Where does electricity come from? How does current appear in our sockets? Why do car alternators produce alternating current? How electric current is generated

Ten times a day, turning on and off the light and using household appliances, we do not even think about where the electricity comes from and what its nature is. It is clear, of course, that according to power lines ( power line) it comes from the nearest power plant, but this is a very limited idea of ​​\u200b\u200bthe world around us. But if electricity generation around the world stops for at least a couple of days, the death toll will be measured in hundreds of millions.

How is current generated?

From the physics course we know that:

• All matter is made up of atoms, the smallest particles.
• Electrons revolve in an orbit around the nucleus of an atom, they have a negative charge.
• The nucleus contains positively charged protons.
• Normally, this system is in a state of equilibrium.

But if at least one atom loses only one electron:

1. Its charge becomes positive.
2. A positively charged atom will begin to attract an electron towards itself, due to the difference in charges.
3. To get the missing electron for yourself, it will have to be "plucked" from someone's orbit.
4. As a result, one more atom will become positively charged and everything will be repeated, starting from the first point.
5. Such cyclicity will lead to the formation of an electrical circuit and the linear distribution of current.

So from the point of view of nuclear physics, everything is extremely simple, the atom is trying to get what it lacks the most, and thus starts the reaction .

The "golden age" of electricity

Man adapted the laws of the universe to his needs relatively recently. And it happened about two centuries ago, when an inventor named Volt developed the first battery capable of maintaining a charge of sufficient power for a long time.

Attempts to use the current for their own benefit have an ancient history. Archaeological excavations have shown that even in Roman sanctuaries, and then in the first Christian churches, there were handicraft "batteries" made of copper, which gave minimal voltage. Such a system was connected to the altar or its enclosure, and as soon as the believer touched the structure, he immediately received divine spark". Rather, this is the invention of one craftsman than widespread practice, but the fact is curious, in any case.

The twentieth century has become power boom:

1. Not only new types of generators and batteries appeared, but also unique concepts for the production of this very energy were developed.
2. For several decades, electrical appliances have tightly entered the life of every person on the planet.
3. There are no countries left, except for the least developed ones, where power plants and held power lines.
4. All further progress was based on the possibilities of electricity and the devices that work from it.
5. The era of computerization has made a person addicted to current, in the truest sense of the word.

How to get electricity?

To imagine a person as a drug addict who regularly needs a “life-giving dose of electricity” is a bit naive, but try to completely de-energize your home and live quietly for at least a day. Despair can make you remember the original ways of extracting current. In practice, this is of little use to anyone, but maybe a couple of Volts will save a life or help impress a child:

• Dead battery phone can be rubbed on clothes, jeans or a woolen sweater will do. Static electricity won't last long, but it's at least something.
• If there is nearby sea ​​water, you can pour it into two jars or glasses, connect them with a copper wire, after wrapping both ends of it with foil. Of course, for all this, in addition to salt water, you will also need containers, copper and foil. Not the best option for extreme situations.
• Much more realistic iron nail and a small brass instrument. Two pieces of metal should be used as the anode and cathode - a nail in the nearest tree, copper in the ground. Pull any thread between them, a simple design will give about one Volt.
• If use precious metals- gold and silver, it will be possible to achieve greater tension.

How to save electricity?

Saving electricity can have different reasons - a desire to save the environment, an attempt to reduce monthly bills, or something else. But the methods are always about the same:

It is not always necessary to severely limit yourself in something in order to reduce costs. There is another good tip - unplug all appliances while you are not using them.

The refrigerator, of course, does not count. Even being in "standby" mode, the equipment consumes a certain amount of electricity. But if you think even for a second, you can come to the conclusion that you don’t need almost all the devices for most of the day. And all this time they keep burning your electricity .

Modern technologies are also aimed at reducing the overall level of electricity consumption. What are at least worth energy saving light bulbs, which can reduce the cost of lighting a room, five times as much. The advice to live by "sundial" may seem wild and absurd, but it has long been proven that artificial lighting increases the risk of depression.

How is electricity generated?

