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11	Modelling, characterisation and application of GaN switching devices Murillo Carrasco, Luis January 2016 (has links) The recent application of semiconductor materials, such as GaN, to power electronics has led to the development of a new generation of devices, which promise lower losses, higher operating frequencies and reductions in equipment size. The aim of this research is to study the capabilities of emerging GaN power devices, to understand their advantages, drawbacks, the challenges of their implementation and their potential impact on the performance of power converters. The thesis starts by presenting the development of a simple model for the switching transients of a GaN cascode device under inductive load conditions. The model enables accurate predictions to be made of the switching losses and provides an understanding of the switching process and associated energy flows within the device. The model predictions are validated through experimental measurements. The model reveals the suitability of the cascode device to soft-switching converter topologies. Two GaN cascode transistors are characterised through experimental measurement of their switching parameters (switching speed and switching loss). The study confirms the limited effect of the driver voltage and gate resistance on the turn-off switching process of a cascode device. The performance of the GaN cascode devices is compared against state-of-the-art super junction Si transistors. The results confirm the feasibility of applying the GaN cascode devices in half and full-bridge circuits. Finally, GaN cascode transistors are used to implement a 270V - 28V, 1.5kW, 1 MHz phase-shifted full-bridge isolated converter demonstrating the use of the devices in soft-switching converters. Compared with a 100 kHz silicon counterpart, the magnetic component weight is reduced by 69% whilst achieving a similar efficiency of 91%.
12	Částečné výboje v elektronických zařízeních / Partial Discharge in Electronic Equipments Mammadov, Anar January 2009 (has links) Tato disertační práce se věnuje studiu částečných výbojů (PD) způsobených poklesem spolehlivosti a životnosti elektronických zařízení a systémů. Diagnostika PD je dnes známá metoda pro vysoké napětí u vysoko-výkonných zařízení. V případě elektronických zařízení PD testování není ale běžně používáná metoda, přestože je zde také potenciál pro vysoké elektrické zatížení vzhledem k velmi krátké vzdálenosti. Tato práce je zaměřena na vyšetřování PD činnosti u elektronických zařízení. Bylo navrženo a provedeno pracoviště pro diagnostiku PD v elektronických zařízeních. Pracovní frekvence se pohybuje od několika stovek Hz až 100 kHz. Maximální amplituda PD testovaného napětí je vyšší než 10 kV. Navzdory jednoduché konstrukci toto zařízení přináší vysokou spolehlivost měření. Více než 300 PD testů bylo provedeno na různých elektronických zařízeních a elektronických součástí,např. na planárních transformátorech a elektronických komponentách používaných při vysoko-napěťových měničích
13	Methodologies for Design-Oriented Electromagnetic Modeling of Planar Passive Power Processors Prasai, Anish 15 August 2006 (has links) The advent and proliferation of planar technologies for power converters are driven in part by the overall trends in analog and digital electronics. These trends coupled with the demands for increasingly higher power quality and tighter regulations raise various design challenges. Because inductors and transformers constitute a rather large part of the overall converter volume, size and performance improvement of these structures can subsequently enhance the capability of power converters to meet these application-driven demands. Increasing the switching frequency has been the traditional approach in reducing converter size and improving performance. However, the increase in switching frequency leads to increased power loss density in windings and core, with subsequent increase in device temperature, parasitics and electromagnetic radiation. An accurate set of reduced-order modeling methodologies is presented in this work in order to predict the high-frequency behavior of inductors and transformers. Analytical frequency-dependent expressions to predict losses in planar, foil windings and cores are given. The losses in the core and windings raise the temperature of the structure. In order to ensure temperature limitation of the structure is not exceeded, 1-D thermal modeling is undertaken. Based on the losses and temperature limitation, a methodology to optimize performance of magnetics is outlined. Both numerical and analytical means are employed in the extraction of transformer parasitics and cross-coupling. The results are compared against experimental measurements and are found to be in good accord. A simple near-field electromagnetic shield design is presented in order to mitigate the amount of radiation. Due to inadequacy of existing winding technology in forming suitable planar windings for PCB application, an alternate winding scheme is proposed which relies on depositing windings directly onto the core. / Master of Science core losses electromagnetic radiation multiple windings analytical modeling shield design finite element modeling cross-coupling high frequency planar windings planar core planar transformer electroplating sputtering leakage inductance winding capacitances winding losses
14	Capacitorless Power Electronics Converters Using Integrated Planar Electro-Magnetics Haitham M Kanakri (18928150) 03 September 2024 (has links) <p dir="ltr">The short lifespan of capacitors in power electronics converters is a significant challenge. These capacitors, often electrolytic, are vital for voltage smoothing and frequency filtering. However, their susceptibility to heat, ripple current, and aging can lead to premature faults. This can cause issues like output voltage instability and short circuits, ultimately resulting in catastrophic failure and system shutdown. Capacitors are responsible for 30% of power electronics failures.</p><p dir="ltr">To tackle this challenge, scientists, researchers, and engineers are exploring various approaches detailed in technical literature. These include exploring alternative capacitor technologies, implementing active and passive cooling solutions, and developing advanced monitoring techniques to predict and prevent failures. However, these solutions often come with drawbacks such as increased complexity, reduced efficiency, or higher upfront costs. Additionally, research in material science is ongoing to develop corrosion-resistant capacitors, but such devices are not readily available.</p><p dir="ltr">This dissertation presents a capacitorless solution for dc-dc and dc-ac converters. The proposed solution involves harnessing parasitic elements and integrating them as intrinsic components in power converter technology. This approach holds the promise of enhancing power electronics reliability ratings, thereby facilitating breakthroughs in electric vehicles, compact power processing units, and renewable energy systems. The central scientific premise of this proposal is that the capacitance requirement in a power converter can be met by deliberately augmenting parasitic components.