Dissertations / Theses on the topic 'High frequency currents'
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Kim, Kyung Cheol. "Calibration and validation of high frequency radar for ocean surface current mapping." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FKim.pdf.
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Skutt, Glenn R. "High-Frequency Dimensional Effects in Ferrite-Core Magnetic Devices." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/30596.
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MnZn ferrites are widely used in power electronics applications where the switching frequency is in the range of several tens of kilohertz to a megahertz. In this range of frequencies the combination of relatively high permeability and relatively low conductivity found in MnZn ferrite helps to minimize the size of magnetic devices while maintaining high efficiency. The continuing improvement in semiconductor switches and circuit topologies has led to use of high-frequency switching circuits at ever increasing power levels. The magnetic devices for these high-power, high-frequency circuits require magnetic CORES that are significantly larger than standard ferrite-core devices used at lower power levels. Often such large ferrite cores must be custom designed, and at present this custom design is based on available material information without regard for the physical size of the structure.
This thesis examines the issues encountered in the use of larger MnZn ferrite cores for high-frequency, high-power applications. The two main issues of concern are the increased power dissipation due to induced currents in the structure and the change in inductance that results as the flux within the core is redistributed at higher frequencies. In order to model these problems using either numerical or analytical methods requires a reliable and complete set of material information. A significant portion of this work is devoted to methods for acquiring such material information since such information is not generally available from the manufacturers. Once the material constants required for the analysis are determined, they are used in both closed-form and numerical model to illustrate that large ferrite cores suffer significant increases in loss and significant decreases in inductance for frequencies as low as several hundred kilohertz. The separate impacts of the electrical and magnetic losses in the core are illustrated through the use of linear finite element analyses of several example core structures. The device impedances calculated using the FEA tools show fair agreement with measurement. An analysis of gapped structures and segmented cross-sections shows that these design options can reduce the severity of the dimensional problems for some designs.Ph. D.
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Simmons, N. J. "The use of high frequency currents for the electrical stunning of pigs." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336227.
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Toh, Kwang Yong Daniel. "Evaluation of surface current mapping performance by SeaSonde High Frequency radar through simulations." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FToh.pdf.
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Wong, Fu Keung, and n/a. "High Frequency Transformer for Switching Mode Power Supplies." Griffith University. School of Microelectronic Engineering, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050211.110915.
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A power supply is an essential part of all electronic devices. A switching mode power supply is a light weight power solution for most modern electronic equipment. The high frequency transformer is the backbone of modern switched mode power supplies. The skin effect and proximity effects are major problems in high frequency transformer design, because of induced eddy currents. These effects can result in transformers being destroyed and losing their power transferring function at high frequencies. Therefore, eddy currents are unwanted currents in high frequency transformers. Leakage inductance and the unbalanced magnetic flux distribution are two further obstacles for the development of high frequency transformers. Winding structures of power transformers are also a critical part of transformer design and manufacture, especially for high frequency applications. A new planar transformer with a helical winding structure has been designed and can maintain the advantages of existing planar transformers and significantly reduce the eddy currents in the windings. The maximum eddy current density can be reduced to 27% of the density of the planar transformer with meander type winding structure and 33% of the density of the transformer with circular spiral winding structure at an operating frequency of 1MHz. The voltage ratio of the transformer with helical winding structure is effectively improved to 150% of the voltage ratio of the planar transformer with circular spiral coils. With the evenly distributed magnetic flux around the winding, the planar transformer with helical winding structure is excellent for high frequency switching mode power supplies in the 21st Century.
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Sefi, Sandy. "Computational electromagnetics : software development and high frequency modeling of surface currents on perfect conductors." Doctoral thesis, KTH, Numerisk Analys och Datalogi, NADA, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-590.
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In high frequency computational electromagnetics, rigorous numerical methods be come unrealistic tools due to computational demand increasing with the frequency. Instead approximations to the solutions of the Maxwell equations can be employed to evaluate th electromagnetic fields. In this thesis, we present the implementations of three high frequency approximat methods. The first two, namely the Geometrical Theory of Diffraction (GTD) and th Physical Optics (PO), are commonly used approximations. The third is a new invention that will be referred to as the Surface Current Extraction-Extrapolation (SCEE). Specifically, the GTD solver is a flexible and modular software package which use Non-Uniform Rational B-spline (NURBS) surfaces to model complex geometries. The PO solver is based on a triangular description of the surfaces and includes fas shadowing by ray tracing as well as contribution from edges to the scattered fields. GTD ray tracing was combined with the PO solver by a well thought-out software architecture Both implementations are now part of the GEMS software suite, the General ElectroMag netic Solvers, which incorporates state-of-the-art numerical methods. During validations both GTD and PO techniques turned out not to be accurate enough to meet the indus trial standards, thus creating the need for a new fast approximate method providing bette control of the approximations. In the SCEE approach, we construct high frequency approximate surface currents ex trapolated from rigourous Method of Moments (MoM) models at lower frequency. T do so, the low frequency currents are projected onto special basis vectors defined on th surface relative to the direction of the incident magnetic field. In such configuration, w observe that each component displays systematic spatial patterns evolving over frequenc in close correlation with the incident magnetic field, thus allowing us to formulate a fre quency model for each component. This new approach is fast, provides good control of th error and represents a platform for future development of high frequency approximations. As an application, we have used these tools to analyse the radar detectability of a new marine distress signaling device. The device, called "Rescue-Wing", works as an inflatabl radar reflector designed to provide a strong radar echo useful for detection and positionin during rescue operations of persons missing at sea.QC 20101004
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Sefi, Sandy. "Computational electromagnetics : software development and high frequency modelling of surface currents on perfect conductors /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-590.
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García-Moreno, Aracelys. "Construction of injectable wireless microstimulators based on rectification of volume conducted high frequency currents." Doctoral thesis, Universitat Pompeu Fabra, 2022. http://hdl.handle.net/10803/673986.
