DC motors and their applications

car battery

Many novice motorists are concerned about the question of how many amperes can be contained in a fully charged vehicle battery. In order to understand this parameter, you should carefully read the data indicated on the battery itself.

For example, if the battery capacity is 55 Ah, then this car unit can transmit a current of five amperes for eleven hours, provided that the battery is fully charged.

To find out how many amperes there are in a charged battery, you should understand its basic parameters and learn how to calculate everything correctly. Do not think that a capacity of 55 amperes per hour will allow you to deliver a current of 1A for 55 hours, since this is fantastic data.

What is current strength

Under the influence of charged particles and an electric field, an electric current arises, which is one of the key sources of energy. When talking about charged particles moving in one direction, we mean the concept of current strength. So, from the point of view of physics, this will be the magnitude of the movement of electric charges. A certain amount of charge can pass through a certain cross-section of a conductor per unit time.

The unit of current is considered one of the main electrochemical indicators, and amperes are used to measure it. Important factors that influence this physical quantity are conductor materials, environmental conditions, and temperature. Current can be constant or alternating (an example of the latter is the lighting of any household appliances in a home apartment or office).

If we talk about other basic indicators, the current strength is directly proportional to the voltage created in the network and inversely proportional to the resistance in it. To determine the current strength, in practice they often use a special device - an ammeter. It wedges itself into the circuit in the required area and measures the strength of the charge that has passed through the time interval, taking into account the cross-section of the wire.

Ksenia Sobchak dispelled rumors of a break in relations with Channel One

The evening talk show “Doc-Tok” has been airing on Channel One since February 4. From the very beginning, two presenters were announced for the project - Alexander Gordon, who already hosts the “Male and Female” program on the First, and Ksenia Sobchak, who by that time had not appeared on federal air as a presenter for a long time. The ambiguous concept of the talk show - initially it showed actors' dramatizations of high-profile events, which were then discussed by experts in the studio - did not impress the audience; the program's ratings were far from record-breaking.

The project looked ridiculous and crude - they even aired test episodes of the show, where they discussed topics that had already been forgotten by the public against the backdrop of screens with the working title of the program (“Red and Black”). The most unsuccessful episodes were hosted by Ksenia. Then the producers hastily focused on Alexander Gordon, adored by the public, stopped with dramatizations, switched to current topics, and things went well - it turned out to be a good talk show, albeit not with record ratings. And Ksenia somehow disappeared from the air unnoticed, which gave her enemies reason to gloat. Like, she sat in a puddle in front of all the honest people, and there was so much noise.

Sobchak herself did not comment on her departure from the show and focused on the development of her YouTube project. There she had serious successes - such as an interview with Lars von Trier, but keeping up the pace in a highly competitive environment is very difficult. After all, besides her, at least Yuri Dud and Irina Shikhman do excellent interviews on the Internet. In addition, Ksenia clearly wants to work in the journalistic field - to talk about politics, important social issues, but she does not have enough such experience. Meanwhile, the success on YouTube of former Entveshnik Alexey Pivovarov with the “Editorial” project clearly haunts her: recently, in addition to interviews, Ksenia began to release “Beware, News” - a kind of final information and analytical review of the week, if we resort to television parallels.

But it turned out that she did not completely break with Channel One. On June 18, Sobchak appeared on the air of Dok-Tok as if nothing had happened. The program was dedicated to Bill Gates, who is now often mentioned in connection with the pandemic - there are half-crazy theories that the American billionaire and philanthropist was either involved in the spread of the coronavirus, or even invented it himself.

The secular telegram crowd was amazed: Ksenia is still on First? “At least check the information,” Sobchak did not remain silent this time. — I have appeared on Dok-Tok periodically all this time — [and hosted issues] on topics on which I consider it possible to express my opinion. About Bill Gates and conspiracy theories - with pleasure.”

It turns out that Ksenia is in a privileged position on First - she hosts the show only if the topic of the episode coincides with her socio-political views. It just happens so rarely that the only host of Doc-Tok seems to be Alexander Gordon.

Battery types

Before looking for the answer to the question of how many amperes are in a car battery, you need to become more familiar with their classification. For a long time they were made mainly on the basis of lead and acid. Naturally, such equipment requires the most careful handling due to its high chemical hazard.