</p><p dir="ltr">Our research hypothesis that incorporating high dielectric material-based thin-films, fabricated using nanotechnology, into planar magnetics will enable the development of a family of capacitorless electronic converters that do not rely on discrete capacitors. This innovative approach represents a departure from the traditional power converter schemes employed in industry.</p><p dir="ltr">The first family of converters introduces a novel capacitorless solid-state power filter (SSPF) for single-phase dc-ac converters. The proposed configuration, comprising a planar transformer and an H-bridge converter operating at high frequency, generates sinusoidal ac voltage without relying on capacitors. Another innovative dc-ac inverter design is the twelve step six-level inverter, which does not incorporate capacitors in its structure.</p><p dir="ltr">The second family of capacitorless topologies consists of non-isolated dc-dc converters, namely the buck converter and the buck-boost converter. These converters utilize alternative materials with high dielectric constants, such as calcium copper titanate (CCTO), to intentionally enhance specific parasitic components, notably inter capacitance. This innovative approach reduces reliance on external discrete capacitors and facilitates the development of highly reliable converters.</p><p dir="ltr">The study also includes detailed discussions on the necessary design specifications for these parasitic capacitors. Furthermore, comprehensive finite element analysis solutions and detailed circuit models are provided. A design example is presented to demonstrate the practical application of the proposed concept in electric vehicle (EV) low voltage side dc-dc power converters used to supply EVs low voltage loads.</p> Circuits and systems Electrical circuits and systems Electrical machines and drives Engineering electromagnetics Solid-state power filter (SSPF) capacitorless topology active output power filter planar transformer electrolytic capacitor lifetime wear-out mechanisms notch resonant filter LLC-resonant converter calcium copper titanate (CCTO) intra capacitance Miniaturizing EV Chargers Multilevel inverters twelve-step inverter three-phase inverter six-level output voltage planar transform design Finite Element Analysis (FEA) Ansys Maxwell Ansys PEmag Ansys PExpert Ansys Simplorer Ansys Twin Builder planar electromagnetic buck-boost converter integrated magnetic hybrid LC filter high-power density converters CaCu3Ti4O12 electric vehicle chargers Nano graphene layer heat sink IGBT thermal response composite substrate planar transformer circuit models h-parameter voltage gradient dual transformer LLC resonant converter DC-DC Buck converter fundamental harmonic analysis power quality Total harmonic distortion (THD)
15	Částečné výboje v elektronických zařízeních pracujících na vyšších kmitočtech / Partial Discharge in High Frequency Electronic Equipment Havlíček, Tomáš January 2009 (has links) The presented thesis is focused on knowledge extension in the area of partial discharge measurements and evaluation at frequencies higher than 1 kHz. The thesis includes the design and set up of the measuring workplace equipped for measuring partial discharges, including the methodology of the measuring and calibration procedures necessary for the achievement of reproducible results. Another part of the thesis deals with the technology of acoustical and electromagnetic sensors convenient for the diagnostics and localization of partial discharges in devices, that work at voltages above 500 V. Electrical circuits that enable data evaluation by using the signal from a sensor working on amplitude analysis principle were developed. For PD detection a PC controlled measuring device working on amplitude analysis principle had to be designed and realized. The possibilities of the workplace have been demonstrated in the process of development of the insulating systems for pulse transformers. Thesis results can significantly contribute to a higher quality of newly designed electronic devices and systems working at voltages above 500 V.
16	Analysis of high-voltage low-current DC/DC converters for electrohydrodynamic pumps Axelsson, Sigge, Gartner, Jonas, Stafström, Axel January 2023 (has links) Moving parts cause vibrations and tend to wear out. In applications where maintenance is complicated, solutions without moving parts are therefore advantageous. Electrohydrodynamic pumps are such a solution. Instead of mechanical propulsion, they use strong electric fields to induce movement in a dielectric cooling liquid. These pumps require very little power, but to generate sufficiently strong electric fields, they need to be fed with very high voltage. This project explored various methods for designing DC/DC-converters which fulfil the demands of an electrohydrodynamic pump. This was done by altering and combining existing topologies that were deemed to be relevant. The main method for testing and evaluation was by simulating in LTspice. The project also briefly investigated methods of overcurrent protection. This was relevant because gas bubbles in the cooling fluid can cause electric arcs which damage the pumps. Three converter topologies were chosen for further evaluation. First, a conventional resonant Royer-based converter that has previously been used by APR Technologies which was altered by the inclusion of a feedback loop. Second, a high-frequency resonant Royer-based converter with a planar air-core transformer. Third, a transformerless converter with a switched boost converter IC. All circuits included a Cockroft-Walton voltage multiplier bridge. The two resonant Royer-based converters fulfilled all requirements except the one on efficiency, while the transformerless converter fulfilled all requirements except the one on cost, set by APR. The more expensive transformerless converter had a significantly higher efficiency and a wider range of acceptable input voltages. Furthermore three general conclusions were drawn. The first was that planar air-core transformers are not beneficial compared to conventional transformers in these type of applications. The second was that a discrete voltage regulator controlled by feedback from the output is more effective than using a voltage regulator without feedback, as it also eliminates temperature and load variations. The third conclusion was that to protect the circuits from overcurrent, a large series resistor is needed, which causes significantly lowered efficiency. high-voltage low-current low-power DC/DC DC-DC high-gain converter electrohydrodynamic pump EHD transformerless converter Royer-based converter resonant Royer oscillator Cockroft-Walton voltage multiplier CWVM voltage multiplier SPNVM planar air-core transformer planar transformer high-freqency Royer-based converter overcurrent protection LT8331 gallium nitride GaN planar PCB-integrated transformers Elektroteknik och elektronik

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