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Functional neuromuscular stimulation (FNS) refers to the delivery of
electrical stimuli to nerves or muscles to enhance, modify or restore motor
functions. Despite their invasiveness, implantable systems for FNS offer key
advantages over surface and percutaneous systems in terms of selectivity and
safety. Most implantable FNS systems consist of a relatively bulky
subcutaneous pulse genera-tor connected through leads to electrodes at the
target stimulation sites. In the case of FNS systems for restoring motor
functions in patients with paralysis, the leads are long and the electrodes are
distributed over large and mobile body parts, thus making them highly invasive
and prone to failure. Miniaturized wireless implantable stimulators represent a
safer and more reliable alternative. By integrating all the components in the
same device, long leads are avoided and minimally invasive implantation
procedures are enabled. In this thesis, architectures and construction methods
were devised to implement thin (diameter < 1 mm), flexible and biocompatible
wireless microstimulators whose operation principle is based in rectifying high
frequency currents delivered to tissues by volume conduction. These threadlike
devices, which were successfully in vivo assayed, are intended to be deployed
by injection forming a dense network of intramuscular addressable stimulators
for the development of motor neuroprostheses. They were implemented
adapting techniques well accepted in industry to facilitate early clinical
adoption. A noteworthy feature of their construction is the inclusion of a
biterminal hermetic metallic capsule housing the sophisticated microelectronic
circuitry required for their operation. The applicability of the same technology
and operation methods to an alternative clinical field was also explored in the
scope of this thesis through the development and in vivo assay proof-of-concept
novel leadless microstimulators. Furthermore, this thesis has contributed to the
development of refined computer models to characterize the stimulation
method previously described.La estimulación neuromuscular funcional (FNS) se refiere a la aplicación de estímulos eléctricos a nervios o músculos para mejorar, modificar o restaurar fun-ciones motoras. A pesar de ser invasivos, los sistemas implantables para FNS ofrecen ventajas en selectividad y seguridad sobre los superficiales y percutáneos. La mayoría de los sistemas FNS implantables consisten en un generador de pulsos subcutáneo relativamente voluminoso conectado por cables a electrodos en los puntos de estimulación. En el caso de sistemas FNS para restaurar funciones motoras en pacientes con parálisis, los cables son largos y los electrodos están distribuidos por partes del cuerpo grandes y móviles, haciéndolos altamente invasivos y propensos a fallar. Estimuladores implantables inalámbricos miniaturizados representan una alternativa más segura y confiable. Al integrar todos los componentes en el mismo dispositivo, se evitan los cables largos y se habilitan procedimientos de implantación mínimamente invasivos. En esta tesis se han diseñado arquitecturas y métodos de construcción para implementar microestimuladores inalámbricos delgados (diámetro < 1 mm), flexibles y biocompatibles basados en la rectificación de corrientes de alta frecuencia aplicadas a los tejidos por conducción volumétrica. Estos dispositivos filiformes, ensayados con éxito in vivo, serían implantados mediante inyección formando una densa red de estimuladores direccionables intramusculares para desarrollar neuroprótesis motoras. Éstos se han implementado adaptando técnicas bien aceptadas en la industria para facilitar la adopción clínica temprana. Una característica notable de su construcción es la inclusión de una cápsula metálica hermética biterminal que aloja los sofisticados circuitos microelectrónicos necesarios para su funcionamiento. La aplicabilidad de la misma tecnología y métodos de operación a un campo clínico alternativo también se ha explorado en esta tesis mediante el desarrollo y prueba de concepto in vivo de novedosos microestimuladores sin cables. Además, esta tesis ha contribuido al desarrollo de modelos informáticos refinados para caracterizar el método de estimulación descrito anteriormente.
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Kim, Sung Yong. "Coastal ocean studies in southern San Diego using high-frequency radar derived surface currents." Diss., [La Jolla, Calif.] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3344796.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed April 16, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 179-188).
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Enriquez, Andres E. "An investigation of surface current patterns related to upwelling in Monterey Bay, using high frequency radar." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1595.
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Approved for public release; distribution is unlimitedHigh Frequency (HF) radar backscatter instruments are under development and testing in the marine science and defense science communities for their abilities to remotely sense surface parameters in the coastal ocean over large areas. In the Navy context, the systems provide real-time mapping of ocean surface currents and waves critical to characterization and forecasting of the battlespace environment. In this study, HF radar, aircraft and satellite information were used to investigate and describe surface current in Monterey Bay, California, for a period of ten months, from June 01st, 2003 to March 31st, 2004. A network of five CODAR-type HF radar instruments measured hourly surface currents over the bay. The measurements were averaged over one-hour intervals and total surface velocities were mapped on a grid in the Monterey Bay. From the M1 Buoy located in the middle of the bay, an uninterrupted time series of wind intensity and direction was obtained for the whole period. Major upwelling events were observed during the period of June 14 to June 27, July 4 to July 19, August 8 to August 18 and other upwelling events were observed until late October. These periods of upwelling favorable winds are common during summer with durations of 10 to 20 days. Often they are interrupted by periods of relaxation state of just a few days as the winds veer to the northwest or northeast. Cyclonic circulation cells are developed on shore during upwelling conditions and an anticyclonic circulation in the middle of the bay is observed when the wind shifts to the southwest producing a strong flow out of the bay close to the coastline off Point Piǫs. Downwelling conditions are much common less than upwelling, with occurrences during winter and early fall storms with events lasting between two to five days. When the wind blows to the northeast with an intensity of 4 m/s or more for more than 12 hours, a well developed anticyclonic gyre forms in the middle of the bay. This is associated with a strong current, 35 to 40 cm/s, which flushes out in the southern part of the bay close to the coast off Point Piǫs. This flow reverses when the winds veer to the southwest and enter into the Bay with less intensity.
First Lieutenant, Chilean Navy
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Enriquez, Andres. "An investigation of surface current patterns related to upwelling in Monterey Bay, using high frequency radar /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FEnriquez.pdf.
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Hickey, Kenneth J. "Ocean surface current estimation using a long-range, single-station, high-frequency ground wave radar." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0008/MQ42394.pdf.
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Wojda, Rafal P. "Winding Resistance and Winding Power Loss of High-Frequency Power Inductors." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1345746593.
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Fox, Alan David. "The use of high-frequency radar to study surface currents associated with a shelf sea frontal system." Thesis, Bangor University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316344.
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Wang, Weili. "Remote sensing of swell and currents in coastal zone by HF radar." Thesis, Toulon, 2015. http://www.theses.fr/2015TOUL0011/document.
