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Concept# Générateur électrique

Résumé

thumb|Un générateur General Electric
Un générateur électrique est un dispositif permettant de produire de l'énergie électrique à partir d'une autre forme d'énergie. Par opposition, un appareil qui consomme de l'énergie électrique s'appelle un récepteur électrique.
Modélisation
Un générateur réel peut se modéliser de deux manières différentes :

- un générateur idéal de tension avec une résistance en série ;
- un générateur idéal de courant avec une résistance montée en parallèle.

- En circuit ouvert, la tension qui existe à ses bornes lorsqu'il ne débite aucun courant est la tension à vide. Le générateur de tension est donc un dipôle virtuel dont la tension à

Source officielle

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EE-470: Power systems dynamics

This course focuses on the dynamic behavior of a power system. It presents the basic definitions, concepts and models for angular stability analysis with reference to transient stability, steady state stability and long term stability.Fundamentals related to voltage stability are introduced as well.

PHYS-201(e): General physics: electromagnetism

Introduction to electromagnetism.

EE-570: Power system restructuring and deregulation

This course presents different types and mechanisms of electricity markets. It addresses in particular their impacts on power/distribution systems operation and consequently the appropriate strategies capable to ensure a secure and reliable functioning.

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Transformateur électrique

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In recent years the use of solid state frequency converters is rapidly increasing in the industrial and power plants where electric machines are installed, since it allows variable speed operations for the electric system, thus becoming a key factor which is capable of increasing the overall efficiency, as well as the global plant flexibility. The benefits that can be reached when electric motors are under investigation can be so enticing, in particular from the perspective of the operating machine coupled to the motor, that drawbacks take a back seat and can be overcome. On the contrary, power electronic for variable speed is generally not used in power generation, since the gains brought out by the present technology are not sufficient to attract anyone's interest. There are some exceptions in the wind- and the hydro power plant businesses, where there are some cases of variable speed already introduced. However in the former applications the output power is limited to some MW, while in the latter the converter is sized only to a fraction of the whole generating power, since it feeds the machine's rotor.This dissertation investigates on a possible electronic converter for power generation in the 40 MW range and above, which is also attracting from both the cost's and the efficiency's point of view, as well as from the operation reliability perspective and thus may be proposed as a breakthrough in this field. Among the possible frequency converters, those ones have been selected which perform natural commutations only, i.e. those that employ thyristors as the semiconductor devices, since the efficiency, the robustness and the relatively high performances are actually the key success factors to be addressed from the beginning. Well known matrix converter topologies will be referred to, as well as new matrix converter arrangements will be brought out and analyzed: their behaviours will be targeted by the dissertation, in particular when different strategies are adopted for controlling the operations. Specifically comparisons will be carried out when the same converter topology is used, but driven by either the well-known cycloconverter strategy or the newly brought out "active generator" one. In addition several generator winding arrangements will be proposed and analyzed, with the aim of increasing the actual feasibility of the proposed solution. Finally some test results on a sized down experimental rig will be analyzed and compared to the simulation outcomes.

Electric motors consume over half of the electrical energy produced by power stations, almost the three-quarters of the electrical consumption in industry and almost the half of commercial electrical consumption in developed countries. Motors are by far the most important type of electric charges, and so constitute the main targets to achieve energy saving. Owing to their simple and robust construction, the asynchronous motors and especially those of squirrel-cage types, represent about 90-95% of the electrical energy consumption of electric motors, which is equivalent to about 53% of total electrical energy consumption. They are widely used as electrical drives in industrial, commercial, public service, traction and domestic applications. Owing to the importance of induction motors, this thesis is aimed at contributing to energy saving efforts, more specifically in the field of low power induction motors. A contribution is kept in perspective by taking into consideration the energy saving potential during the motor design stage as well as during its operation. Every effort to save energy in motor application can be made by always attempting to use energy only as much as what needed during its operation. The best way is to exploit the saving potential during motor design, while at the same time taking into account its intended application. It can be achieved either through the improvement of motor design or through the reduction of its input electrical energy when the motor has already been built. These two efforts are studied, elaborated and worked out thoroughly in this thesis. To attain this objective, a synthesis has been started with the description of how to model an induction motor. To obtain a better model, an improvement is proposed by using the Schwarz-Christoffel mapping to calculate the slot leakage inductance in induction motor. With such method, slot-leakage inductance can be determined more precisely, resulting in more accurate prediction of motor characteristics. It is based on the stored magnetic energy calculation using two-directional field distribution in the slot. The air gap influence can be observed easily, so that a reasonable slot leakage definition can be adopted. Unlike the conventional method, which is only suitable for rectangular slots (otherwise empirical corrections are required), the proposed general slot form can be extended to any desired polygonal slot form. Consideration of saturation is also indispensable because ignoring it could result in inaccuracy in motor performance prediction. Considering the saturation is essential owing to its important role in self-excitation phenomenon to establish voltage build-up in induction generator. However, the self-excitation phenomenon is undesirable in certain group of capacitor motors as it may hinder the switching-off process and mechanical braking at a desired moment. The undesirable switching-off failure condition is to be avoided by properly designing the capacitor motor. Like in this capacitor motor special application, where a proper design is useful from the point of view of operation safety, designing properly a motor is also very important in energy saving efforts. Motor design and optimization to minimize losses as well as to make possible wide speed-range motor operation are some of the efforts. However, when induction motor has already been built, saving energy is only possible by managing its supplying electrical energy. Various strategies are possible and a particular emphasis on the use of triac to reduce motor input voltage is presented. Besides, a brief economic saving evaluation is given to draw attention to the energy saving potential.

Karin Andersson, Francesco Baldi, Tuong-Van Nguyen

In recent years, the International Maritime Organization agreed on aiming to reduce shipping’s greenhouse gas emissions by 50% with respect to 2009 levels. Meanwhile, cruise ship tourism is growing at a fast pace, making the challenge of achieving this goal even harder. The complexity of the energy system of these ships makes them of particular interest from an energy systems perspective. To illustrate this, we analyzed the energy and exergy flow rates of a cruise ship sailing in the Baltic Sea based on measurements from one year of the ship’s operations. The energy analysis allows identifying propulsion as the main energy user (46% of the total) followed by heat (27%) and electric power (27%) generation; the exergy analysis allowed instead identifying the main inefficiencies of the system: while exergy is primarily destroyed in all processes involving combustion (76% of the total), the other main causes of exergy destruction are the turbochargers, the heat recovery steam generators, the steam heaters, the preheater in the accommodation heating systems, the sea water coolers, and the electric generators; the main exergy losses take place in the exhaust gas of the engines not equipped with heat recovery devices. The application of clustering of the ship’s operations based on the concept of typical operational days suggests that the use of five typical days provides a good approximation of the yearly ship’s operations and can hence be used for the design and optimization of the energy systems of the ship.

2018