Going into scientific details:

1. The current appears due to the loss of an electron by an atom.
2. A positively charged atom attracts negatively charged particles to itself.
3. Another atom loses its electrons from orbit and history repeats itself.
4. This explains the directed movement of the current and the presence of a propagation vector.

But in general electricity is generated by power plants. They either burn fuel, or use the energy of splitting atoms, or maybe even use natural elements. We are talking about solar panels, windmills and power plants.

The resulting mechanical or thermal energy, due to the generator, is converted into a current. It accumulates in batteries and enters every house through power lines.

Today, it is not necessary to know where electricity comes from in order to enjoy all the benefits that it provides. People have long moved away from the original essence of things and slowly begin to forget about it.

Video: where does electricity come from?

This video will clearly show the path of electricity from the power plant to us, where it comes from and how it enters our house:

Generators are devices that convert mechanical energy into electrical energy. As a rule, they produce two types of electric current - direct and alternating.

DC and AC generators

If we consider DC generator, then its structure includes a fixed stator with a rotating rotor and an additional winding. Due to the movement of the rotor, an electric current is generated. DC generators are mainly used in the steel industry, marine vessels and public transportation.

Alternators generate energy by rotating the rotor in a magnetic field. By rotating a rectangular circuit around a fixed magnetic field, mechanical energy is converted into electrical current. This type of generator has the advantage that the rotor (the main driving element) rotates faster than in alternators.

Synchronous and asynchronous generators

Alternating current generators are synchronous And asynchronous. They differ from each other in their capabilities. We will not consider in detail their principle of operation, but will dwell only on some features.

Synchronous generator structurally more complex than asynchronous, it produces a cleaner current and at the same time easily tolerates starting overloads. Synchronous units are great for connecting equipment that is sensitive to voltage drops (computers, TVs and various electronic devices). Also, they do an excellent job with the power supply of electric motors and power tools.

Asynchronous generators, due to the simplicity of the design, it is sufficiently resistant to short circuits. For this reason, they are used to power welding equipment and power tools. In no case can high-precision equipment be connected to these units.

Single-phase and three-phase generators

It is necessary to take into account the characteristic associated with the type of current generated. single phase models give out 220 V, three-phase- 380 V. These are very important technical parameters that every buyer needs to know.

Single-phase models are considered the most common, as they are often used for domestic needs. Three-phase allow you to directly supply electricity to large industrial facilities, buildings and entire villages.

Before buying a generator, you need to have certain technical information, understand how they differ, as this will help you choose a decent model, specifically for your needs, as well as get rid of unnecessary trouble and save money.

LLC "Kronvus-South" sells and manufactures , and which you can buy at a bargain price.

An electrical generator is a machine or installation designed to convert non-electrical energy into electrical energy: mechanical energy into electrical energy, chemical energy into electrical energy, thermal energy into electrical energy, etc. energy into electricity.

It can be a diesel or gasoline portable generator, a nuclear power plant generator, a car generator, a homemade generator from an asynchronous electric motor, or a low-speed generator for a low-power windmill. At the end of the article, we will look at two of the most common generators as an example, but first we will talk about how they work.

One way or another, from a physical point of view, the principle of operation of each of the mechanical generators is the same: when, when the lines of the magnetic field cross the conductor, an EMF of induction arises in this conductor. The sources of force leading to the mutual movement of the conductor and the magnetic field can be various processes, however, as a result, the generator always needs to receive EMF and current to power the load.

The principle of operation of an electric generator - Faraday's Law

The principle of operation of an electric generator was discovered back in 1831 by the English physicist Michael Faraday. This principle was later called Faraday's law. It lies in the fact that when a conductor crosses a magnetic field perpendicularly, a potential difference arises at the ends of this conductor.

The first generator was built by Faraday himself according to the principle he discovered, it was the "Faraday disk" - a unipolar generator in which a copper disk rotated between the poles of a horseshoe magnet. The device gave a significant current at low voltage.

Later it was found that individual insulated conductors in generators are much more effective from a practical point of view than a solid conductive disk. And in modern generators, it is the wire windings of the stator that are now used (in the simplest demonstration case, a coil of wire).