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L’environnement maritime du littoral implique de nombreux processus complexes, mais le manque de données en haute résolution couvrant une large zone sur une longue période est souvent l’obstacle principal à des recherches plus approfondies. Le radar haute-fréquence (HF) est un moyen de faire de la télédétection afin d’obtenir pratiquement en temps réel de l’information sur la surface de la mer et sur une large zone. Ainsi l’étude de l’inversion des paramètres marins à partir de données issues de radars HF est réellement porteuse de sens. Cette thèse fait l’usage d’un jeu de données collectées durant 13 mois par deux réseaux de radar HF à commande de phase pour étudier les caractéristiques de signaux d’échos de la mer, étudier les données à traiter et les méthodes d’inversion, calculer les paramètres de la surface de la mer et évaluer la précision de l’inversion radar des paramètres de la houle.Cette thèse se réfère à l’onde de sol radar HF, dont les ondes radio interagissent avec l’océan du fait de la diffraction de résonance de Bragg. Nous passons en revue l’historique et les applications du radar HF. Nous rappelons les bases de la théorie des ondes électromagnétiques. Nous décrivons les principes d’inversion des courants de surface de la mer, direction du vent et paramètres de houles. La faisabilité de l’inversion de paramètres de houle est examinée. A partir de l’analyse théorique et des études statistiques de nombreux échantillons de données, cette thèse propose une série de méthodes sur le traitement du signal brut et le contrôle de qualité, ce qui inclut la détermination du niveau de bruit, le moyennage des données dans l’espace et le temps, l’identification correcte des pics spectraux, le seuil de largeur de pic, etc. Respectant les caractéristiques de différents processus physiques, les inversions de courant et de vent utilisent des spectres collectés toutes les 20 minutes ; l’inversion des paramètres de houle utilise des spectres moyennés sur 1 heure. Les statistiques des spectres utilisés pour le calcul des paramètres de houle sont présentées pour chacune des stations. Un ensemble de programme efficaces de calculs automatiques avec une complexité algorithme réduite sont développés pour réaliser le traitement et en tirer les paramètres marins.Les vitesses de courants radiales sont obtenues à partir d’une unique station radar. Les champs de vecteurs de courants sont obtenus en combinant chaque station. On montre une année de débit moyen dans la mer d’Iroise, ainsi que le calcul de la vorticité et de la divergence. On étudie un ensemble de données d’un mois du radar SeaSonde de Qingdao. Les schémas de débit moyen, ainsi que la vorticité et la divergence sur un mois sont présentés.La direction relative du vent par rapport à la direction de visée du radar est mesurée à travers le ratio des amplitudes des pics de Bragg. Différents modèles empiriques sont employés pour obtenir la vitesse relative du vent par inversion radar. Les résultats présentés sont en accord avec les estimations prédites par le modèle. Différents modèles de distribution directionnelle sont utilisés pour mesurer le facteur de diffusion pour la mer d’Iroise.Cette thèse se concentre sur l’étude des paramètres de houle. Les résultats sont validés à l’aide de bouées et de données du modèle de vagues (Wavewatch III). L’estimation montre que la précision de la fréquence de houle est très bonne, la précision sur la hauteur significative de houle est très raisonnable et la précision sur la direction absolue de la houle est faible. La cohérence des mesures par chacune des stations radars est vérifiée par comparaison entre les deux. L’utilisation conjointe des échantillons est également prise en charge pour réaliser l’inversion. L’utilisation de deux radars n’améliore pas seulement la précision, mais résout aussi l’ambiguïté de direction relative de houle à partir d’une unique station et donne la direction absolue de vague avec une certaine précisionNearshore marine environment contains many complex processes, but the lack of high-resolution data over a large area during a long time is often the primary obstacle to further research. High-frequency (HF) radar is a mean of remote sensing which obtains continuous near-real time sea surface information over a large area. Thus the study of inversion of marine parameters from HF radar data is very meaningful. Thisthesis makes use of a 13-month-long dataset collected by two phased array HF radar to investigate the characteristics of the sea echo signals, study the data processing and inversion methods, compute sea surface parameters and evaluate the accuracy of radarinversion of swell parameters.The thesis refers to the ground wave HF radar, whose radio waves interact with ocean by Bragg resonance scattering. The development history and applications of HF radar is introduced. The basic theory of electromagnetic wave is reviewed. The principles of inversion of sea surface current, wind direction and swell parameters are described. The feasibility of the swell parameter inversion is investigated. Based on theoretical analysis and statistical studies of a large number of samples, the thesis proposes a series of methods on raw signal processing and quality control, including the determination of the noise level, data averaging in space and time, the proper identification of spectral peaks, the peak width threshold, etc. Respecting the characteristics of different physical processes, inversions of current and wind use spectra collected every 20 min; inversion of swell parameters uses one-hour averaged spectra. The statistics of qualified spectra for swell parameter calculations are presented for both stations. A set of efficient, with a reduced computational cost, automatic computing programs are developed to do the processing and derive marine parameters. Radial current velocities are derived from single radar station. Current vector fields are obtained by combination of both stations. One-year mean flow field in the Iroise Sea is shown, together with the computation of vorticity and divergence. A one-month SeaSonde radar dataset off Qingdao is studied. One-month mean flow pattern together with vorticity and divergence are presented.Relative wind direction with respect to radar look direction is measured through ratio of Bragg peaks amplitudes. Different empirical models are employed to derive radar-inverted relative wind direction. Results show reasonable agreement with model estimations. Different directional distribution models are used to measure the spreading factor for the Iroise Sea. The thesis focuses on the study of swell parameters. Results are validated by buoy and wave model (WAVEWATCH III) data. The assessments show that the accuracy of swell frequency is very good, the accuracy of swell significant waveheight is reasonable, and the accuracy of relative swell direction is low.Consistency of measurements by both radar stations is verified by comparison between the two. This also supports the use of double samples to do the inversion. Use of two radars not only further improves the accuracy but also solves the ambiguity of relative swell direction from single station and gives the absolute wave direction to a certain precision. The thesis proposes a constant relative directionmethod to derive swell significant waveheight, based on the studies of radar integral equation and the inverted results of relative swell direction. This proposal is demonstrated to improve the agreement of radar inversion and buoy/model provided significant waveheight and increases significantly the number of samples. The thesis investigates the accuracy of swell parameters obtained by HF radar. Contributions of random errors in radar observations are quantified. Comparing the differences between radar and buoy/model estimations gives assessments of the contribution of radar intrinsic uncertainty and contribution of other factors
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Zelenke, Brian Christopher. "An empirical statistical model relating winds and ocean surface currents : implications for short-term current forecasts." Thesis, Connect to the title online, 2005. http://hdl.handle.net/1957/2166.
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Medard, Fabien. "Contribution à la modélisation prédictive des comportements hautes fréquences des moteurs de traction." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT029/document.
