Optimization of a Porous Electroosmotic Pump, used in Thermal Cooling System of Power Electronics

International audienceThe liquid cooling of electronic components is generally implemented by a mechanical pump, which requires a minimal maintenance to ensure the reliability of the device. To solve this problem, it is proposed to replace the mechanical pump by a static one, for example an electro-osmotic (EO) pump. In this paper, firstly we present the theory of the electro-osmosis phenomena, and a model of a porous EO pump. Then an optimization of a porous EO pump made of sintered silica is presented. It was found that for any porous EO pump the optimum operating point of the pump is determined by controlling the diameter of the effective pore radius of the porous silica and the Debye length. Using deionised (DI) water as pumping liquid, the EO pump generates 13.6 ml/min and 2 kPa at 150 V applied voltage. The power consumed by the pump is less than 0.4 W. The EO pump works without any bubbles in the hydraulic circuit. This design can be used to cool 47 W of power generated by the power components with a forced convection without evaporation and 270 W with evaporation

LES DIPOLES REACTIFS MODULES ET LA GESTION DE L'ENERGIE REACTIVE DANS LES CONVERTISSEURS A DECOUPAGE

The presented work aims mainly at simplifying the study of energy transfers involved in converters. A preliminary mathematic* study leads to introduce a new element in equivalent circuits. We name it "loss less modulator". This modulator is something like an ideal transformer, the ratio of which cart vary, under control, with time. Such a function is obtained by associating a chopper with low pass filters. Then, we study the association of a ~oss less modulator with a standard reactive element and we named such a dipole "modulated reactive dipole". We show that not only such *a device behaves as a time varying reactive element, but it can also behave as an inductive one, even if energy storage is capaci~ive.. Thus, a large part of converters appear as* assemblies of a small number of loss less modulators and modulated reactive dipoles. Finally and independently, we show that someconversions require the storage of a minimum energy. It is thus necessary to manage the energy by minimizing the stored amolint, i.e. in "taut flow". This concept,applied to a PFC ac-de converter; leads to reduce by a factor* higher than 10 the stored energy as weil as the output rise time. This is supported by a practical realization.Le travail présenté vise essentiellement à simplifier l'étude des transferts énergétiques qui prennent place au sein des convertisseurs statiques. Une étude mathématique préliminaire nous amène à introduire, dans les schémas, un nouvel élément de représentation que nous nommons "modulateur sans pertes". Ce modulateur peut être présenté comme un transformateur idéal dont le rapport varie au court*du temps sous l'effet d'une commande. .Une telle fonction s'obtient en associant un hacheur bien choisi à des filtres appropriés. Nous étudions ensuite l'association d'un modulateur sans pertes et d'un élément réactif standard que nous appelons udipôle réactif modulé". Nous montrons qu'il est* possible d'obtenir, non seulement, des éléments- réactifs* dont la valeur varie dans le temps, mais aussi un comportement inductif avec un stockage capacitif. Dès lors, nombre de convertisseurs apparaissent comme un assemblage d'~n petit nombre de modulateurs sans pertes et de dipôles réactifs modulés. Enfin et indépendamment, nous montrons que certaines conversions nécessitent le stockage d'une énergie minimum: il faut donc gérer l'énergie en minimisant le stock, c'est à dire en flux. tendu. Ce. concept, appliqué à un convertisseur AC~DC à absorption sinusoïdale, permet de réduire par un facteur supérieur à 10 l'énergie stockée et, par-là même, le temps d'établissement de la sortie. Ceci est étayé par une réalisation pratique

Is Loss free Modulator the Central Component of Switching Power Electronics? Application to Flyback Structure.

International audienceAbstract—To account for time variation in equivalent circuits, we introduce a macro component: the loss free modulator (lfm). In practice, it is made of a chopper inserted between two loss free smoothing filters so it behaves as an ideal transformer with a time varying voltage ratio. That way, a converter can be presented as a set of inductors and capacitors, only required to temporally store energy, associated to one or more lfm. As a first illustration, behavior of modulated inductors and capacitors, made of an lfm loaded respectively by an inductor or a capacitor, is derived and some surprising applications of these circuits are described. Then, it is shown that, whatever its structure, a power factor corrected ac-dc converter must store a minimum energy to work properly. In most of practical designs, this minimum is overcome by a 10 ratio. Lowering this energy close to its minimum, offers an opportunity to use the lfm concept. Owing to two lfm, one of which being digitally controlled, the goal is reached. Simulated and measured results are presented and discussed. Finally, the approach followed in this paper is summed up and it is suggested that it can be useful for many converter designs

Design of a Porous Electroosmotic Pump, used in Power Electronics Cooling

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