Alternator

The vast majority of modern generators are synchronous alternators. They have an armature winding on the stator, from which the generated electrical energy is diverted. A field winding is located on the rotor, to which a direct current is applied through a pair of slip rings in order to obtain a rotating magnetic field from a rotating rotor.

Due to the phenomenon of electromagnetic induction, when the rotor rotates from an external drive (for example, from an internal combustion engine), its magnetic flux intersects in turn each of the phases of the stator winding, and thus induces an EMF in them.

Most often, there are three phases, they are physically displaced at anchor relative to each other by 120 degrees, so a three-phase sinusoidal current is obtained. Phases can be connected according to the "star" or "triangle" scheme to get.

The frequency of the sinusoidal EMF f is proportional to the rotor speed: f = np/60, where - p is the number of pairs of magnetic pluses of the rotor, n is the number of rotor revolutions per minute. Typically, the maximum rotor speed is 3000 rpm. If you connect a three-phase rectifier to the stator windings of such a synchronous generator, you get a DC generator (this is how, by the way, all car generators work).

Three Machine Synchronous Generator

Of course, the classic synchronous generator has one serious drawback - slip rings and brushes adjacent to them are located on the rotor. Brushes spark and wear due to friction and electrical erosion. This is not allowed in an explosive atmosphere. Therefore, non-contact synchronous generators, in particular, three-machine ones, are more common in aviation and in diesel generators.

For three-machine devices, three machines are installed in one housing: pre-exciter, exciter and generator - on a common shaft. The preexciter is a synchronous generator, it is excited by permanent magnets on the shaft, the voltage it generates is applied to the exciter stator winding.

The exciter stator acts on the winding on the rotor, connected to a three-phase rectifier fixed on it, from which the main excitation winding of the generator is powered. The generator generates current in its stator.

Gas, diesel and petrol portable generators

Today, it is very common in households that use internal combustion engines as drive engines - an internal combustion engine that transmits mechanical rotation to the generator rotor.

Liquid fuel generators have fuel tanks, gas generators need to supply fuel through a pipeline so that the gas is then fed into the carburetor, where it turns into an integral part of the fuel mixture.

In all cases, the fuel mixture is burned in the piston system, causing the crankshaft to rotate. It is similar to how a car engine works. The crankshaft rotates the rotor of a contactless synchronous generator (alternator).

Andrey Povny

This is the ordered movement of certain charged particles. In order to competently use the full potential of electricity, it is necessary to clearly understand all the principles of the device and the operation of electric current. So, let's figure out what work and current power are.

Where does electrical current come from?

Despite the apparent simplicity of the question, few are able to give an intelligible answer to it. Of course, nowadays, when technology is developing at an incredible speed, a person does not particularly think about such elementary things as the principle of operation of an electric current. Where does electricity come from? Surely many will answer "Well, from the socket, of course" or simply shrug their shoulders. Meanwhile, it is very important to understand how the current works. This should be known not only to scientists, but also to people who are in no way connected with the world of sciences, for their general versatile development. But to be able to correctly use the principle of current operation is not for everyone.

So, for starters, you should understand that electricity does not arise from nowhere: it is produced by special generators that are located at various power plants. Thanks to the work of rotating the blades of turbines, steam obtained as a result of heating water with coals or oil generates energy, which is subsequently converted into electricity with the help of a generator. The generator is very simple: in the center of the device is a huge and very strong magnet, which causes electric charges to move along copper wires.

How does electricity reach our homes?

After a certain amount of electric current has been obtained with the help of energy (thermal or nuclear), it can be supplied to people. Such a supply of electricity works as follows: in order for electricity to successfully reach all apartments and enterprises, it must be “pushed”. And for this you need to increase the force that will do it. It is called the voltage of the electric current. The principle of operation is as follows: the current passes through the transformer, which increases its voltage. Further, the electric current flows through cables installed deep underground or at a height (because the voltage sometimes reaches 10,000 volts, which is deadly for humans). When the current reaches its destination, it must again pass through the transformer, which will now reduce its voltage. It then passes through wires to installed shields in apartment buildings or other buildings.