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La diminution drastique des temps de commutation des convertisseurs MLI, due aux technologies émergentes comme le SiC (Carbure de Silicium), engendre un nombre important de phénomènes hautes fréquences dans les moteurs électriques notamment des tensions inter-spires et des courants de paliers. Ces travaux portent sur l'établissement d'un modèle impédant prédictif, valable sur une large bande de fréquence, fournissant les valeurs des tensions et des courants dangereux pour les moteurs. Pour cela, une maquette à échelle réduite a été étudiée dans un premier temps pour comprendre les phénomènes et offrir un cas simplifié de modélisation. Un bobinage en circuit imprimé a été fabriqué à cet effet. Un modèle de ligne a été développé et offre des résultats satisfaisants en prenant en compte les effets dus à la montée en fréquence. La même démarche de modélisation a été adoptée dans le cas du moteur réel dans la suite des travaux. Des campagnes de mesures sur un moteur instrumenté ont permis d'observer la propagation des ondes dans le bobinage. Une bobine a également été instrumentée pour offrir un accès au potentiel de chaque spire. Un modèle présenté dans la littérature a été approfondi en proposant une méthode d'identification des paramètres à partir de quelques points de mesures. Ce modèle sert de comparaison avec le modèle prédictif établi à la fin de ces travaux. La dernière partie de ces travaux s'intéresse à la modélisation du même moteur de traction. Un modèle de ligne dont les valeurs de paramètres ont été issues de calculs analytiques ou de simulations numériques a été réalisé tout en évitant d'avoir recours à des mesures. Ce modèle a donc un comportement prédictif puisque les données d'entrées sont pour la plus grande majorité uniquement géométriques. Il donne accès aux valeurs de tensions dans le bobinage et à l'amplitude des éventuels courants de paliers. Ce modèle peut alors servir d'outil d'aide à la conception des machines électriques en montrant les conséquences des choix de géométriesIn PWM converter, emerging technologies, like Sic and GAN, tend to decrease the rise time commutation which increases the occurrence of high frequency phenomenon such as bearing currents and voltage between coils. In this thesis, we aim to develop a predictive model able to give the currents and voltages amplitudes of those parasites. To simplify the understood of the phenomenon, a mock-up was built. It consists of a winding coil in a flexible PCB which represents the wave propagation in a real winding. Therefore, a first model was developed taking into account the effects produced by an increasing frequency. The model gives good results. It will be used in the real traction motor. Measures on a modified motor allowed observing the wave propagation across the coil. Those measures results will be compared to our motor model ones. A model found in the literature has also been studied. For this model, we built a parameters identification method based on several measurement points. This model will also be a compared to our motor model. The last part of this work explains the method used to build the predictive model. A line model is used to give an access to the winding. All parameters have been found with analytical formulations or with numerical simulations to avoid the use of measures. This model gives an access to a voltage between coils and to bearings currents. It can be used during the conception of motor to predict those problems
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Zhou, Jinghai. "High Frequency, High Current Density Voltage Regulators." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27268.
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As a very special DC-DC converter, VRM (Voltage Regulator Module) design must follow the fast-developing trend of microprocessors. The design challenges are the high current, high di/dt, and stringent load-line requirement. When the energy is transferred from the input of a VRM, through the VRM, then through the power delivery path to the processor, it needs sufficient capacitors to relay this energy. The capacitorsâ number appears to be unrealistically large if we follow todayâ s approach for the future processors. High frequency VRM with high control bandwidth can solve this problem, however, the degradation of efficiency makes the conventional buck converter and the hard-switching isolated topologies incapable of operating at higher frequency. The research goal is to develop novel means that can help a high-output- current VRM run efficiently at high frequency.
A novel Complementary Controlled Bridge (CCB) self-driven concept is proposed. With the proposed self-driven scheme, the combination of the ZVS technique and the self-driven technique recycles the gate driving energy by making use of the input capacitor of the secondary- side synchronous rectifier (SR) as the snubber capacitor of the primary-side switches. Compared to the external driver, the proposed converter can save driving loss and synchronous rectifier body diode conduction loss. Additionally, compared to the existing level-shifted self-driven scheme for bridge-type symmetrical topologies, its gate signal ringing is small and suitable for high-frequency applications.
Although the CCB self-driven VRM reduces the switching frequency-related losses significantly, the conduction loss is still high. Inspired by the current-doubler concept, a novel ZVS current-tripler DC-DC converter is proposed in this work. By utilizing more SR devices to share the current during the freewheeling period, the SR conduction loss is reduced. The current-tripler DC-DC converter has a delta/delta connected transformer that can be implemented with integrated magnetics. The transformer then becomes an integrated magnetic with distributed windings, which is preferred in high current applications. The current-tripler DC-DC converter in fact meets the requirements for the CCB self-driven scheme. The two concepts are then combined with an integrated gate drive transformer.
The proposed CCB self-driven concept and current-tripler concept can both be applied to the 12V non-isolated VRMs. The proposed topology is basically a buck-derived soft-switching topology with duty cycle extension and SR device self-driven capabilities. Because there is no isolation requirement, the SR gate driving becomes so simple that the voltage at the complementary controlled bridge can be used to directly drive the SR gate. Both the gate driving loss and the SR body diode conduction loss are reduced. The proposed circuit achieves similar overall efficiency to a conventional 300kHz buck converter running at 1MHz.
All the circuits proposed in this dissertation can use coupling inductors to improve both the steady-state efficiency and dynamic performances. The essence of the coupling inductors concept is to provide different equivalent inductances for the steady state and the transient. Moreover, when a current loop becomes necessary to achieve proper current sharing among phases, the current loop sample hold effect will make it difficult to push the bandwidth. The sample hold effect is alleviated by the coupling inductors concept. A small-signal model is proposed to study the system dynamic performance difference with different coupling inductor designs. As the verification, the coupling concept is applied to the 12V non-isolated CCB self-driven VRM and the bandwidth as high as one third of the switching frequency is achieved, which means a significant output capacitor reduction.Ph. D.
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Hayatleh, Khaled. "High frequency current-mode precision rectifiers." Thesis, Oxford Brookes University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308928.
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Reusch, David Clayton. "High Frequency, High Current Integrated Magnetics Design and Analysis." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/35420.
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The use of computers in the modern world has become prevalent in all aspects of life. The size of these machines has decreased dramatically while the capability has increased exponentially. A special DC-DC converter called a VRM (Voltage Regulator Module) is used to power these machines. The VRM faces the task of supplying high current and high di/dt to the microprocessor while maintaining a tight load regulation. As computers have advanced, so have the VRM's used to power them. Increasing the current and di/dt of the VRM to keep up with the increasing demands of the microprocessor does not come without a cost. To provide the increased di/dt, the VRM must use a higher number of capacitors to supply the transient energy. This is an undesirable solution because of the increased cost and real estate demands this would lead to in the future. Another solution to this problem is to increase the switching frequency and control bandwidth of the VRM. As the switching frequency increases the VRM is faced with efficiency and thermal problems. The current buck topologies suffer large drops in efficiency as the frequency increases from high switching losses.
Resonant or soft switching topologies can provide a relief from the high switching loss for high frequency power conversion. One disadvantage of the resonant schemes is the increased conduction losses produced by the circulating energy required to produce soft switching. As the frequency rises, the additional conduction loss in the resonant schemes can be smaller than the switching loss encountered in the hard switched buck. The topology studied in this work is the 12V non-isolated ZVS self-driven presented in [1]. This scheme offered an increased efficiency over the state of the art industry design and also increased the switching frequency for capacitor reduction. The goal of this research was to study this topology and improve the magnetic design to decrease the cost while maintaining the superior performance.
The magnetics used in resonant converters are very important to the success of the design. Often, the leakage inductance of the magnetics is used to control the ZVS or ZCS switching operation. This work presents a new improved magnetic solution for use in the 12V non-isolated ZVS self-driven scheme which increases circuit operation, flexibility, and production feasibility. The improved magnetic structure is simulated using 3D FEA verification and verified in hardware design.
Master of Science
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Mahattanakul, Jirayuth. "High frequency, low distortion current-mode filters." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300970.
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Worapishet, Apisak. "High frequency low power switched-current techniques." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392911.
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Liu, Kwang-Hwa. "High-frequency quasi-resonant converter techniques." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74737.
