Current transformer | EPFL Graph Search

A current transformer (CT) is a type of transformer that is used to reduce or multiply an alternating current (AC). It produces a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or potential transformers, are instrument transformers. Instrument transformers scale the large values of voltage or current to small, standardized values that are easy to handle for measuring instruments and protective relays. The instrument transformers isolate measurement or protection circuits from the high voltage of the primary system. A current transformer provides a secondary current that is accurately proportional to the current flowing in its primary. The current transformer presents a negligible load to the primary circuit. Current transformers are the current-sensing units of the power system and are used at generating stations, electrical substations, and in industrial and commercial electric power distribution. Functio

Prise de conscience sur l'environnement, un langage architectural. Une usine d'incinération des ordures ménagères - UIOM (Giubiasco, TI)

Grande infrastructure, l'image visuelle d'une usine d'incinération n'est pas négligeable. Pourtant, l'attention a toujours été portée sur les machines, reléguant l'architecture à une signification mineure, celle d'une enveloppe n'ayant pour but que de protéger la technologie du process. Cependant, suite à un engouement pour la revalorisation des déchets en constante croissance, les maîtres d'ouvrage s'engagent à soigner l'image de ces bâtiments, travaillant l'enveloppe en tant qu'élément médiateur visuel et symbolique entre l'homme et la technologie. Une architecture s'intégrant dans son territoire et son environnement. En tant que grands consommateurs, nous produisons des ordures que nous côtoyons de sa fabrication à nos poubelles. Reflets de notre société de production-consommation, l'UIOM est l'aboutissement du parcours de nos biens consommés. L'image qu'elle véhicule est souvent péjorative. Le projet propose de mettre en scène le spectacle que l'usine d'incinération peut offrir et amener l'acteur-spectateur à une prise de conscience sur l'impact de l'élimination et du recyclage des déchets sur l'environnement. L'art a su démontrer une véritable redéfinition du déchet et proposer une approche positive de l'ordure. L'architecture est un moyen, dans le cas d'une UIOM, de transformer un mal en bien en développant un intérêt suscitant une prise de conscience sur l'environnement «Il faut passer du rejet au projet», METTELET, CHRISTIAN.

2006

High voltage power supply system for tethered drone part II

Clément Bongini

A high voltage power supply system for a tethered drone is presented. The project is a follow-up to a previous semester project and the purpose of this project is to review the implementation, improve the design and solve problems. The system consists of an inverter part, a transformer part and a rectifier part. The input voltage is 600 VDC and the output voltage is 12VDC for a maximum power of 1500W. The inverter part is composed of 4 transistors controlled by two gate drivers. On the other side of the transformer, we have a bridge rectifier which will be implemented in 3 different ways: a full-bridge diode and two new active rectification systems, including mosfets and controllers. We will first present the different systems chosen, review the previous part and make improvements, then we will implement these new systems, design the prototypes and make tests for each system. Finally, we will test the whole converter.

2021

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