The electricity carried through the wires can be used thanks to the system of sockets, connecting household appliances to them. Additional wires are carried in the walls, through which electric current flows, and thanks to it, the lighting and all the appliances in the house work.

What is current work?

The energy that an electric current carries in itself is converted over time into light or heat. For example, when we turn on a lamp, the electrical form of energy is converted into light.

Speaking in an accessible language, the work of the current is the action that electricity itself produced. Moreover, it can be very easily calculated by the formula. Based on the law of conservation of energy, we can conclude that electrical energy has not disappeared, it has completely or partially changed into another form, while giving off a certain amount of heat. This heat is the work of the current when it passes through the conductor and heats it (heat exchange occurs). This is how the Joule-Lenz formula looks like: A \u003d Q \u003d U * I * t (work is equal to the amount of heat or the product of the current power and the time during which it flowed through the conductor).

What does direct current mean?

Electric current is of two types: alternating and direct. They differ in that the latter does not change its direction, it has two clamps (positive "+" and negative "-") and always starts its movement from "+". And alternating current has two terminals - phase and zero. It is because of the presence of one phase at the end of the conductor that it is also called single-phase.

The principles of the device of single-phase alternating and direct electric current are completely different: unlike direct, the alternating current changes both its direction (forming a flow both from the phase towards zero, and from zero towards the phase), and its magnitude. So, for example, alternating current periodically changes the value of its charge. It turns out that at a frequency of 50 Hz (50 oscillations per second), the electrons change the direction of their movement exactly 100 times.

Where is direct current used?

Direct electric current has some features. Due to the fact that it flows strictly in one direction, it is more difficult to transform it. The following elements can be considered as sources of direct current:

• batteries (both alkaline and acid);
• conventional batteries used in small appliances;
• as well as various devices such as converters.

DC operation

What are its main characteristics? These are work and current power, and both of these concepts are very closely related to each other. Power means the speed of work per unit time (per 1 s). According to the Joule-Lenz law, we obtain that the work of a direct electric current is equal to the product of the strength of the current itself, the voltage and the time during which the work of the electric field was completed to transfer charges along the conductor.

This is how the formula for finding the work of the current, taking into account Ohm's law of resistance in conductors, looks like: A \u003d I 2 * R * t (work is equal to the square of the current strength multiplied by the value of the resistance of the conductor and once again multiplied by the value of the time for which the work was done).

Electric current is the main type of energy that performs useful work in all spheres of human life. It sets in motion various mechanisms, gives light, heats houses and enlivens a whole host of devices that ensure our comfortable existence on the planet. Truly, this kind of energy is universal. Anything can be obtained from it, and even great destruction if used ineptly.

But there was a time when electrical effects were still present in nature, but did not help man in any way. What has changed since then? People began to study physical phenomena and came up with interesting machines - converters, which, in general, made a revolutionary leap in our civilization, allowing a person to receive one energy from another.

So people learned to generate electricity from ordinary metal, magnets and mechanical movement - that's all. Generators were built capable of producing colossal power flows of energy, calculated in megawatts. But it is interesting that the principle of operation of these machines is not so complicated and may well be clear even to a teenager. What is Let's try to understand this issue.

Effect of electromagnetic induction

The basis for the appearance of an electric current in a conductor is the electromotive force - EMF. It is able to make charged particles move, which are many in any metal. This force appears only if the conductor experiences a change in the intensity of the magnetic field. The effect itself is called electromagnetic induction. EMF is greater, the greater the rate of change in the flux of magnetic waves. That is, it is possible to move a conductor near a permanent magnet, or to influence a fixed wire by the field of an electromagnet, changing its strength, the effect will be the same - an electric current will appear in the conductor.

Scientists Oersted and Faraday worked on this issue in the first half of the 19th century. They also discovered this physical phenomenon. Subsequently, current generators and electric motors were created on the basis of electromagnetic induction. Interestingly, these machines can easily be converted into each other.

