Thesis (M.S.)--Ohio University, November, 1999. / Title from PDF t.p.

Thesis (MScIng)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Ohio University, August, 1999. / Title from PDF t.p.

Fundação Araucária / Neste trabalho foi realizado um estudo sobre um sistema de iluminação de emergência não permanente. Este sistema é constituído de baterias, conversor boost e o LED de potência. O foco do trabalho é analisar o conversor boost, que emprega duas técnicas de comutação, sendo elas: comutação dissipativa e comutação suave. As análises feitas no conversor são referentes a comutação da chave semicondutora principal ocorrer de forma dissipativa ou suave para a técnica de comutação dissipativa e verificar se para a comutação suave as chaves semicondutoras (principal e auxiliar) comutam de forma dissipativa ou suave. Outro fato importante é avaliar o rendimento do conversor boost para as duas técnicas de comutação. Ainda é averiguada a autonomia do sistema de iluminação de emergência e também se ele está em conformidade com que cita a norma IEEE 446, referente a autonomia do sistema. Por fim é apresentada as formas de onda da corrente fornecida ao LED. Em suma, o conversor que emprega a técnica de comutação dissipativa demonstrou que a comutação ocorre de forma dissipativa, já para a técnica de comutação suave, a comutação transcorreu de forma suave. A eficiência do conversor mensurada através da autonomia do sistema de iluminação de emergência comprovou que a comutação suave apresenta maior eficiência do que a comutação dissipativa, em torno de 34%, devido a redução das perdas no chaveamento. Foi relatado que o conversor com a técnica de comutação suave empregado no sistema de iluminação de emergência obteve uma autonomia de uma hora e quatro minutos, já o conversor que utiliza a técnica de comutação dissipativa obteve uma autonomia de quarenta e dois minutos. Portanto, os sistemas de iluminação de emergência, no qual o conversor boost faz uso das duas técnicas de comutação estão em conformidade com a norma IEEE- Std 446. Em análise última observou-se que a corrente fornecida ao LED proveniente de um conversor com comutação suave possui uma ondulação em torno de 35% menor que a corrente oriunda de um conversor com comutação dissipativa e, ainda não possui oscilação do nível de corrente, tais características elevam a vida útil do LED e não alteram as características fotométricas do LED. / In this paper we present a study of an emergency lighting system is not permanent. This system consists of batteries, LED boost converter and power. The focus of the paper is to analyze the boost converter, which employs two switching techniques, which are: hard switching and soft switching. The analysis made in the converter are related to the commutation of the main semiconductor switch occur hard or soft switching technique for hard and check for soft switching the switches (main and auxiliary) switch in a hard or soft. Another important fact is to evaluate the performance of the boost converter for the two switching techniques. Also investigated is the autonomy of the emergency lighting system and also if he is quoting in accordance with IEEE 446, regarding the autonomy of the system. Finally is shown the waveform of the current supplied to the LED. In short, the converter that employs the technique of switched hard demonstrated that switching occurs in a hard, since the techniques of soft switching, the switch went soft. The measured efficiency of the converter through the autonomy of the emergency lighting system has proven that soft switching is more efficient than the hard switching, around 34% due to reduction in switching losses. It was reported that the converter with soft switching technique used in emergency lighting system achieved an endurance of one hour and four minutes, as the converter using the switching technique obtained a hard range of forty-two minutes. Therefore, emergency lighting systems, in which the boost converter makes use of two switching techniques are in accordance with IEEE Std-446. In ultimate analysis it was observed that the current supplied to the LED from a converter with soft switching has a ripple around 35% lower than the current coming from a switching converter with hard and does not have oscillation current level, such features increase the lifetime of the LED and do not alter the photometric characteristics of the LED.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / This thesis discuss an investigation into the applicability of modern high frequency power conversion technology in the plasma mineral processing industry. The physics governing the plasma in a processing environment are analysed to provide a clear understanding of this plasma as electrical load. This was done to create an electrical model for the plasma as load and gain understanding into the electrical supply requirements. Modern high frequency power conversion technology is contrasted with thyristor controlled line frequency technologies to provide a suitable starting point for the study. A 3 kW soft switched converter is proposed for application with a plasma load. This converter is designed and verified. The small-signal signature of the proposed converter under peak current mode control is investigated and a new model is proposed to describe this control configuration.