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Two waveform-shaping techniques to reduce or eliminate the switching stresses and switching losses in switching-mode power conversion circuits are developed: the zero-current switching technique and the zero-voltage switching technique.
Based on these two techniques two new families of quasi-resonant converters are derived. Since the stresses on semiconductor switching devices are significantly alleviated, these quasi-resonant (QRC) converters are suitable for high-frequency operations with much improved performances and equipment power density.
Employing the duality principle, the duality relationship between these two families of quasi-resonant converters are derived. The establishment of the duality relationship provides a framework allowing the knowledge obtained from one converter family to be readily transferred to the other.
Further topological refinements are derived through the utilization of parasitic elements in the devices and the circuit. In particular, the two most significant parasitic elements, the leakage inductance of the transformer and the junction capacitances of the semiconductor switch, are incorporated as part of the resonant-tank circuit required by these quasi-resonant converters. Consequently, the detrimental effects due to these parasitic elements are eliminated, and the converters can be operated at very high frequencies.Ph. D.
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Egnor, Dianne Elizabeth. "High-frequency acoustic tomography in a high-current coastal environment." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88350.
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Su, Yipeng. "High Frequency, High Current 3D Integrated Point-of-Load Module." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51248.
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Point-of-load (POL) converters have been used extensively in IT products. Today, almost every microprocessor is powered by a multi-phase POL converter with high output current, which is also known as voltage regulator (VR). In the state-of-the-art VRs, the circuits are mostly constructed with discrete components and situated on the motherboard, where it can occupy more than 1/3 of the footprint of the motherboard. A compact POL is desirable to save precious space on motherboards to be used for some other critical functionalities. Recently, industry has released many modularized POL converters, in which the bulky inductor is integrated with the active components to increase the power density. This concept has been demonstrated at current levels less than 5A and power density around 600-1000W/in3. This might address the needs of small hand-held equipment such as smart phones, but it is far from meeting the needs for the applications such as laptops, desktops and servers, where tens and hundreds of amperes are needed.
A 3D integrated POL module with an output current of tens of ampere has been successfully demonstrated at the Center for Power Electronic Systems (CPES), Virginia Tech. In this structure, the inductor is elaborated with low temperature co-fire ceramic (LTCC) ferrite, as a substrate where the active components are placed. The lateral flux inductor is proposed to
achieve both a low profile and high power density. Generally, the size of the inductor can be continuously shrunk by raising the switching frequency. The emerging gallium-nitride (GaN) power devices enable the creation and use of a multi-MHz, high efficiency POL converter. This dissertation firstly explores the LTCC inductor substrate design in the multi-MHz range for a high-current POL module with GaN devices. The impacts of different frequencies and different LTCC ferrite materials on the inductor are also discussed. Thanks to the DC flux cancellation effect, the inverse coupled inductor further improves the power density of a 20A, 5MHz two-phase POL module to more than 1kW/in3. An FEA simulation model is developed to study the core loss of the lateral flux coupled inductor, which shows the inverse coupling is also beneficial for core loss reduction.
The ceramic-based 3D integrated POL module, however, is not widely adopted in industrial products because of the relatively high cost of the LTCC ferrite material and complicated manufacturing process. To solve that problem, a printed circuit board (PCB) inductor substrate with embedded alloy flake composite core is proposed. The layerwise magnetic core is laminated into a multi-layer PCB, and the winding of the inductor then is formed by the copper layers and conventional PCB vias. As a demonstration of system integration, a 20A, 1.5MHz integrated POL module is designed and fabricated based on a 4-layer PCB with embedded flake core, which realizes more than 85% efficiency and 600W/in3 power density. The application of standardized PCB processes reduces the cost for manufacturing the integrated modules due to the easy automation and the low temperature manufacturing process. Combining the PCB-embedded coupled inductor substrate and advanced control strategy, the two-phase 40A POL modules are elaborated as a complete integrated laptop VR solution. The coupled inductor structure is slightly modified to improve its transient performance. The nonlinearity of the inductance is controlled by adding either air slots or low permeability magnetic slots into the leakage flux path of the coupled inductor. Then the leakage flux, which determines the transient response of the coupled inductor, can be well controlled. If we directly replace the discrete VR solution with the proposed integrated modules, more than 50% of the footprint on the motherboard can be saved.
Although the benefits of the lateral flux inductor have been validated in terms of its high power density and low profile, the planar core is excited under very non-uniform flux. Some parts of the core are even pushed into the saturation region, which totally goes against the conventional sense of magnetic design. The final part of this dissertation focuses on evaluating the performance of the planar core with variable flux. The counterbalance between DC flux and AC flux is revealed, with which the AC flux and the core loss density are automatically limited in the saturated core. The saturation is essentially no longer detrimental in this special structure. Compared with the conventional uniform flux design, the variable flux structure extends the operating point into the saturation region, which gives better utilization of the core. In addition, the planar core with variable flux also provides better thermal management and more core loss reduction under light load.
As conclusions, this research first challenges the conventional magnetic design rules, which always assumes uniform flux. The unique characteristics and benefits of the variable flux core are proved. As an example of taking advantages of the lateral flux inductor, the PCB integrated POL modules are proposed and demonstrated as a high-density VR solution. The integrated modules are cost-effective and ready to be commercialized, which could enable the next technological innovation for the whole computing and telecom industry.Ph. D.
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Holme, Peter R. "Digital control of high frequency PWM convertors." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/7160.
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The thesis begins with a review of presently available analogue and digital control schemes for high frequency PWM converters. Advantages and disadvantages of each scheme are identified, to determine which features would be desirable in a new digital control scheme. An extensive examination of peak and average current mode control is undertaken, using state-space/sampled data modelling, to gain more detailed information on the properties of current mode control. On the basis of this information, a new digital current mode control scheme is put forward. This uses samples of the inductor current, line voltage and output voltage to implement a control strategy in software. Average inductor current is calculated each switching cycle and compared to the current program level, providing true current mode control. This has some advantages over traditional methods. Accurate inductor current tracking of the current program level is achieved and no slope compensation is required for stable operation over the full range of duty ratios. Line voltage feed-forward is possible in buck derived topologies, which provides an effective null in the audio susceptibility transfer function, independent of compensation parameters. Current loop stability is independent of line voltage or load current in the buck topology, allowing operation with optimum loop compensation under all normal operating conditions. Practical implementation of a digital current mode controlled current-fed converter is described. This includes a modular architecture for the hardware and documentation for the software. Effects of component selection on the achievable converter switching frequency and dynamic performance are discussed. A method is put forward for the direct digital measurement of loop gain and phase in digital control systems. This is used to obtain actual loop responses from a test bed digital current mode controlled current-fed converter. Line and load transient response tests are presented which demonstrate the dynamic characteristics of digital current mode control.
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Garoosi, Shahab. "Trading algorithms for high-frequency currency trading." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-146315.
