Showing papers on "Film capacitor published in 2023"

Electrolytic capacitor: Properties and operation

Abstract: Due to their high specific volumetric capacitance, electrolytic capacitors are used in many fields of power electronics, mainly for filtering and energy storage functions. Their characteristics change strongly with frequency, temperature and aging time. Electrolytic capacitors are among the components whose lifetime has the greatest influence on the reliability of electrical systems. Over the past three decades, many efforts in academic research have been devoted to improving reliability capacitor. Industrial applications require more reliable power electronic products. It is in this context that the different electrolytic capacitors and their characteristics are discussed. The aging process of aluminum electrolytic capacitors is explained. Finally, this paper reviews existing methods of failure prognosis of electrolytic capacitors.

Heterovalent-doping-enabled atom-displacement fluctuation leads to ultrahigh energy-storage density in AgNbO3-based multilayer capacitors

Abstract: Dielectric capacitors with high energy storage performance are highly desired for next-generation advanced high/pulsed power capacitors that demand miniaturization and integration. However, the poor energy-storage density that results from the low breakdown strength, has been the major challenge for practical applications of dielectric capacitors. Herein, we propose a heterovalent-doping-enabled atom-displacement fluctuation strategy for the design of low-atom-displacements regions in the antiferroelectric matrix to achieve the increase in breakdown strength and enhancement of the energy-storage density for AgNbO3-based multilayer capacitors. An ultrahigh breakdown strength ~1450 kV·cm-1 is realized in the Sm0.05Ag0.85Nb0.7Ta0.3O3 multilayer capacitors, especially with an ultrahigh Urec ~14 J·cm-3, excellent η ~ 85% and PD,max ~ 102.84 MW·cm-3, manifesting a breakthrough in the comprehensive energy storage performance for lead-free antiferroelectric capacitors. This work offers a good paradigm for improving the energy storage properties of antiferroelectric multilayer capacitors to meet the demanding requirements of advanced energy storage applications.

Dual Crosslinked PMMA/BaTiO3 Polymer Nanocomposite Dielectrics for Flexible Film Capacitors

Abstract: The BaTiO3(BT) nanoparticles were surface modified by polyethylene glycol methacrylate phosphate, and the C=C groups on the phosphate were used as the reaction sites with methyl methacrylate (MMA) monomers for...

An Ultra‐Thin, Ultra‐High Capacitance Density Tantalum Capacitor for 3D Packaging

Abstract: Although embedded capacitors have been applied and researched for many years, their large‐scale application still faces challenges such as low capacitance density, high thickness, high cost, and incompatibility with integrated processes. In this work, a breakthrough has been made in the fabrication of ultra‐thin tantalum (Ta) capacitors with ultra‐high capacitance density that can be used for 3D packaging. The key to these excellent performances is the application of Ta foil with nano‐porous structure to the anode of the capacitor. The Ta foil with high specific surface area (SSA) is successfully prepared by direct current pulse etching. At a current density of 15 mA cm−2, a pulse frequency of 50 Hz, and a duty cycle of 30%, the SSA of Ta foil is increased by 76 times after etching in an electrolyte with 0.01 v% TOA for 30 min. Based on this, Ta capacitors with a form factor of less than 40 µm, showing a capacitance density of 750 nF mm−2 and a leakage current of less than 2.1 × 10−7 A at 8 V is successfully fabricated. To the best of the authors’ knowledge, this is the highest capacitance density reported to date for the mentioned form factors.

Layer-by-layer printable nano-scale polypropylene for precise control of nanocomposite capacitor dielectric morphologies in metallised film capacitors