Thesis (Ph.D.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (MScEng (Electrical and Electronic Engineering))-- University of Stellenbosch, 2006. / This thesis presents the design and implementation of a high voltage DC-DC converter using a series stacked topology. The converter’s specifications were set by Spoornet and the converter forms part of a DC-AC inverter to be installed in Spoornet substations. Different converter topologies will be considered. A high frequency, high power coaxially wound transformer will be analysed, designed and manufactured for this specific converter application. A thermal analysis of the transformer will be carried out. The merits of different control schemes, leading to the choice of an average current mode controller, will be discussed. This controller will be designed and implemented to control the converter. The converter is then simulated to test and verify the controller functionality. A two-level series stacked converter is built and tested to verify the converter design and to test the functionality of the coaxially wound transformer. Finally, the results obtained will be discussed.

This thesis aims to bring an understanding to the silicon carbide (SiC) bipolar junction transistor (BJT). SiC power devices are superior to the silicon IGBT in several ways. They are for instance, able to operate with higher efficiency, at higher frequencies, and at higher junction temperatures. From a system point of view the SiC power device could decrease the cost and complexity of cooling, reduce the size and weight of the system, and enable the system to endure harsher environments. The three main SiC power device designs are discussed with a focus on the BJT. The SiC BJT is compared to the SiC junction field-effect transistor (JFET) and the metal-oxide semiconductor field-effect transistor (MOSFET). The potential of employing SiC power devices in applications, ranging from induction heating to high-voltage direct current (HVDC), is presented. The theory behind the state-of-the-art dual-source (2SRC) base driver that was presented by Rabkowski et al. a few years ago is described. This concept of proportional base drivers is introduced with a focus on the discretized proportional base drivers (DPBD). By implementing the DPBD concept and building a prototype it is shown that the steady-state consumption of the base driver can be reduced considerably.  The aspects of the reverse conduction of the SiC BJT are presented. It is shown to be of importance to consider the reduced voltage drop over the base-emitter junction. Last the impact of SiC unipolar and bipolar devices in series-resonant (SLR) converters is presented. Two full-bridges are designed and constructed, one with SiC MOSFETs utilizing the body diode for reverse conduction during the dead-time, and the second with SiC BJTs with anti-parallel SiC Schottky diodes. It is found that the SiC power devices, with their absence of tail current, are ideal devices to fully utilize the soft-switching properties that the SLR converters offer. The SiC MOSFET benefits from its possibility to utilize reverse conduction with a low voltage drop. It is also found that the size of capacitance of the snubbers can be reduced compare to state-of-the-art silicon technology. High switching frequencies of 200 kHz are possible while still keeping the losses low. A dead-time control strategy for each device is presented. The dual control (DuC) algorithm is tested with the SiC devices and compared to frequency modulation (FM). The analytical investigations presented in this thesis are confirmed by experimental results on several laboratory prototype converters. / <p>QC 20150529</p>

M. Tech. Electrical Engineering. / Aims to develop these railways applications for a better use of the electrical power to reduce pollution and consumption. The specification of this project is to improve the conversion of the electrical energy. This also involves improving the connection between the train and the electrical networks using the pantograph. In this research, I will propose a new architecture for the converters and a structure to provide to the grid the electricity generated through braking. Another point regards the command of the converters, which is directly involved in the system behaviour. In order to obtain the best behaviour possible, a different control as usual will be described and modelled to reduce the total harmonics distortion rate and reach a better efficiency.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis aims to present a methodology for comparing the performance electrical, mechanical and hydraulic under the focus of the energy efficiency of pumping systems controlled by valves of strangulation or by the frequency converters. The trigger is held by engines of the line standard or high efficiency. Therefore, this paper presents the simulation in domain of time from a computer platform called ATP (Alternative Transient Program). Complementing the aspects earlier, the validation of proposal modeling, is performed by comparing the simulated values and those from the tests. Finally, it should be emphasized that the laboratory experiments were performed in the laboratory for energy efficiency of the Faculty of Electrical Engineering of the Federal University of Uberlândia. / Esta dissertação tem por objetivo apresentar uma metodologia de comparação do desempenho elétrico, mecânico e hidráulico, sob o enfoque da eficiência energética, de sistemas de bombeamento controlados por válvulas de estrangulamento ou por inversores de freqüência. O acionamento é realizado pelos motores da linha padrão ou de alto rendimento. Neste sentido, este trabalho apresenta a simulação no domínio do tempo a partir de uma plataforma computacional denominada ATP (Alternative Transient Program). Complementando os aspectos anteriores, a validação da modelagem proposta, é realizada através da comparação entre os valores simulados e aqueles oriundos dos ensaios experimentais. Finalmente, deve-se destacar que os experimentos laboratoriais foram executados no laboratório de eficiência energética da Faculdade de Engenharia Elétrica da Universidade Federal de Uberlândia. / Mestre em Ciências