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This thesis uses modern portfolio theory together with machine learning techniques to generate stable portfolio returns over eleven currency pairs with spreads included. The backtests show that support vector machine predicted future returns better than neural network and linear regression. Principal component analysis and data smoothing combined with the local outlier factor further improved the performance of the trading algorithm. However, the ensemble of the top performed predictor performed below the individual predictors. Also, the use of different error estimates showed the criticality of mean arctangent absolute percentage error over mean absolute error and over mean squared error for profitability. For obtaining sensible results in a transaction costless setting, adopting risk adjusted leverage proved necessary. Otherwise, the profit-maximizing leverage surpassed the risk adjusted in a spread setting.
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Zhang, Xiaokai. "Novel magnetic composites for high frequency applications /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 190 p, 2009. http://proquest.umi.com/pqdweb?did=1654494811&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Bloomfield, Aaron Paul. "A High Frequency Alternating Current Battery Heater for Military Vehicles." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302312903.
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Xu, Ping. "High-frequency Analog Voltage Converter Design." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4891.
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For many high-speed, high-performance circuits, purely differential inputs are needed. This project focuses on building high-speed voltage converters which can transfer a single-ended signal to a purely differential signal, or a differential input signal to a single-ended signal. Operational transconductance amplifier (OTAs) techniques are widely used in high-speed continuous-time integrated analog signal processing (ASP) circuits because resistors, inductors, integrators, buffers, multipliers and filters can be built by OT As and capacitors. Taking advantage of OT As, very-high-speed voltage converters are designed in CMOS technology. These converters can work in a frequency range from DC (OHz) up to lOOMHz and higher, and keep low distortion over a± 0.5V input range. They can replace transformers so that designing fully integrated differential circuits becomes possible. The designs are based on a MOSIS 2μm n-well process. SPICE simulations of these designs are given. The circuit was laid out with MAGIC layout tools and fabricated through MOSIS. The chip was measured at PSU and Intel circuit labs and the experimental results show the correctness of the designs.
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Pong, Shiu Yan. "Modelling and forecasting currency volatility using high frequency data." Thesis, Lancaster University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429998.
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Chandial, Amarajit Singh. "High frequency fluctuations, timescales and heterokedasticity in currency rates." Thesis, Royal Holloway, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394840.
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Ackermann, Douglas Michael Jr. "REDUCTION OF THE ONSET RESPONSE IN HIGH FREQUENCY NERVE BLOCK." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1259791396.
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Badenhorst, J. "Metrology and modelling of high frequency probes." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/808.
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鐘學仁 and Hok-Yan Chung. "Analysis of losses in power inductor for high-frequency switching power converters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224313.
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Chung, Hok-Yan. "Analysis of losses in power inductor for high-frequency switching power converters." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23273318.
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Becerra, Fajardo Laura. "Microcontrolled injectable stimulators based on electronic rectification of high frequency current bursts." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/402433.
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Neuroprostheses based on dense networks of wireless microstimulators have been proposed in the past for restoring movement in paralysis patients. Yet existing implantable microstimulators are too bulky and invasive for implementing such networks because of the powering approaches they employ.
To overcome this limitation, it was recently proposed an innovative electrical stimulation method incorporating electronic implants. The method consist in delivering, by means of superficial textile electrodes, high frequency current bursts which innocuously flow through tissues by galvanic coupling and which are rectified by the implants, thereby transforming these bursts into low frequency currents capable of performing local stimulation. Since the implants lack bulky components for powering, such as coils and batteries, the method will enable miniaturization levels without precedents for microstimulators.
The method was first demonstrated with very simple implants that could not be controlled externally, impeding independent stimulation of different target muscles. This thesis demonstrates that the method allows the development of digitally addressable microstimulators. In particular, this thesis describes the development, characterization and in vivo assay of addressable stimulators made of off-the-shelf electronic components. The developed microcontrolled and wireless stimulators are semi-rigid and can be easily implanted by injection thanks to their elongated shape (2 mm thick and almost 49 mm long). They perform charge-balanced neuromuscular stimulation in response to commands modulated in high frequency current bursts which meet safety standards. This thesis paves the way to future ultrathin stimulators based on a custom integrated circuit.En el pasado se propusieron neuroprótesis basadas en densas redes de microestimuladores inalámbricos para restablecer el movimiento en pacientes con parálisis. Aún así, los microestimuladores implantables existentes en la actualidad son demasiado voluminosos e invasivos como para implementar dichas redes debido a los métodos de alimentación eléctrica que utilizan. Para superar esta limitación, recientemente se propuso un método de estimulación eléctrica innovador que incorpora implantes electrónicos. El método consiste en aplicar mediante electrodos textiles superficiales, corrientes de alta frecuencia que fluyen inofensivamente por los tejidos por medio de acople galvánico, y que son rectificadas por los implantes. De esta forma las ráfagas se transforman en corrientes de baja frecuencia que pueden estimular localmente. Debido a que los implantes no contienen componentes voluminosos como bobinas y baterías para alimentarse eléctricamente, el método permitirá niveles de miniaturización sin precedentes para microestimuladores. El método fue demostrado por primera vez con implantes muy simples que no podían ser controlados externamente, impidiendo la estimulación independiente de diferentes músculos objetivo. Esta tesis demuestra que el método permite el desarrollo de microestimuladores direccionables digitalmente. En particular, esta tesis describe el desarrollo, caracterización y ensayos in vivo de estimuladores direccionables basados en componentes electrónicos comerciales. Los estimuladores inalámbricos desarrollados son semirrígidos y pueden ser fácilmente implantados por medio de inyección gracias a su forma alargada (2 mm de diámetro y casi 49 mm de largo). Los dispositivos realizan estimulación neuromuscular con balance de carga en respuesta a comandos modulados en las ráfagas de corriente de alta frecuencia. Dichas ráfagas de corriente cumplen con estándares de seguridad. Esta tesis abre el camino hacia futuros estimuladores ultrafinos basados en circuitos integrados diseñados para este propósito.
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Tingleff, Jens. "Current Mode Wave Active Filters : a topology for high frequency integrated filters." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337669.
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Benson, Kirk R. "High frequency subsurface Lagrangian measurements in the California Current with RAFOS floats." Thesis, Monterey, California. Naval Postgraduate School, 1995. http://hdl.handle.net/10945/35108.
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This study presents float observations from four RAFOS floats that were deployed off central California for a twenty-three day period as part of a Tomography Demonstration Experiment. These floats, which sampled hourly, were used to investigate float characteristics and the navigational accuracy of current processing techniques. An ordinary mean least square method is proposed to mathematically estimate values for random and systematic errors, producing navigational trajectories which compliment previous methods when determining the most probable solution of the float trajectory. Potential sources of error in the navigational solution are examined, as well as the importance of float/ source geometry on position accuracy. It was determined that these floats supported previous studies of the California Current System, and proposes that the California Undercurrent may in fact be wider and deeper that previously suspected. (AN)
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Sun, Juanjuan. "Dynamic Performance Analyses of Current Sharing Control for DC/DC Converters." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28071.