Abstract: • A novel technique to fabricate capacitors with nano-scale layer-by-layer printing • Polypropylene gel inks were used to successively print layers as thin as 200 nm • Layer thickness is easily controllable, and the capacitance is highly predictable • Incorporation of BaTiO 3 nanoparticles was demonstrated in a structured dielectric • Presents pathway to the commercial printing of structured nanocomposite capacitors Nanocomposite dielectrics are an increasingly important area of innovation in capacitor research as an avenue to improve capacitive energy density, electrical breakdown strength, and temperature stability of devices. In such devices, morphology control is critical in order to optimise electrical field distribution in the device and to prevent the clustering of nanoparticles lowering breakdown voltages. However, this is difficult to achieve with large-scale fabrication techniques, such as melt extrusion and stretching, as melt processing can induce clustering and offers few possibilities for fine structure control of length scales below 1 µm. Layer-by-layer fabrication offers a potential bottom-up alternative whereby dielectrics are printed by successive depositions of ultra-thin layers of a room-temperature-stable polymer ink. This would allow fine thickness and morphology control and could easily be adapted to industrial-scale printing techniques, like roll-to-roll slot-die coating. This study explores this technique by developing two polypropylene-based inks in industry-friendly solvents that are then used to fabricate capacitor devices. A gel ink was able to be used to deposit ultrathin (sub-200 nm) layers of mostly amorphous polypropylene with high reproducibility. Capacitors based on these polypropylene layers perform commensurate with commercial devices, exhibiting excellent self-clearing and breakdown performance. Successive depositions of the ink were also demonstrated, allowing the fabrication of devices with finely tuned thicknesses and capacitances, as well as nanocomposite capacitors. This demonstrates the viability of layer-by-layer dielectric printing at large scale and paves the way for commercial ultra-thin conformable polypropylene capacitors, multi-component sandwich nanocomposite capacitors, and multilayer polypropylene capacitors, as well as brand new possibilities in dielectrics research.

All-Organic PTFE Coated PVDF Composite Film Exhibiting Low Conduction Loss and High Breakdown Strength for Energy Storage Applications

Abstract: Plastic film capacitors are widely used in pulse and energy storage applications because of their high breakdown strength, high power density, long lifetime, and excellent self-healing properties. Nowadays, the energy storage density of commercial biaxially oriented polypropylene (BOPP) is limited by its low dielectric constant (~2.2). Poly(vinylidene fluoride) (PVDF) exhibits a relatively high dielectric constant and breakdown strength, making it a candidate material for electrostatic capacitors. However, PVDF presents significant losses, generating a lot of waste heat. In this paper, under the guidance of the leakage mechanism, a high-insulation polytetrafluoroethylene (PTFE) coating is sprayed on the surface of a PVDF film. The potential barrier at the electrode–dielectric interface is raised by simply spraying PTFE and reducing the leakage current, and then the energy storage density is increased. After introducing the PTFE insulation coating, the high-field leakage current in the PVDF film shows an order of magnitude reduction. Moreover, the composite film presents a 30.8% improvement in breakdown strength, and a 70% enhancement in energy storage density is simultaneously achieved. The all-organic structure design provides a new idea for the application of PVDF in electrostatic capacitors.

Evolution Characteristics of DC Breakdown for Biaxially oriented Polypropylene Films

Abstract: Biaxially oriented polypropylene (BOPP) films are the preferred storage dielectric for dry-type film capacitors due to excellent dielectric properties. However, the evolution characteristics of DC Breakdown of BOPP film in air remain unclear. This study focuses on the influence of curvature, contact area and material of electrode on the DC breakdown in BOPP films. The on-line/off-line measurements of surface potential and characterizations of trap distribution are achieved. And the simulations of surface charge, electric field and energy injection are accomplished. The breakdown path and degradation traces in BOPP films are also analyzed. The experimental results show that the effective insulation distance is the key to determine the actual performance of the film, affected by the trap distribution and density. This paper has a reference for the optimization of insulation structure for dry-type film capacitors in the field of high-voltage direct current (HVDC).

Effects of Post-γ Irradiation on Voltage Maintaining Performance of High Energy Density Capacitors

Abstract: With the rapid development of the aerospace industry and nuclear technology, metallized film capacitor (MFC), as energy storage unit for pulsed power sources, begin to operate in various high-energy radiation environments. In order to ensure the working reliability of MFC, it is of great significance to study its voltage maintaining performance (VMP) and aging law after irradiation. In this paper, metallized polypropylene (PP) film capacitors (MPPFC) are used as the research object to analyze the irradiation reaction mechanism of polypropylene, and the effect of irradiation dose on the capacitance, dielectric loss and VMP of MPPFC under aerobic conditions is studied. The results show that there is a critical value of 100 kGy for the effect of irradiation dose on MPPFC. When the irradiation dose is less than 100 kGy, the capacitance and dielectric loss of MPPFC remain almost unchanged, and the voltage drop increases with the dose as a power function. When the irradiation dose reached 500 kGy, the macromolecules in PP film were completely cleaved, and the voltage drop of the MPPFC increased from 1.62% to 2.96% without irradiation within 10 s. In order to ensure the energy output efficiency of the power supply, the irradiation dose of MPPFC should be controlled not to exceed 5 kGy. At this time, the voltage drop of the MPPFC within 10 s is 2.30%, and the output efficiency is 95.41%. This paper serves to provide a certain basis for the application of MPPFC in irradiation environment.

