with a good efficiency (ƞ) of 76% as well as an excellent dielectric stability versus temperature (Δεr/εr(150°C) ≤ ±15%) and frequency. The findings in this work demonstrate that the BNT-ST-BMS ceramics have exceptional potential as candidate materials for pulse power and high voltage capacitors applications, and provide a path for the development of the other lead-free energy storage materials.

Preparation of Fe, N co-doped oxygen reduction catalysts from sacrificial templates and their application to Zn-air batteries

Fe, N co-doped non-precious metal oxygen reduction catalysts has been prepared with nitrogen-rich precursor material (g-C3N4) as a self-sacrificing template and N source. The utilization of g-C3N4 as a nitrogen-rich material could anchor the Fe source sufficiently on its surface, and form abundant active sites. The g-C3N4-derived carbon has a high specific surface area, which facilitates the more active sites to be exposed, and the suitable pore structure provides a site for the oxygen reduction reaction. The half-wave potential of the catalyst is optimized to 0.85 V by doping with different Fe-content sources, exceeding that of commercial 20% Pt/C catalysts. The prepared catalysts also exhibit excellent electron transfer numbers along with superior methanol resistance. The prepared catalysts is loaded into Zn-Air battery devices and presenting high open-circuit voltage, power density, and specific capacitance performance. This work provides an economical and feasible preparation strategy to explore nitrogen-rich precursor materials as Fe-N-C type efficient oxygen reduction catalysts.

First-principles investigation of the ultra-wide band gap halides perovskite XBeF3 (X = Na, K) with pressure effects

Based on the first-principles and quasi-harmonic Debye model, the structure, electronic, optical and thermodynamic properties of XBeF3 (X = Na, K) crystals at 0 ∼ 30 GPa are systematically investigated for the first time. The lattice constant, elastic constants, and bulk modulus of NaBeF3 and KBeF3 crystals are calculated under zero temperature and zero pressure, which are consistent with the literature values. The studies of electronic properties show that the ultra-wide band gaps of NaBeF3 and KBeF3 crystals at 0 GPa are 7.096 eV and 7.720 eV, respectively. Their band gaps increase with increasing pressure, while their type is indirect without the influence of pressure. Besides, the band structure of XBeF3 crystals at 0 ∼ 30 GPa is calculated by HSE06 functional. The variation of the XBeF3 band gap calculated by the HSE06 function with pressure is consistent with the trend of GGA functional. Additionally, the optical properties including reflectivity, absorption coefficient, complex refractive index, dielectric function and conductivity of NaBeF3 and KBeF3 crystals from 0 to 30 GPa have been comprehensively investigated. Using the quasi-harmonic Debye model, the relative volume, expansion coefficient, Debye temperature and heat capacity effect with pressures and temperatures of NaBeF3 and KBeF3 at 0 ∼ 30 GPa are also researched. The Debye temperatures of NaBeF3 and KBeF3 at 300 K are calculated to be 656.38 K and 602.6 K respectively. At relatively high temperature, the heat capacity at constant volume gradually approaches the Dulong-Petit limit. The results in this paper show that NaBeF3 and KBeF3 crystals may be used in the fields of lens materials and window materials in the deep ultraviolet range. Additionally, the ultra-wide band gap characteristics of NaBeF3 and KBeF3 enable them to be useful as highly insulating layers and high-voltage capacitors.

High recoverable energy density of Na0.5Bi0.5TiO3-based ceramics by multi-scale insulation regulation and relaxor optimization strategy

Dielectric ceramic capacitors (DCCs) are highly desired for advanced electronic and electrical power systems owing to their ultrahigh power densities and fast charge-discharge speed. However, the low recoverable energy density (Wrec) of dielectric ceramic resulting from the low Weibull breakdown strength (Eb) has been a long-standing challenge. Here, we fabricated 0.8Na0.5Bi0.5TiO3–0.2Sm1/3Sr1/2(Mg1/3Nb2/3)O3 (0.8NBT–0.2SSMN) relaxor ferroelectric (RFE) ceramics display a greatly improved Eb of 480 kV/cm and largely enhanced Wrec of 7.3 J/cm3, far outperforming pure NBT ceramic. We demonstrate that the proposed multi-scale insulation regulation strategy via introducing SSMN with optimal content can effectively reduce grain sizes, increase the bandgap, and create a highly insulating second phase, leading to a high Eb. Additionally, the introduction of Sm3+ and Mg2+–Nb5+ dopants on the A/B-sites of the Na0.5Bi0.5TiO3 lattice created disruptions in the long-range-ordered ferroelectric domains, leading to excellent RFE property. The high Eb and excellent RFE property led to the substantial improvement of Wrec. Else, an exceptional thermal stability of Wrec and efficiency (η) are obtained at 25–200 °C (Wrec ∼ (1.77 ± 0.08) J/cm3, η ∼ 82.9% ± 4.3%). This work offers a route for designing high energy storage performance relaxor ferroelectric ceramics for high-voltage dielectric ceramic capacitors.