The main types of car batteries today are as follows:

Classic, in the plates of which there is a high content of the element of antimony. The electrolysis process in them occurs at an accelerated pace, because of this the electrolyte often evaporates and distilled water has to be added.
Calcium. Instead of antimony, calcium is the main material for electrode grids. To reduce internal resistance, silver is sometimes added in small volumes. The intensity of gas and water release has decreased compared to antimony batteries. This extended the service life and virtually eliminated the need for product maintenance. Such batteries are very sensitive to overdischarge and voltage in the vehicle's on-board network.
Hybrid. They are a combination of the types described above. The negative plates are made of calcium, and the positive ones are made with a small addition of antimony. Their main advantage is resistance to discharge and overdischarge.
Gel or AGM type. One of the most innovative batteries. They got their name due to the fact that the working electrolyte in them is not in a liquid, but in a jelly-like state. Thanks to this, it was immediately possible to solve the problem of leakage, so that their housing can be considered sealed. The gel does not have high fluidity and is practically in a fixed position. For such batteries, you may not be particularly interested in how many amperes they contain due to their low self-discharge ability. They are also characterized by high resistance to vibrations and shocks.
Alkaline. The main working fluid in them is not acid, but alkali. Most often they are nickel-iron or nickel-cadmium. In both options, the electrolyte is the same - it is a potassium solution, but the electrodes are made with the addition of different metals. Even during intense chemical processes, electrolyte does not leak from such batteries. There is practically no need to top it up, and such batteries tolerate overdischarges well. Unlike acidic ones, they are not so dangerous to health, they accumulate energy and work well in low temperatures.
Lithium-ion. They are considered the most promising option for an additional source of electric current. The current carriers are lithium ions, but the manufacturing technology and material of the electrodes are constantly changing. Key advantages include high specific capacity and low self-discharge ability. There is also a certain set of disadvantages: sensitivity to temperature changes, a gradual decrease in capacity in the first years of operation. Their power is not yet enough to start the engine, so they are used as auxiliary ones.

Battery inrush current

If you look at different manufacturers, for example European countries, the USA, Russia or China, then all these batteries will have a different inrush current. So, for example, if you compare 55 Ah China and Europe, the difference can be 30 - 40%! But why is that?

At the moment there is a division of starting values into gasoline and diesel units. After all, a diesel engine initially needs a higher indicator, because its compression ratio is much higher, can reach up to 20 atmospheres.

Number of amperes in a charged car battery

The most civilized and professional way to check the amps on a battery is to use a special device called a multimeter. It allows you to measure both current and voltage. Although it will not directly measure how many amps a particular car battery produces, it is quite possible to make such calculations.

First of all, the product must be charged to the maximum using a special charger that operates from the mains. Having measured the voltage and density of the electrolyte, we make sure that the battery is charged and should give its charge to electrical consumers. We connect the load of the installed power and note the start time of the experiment. For example, such a load can be provided by an ordinary incandescent lamp, the power of which is known to us.

We wait until the voltage in the battery drops to half of its fully charged state. We remove the light bulb and stop discharging the car battery. Now you can measure the new capacity value, which is expressed in amperes/hours. When there is a load in the network, we multiply the current by the number of hours during which the light bulb was on. If as a result we get the value that a car battery should show, close to the nominal value, then it is in good condition.

Despite how many amps a car battery should produce, it is capable of spontaneously discharging. Moreover, this happens even in those moments when it does not power any electrical appliances. Self-discharge is a natural process, the magnitude of which is influenced by surrounding weather conditions. In addition to natural leakage, you should pay attention to areas with high humidity or insufficient insulation. Additional loss of current can lead to a complete discharge of the entire battery and even fire if a number of factors coincide.

How many amps are there in a car battery?

To avoid such problems, you need to be able to navigate the battery markings, accurately identify their types and compare them with your car, and in order for the battery to charge normally, you need to know how many amperes there are in the car battery.

When a battery is faulty, it does not charge fully or runs out of power.
If the battery is faulty, the headlights may shine at different intensities.
Constant noise coming from it can indicate that the generator is not operating correctly.

How to charge a car battery

While driving, the car battery is charged from the generator, which also produces current. However, it is not possible to fully charge it in this way, because there are always certain losses. That is why the need to forcibly recharge the battery periodically arises. Moreover, in warm weather, engine starting can be ensured by even 20% of the actual battery capacity. In the cold season, with thickened oil, this will be almost impossible to do.

As the battery manufacturers themselves recommend, a completely discharged battery must be charged from 10 to 15 hours. In this case, the value of the supplied current is at least 10% of its standard rated capacity. It’s even better to apply a small current to the charge and increase the time itself. This way it will be possible to “overclock” the device to a larger capacity.

Considering that the battery is a source of direct current, it is important to observe the principle of polarity of connections when working with it. Therefore, the positive terminal of the battery is connected to the same one from the charger - they are indicated by the “+” sign. Do the same with negative terminals. If you do not adhere to this rule, the battery will be discharged.

Before charging, remove it and move it to a warm, dry room. It is advisable to immediately clean it of dirt and deposits, and the terminals can be sanded with emery cloth to ensure high-quality current flow. The situation is more complicated with serviced batteries - the plugs should be unscrewed and the accumulated gases allowed to escape freely. If necessary, monitor the electrolyte level and add it to the jars. Most modern chargers are automatic and do not provide manual adjustment of the current.