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Paralleling operation of DC/DC converters is widely used in today's distributed power systems. To ensure balanced output currents among paralleled power modules, current sharing control is usually necessary.Active current sharing controls with current feedback mechanism are widely used in today's power supplies. However, the dynamic performance of these current sharing control schemes are not yet clearly explored. In this work, the dynamic current sharing performance is evaluated for paralleling systems with the output impedance approach. As the representative of the terminal characteristic of a power converter, output impedance is a powerful tool to study the dynamic response under load transients. The dynamic current sharing analyses are then conducted for three different active current sharing control structures and a comprehensive comparison among them helps the designer to choose appropriate controls for different applications.
On the other hand, high-frequency load transients are possible to happen for voltage regulators, which are the power supplies of microprocessors. In order to study the dynamic current sharing performance for a paralleling system when the perturbation frequency is higher than half of the switching frequency,the conventional output impedance concept needs to be extended. Due to the non-linear behavior of a switching modulator, the beat-frequency phenomenon could cause unexpected failure of a power supply when the perturbation frequency is close to the switching frequency. To address this issue, an unconventional multi-frequency model is proposed for high-frequency dynamic current sharing studies. With this model, the sideband components are possible to be included and the beat-frequency oscillations can be predicted. After that, the conventional impedance concept is expanded in the form of extended describing function, so that the terminal characteristics of paralleled converters are represented by a series of impedances. Besides the analyses, this work also proposed several solutions for the beat-frequency oscillation issue which are experimentally verified.
In summary, both low-frequency and high-frequency dynamic current sharing performances are studied in this dissertation. The output impedance concept and its extension in the form of extended describing function are utilized as the tools for researches. With these powerful tools, more insights are obtained to help better design of a paralleling system.Ph. D.
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Dai, Jianxing. "Analysis and Design of a High-Frequency RC Oscillator Suitable for Mass Production." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138423.
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Oscillators are components providing clock signals. They are widely required by low-cost on-chip applications, such as biometric sensors and SoCs. As part of a sensor, a relaxation oscillator is implemented to provide a clock reference. Limited by the sensor application, a clock reference outside the sensor is not desired. An RC implementation of the oscillator has a balanced accuracy performance with low-cost advantage. Hence an RC relaxation oscillator is chosen to provide the clock inside the sensor. This thesis proposes a current mode relaxation oscillator to achieve low frequency standard deviation across different supplies, temperatures and process corners. A comparison between a given relaxation oscillator and the proposed design is made as well. All oscillators in this thesis use 0.18 μm technology and 1.8 V nominal supply. The proposed oscillator manages to achieve a frequency standard deviation across all PVT variations less than ±6.5% at 78.4 MHz output frequency with a power dissipation of 461.2 μW. The layout of the oscillator's core area takes up 0.003 mm2.
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Jovanović, Milan Miodrag. "High-frequency off-line power conversion using quasi-resonant and multi-resonant techniques." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53542.
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Three recently-proposed power conversion technologies, the zero-current-switching (ZCS) and zero-voltage-switching (ZVS) quasi-resonant techniques, and the zero-voltage-switching multi-resonant technique, are evaluated for high-frequency, off-line applications. The study is performed with emphasis on the conversion-frequency range, efficiency, load range, input-voltage range, output power, dynamic response, and power density.
A comprehensive dc analysis of the half-wave and full-wave, half-bridge zero-current-switched quasi-resonant converters (QRCs) is presented. Design procedures for closed-loop design of the converters are also derived. The procedures are used to design and fabricate half-wave and full-wave converters operating in the low-megahertz range and experimentally assess their suitability for high-frequency, off-line power conversion.
The zero-voltage-switching technique is employed to further increase the conversion frequency. First, the half-bridge zero-voltage-switched quasi-resonant converter is analyzed and the trade-offs between its frequency range, load range, and efficiency are examined in detail. The multi-resonant-switch concept is applied to this converter to improve its characteristics, primarily its load range.
A complete dc analysis of the zero-voltage-switched multi-resonant converter (MRC) is given and the dc voltage-conversion-ratio characteristics are derived. A graphic design procedure for the converter is established and is used to build an experimental 100 W, off-line converter operating in the frequency range of 2 MHz to 8 MHz.
Finally, a comprehensive comparison of the QRCs and MRCs is performed and conditions where their applications appears most desirable are defined.Ph. D.
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Mbeutcha, France Gaspari. "A High-Side Wideband Current and Voltage Sensor for Radio-Frequency Power Amplifiers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17464/.
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The radio-frequency power amplifier (RF PA) is one of the critical elements within the wireless, as it is expected to provide a suitable output power with high efficiency and linearity. Improving the power efficiency of the RF power amplifier is a key challenge of the modern wireless communications, especially in the presence of wideband modulations signals. In fact, to achieve this goal, various techniques are investigated, including supply voltage modulation (e.g., envelope- tracking). In the supply-modulated Pas employed in modern telecom base stations, it is important to measure the dynamic current drained by the power amplifier and the dynamic voltage at the supply terminal.
This thesis project is focused on the design and realization of a high-side wideband (frequency response from dc up to > 100 MHz) voltage and current sensor suitable for supply-modulated power amplifiers. In order to be used with Gallium Nitride (GaN) PAs, the sensor must be able to withstand dynamic supply voltages up to 80 V and dynamic drain currents up to 2 A. The proposed current sensor is based on a shunt resistor approach, where the voltage drops across the resistor is firstly attenuated, and then amplified by a balanced differential circuit consisting of two cascaded stages. The voltage sensor consists of an operational amplifier configured as a buffer.
The first part of the project, developed at the DEI EDM Lab (UNIBO), was dedicated to the analysis of the sensing architecture, the simulation of the resulting circuit. The design of the board its characterization and board test were realized in at the Warsaw University of Technology in Poland.
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Kanazawa, Kyoko. "Intracranially-recorded ictal direct current shifts may precede high frequency oscillations in human epilepsy." Kyoto University, 2014. http://hdl.handle.net/2433/193569.
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Miller, Douglas P. "Introduction of a current waveform, waveshaping technique to limit conduction loss in high-frequency dc-dc converters suitable for space power." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237903.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Ewing, Gerald D. Second Reader: Michael, Sherif. "June 1990." DTIC Indentifier(s): Dc to dc converters, waveform generators, program listings, theses. Author(s) subject terms: dc-dc converter, quasi-resonant, Buck converter. Includes bibliographical references (p. 142-145). Also available in print.
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Basset, Julien. "High frequency quantum noise of mesoscopic systems and current-phase relation of hybrid junctions." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00635825.