Design a microwave transmitter using magnetron and two layers waveguides

A magnetron is a power oscillator device used in several radar transmitters for generating the electromagnetic wave (EMW) with a constructive and fixed frequency. In this work, a radar transmitter has been carried out using magnetron operates at 2,458 MHz and two conducting layers waveguides to achieve minimum loss of the signal due to the increased temperature. The magnetron is connected with the high voltage capacitor (1.0 μF) in order to store the alternating current (AC) signal delivered from the high voltage transformer. A waveguide parts have been used as transmission lines in view of connecting the magnetron to the antenna. These parts include two metal layers, the upper layer (outer) is advanced audio coding (AAC) 1350 aluminum conductor and the lower (inner) is copper. The waveguide dimension should be suitable to flow frequency from 2.2 GHz to 3.3 GHz. To measure the operating frequency, a waveguide adapter and a coaxial cable which combined with n-female connector have been connected to magnetron. The wave is delivering to the frequency counter by Bayonet Neill–Concelman (BNC) to n-female connectors. The promising results of the proposed work have been achieved with a maximum power, efficient return loss, acceptable voltage standing wave ratio (VSWR) and low-cost manufacturing.

The effect of chemistry and thermal fluctuations on charge injection barriers at aluminum/polyolefin interfaces

Charge injection at metal/polymer interfaces is a critical process in many technological devices, including high voltage capacitors and cables in which polyolefin materials, such as polyethylene (PE) and polypropylene (PP), are often used as insulation materials. We use simulations based on density-functional theory to study charge injection at aluminum/PE and aluminum/PP interfaces. Specifically, we investigate the influence of incorporating a variety of polar chemical impurities at the PE and PP chain ends on electron and hole injection barriers. Crucially, we account for the effect of thermal disorder by considering ensembles of thousands of interface structures obtained from ab initio molecular dynamics trajectories at 373 K. We show that the mean injection barrier can change by up to 1.1 eV for Al/PE and 0.6 eV for Al/PP, as compared to the pristine case, depending on which chemical impurity is introduced. We also show that the spread of injection barriers from thermal fluctuations also depends strongly on the chemistry of the impurity. The observed trends can be understood with a simple model based on thermal fluctuations of the dipole moment density associated with the chemical impurity at the interface. We further verify this model by considering larger interface models with lower impurity densities. Our results demonstrate that small chemical modifications, which may arise from oxidation, for example, have a significant influence on charge injection barriers in metal/polyolefin interfaces.

Design of A New Electromagnetic Launcher Based on the Magnetic Reluctance Control for the Propulsion of Aircraft-Mounted Microsatellites

Recent developments in electromagnetic launchers have created potential applications in transportation, space, and defense systems. However, the total efficiency of these launchers has yet to be fully realized and optimized. Therefore, this paper introduces a new design idea based on increasing the magnetic flux lines that facilitate high output velocity without adding any excess energy. This design facilitates obtaining a mathematical equation for the launcher inductance which is difficult to analytically represent. This modification raises the launcher efficiency to 36% higher than that of the ordinary launcher at low operating voltage. The proposed design has proven its superiority to traditional launchers, which are limited in their ability to accelerate microsatellites from the ground to low Earth orbit due to altitude and velocity constraints. Therefore, an aircraft is used as a flying launchpad to carry the launcher and bring it to the required height to launch. Meanwhile, it is demonstrated experimentally that magnetic dipoles in the projectile material allow the launcher coil’s magnetic field to accelerate the projectile. This system consists of the launcher coil that must be triggered with a high amplitude current from the high DC voltage capacitor bank. In addition, a microcontroller unit controls all processes, including the capacitor bank charging, triggering, and velocity measurement.

An approach for voltage drop improvement in 22 kV PEA distribution system based on high voltage capacitor placement

The distribution system has been constantly expanded with rising load demand due to population and economic growth. The result is a distribution line facing a voltage drop issue voltage drop, which results from increasing interconnected load and the distance from the substation. To mitigate this issue, this paper proposed an approach to improve the voltage level on the distribution line using a high-voltage capacitor bank. The system under study is modeled after the Provincial Electricity Authority (PEA) 22-kV distribution line. The placement of the high voltage capacitor bank will be based on the 2/3 rule technique. The PSCAD/EMTDC has been used to simulate the characteristics of the case study distribution system and evaluate the performance of the proposed technique in comparison with the PEA voltage regulation standard. The result has demonstrated the ability to use the proposed high voltage capacitor bank placement technique to improve voltage levels in the distribution system.

Analysis and Design Considerations of Input Parallel Output Series-Phase Shifted Full Bridge Converter for a High-Voltage Capacitor Charging Power Supply System

Capacitor charging power supply (CCPS) is used for impulse-power applications such as electromagnetic rail guns, flash lamps, medical sterilization, and rock crushing, among many other application fields. This paper describes the design and analysis of an Input Parallel Output Series-Phase Shifted Full Bridge converter for CCPS. The proposed system has a low output current ripple to improve the lifetime of the high-voltage pulsed capacitor. Design considerations of topology's electrical parameters such as HF transformer's leakage inductor and output inductor for the CCPS application are presented. The intermediate DC-link capacitance is provided as an energy storage element to minimize the disturbances (power variation) on the source for the CCPS application. Analysis and sizing of the capacitance for two different charging methods are analyzed and compared. A controller design procedure for the Active Front End Converter (AFEC) is also included to ensure near-constant power drawn, rejecting the load disturbances. Finally, a complete design procedure for the whole CCPS system is presented. Design and simulation results are presented for a rated system, followed by experimental results from a scaled-down hardware prototype to validate the design.