Dielectric Property Optimization of Polypropylene Based All Organic Capacitor Film under High Magnetic Field

Abstract: Some kinds of dielectric capacitors are likely to operate in magnetic fields. Therefore, it is in need of investigating the influence of magnetic field on the basic parameters of capacitor films. The performance of polypropylene (PP) decreases in a magnetic field, so it is necessary to find methods for improving performance With the increasing magnetic flux density from 0 to 12 T, the leakage conductivity of the pure PP increases to 340%, the breakdown strength declines to 83%, and the dielectric constant @ 1 kHz decreases by 0.1. The magnetic field influences the dielectric properties by changing charge behaviors. After doping 0.05 wt% 3-aminobenzoic acid, the performance of the composite films under magnetic field is significantly improved. At 12 T, the conductivity of the modified films decreases by 50%, the breakdown strength increases by 11%, and the dielectric constant is also enlarged.

Design of Increasing Dielectric Constant of Metallized Film Capacitor to Reduce Its Volume in MMC

Abstract: Metallized polypropylene film capacitors (MPPFC) are usually used in modular multilevel converters (MMC) in HVDC transmission due to their good self-healing, strong current capacity, high energy density, and high reliability. However, due to the low dielectric constant of polypropylene film material (only 2.2), the capacitance value of polypropylene film capacitors is constrained, so the volume, weight, and cost of metallized film capacitors occupy a large part of the MMC system. For this reason, this paper considers reducing the volume of metallized film capacitors by increasing the dielectric constant of polypropylene film and analyzes a feasible range for the increased dielectric constant. Through the Comsol finite element simulation calculation, it is found that the volume can be reduced by 26.7%. Although the ESR of the capacitor increases, the capacitor temperature drops by 3.5 ℃ when the capacitor temperature is close to the steady-state due to the reduced diameter of the capacitor and better heat dissipation. This result can provide a reference for the optimal design of film capacitors in MMC applications.

Study on High Energy Storage Dielectric Capacitor

Abstract: With the continuous consumption of energy, more and more energy storage devices have attracted the attention of researchers. Among them, dielectric capacitors have the advantages of high power density, fast charging and discharging efficiency, long cycle life and good reliability, which can be widely used in new energy, electronic equipment and other fields. However, the energy density of dielectric capacitors is not high, so it is important to study dielectric capacitors with high energy storage density. The performance of dielectric capacitors is related to dielectric materials. Therefore, dielectric materials with excellent dielectric properties have been widely studied. In this paper, the research on high energy storage dielectric capacitors in recent years is reviewed, and the performance of these materials is analyzed.

Composite design of two-dimensional inorganic nanosheets for flexible energy storage capacitors

Abstract: We present a new approach for designing flexible energy storage capacitors using two-dimensional (2D) inorganic nanosheets. 2D dielectric Ca2Nb3O10 nanosheet and ferroelectric poly(vinylidene fluoride) (PVDF) were selected as model material systems. Langmuir–Blodgett deposition was utilized for layer-by-layer engineering of (Ca2Nb3O10/PVDF) nanocomposite films on an indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrate. Such a new composite design realized the simultaneous improvement of energy density (∼7 J cm−3) and efficiency (∼78 %) even in the ultrathin form (∼20 nm) on the ITO-coated PET substrate. Nanosheet-based flexible capacitors also maintained a stable performance even after 104 times bending cycles. These results indicate that our nanosheet approach is of technological importance for exploring new flexible dielectric capacitors.

Cold-sprayed aluminum capacitors on leadframes for 3D power packaging

Abstract: Size and weight have always been key concerns for power supplies. Today’s approaches of manufacturing integrated power electronics building block modules with the assembly of pre-packaged devices and low-volumetric density capacitors and inductors create major fundamental system integration limitations in reaching high power densities and efficiencies to meet the target SWaP-C (size, weight and performance with low cost). Cold-sprayed aluminum capacitors on leadframe metal foils are demonstrated for the first time for applications in 3D power package integration. This additive manufacturing process allows low-temperature processing of pre-patterned aluminum electrodes on metal lead-frames, insulated metal substrates or even heat-spreaders and cold-plates. Process optimization of cold-spray technologies requires careful study of particle velocity, deposition atmosphere and particle morphology design. Initial process design led to ~22X enhancement in surface area compared to planar capacitors. With further process design and optimization, this approach can extend to above 100X enhancement. Cold-sprayed capacitors are projected to eliminate several process integration and reliability issues that are associated with traditional discrete surface-assembled capacitors.

