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Electric Generator, Types And Operation

Electric generator, types and operation

An electric generator is a device designed to produce electricity from other types of energy. The most common is the one that transforms mechanical energy into electrical energy. Sometimes it is also called a generator set.

An electric generator is an instrument that converts mechanical energy into electrical energy. The operating principle of it is based on the principle of electromagnetic induction.

The electric generators can be used for:

  • Generate electricity in order to transmit and distribute it over power lines to domestic.

  • As an emergency backup power or in order to generate electricity permanently. They work as standby generators.

  • Supply the electrical power required for automobiles, ships, trains, or aircraft.

Michael Faraday devised the first electromagnetic generator: the Faraday disk. Faraday's disk showed that electricity could be generated using magnetism. Faraday's Law states that the induced voltage in a circuit is directly proportional to the change in magnetic flux in a conductor or coil.

How does an electric generator work?

The electric generators used in plants for the production of electricity are quite complex, but their operating principle is very simple:

Schematically they consist of one or more conductive wire windings (coils). These coils are supplied with mechanical energy to rotate them within an intense magnetic field.

Mechanical energy can be supplied by a turbine. The coil, free to rotate, is called a rotor, while the fixed magnet is called a stator. There are three types of turbines:

In some hydroelectric power plants, the generator can work in reverse. In this way, it works like a water pump. When there is a surplus of energy transfer switches and it starts pumping water.

Similarity to an electric motor

What happens in an electric current generator is the exact opposite of what happens in an electric motor.

In an electric motor the force exerted by the magnet on the current-covered circuit is translated into a couple of forces. This pair of forces imparts a rotary motion to the rotor.

In the case of the electric generator, no current flows to the circuit. Rotation is imparted through some form of mechanical energy.

To understand the operating system, imagine that we have a simple coil that consists of a square coil. The rotary movement of the loop in relation to the field generates the phenomenon of electromagnetic induction. It generates a current in the loop.

The intensity of the current, like the intensity of the induced emf, will be proportional to the flux of the magnetic field:

  • When the loop is perpendicular to the magnetic field, the intensity of the induced current will be maximum;

  • The induced current decreases as the coil rotates to positions more oblique than the lines of force of the magnetic field. When the coil is parallel to the field the flow of the field with respect to the coil is zero.

The magnetic field will interfere with the electrons in the conductor to induce a flow of electric current inside it.

By continuing to rotate the loop, the direction of the current is reversed. The current strength increases as the loop returns to offer a greater surface area of ​​the field force lines. Until it reaches a new maximum value.

This maximum is the same as the previous one but with an opposite sign. It continues to decrease as the rotation of the loop continues.

The current produced by such a generator, therefore, does not have a constant intensity. However, it follows a sinusoidal trend: such a current is called alternating current.

Typically, the coils of an alternator are connected together to form three AC generators out of phase with each other. The alternator is said to produce a three-phase current, which is what is supplied in our homes.

The transformer is an instrument capable of transforming an alternating current with a certain effective voltage to a different voltage. The transformation happens with small energy losses.

Types of electric generators

If we want to buy an electric generator, we must first know what types there are and what characteristics they have:

Portable generators or stationary power generator

Stationary generators are generally placed in special rooms. They are used regularly or kept ready at any time to start operating. Sometimes they work autonomously in the event of a power outage.

Laptops range from the smallest and lightest leisure generators to giant truck-mounted generators.

Type of motor

The generators are also classified according to the fuel they use and, therefore, according to the type of engine that equips them:

  • 2-stroke generator

  • 4-stroke gasoline generator

  • diesel electric generator

The gasoline electric generator is more popular than the diesel generator.

The 2-stroke generator is the smallest and most compact. It is the one with the simplest engine. That makes it to be a good option for portable generators.

The 4-stroke only works with gasoline. It also produces less greenhouse gas emissions. It also has bigger power cuts: power increases with the available range of 4-stroke models and even more with diesel generators.

In the 4-stroke sector, there are also those that run on gas (LPG, butane, propane) that emit less gas.

Inverter power generator

Another important difference between the various generators is the control electronics they have on board. The simplest models provide 12V in direct current and 220V in alternating current.

However, the current supplied suffers from fluctuations in emissions depending on the instantaneous absorption of the applied load.

Power inverters are capable of supplying a very stable and regular current.

Output voltage

Depending on the needs, there is the possibility of having single-phase (230V output) or three-phase (400V) current generators.

However, it should be noted that there is also a DC or 12V generator. This generator is generally combined with the common 230V AC supply.

The use of electromagnets rather than permanent magnets greatly increased the power output of a dynamo and enabled high power generation for the first time.

Electric start current generator

Most portable UPSs start with a manual pull-out system. Others have integrated a starter motor and battery to operate it. This implies an increase in the weight and dimensions of the entire device. However, it has undeniable advantages if frequent starts are necessary.

In addition, an evolution of the models with a starter motor are those that have an automatic starter. This evolution is due to an electronic section for control and interface with the house's electrical network.

For example, when there is no energy the system detects the voltage drop and automatically starts the generator. It keeps the house under an electrical load.

Silenced Power Generator

A final category is that of generators designed to emit as little noise as possible.

The silent power generator is sought when it is designed to work in the areas where people stay and / or work.

The machine is equipped with soundproofing systems and reduction of vibrations emitted. The reduction in perceived noise is noticeable. When approaching the purchase of one of these generators, the noise level in decibels expressed in the technical manual should be verified.

Generators that are not powered by mechanical energy

There are several electric generators that the input source is not mechanical energy.

Among this type of generators we find:

Photovoltaic generators

Photovoltaic generators use photovoltaic solar panels. Each solar panel is made up of an arrangement of photovoltaic cells. Photovoltaic cells are responsible for generating electricity thanks to the photovoltaic effect.

Electrochemical generators

When the flow of electrons is produced by an oxidation-reduction reaction, there is an electrochemical generator. The most common are batteries and fuel cells.

Radioisotope generators

Generation in the radioisotope thermoelectric generator is based on the decomposition of radioactive isotopes. Radioactive decomposition produces emission of particles and heat. Electricity production can be obtained directly from the displacement of electrically charged particles, or indirectly from the heat produced.

Differential thermal generators

Electricity production is obtained from a temperature difference for the Seebeck effect. This system can work with any thermal gradient.

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Published: May 13, 2015
Last review: June 19, 2020