How DC and AC generators work

It is clear that an electric current generator is an electromechanical machine that generates current. But in fact, it is an energy converter: wind, water, heat, anything in the EMF, which already causes a current in the conductor. The device of any generator is fundamentally no different from a closed conducting circuit that rotates between the poles of a magnet, as in the first experiments of scientists. Only the magnitude of the magnetic flux created by powerful permanent or more often electric magnets is much greater. A closed circuit has the form of a multi-turn winding, which in a modern generator is not one, but at least three. All this is done in order to get as much EMF as possible.

A standard AC (or DC) electric generator consists of:

• Corps. Performs the function of a frame, inside which a stator with electromagnet poles is mounted. It contains rolling bearings of the rotor shaft. It is made of metal, it also protects the entire internal filling of the machine.
• Stator with magnetic poles. A magnetic flux excitation winding is fixed on it. It is made of ferromagnetic steel.
• Rotor or anchor. This is the moving part of the generator, the shaft of which is driven by an extraneous force. A self-excitation winding is placed on the armature core, where an electric current is generated.
• Switch node. This structural element serves to divert electricity from the movable shaft of the rotor. It includes conductive rings that are movably connected to graphite slip contacts.

Creation of direct current

In a generator producing direct current, the conducting circuit rotates in the space of magnetic saturation. Moreover, for a certain moment of rotation, each half of the circuit is near one or another pole. The charge in the conductor moves in one direction during this half-turn.

To obtain the removal of particles, an energy removal mechanism was made. Its peculiarity is that each half of the winding (frame) is connected to a conductive half ring. The semirings are not closed to each other, but fixed on a dielectric material. During the period when one part of the winding begins to pass a certain pole, the half-ring is closed into the electrical circuit by brush contact groups. It turns out that only one type of potential comes to each terminal.

It is more correct to call the energy not constant, but pulsating, with an unchanged polarity. Ripple is caused by the fact that the magnetic flux on the conductor during rotation has both a maximum and a minimum effect. To equalize this ripple, several windings on the rotor and powerful capacitors are used at the input of the circuit. To reduce the loss of magnetic flux, the gap between the armature and the stator is made minimal.

Alternator circuit

When the moving part of the current-generating device rotates, an EMF is also induced in the frame conductors, as in a DC generator. But a small feature - the alternator collector node device has something else. In it, each terminal is connected to its own conductive ring.

The principle of operation of an alternator is as follows: when half of the winding passes near one pole (the other, respectively, near the opposite pole), the current in the circuit moves in one direction from a minimum to its highest value and again to zero. As soon as the windings change their position relative to the poles, the current begins to move in the opposite direction with the same pattern.

At the same time, at the input of the circuit, a signal form is obtained in the form of a sinusoid with a half-wave frequency corresponding to the period of rotation of the rotor shaft. In order to obtain a stable signal at the output, where the frequency of the alternator is constant, the rotation period of the mechanical part must be constant.

gas type

The designs of current generators, where a conductive plasma, liquid or gas is used as a charge carrier instead of a metal frame, are called MHD generators. Substances under pressure are driven in a magnetic field. Under the influence of the same EMF of induction, charged particles acquire a directed movement, creating an electric current. The magnitude of the current is directly proportional to the speed of passage through the magnetic flux, as well as its power.

MHD generators have a simpler design solution - they do not have a rotor rotation mechanism. Such power supplies are capable of delivering large amounts of energy in short periods of time. They are used as backup devices and in emergency situations. The coefficient that determines the useful action (COP) of these machines is higher than that of an electric alternator.

Synchronous alternator

There are such types of alternators:

• Machines are synchronous.
• Machines are asynchronous.

The synchronous alternator has a strict physical relationship between the rotational motion of the rotor and electricity. In such systems, the rotor is an electromagnet assembled from cores, poles and exciting windings. The latter are powered from a DC source by means of brushes and ring contacts. The stator is a coil of wire interconnected according to the principle of a star with a common point - zero. EMF is already induced in them and current is generated.

The rotor shaft is driven by an external force, usually turbines, whose speed is synchronized and constant. The electrical circuit connected to such a generator is a three-phase circuit, the frequency of the current in a single line of which is shifted by a phase of 120 degrees relative to other lines. To obtain the correct sinusoid, the direction of the magnetic flux in the gap between the stator and rotor parts is regulated by the design of the latter.