Packaged Flexible Planar Copper Foil Fractional-Order ‘0.61–0.87’ Capacitors: Series/Parallel Combinations

Abstract: The fabrication of packaged, flexible, and planar fractional-order capacitors (FOCs) using copper foil electrodes and thin films of PVDF polymer nanocomposite dielectric is presented in this paper. An extensive comparison of FOC properties is made by using two separate conductive fillers, i.e., graphene nanosheets (GNS) and reduced graphene oxide (rGO). Similar fractional-order is observed at a particular filler loading in both types of FOCs; however, differences in the pseudocapacitance values and width of the constant phase (CP) zone exists. Fractional order α (alpha) is reported to vary in the range 0.61–0.87 in impedance measurements made on individual samples of rGO/PVDF and GNS/PVDF FOCs and series/parallel connections of two identical-order FOCs. For series/parallel connection of arbitrary-order FOCs, α varies from 0.61 to 0.83. Phase angle variation ranges from − 56.2° to − 79° for standalone pure FOC samples, whereas, for series/parallel connection of identical or arbitrary order FOCs, phase ranges from − 54.94° to − 77.75°. Phase ripple varies between ± 1.1° and ± 4.8°, and a maximum CP zone of 4 decades (1 kHz to 10 MHz) for the fabricated samples is reported. Industrial manufacturing of large-value capacitors demands materials to be flexible to enable rolling of large-area electrodes into a miniature device. FOCs fabricated in this work match the design specifications of commercial standard thin film capacitors and show high-value capacitances as well as flexibility of materials and structure.

Electrochemical power sources: Capacitors

Abstract: This overview chapter compares electrostatic capacitors, electrolytic capacitors, and electrochemical capacitors. Conventional electrostatic capacitors contain a dielectric whereas electrochemical capacitors have a liquid electrolyte and do not operate simply in an “electrostatic” way. Principle, function and design of classical capacitors using polymer dielectrics, solid-state electrolytes, metal-films and ceramics, and so-called supercapacitors are outlined.

Internal State Estimation Method of Film Capacitors used in Three-Phase DC to AC Converters and Comparisons with Electrolytic Capacitors

Abstract: Metalized polymer-film capacitors have acquired a distinctive position among a variety of capacitor types due to their self-healing ability. Therefore, these devices are appropriate for critical power applications that demand reliability and durability. Nevertheless, as converters are increasingly being used for transmissions in networks, it is essential to improve stability to ensure the safety of system operations. Therefore, it is necessary to have a monitoring process that enables predictive maintenance to evaluate the health status and ensure the stability of electrical systems. However, the research in this field concentrates on electrolytic capacitors; and the characteristics of electrolytic and film capacitors differ. Hence, the need for further investigation into film capacitors is evident. This research proposes a condition monitoring approach that employs frequency signal analysis to assess the health status of capacitors in a three-phase AC-DC converter. The capacitor current is subjected to discrete wavelet transform and normalized by various indices, which serve as the input for learning algorithms. In addition, for comparison, capacitor voltage, output current, and output voltage are investigated using the discrete wavelet transform and fast Fourier transform. In this study, various indexes including root-mean-squared value, variance, average, and median, are utilized as inputs for artificial intelligent models to investigate factors affecting film capacitors. Eight learning algorithms are implemented to monitor the health status of film capacitors. The results show that utilizing the discrete wavelet transform combined with indexes for capacitor current yields a high accuracy of approximately 99.85%. These findings offer valuable insights into monitoring film capacitors using advanced techniques, and are anticipated to be informative for practical applications of film capacitor monitoring.

