32 research outputs found

    Capacitor Technologies, Applications and Reliability

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    Various aspects of capacitor technologies and applications are discussed. Major emphasis is placed on: the causes of failures; accelerated testing; screening tests; destructive physical analysis; applications techniques; and improvements in capacitor capabilities

    Polypropeeni-nanokomposiittien soveltaminen metalloiduissa ohutkalvokondensaattoreissa tasajännitteellä

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    At the present, electrical insulation is widely based on synthetic polymers which have largely superseded traditional insulation materials such as paper and ceramics. Polymer composite materials incorporating various amounts of inorganic filler particles are often used to improve the properties and to reduce the cost of the composite. During the last years, a considerable interest has risen towards dielectric polymer nanocomposites which incorporate low mass amounts of inorganic filler particles with one or more dimension in the nanometric scale. Due to the large interfacial area between the nanoparticles and the surrounding polymer matrix, improved material properties may be achieved. Regarding to dielectric properties, improvements in e.g. dielectric strength and permittivity as well as reduction of dielectric losses may be achieved, all of which would be desirable for capacitor applications. In the NANOPOWER –project (Novel Polymer Nanocomposites for Power Capacitors), funded mainly by the Finnish funding agency for technology and innovation (TEKES), the application possibilities of novel dielectric polymer nanocomposites in power capacitors are studied. This thesis was done as a part of the NANOPOWER-project with the focus on metallized film capacitors which incorporate thin electrodes directly evaporated on dielectric polymer film instead of separate sheets of aluminium foil traditionally used in film capacitors. Although metallized film capacitors already enable high energy density and high reliability, demands for even higher energy density, better reliability and longer life-time exist. It may be possible to fulfil these demands by utilizing nanodielectric films and thus, metallized film capacitor technology offers an interesting platform for further research and development. The main objective of this thesis is to study the application possibilities of polypropylene nanocomposites in metallized film capacitors. The subject is approached by performing an extensive literature research on polymers, dielectric polymer nanocomposites and metallized film capacitors. In the empirical part, a measurement system which could be used in the future to conduct various DC tests on single metallized nanocomposite film samples is planned, constructed and tested. The studied electrical properties included dielectric strength, maximum permissible electric field stress and self-healing capability of the film. In addition, the dependency of these properties on external pressure was studied with the measurement setup. /Kir1

    Index to NASA Tech Briefs, 1974

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    The following information was given for 1974: (1) abstracts of reports dealing with new technology derived from the research and development activities of NASA or the U.S. Atomic Energy Commission, arranged by subjects: electronics/electrical, electronics/electrical systems, physical sciences, materials/chemistry, life sciences, mechanics, machines, equipment and tools, fabrication technology, and computer programs, (2) indexes for the above documents: subject, personal author, originating center

    Electrical and thermal modelling of low power metallised polypropylene capacitors

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    Metallised polypropylene (MPP) capacitors, the dominant capacitor type used in a wide range of power and electronic circuit applications, offer high volumetric capacitor density, low cost, excellent frequency characteristics and a unique ability to recover from point failures in the dielectric film. However MPP capacitors have a generic weakness that is not well understood, failure of the self-healing process leading to ongoing catastrophic failure. The work described in this thesis includes the derivation of an improved electrical model of a capacitor and the uncovering of a mechanism for the catastrophic failure mode. Corrosion of the thin metallic field is firmly linked to drastic increases in metal film current densities and generation of hot spots in capacitors. In the work, novel formulae were derived relating capacitor parameters such as equivalent series resistance and equivalent series capacitance to frequency and physical characteristics such as metal film resistivity and physical dimensions of multiple layer capacitors. Modelling using numerical methods and diffusion equation showed that capacitors with double-end connection topology have more uniform voltage and power distribution than single-end connected capacitors. External characteristics of both connection topologies were shown to be virtually identical up to frequencies well above typical self-resonance. The aggregate spatial distribution of power from both layers and the voltage across the dielectric were found to be fundamentally different in the two circuit connection topologies. In this work it was shown that above singularity frequencies defined by distributed capacitance and metal film spreading resistance, equivalent series resistance and capacitance both fall with the square root of frequency Analysis of the inductance of typical MPP capacitors for single-end and double-end connected topologies and for circumferentially connected capacitor metallization showed that the magnitude and effect of distributed inductance in typical MPP power capacitors was insignificant compared to packaging inductance. Thermal and electrical modelling and experimental measurements showed that corrosion effects could readily account for the generic catastrophic failure mode of metallised polypropylene capacitors. Modelling showed that remnant vestiges of metal bridging corrosion gaps between the schooping and the metallic film could also pose serious thermal danger to the affected capacitor. Fusing current modelling and experimental measurement showed that fusing in metallic films typically occurred for current densities of several hundred thousand amperes per square centimetre. The partial disconnection of the metallic layers from the schooping edge by corrosion for example, was shown to result in large increases in dissipation factor and power loss in a capacitor readily explaining how capacitors "go high". Simple additions to the standard capacitor equivalent circuit model were developed to encompassing dielectric loss, shunt conductance effects and the impact of source resistance on capacitor parameters. The work reported in this thesis describes a most likely mechanism for the generic catastrophic failure of MPP capacitors and proposes a simple preventative measure

    Inertial Confinement Fusion quarterly report, October--December 1994. Volume 5, No. 1

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    Core science and technology development plan for indirect-drive ICF ignition. Revision 1

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    Cumulative index to NASA Tech Briefs, 1970-1975

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    Tech briefs of technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Abstracts and indexes of subject, personal author, originating center, and tech brief number for the 1970-1975 tech briefs are presented