The excitation of the alternator is implemented by two methods:

1. Contact.
2. Contactless.

In the contact excitation circuit, electric power is supplied to the electromagnet windings through a brush pair from another generator. This generator can be combined with the main shaft. It usually has less power, but enough to create a strong magnetic field.

The non-contact principle provides that the synchronous alternator has additional three-phase windings on the shaft, in which EMF is induced during rotation and electricity is generated. It is fed through the rectifying circuit to the excitation coils of the rotor. Structurally, there are no moving contacts in such a system, which simplifies the system, making it more reliable.

Asynchronous generator

There is an asynchronous alternator. Its device is different from the synchronous one. It does not have an exact dependence of the EMF on the frequency with which the rotor shaft rotates. There is such a thing as "slip S", which characterizes this difference in influence. The amount of slip is determined by calculation, so it is wrong to think that there is no regularity in the electromechanical process in an induction motor.

If the idling generator is loaded, then the current flowing in the windings will create a magnetic flux that prevents the rotor from rotating at a given frequency. This is how slip is formed, which naturally affects the production of EMF.

A modern asynchronous alternator has a moving part device in three different versions:

1. hollow rotor.
2. squirrel-cage rotor.
3. Phase rotor.

Such machines can have self- and independent excitation. The first scheme is implemented by including capacitors and semiconductor converters in the winding. An independent type of excitation is created by an additional AC source.

Generator switching circuits

All high-power transmission line power sources produce three-phase electric current. They contain three windings in which alternating currents are formed with a phase shifted from each other by 1/3 of the period. If we consider each individual winding of such a power source, we get a single-phase alternating current going into the line. A voltage of tens of thousands of volts can be generated by a generator. the consumer receives from the distribution transformer.

Any alternator has a standard winding device, but there are two types of connection to the load:

• star;
• triangle.

The principle of operation of an alternator turned on by a star involves the combination of all wires (zero) into one, which go from the load back to the generator. This is due to the fact that the signal (electrical current) is transmitted mainly through the outgoing wire of the winding (linear), which is called the phase. In practice, this is very convenient, because you do not need to pull three additional wires to connect the consumer. The voltage between the line wires and the line and neutral wire will be different.

By connecting the generator windings with a triangle, they are closed with each other in series in one circuit. From the points of their connection, lines are led to the consumer. Then a neutral wire is not needed at all, and the voltage on each line will be the same regardless of the load.

The advantage of a three-phase current over a single-phase one is its lower ripple when rectified. This has a positive effect on powered devices, especially DC motors. Also, a three-phase current creates a rotating flux of a magnetic field, which is capable of driving powerful asynchronous motors.

Where DC and AC generators are applicable

DC generators are much smaller in size and weight than AC machines. Having a more complex design than the latter, they still found application in many industries.

They are mainly used as high-speed drives in machines where speed control is required, for example, in metalworking mechanisms, mine hoists, rolling mills. In transport, such generators are installed on diesel locomotives and various ships. Many models of wind turbines are assembled on the basis of DC voltage sources.

DC generators for special purposes are used in welding, to excite the windings of synchronous generators, as DC amplifiers, to power galvanic and electrolysis plants.

The purpose of an alternator is to generate electricity on an industrial scale. This type of energy was given to humanity by Nikola Tesla. Why is it that the polarity-changing current, and not the constant one, has found wide application? This is due to the fact that during the transmission of direct voltage there are large losses in the wires. And the longer the wire, the higher the losses. AC voltage can be transported over vast distances at a much lower cost. Moreover, it is easy to convert the alternating voltage (lowering and raising it), which was generated by the 220 V generator.

Conclusion

Man has not fully known which permeates everything around. And electrical energy is only a small part of the open secrets of the universe. The machines that we call power generators are very simple in essence, but what they can give us is simply amazing. Nevertheless, the real miracle here is not in technology, but in human thought, which was able to penetrate into the inexhaustible reservoir of ideas spilled in space!