Research on Temperature Rise Characteristics of Film Capacitors During Charge and Discharge

Abstract: Polyvinylidene fluoride based materials have good dielectric properties and withstand voltage. The film capacitors made of polyvinylidene fluoride based materials have high energy storage density. It is of guiding significance to study the charging and pulse discharge temperature characteristics of polyvinylidene fluoride film capacitors for their application in the field of pulse power. In this paper, the influence of capacitor structure and heat generation mechanism on temperature rise is studied. Through capacitor charging and pulse and slow discharge tests and temperature measurement experiments combined with simulation analysis, it is found that the central temperature of the capacitor is the highest, the heat generated by the capacitor during discharge only accounts for a part of the charging and discharging process, and the heat generated during charging contributes the most to the temperature rise. Polyvinylidene fluoride capacitors generate more heat than polypropylene film capacitors, and the temperature rise can be further reduced by reducing the equivalent series resistance through material research or improved process.

Promising polymer dielectrics for creating new generation high voltage capacitors

Abstract: The results of the analysis of literature on polymer films for high-voltage pulse capacitors are presented. To design a capacitor with high specific characteristics and to expand capacitor nomenclature, new materials with predetermined properties based on modern technologies must be created.

Diagnostics of Pre-Fault Conditions Using The Impact of Electrolytic Capacitor Aging on Power Supply Dynamics

Abstract: The modern power electronics is indistinctive to questions on a reliability. The electrolytic capacitors despites their excessive properties in terms of affordability, power density to volume and weight, remains an element that can cause device fail. The paper is dedicated to a solution to diagnostics, monitoring and prediction of remain lifetime of electrolytic capacitors. The main idea is that ESR (Equivalent Series Resistance) of capacitor grows while capacitor is getting to the end of the lifespan. ESR in combination with the capacitance is forming a Left Half-Plane zero and thus change in listed parameters is affecting overall transfer function. This paper uses buck converter as an example. The data for capacitors models is obtained from real accelerated aging experimental results. Modelling at different lifespan periods shows change in response to disturbance. The paper proposes to use band-pass filter to get signal that is easy to process further. The paper also has a little discussion on potential uses of the signal and their advantages and disadvantages.

The role of electron extinction in the breakdown strength of nanocomposite capacitors

Abstract: A first-principles theory of electrical breakdown in nanocomposite capacitors, which considers the trapping and scattering (extinction) of electrons originating from the presence of nanoinclusions in the polymer matrix, is developed. The breakdown strength relative to its value for a neat polymer is expressed in terms of two parameters, one of which is determined by the volume density of the nanoinclusion polarizability and the other one is proportional to the electron trap surface density around an inclusion, while the effect of electron scattering is shown to be insignificant. A comparison of the theoretical predictions with diverse experimental data demonstrates an excellent agreement and suggests an effective tool for the design of nanocomposite capacitors.

Ultrahigh Capacitive Energy Density in Stratified 2D Nanofillers based Polymer Dielectric Films

Abstract: Dielectric capacitors are critical components in electronics and energy storage devices. The polymer based dielectric capacitors have advantages of flexibility, fast charge and discharge, low loss, and graceful failure. Elevating the use of polymeric dielectric capacitors for advanced energy applications such as electric vehicles (EVs) however requires significant enhancement of their energy densities. Here, we report a polymer thin film heterostructure based capacitor of poly(vinylidene fluoride)/poly(methyl methacrylate) with stratified 2D nanofillers (Mica or h-BN nanosheets) (PVDF/PMMA-2D fillers/PVDF), that shows enhanced permittivity, high dielectric strength and an ultra-high energy density of 75 J/cm3 with efficiency over 79%. Density functional theory calculations verify the observed permittivity enhancement. This approach of using oriented 2D nanofillers based polymer heterostructure composites is expected to be universal for designing high energy density thin film polymeric dielectric capacitors for myriads of applications.

Theoretical connection from the dielectric constant of films to the capacitance of capacitors under high temperature

Abstract: In the process of coping with energy and environmental protection issues, technologies such as energy materials, energy devices, and energy systems have made great progress. With excellent performance, film capacitors play an increasingly important role in energy-related fields. With the increase of application scenarios and the continuous development of film material technology, it is urgent to establish a better theoretical connection from films to capacitors. First, the main components of the capacitor including the film and the positional relationships among them are given. Then, from the two perspectives of indirect calculation according to the volume and the direct calculation according to the winding process, the equation between the dielectric constant of films and the corresponding capacitance of capacitors is established. Further, the measurement data and error analysis results of the built test platform prove the accuracy and great potential of the proposed calculation methods. In addition, error sources, including film thickness uniformity, are listed. Finally, the challenges faced by the proposed calculation methods and the paths that can be referenced for future research are summarised and discussed.