Characterization of an integrated buck converter using infrared thermography

This study deals with new integrated systems for power electronics applications including wide-gap semiconductors. Integration of Silicon carbide (SiC) components provides for instance new perspectives with higher temperature operating points than conventional Silicon (Si) semiconductors. The present work intends to study an integrated buck converter composed of a Silicon IGBT (Insulated-Gate Bipolar Transistor) and a Silicon carbide diode. By means of infrared thermography, an analysis of the thermal disparities induced within such a hybrid assembly under various electrical loads is proposed, regarding especially the consequences of the electrical power transfer and the spatial distribution of the thermal field

Étude et caractérisation d’une fonction hacheur intégrée par thermographie infrarouge

Cet article présente une méthode d’étude et de caractérisation des fonctions d’électronique de puissance basée sur la thermographie infrarouge. Cette dernière permet d’accéder, sans contact, à l’évolution temporelle du champ surfacique de température de la structure fonctionnelle, basée ici sur un IGBT Silicium et une diode SiC. Cette étude apparaît comme essentielle dans le cadre de l’intégration de puissance, lors du dimensionnement thermique au sein d’une fonction spécifique, afin de réduire le volume des fonctions et des systèmes de refroidissement associés. Le suivi thermique est ainsi réalisé jusqu’à l’obtention du régime permanent de la structure, à la fois au niveau des composants IGBT et diode mais également des fils de bonding. L’étude de la fonction hacheur 1 quadrant est menée par ailleurs pour différents points de fonctionnement afin de valider l’approche proposée. Par la suite, les sollicitations thermiques auxquelles sont soumis les éléments de la fonction sont comparées et discutées

Simulations of the irradiation and temperature dependence of the efficiency of tandem photoelectrochemical water-splitting systems

The instantaneous efficiency of an operating photoelectrochemical solar-fuel-generator system is a complicated function of the tradeoffs between the light intensity and temperature-dependence of the photovoltage and photocurrent, as well as the losses associated with factors that include ohmic resistances, concentration overpotentials, kinetic overpotentials, and mass transport. These tradeoffs were evaluated quantitatively using an advanced photoelectrochemical device model comprised of an analytical device physics model for the semiconducting light absorbers in combination with a multi-physics device model that solved for the governing conservation equations in the various other parts of the system. The model was used to evaluate the variation in system efficiency due to hourly and seasonal variations in solar irradiation as well as due to variation in the isothermal system temperature. The system performance characteristics were also evaluated as a function of the band gaps of the dual-absorber tandem component and its properties, as well as the device dimensions and the electrolyte conductivity. The modeling indicated that the system efficiency varied significantly during the day and over a year, exhibiting local minima at midday and a global minimum at midyear when the solar irradiation is most intense. These variations can be reduced by a favorable choice of the system dimensions, by a reduction in the electrolyte ohmic resistances, and/or by utilization of very active electrocatalysts for the fuel-producing reactions. An increase in the system temperature decreased the annual average efficiency and led to less rapid ramp-up and ramp-down phases of the system, but reduced midday and midyear instantaneous efficiency variations. Careful choice of the system dimensions resulted in minimal change in the system efficiency in response to degradation in the quality of the light absorbing materials. The daily and annually averaged mass of hydrogen production for the optimized integrated system compared favorably to the daily and annually averaged mass of hydrogen that was produced by an optimized stand-alone tandem photovoltaic array connected electrically to a stand-alone electrolyzer system. The model can be used to predict the performance of the system, to optimize the design of solar-driven water splitting devices, and to guide the development of components of the devices as well as of the system as a whole

Modeling, simulation, and design criteria for photoelectrochemical water-splitting systems

A validated multi-physics numerical model that accounts for charge and species conservation, fluid flow, and electrochemical processes has been used to analyze the performance of solar-driven photoelectrochemical water-splitting systems. The modeling has provided an in-depth analysis of conceptual designs, proof-of-concepts, feasibility investigations, and quantification of performance. The modeling has led to the formulation of design guidelines at the system and component levels, and has identified quantifiable gaps that warrant further research effort at the component level. The two characteristic generic types of photoelectrochemical systems that were analyzed utilized: (i) side-by-side photoelectrodes and (ii) back-to-back photoelectrodes. In these designs, small electrode dimensions (mm to cm range) and large electrolyte heights were required to produce small overall resistive losses in the system. Additionally, thick, non-permeable separators were required to achieve acceptably low rates of product crossover

Couplages électro-thermo-mécaniques dans les modules de puissance fortement intégrés

Ce travail fait un bilan des actions de recherche menées dans le cadre de la thématique Electronique de puissance au sein du laboratoire Génie de Production de Tarbes (études expérimentales et modélisation)

Doctor of Philosophy

dissertationPactamycin was isolated in 1961 by the former UpJohn Company and to date is the most complex aminocyclopentinol known. This natural metabolite is decorated by six contiguous stereocenters, three of which are quaternary, with each position of the cyclopen

Numerical Quantification of Coupling Effects for Radiation-Conduction Heat Transfer in Participating Macroporous Media: Investigation of a Model Geometry

Radiative-conductive heat transfer in porous media is usually investigated by decoupling the heat transfer modes and solving the volume-averaged continuum equations using effective transport properties. However, both modes are naturally coupled and coupling effect might significantly affect the results. We aim at providing quantitative understanding of the coupling effects occurring in a model geometry. This is an important first step towards improving the accuracy of heat transfer predictions in engineering applications. We developed a numerical method using a structured mesh and cell centered finite volumes and Monte Carlo ray tracing techniques in order to simulate the 3-dimensional and unsteady coupled radiative-conductive heat transfer in semitransparent macroporous media. We have optimized the numerical method with regards to memory and computational requirements leading to optimal performance and allowing to perform a parameter variation study for various steady state cases. We conducted a parameter study considering different optical and thermal material properties and boundary conditions in order to quantify the coupling effect between conduction and radiation, and to demonstrate its dependencies. In terms of thermal properties, it was found that the ratio of bulk thermal conductivities is governing the coupling effect. A distinct peak at a given conductivity ratio was found. The influence of optical properties is discussed in details. It was found that a significant coupling effect exists, reaching up to 15% of the total thermal heat flux. The verified modeling framework in conjunction with our non-dimensionalization offers a tool to investigate the importance of radiationconduction coupling in a quantitative manner. It is an important step towards understanding the detailed mechanisms of radiation and conduction coupling and provides engineering guidelines on the importance of these effects