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Cette thèse est consacrée à l'étude de deux aspects de la physique mésoscopique que sont le bruit quantique haute fréquence et l'effet de proximité supraconducteur en se focalisant toutefois sur un système modèle: le nanotube de carbone.Ainsi la première partie de cette thèse est dédiée à la mesure de bruit quantique haute fréquence. Afin de mesurer ces fluctuations nous avons développé un système de détection "on-chip" original dans lequel la source de bruit et le détecteur, une jonction Supraconducteur/Isolant/Supraconducteur, sont couplés par un circuit résonant. Cela nous a permis dans un premier temps de mesurer le bruit à l'équilibre du résonateur. Son bruit comporte une forte asymétrie entre émission et absorption reliée aux fluctuations de point zéro. Une seconde étape a été de mesurer le bruit hors équilibre d'émission du passage tunnel de quasi-particules dans une jonction Josephson. Ce bruit comporte une forte dépendance en fréquence en accord avec les prédictions théoriques et nous a permis de valider le principe de détection. Finalement, nous avons pu mesurer le bruit associé au régime Kondo hors équilibre d'une boîte quantique à nanotube de carbone (énergie caractéristique kBTK avec TK la température Kondo). Ce bruit d'émission à kBTK~hν possède une forte singularité à la tension V=hν/e (ν étant la fréquence de mesure). Cette singularité est reliée aux résonances Kondo dans la densité d'états de la boîte associés aux niveaux de Fermi de chaque réservoir. A plus haute fréquence hν~3kBTK, la singularité disparaît, ce qui est compris par des effets de décohérence induits par la tension.Dans la seconde partie, nous avons développé une technique permettant de mesurer à la fois la relation courant/phase et la caractéristique courant/tension d'un lien faible séparant deux supraconducteurs. Nous avons ainsi caractérisé une jonction à base de nanotube de carbone au travers de laquelle une relation courant-phase modulable par une tension de grille a été observée. Cette relation courant/phase exhibe une forte anharmonicité lorsque le supercourant présente une relativement grande amplitude.
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Antaloae, C. C. "Feasibility of high frequency alternating current power distribution for the automobile auxiliary electrical system." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6792.
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This study investigates the feasibility and potential benefits of high frequency
alternating current (HFAC) for vehicle auxiliary electrical systems.
A 100Vrms, 50kHz sinusoidal AC bus is compared with 14V DC and 42V DC electrical
systems in terms of mass and energy efficiency. The investigation is focused on the four
main sub-systems of an on-board electrical network, namely: the power generation,
power distribution, power conversion and the electrical loads. In addition, a systemlevel
inquiry is conducted for the HFAC bus and a comparable 42V DC system.
A combination of computer simulation, analytical analysis and experimental work has
highlighted benefits for the HFAC power distribution sub-system and for low-torque
motor actuators. Specifically, the HFAC conductor mass is potentially 70% and 30%
lighter than comparable 14V DC and 42V DC cables, respectively. Also, the proposed
cable is expected to be at least 80% more energy efficient than the current DC
conductor technology. In addition, it was found that 400Hz AC machines can
successfully replace DC motor actuators with a rated torque of up to 2Nm. The former
are up to 100% more efficient and approximately 60% lighter and more compact than
the existing DC motors in vehicles. However, it is argued that the HFAC supply is not
feasible for high-torque motor actuators. This is because of the high energy losses and
increased machine torque ripple associated with the use of HFAC power.
The HFAC power conversion sub-system offers benefits in terms of simple power
converter structure and efficient HFAC/DC converters. However, a significant limitation
is the high power loss within HFAC/AC modules, which can be as high as 900W for a
2.4kW load with continuous operation. Similar restrictions are highlighted for the
HFAC power generation sub-system, where up to 400W is lost in a 4kW DC/HFAC
power module.
The conclusion of the present work is that the HFAC system offers mass and energy
efficiency benefits for the conventional vehicle by leveraging the use of compact lowtorque
motor actuators and lightweight wiring technology.
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Patsora, Iryna, Dmytro Tatarchuk, Henning Heuer, and Susanne Hillmann. "Study of a Particle Based Films Cure Process by High-Frequency Eddy Current Spectroscopy." Multidisciplinary Digital Publishing Institute, 2016. https://tud.qucosa.de/id/qucosa%3A30206.
Full textAbstract:
Particle-based films are today an important part of various designs and they are implemented in structures as conductive parts, i.e., conductive paste printing in the manufacture of Li-ion batteries, solar cells or resistive paste printing in IC. Recently, particle based films were also implemented in the 3D printing technique, and are particularly important for use in aircraft, wind power, and the automotive industry when incorporated onto the surface of composite structures for protection against damages caused by a lightning strike. A crucial issue for the lightning protection area is to realize films with high homogeneity of electrical resistance where an in-situ noninvasive method has to be elaborated for quality monitoring to avoid undesirable financial and time costs. In this work the drying process of particle based films was investigated by high-frequency eddy current (HFEC) spectroscopy in order to work out an automated in-situ quality monitoring method with a focus on the electrical resistance of the films. Different types of particle based films deposited on dielectric and carbon fiber reinforced plastic substrates were investigated in the present study and results show that the HFEC method offers a good opportunity to monitor the overall drying process of particle based films. Based on that, an algorithm was developed, allowing prediction of the final electrical resistance of the particle based films throughout the drying process, and was successfully implemented in a prototype system based on the EddyCus® HFEC device platform presented in this work. This prototype is the first solution for a portable system allowing HFEC measurement on huge and uneven surfaces.
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Patsora, Iryna, Dmytro Tatarchuk, Henning Heuer, and Susanne Hillmann. "Study of a Particle Based Films Cure Process by High-Frequency Eddy Current Spectroscopy." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-220609.
Full textAbstract:
Particle-based films are today an important part of various designs and they are implemented in structures as conductive parts, i.e., conductive paste printing in the manufacture of Li-ion batteries, solar cells or resistive paste printing in IC. Recently, particle based films were also implemented in the 3D printing technique, and are particularly important for use in aircraft, wind power, and the automotive industry when incorporated onto the surface of composite structures for protection against damages caused by a lightning strike. A crucial issue for the lightning protection area is to realize films with high homogeneity of electrical resistance where an in-situ noninvasive method has to be elaborated for quality monitoring to avoid undesirable financial and time costs. In this work the drying process of particle based films was investigated by high-frequency eddy current (HFEC) spectroscopy in order to work out an automated in-situ quality monitoring method with a focus on the electrical resistance of the films. Different types of particle based films deposited on dielectric and carbon fiber reinforced plastic substrates were investigated in the present study and results show that the HFEC method offers a good opportunity to monitor the overall drying process of particle based films. Based on that, an algorithm was developed, allowing prediction of the final electrical resistance of the particle based films throughout the drying process, and was successfully implemented in a prototype system based on the EddyCus® HFEC device platform presented in this work. This prototype is the first solution for a portable system allowing HFEC measurement on huge and uneven surfaces.
50
Van, Rhyn P. D. "High voltage DC-DC converter using a series stacked topology." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1269.
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