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Electric Generator

Electric generator

An electric generator is a machine that transforms rotating mechanical energy into electrical energy. In this sense, it works in the opposite direction to how an electric motor works.

An electric generator is any device capable of maintaining a difference in electrical potential (voltage) between two points, called poles or terminals. Electric generators are electric machines intended to transform mechanical energy into electrical. This transformation is achieved by the action of a magnetic field on the electrical conductors arranged in coils on a sheet metal frame. If a relative movement between the conductors and the field is mechanically produced, an electromotive force is generated, as physicist Michael Faraday discovered.

It could also be called a fem generating machine (electric driving force).

Electric current generators can be of two types:

  • Electric DC generator. In the direct current electric generator, a coil of wire that rotates in a magnetic field produces a current that changes direction with each 180 ° rotation.
  • AC electric generator. The latter is usually called alternator or synchronous generators. Synchronous machines are directly connected to the network and must be correctly synchronized during startup.9 In addition, they are excited with special control to improve the stability of the power system.

All generators need a driving machine (motor) of some kind to produce the rotational force, whereby a conductor can cut the magnetic force lines and produce a fem (electric driving force). The simplest machine of engines and generators is the alternator.

How does an electric generator work?

All electric generators (except electrostatic generators) operate according to the principle of electric induction, where electric current is generated when the conductor intersects with the forces of the magnetic field. In smaller generators, the magnetic field is provided by permanent magnets. On the other hand, larger units have more common electromagnets, which in turn require an additional source of excitation current.

With modern AC generators, the excitation current provides a separate external source (DC generator or rectifier), and in the case of DC generators, the excitation circuit can also be connected to the inductor winding (i.e. , the voltage inductor winding).

Because the excitation current is much smaller than the current in the inductor, the excitation circuit is generally mounted on the generator rotor, since the collector rings are not suitable for conducting a large current. On the contrary, in the case of a direct current generator, where the switch mounted on the rotor provides the conversion of alternating current to direct current, the excitation coil is mounted on the stator and the inductor on the rotor.

In general, the operation of generators is exactly the opposite of electric motors.

Types of electric generators

There are different ways to classify electric generators depending on the criteria that are followed. One of the ways to classify the different types of generator is to do it depending on where the primary energy appears.

  • Chemical electric generators Such as batteries, since they convert the energy of certain chemical reactions into electricity. An electrochemical generator is a type of electric generator that directly converts chemical energy stored in chemical substances into an electric current, through a chemical reaction, without going through other types of energy such as thermal, mechanical or magnetic energy.
  • Mechanical electrical generators Wind turbines and hydroelectric plants include alternators, formerly dynamos that transform mechanical energy into electrical energy. They are based on the phenomenon of electromagnetic induction.
  • Photovoltaic electric generators. These types of electric generators are those used in photovoltaic solar energy to generate electricity. Thanks to the photovoltaic effect, photovoltaic panels generate electricity from solar radiation.

    History of electric generators

    First, there were only battery systems to supply electricity consumption, until in 1831 physicist Michael Faraday published his work on electromagnetic induction, then physicist Franz Ernst Neumann finished them in 1841, this concluded in the manufacture of dynamos , which supply direct current. But the direct current could not be distributed over great distances, and with the invention of the alternator, and the transformer, this was possible.

    These first electric machines were moved by steam engines, and then internal combustion engines, hydraulic turbines and wind turbines were used.

    It is also noteworthy, the momentum that photovoltaic devices formed by semiconductors are having today.

    The first industrial-scale use of alternators The Alliance alternator, developed by Floris Nollet (Brussels) in 1849, was the first generator used in the industry. The intended use of the machines was to disassemble the water electrochemically to obtain luminous gas for lighting. In fact, most of the machines without switches in English and French headlights were used to operate arc lamps. The latter were only out of service at the beginning of the 20th century.


    Published: November 17, 2016
    Last review: February 26, 2020