    The impact of printed electronics on product design

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    Printed electronics (PE) is a disruptive but growing technology that is beginning to integrate its way into viable applications for product design. However, the potential for future impact of the technology on product design and the designer s role and contribution to this has yet to be established. Interest is increasing in the potential for product designers to explore and exploit this technology. Technologies can be seen as being disruptive from both a business, and an adoption point of view. For a business, changing from one technology to another or incorporating a new technology and its production processes can be difficult if they already have their suppliers established and existing relationships in place. Understanding and adopting a new technology can be challenging for a business and individuals working within an established industry as it can cause many questions to be raised around its performance, and direct comparison with the technology they already have in place. However, there have been many technologies that could be seen as disruptive in the past, as they offered an alternative way of working or method of manufacture, such as Bluetooth, 3D printing, and automation (manufacturing/assembly/finishing), etc., and their success has been dictated by individual s perception and adoption of the technology, with their ability to see the worth and potential in the technology. Cost comparison is also an important aspect for a business to consider when choosing whether to change to a new technology or to remain with their existing technology, as changing can disrupt the manufacturing line assembly of a product, and direct cost comparisons of components themselves, such as the cost of buying silicon components in bulk verses printing the components. The new technology needs to offer something different to a product to be worth implementing it in a product, such as its flexible form or lightweight properties of printed electronics being of benefit to the product over what a silicon electronic component/circuit could offer (restricted to rigid circuit boards), the functionality/performance of the components themselves also need to be considered. Performance, availability and maturity of the technology are some of the essential aspects to consider when incorporating a new technology into a product and these can be evaluated using a Technology Readiness Level (TRL) scale. Interest in the stage of development for a technology lies not only with designers; industry and academia also contribute to knowledge by playing a central role in the process of determining a TRL scale that is universally recognised. However, a TRL separation issue occurs between academia (often the technology only reaching an experimental proof of concept stage, a lower number on the TRL scale indicating that the technology is at an early stage of development) and industry (not considering technology for commercialisation until it reaches a stage where there is a demonstration of pre-production capability validated on economic runs, a much higher number on the TRL scale - indicating that the technology is at a much more advanced stage of development). The aim of this doctoral research was to explore the contribution of PE to product design. The researcher experienced the scientific development of the technology first-hand, and undertook a literature review that covered three main topics: 1) printed electronics (the technology itself), 2) impact (approaches to assessing impact and methods of judging new technology) because together they will identify the state of the art of printed electronics technology, and 3) education - educational theories/methods for designers - studying how designers learn, explore different methods in educating them about new technologies, and start to find appropriate methods for educating them about printed electronics technology. A knowledge framework for PE technology was generated and utilised to produce a taxonomy and TRL scale for PE and confirmed by PE expert interview. Existing case studies in which PE technology had been presented to student designers were investigated through interviews with participants from academia and industry to solicit perception and opinions on approaches for the effective communication of PE knowledge to student designers within an educational environment. The findings were interpreted using thematic analysis and, after comparing the data, three main themes identified: technical constraints, designer s perspective, and what a designer is required to do. The findings from the research were combined to create an educational approach for knowledge transfer aimed specifically at meeting the needs of product designers. This resulted in the need for PE technology to be translated into both a visual and written format to create structure and direct links between the technological elements and their form and function in order to facilitate understanding by designers. Conclusions from the research indicate that the translation of this technology into an appropriate design language will equip designers with accessible fundamental knowledge on PE technology (i.e. electrical components: form, function, and area of the technology), which will allow informed decisions to be made about how PE can be used and to utilise its benefits in the design of products. The capabilities and properties of this technology, when paired with product design practice, has the capacity to transform the designs of future products in terms of form/functionality and prevailing/views towards design approaches with electronics. If exposed to a variety of PE elements ranging across different TRLs, designers have the capacity to bridge the TRL separation issue (the gap between academia and industry) through their ability to create design solutions for an end user and provide a commercial application for the technology

    Thermally reversible thermoset materials based on the chemical modification of alternating aliphatic polyketones

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    This thesis focused on the synthesis and characterization of different kinds of reversible thermosets and thermoset nanocomposite materials by using alternating aliphatic polyketone (PK) as raw material. Fundamental knowledge was generated regarding the molecular design of new polymers via chemical modification of PK with aliphatic and aromatic amine compounds. The resulting thermally reversible thermoset systems were investigated to outline the benefits for the synergistic cooperation between reversible covalent and supramolecular interactions. Moreover, improvements regarding the mechanical performance, reversibility, recyclability, self-healing and electrical conductivity of the thermosets were investigated by incorporating rubber particles and nanofillers into the thermoset matrices. In first instance we investigated the chemical modification of alternating aliphatic polyketones with aliphatic and aromatic amine compounds using the Paal-Knorr reaction to obtain thermally reversible polymers with relatively high glass transition temperatures. These materials display the desired mechanical properties with the exception of toughness. This could be achieved by preparing a reversible and toughened thermoset system based on the covalent incorporation of furan-functionalized ethylene-propylene rubber into a thermoset furan-functionalized polyketone. In order to confer also electrical properties to these materials, conductive nanocomposites containing well-distributed, exfoliated and undamaged MWCNTs were prepared. These new materials, designed by mixing furan-functionalized polyketone cross-linked with aromatic bis-maleimide and MWCNTs via Diels-Alder (DA) reversible cycloaddition, display electrically-induced self-healing properties

    NASA Tech Briefs, January 1987

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    Topics include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Fabrication Technology; Machinery; Mathematics and Information Sciences; Life Sciences
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