Disjoncteur | EPFL Graph Search

thumb|upright=1.2|Un disjoncteur bipolaire monté sur rail. Les deux contacteurs solidaires sont en parallèle, mais il existe aussi des disjoncteurs bipoles en monocontacteur. Un disjoncteur est un interrupteur électrique à commande automatique conçu pour laisser circuler le courant électrique, et, protéger un circuit électrique contre les dommages causés par un courant excessif provenant d'une surcharge, d'un court-circuit ou d'une fuite à la terre (disjoncteur différentiel). Il est capable d'interrompre un courant de surcharge ou un courant de court-circuit dans une installation. Suivant sa conception, il peut surveiller un ou plusieurs paramètres d'une ligne électrique. Sa principale caractéristique par rapport au fusible est qu'il est réarmable manuellement (il est conçu pour ne subir aucune avarie lors de son fonctionnement). Différentes techniques de détection de défauts thumb|(a) thermique (b) magnétique (c) magnéto-thermique. Thermique Ce type de disj

Finite Element Model of Hydro Generators Coupled to a Grid Simulation Software

Gilles Rosselet

For the simulation of electrical power systems (adjustable speed drives, wind farms, complete grids, etc.) the Kirchhoff's model is used. Each of the components of this model (transmission line, circuit breaker, electrical machines, etc.) is represented by an equivalent circuit. These equivalent circuit models are unable to take precisely into account the non-linearities of the electrical machines. These non-linearities (eddy currents, magnetic saturation of the materials, skin effect) are however accurately predicted by the finite element method. The goal of this thesis is to add a finite element model of an electrical machine, the hydro generator, to a grid solver. The nature of the link between the grid solver and the finite element model is first investigated. Then, a finite element program used solely to the simulation of the hydro generator and to its link with a grid solver is designed. The features required for such a program are mandated by the physic of the device modelled: dealing with non-linear materials, eddy currents and taking the movement of the rotor into account. Furthermore, it is possible to use the symmetries of the studied device to reduce both the calculating time and the necessary memory. All these features were validated individually, before being used together in the simulation of a hydro generator.

EPFL2010

Efficiency enhancement and frequency-tunable capability in linear CMOS RF power amplifiers for wireless applications

Paulo Augusto Dal Fabbro

This research work deals with the design of linear CMOS RF power amplifiers. Two important aspects are treated: efficiency enhancement and frequency-tunable capability. For this purpose, two different integrated circuits were realized in a 0.11 µm technology, each one addressing a different aspect. With respect to efficiency enhancement, a dynamic supply RF power amplifier was realized. The circuit was designed for an operating frequency of 5.2 GHz, but measurements were also performed at 2.4 GHz. The integrated circuit includes a class A amplifier and a high-efficiency, switched-mode modulator. It occupies an area of 1.35 mm2. Two-tone measurement results at 2.4 and 5.2 GHz showed that the system can deliver over 16 dBm (40 mW) linear output power with efficiencies of 22.7% and 12.6%, respectively. Compared to a constant 2.5 V supply operation, the power amplifier operating with the dynamic supply delivers higher linear output power. Moreover, a relative efficiency improvement of a factor of 2.3 at 2.4 GHz and of a factor of 1.6 at 5.2 GHz at low output power levels is achieved. OFDM measurements at 2.4 GHz demonstrated that for an EVM lower than 3% and for an equal output power of 11 dBm (12.6 mW), the absolute improvement in efficiency is over 3.2%. In this work we also propose a tunable impedance matching network for use in multiband RF power amplifiers. This novel network is based on coupled inductors. A frequency-tunable RF power amplifier using this network was designed for operation at 3.7 and 5.2 GHz. Simulation results for the complete system integrated in a CMOS technology showed good results. However, the frequency-tunable behavior could not be observed in the characterization of the integrated circuit because of the low coupling factor of the integrated coupled inductors. A hybrid implementation using the integrated CMOS power amplifier, a discrete commercial RF transformer and a discrete bipolar transistor to control the current in the secondary winding of the transformer was carried out. The circuit was designed for operation at 200 and 300 MHz. The measurements have shown that at 200 MHz a relative improvement in efficiency of a factor of 1.4 was achieved. Moreover, less distortion was generated with the proposed tunable output matching network. The hybrid implementation allowed us to demonstrate the feasibility of the frequency-tunable RF power amplifier based on coupled inductors.

EPFL2009

Efficiency enhancement and frequency-tunable capability in linear CMOS RF power amplifiers for wireless applications

Paulo Augusto Dal Fabbro

EPFL2009