Engineers from leading research centers and laboratories are steadily looking for new solutions in the field of creating and operating automobile batteries. New power sources are discovered, capacity increases, and the ability to self-discharge decreases. One of the important directions in the search is to increase environmental safety for the environment. AGM type batteries meet these requirements, however, most likely, they act as an intermediate stage in the prospects for creating reliable automotive batteries.

How to test a battery with a multimeter

The battery is disconnected from the generator;
The load is connected;
The battery should run under load for about two minutes;
The load is turned off;
A multimeter is connected to the battery in voltage measurement mode;
Indicators are taken.

If the multimeter shows that the voltage is 12.6 volts, then this indicates that the battery does not need to be charged and is fully functional. If the readings are below 12.6, this indicates the need to recharge the battery.

How much current does a car's alternator produce? variable or constant?

variable, then made constant using a diode bridge

three-phase before the bridge, and after the bridge constant pulsating

At the output of the generator we have 12.5-14 volts DC. What happens inside the generator does not affect the speed.

And I don’t care if the battery was charging and the lamps were shining.

I don’t know your role and I don’t want to guess. The question is posed incorrectly. Because the cars are DIFFERENT and their generators are also different. The Moskvich 401 car has a DC generator with a collector electromechanical converter. And Moskvich has 2141 three-phase alternating voltage generator with a bridge rectifier.

A DC generator is found on almost every car. The automobile generator is a three-phase alternating current generator with a three-phase rectifier with six diodes according to the scheme of Academician Larionov. (wiki). I personally think (delicately) that direct current is only possible by chemical means - for example, the notorious batteries...

Three windings - which means which one? The alternator cannot be straightened with diodes alone. The pulsations still need to be smoothed out. I can say with confidence that there is clean constant in the battery.

On the Gas-51 there was a direct current generator, now mostly alternating current on the collector, but after the tablet (U and I regulator) it is still constant - is this answer suitable for certification?

How much is the output power for the car radio in volts, watts and amperes? Thank you

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Starting current of car battery and starter

The starting current (cold cranking current), which is indicated on the car battery, is the current that a fully charged battery can supply within 30 seconds. The starting current of a car battery depends on the total area of its electrodes. In practice, a battery with a large number of plates, and as a result of greater weight and larger size, has a higher cold cranking current.

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Alternating current generator device

The operation of any generator can be compared to an electric motor that operates in reverse mode, that is, it does not consume, but produces current. Based on the type of design, modern generators are divided into two types: compact and traditional. They have a common device, but differ in the layout of the housing, fan, rectifier assembly and drive pulley. Also, modern devices have three phases.

Generator device

The generator consists of the following main elements:

drive with pulley, bearings and shaft;
rotor with field winding and slip rings;
stator with core and winding;
a housing consisting of two covers;
voltage regulator;
rectifier block or diode bridge;
brush assembly.

Let's analyze each element of the device separately and in detail.

Frame

The housing contains all the main elements of the generator. It consists of two covers (front and back). The covers are connected to each other with bolts. For the manufacture of covers, light aluminum alloys are used, which are not magnetized and dissipate heat well. The covers have ventilation holes and mounting flanges.

The back cover contains a diode bridge and a brush holder with brushes. Also in the back cover there is an output contact through which current flows from the generator.

Drive unit

Rotation from the crankshaft is transmitted to the generator pulley and rotates the rotor. The pulley rotation speed is 2-3 times higher than the crankshaft speed. Torque from the engine is transmitted through a belt drive. Poly V-belts and V-belts can be used depending on the design. The poly V-belt is considered more versatile and modern.

On the rotor shaft there is an excitation winding, which creates a magnetic field and, in fact, is an ordinary electromagnet. The winding is located between two pole halves (cores) necessary to regulate and direct the magnetic field. Each half has six triangular projections called beaks.

Generator rotor
At the front end of the rotor shaft there is a drive pulley, and at the other end the fan impeller is mounted. There may be two of them. They are needed to cool the internal parts of the generator. There are also maintenance-free ball bearings at both ends of the rotor.

Stator

Stator
Structurally, the stator has the shape of a ring. This is the main part used to create alternating current from the magnetic field of the rotor. Consists of a winding and a core. In turn, the core consists of connected steel plates, in which 36 grooves are formed. Three windings are wound into the slots, which form a three-phase connection.

The rectifier unit performs the task of converting the generator's alternating current into direct current, which is necessary to power the vehicle's on-board network. In other words, it produces a voltage that is stable and uniform.

Diode bridge

The block is also called a diode bridge, which consists of two radiator plates (positive and negative) and diodes. There are two diodes per phase. The diodes themselves are hermetically mounted into the plates. The diode bridge is shaped like a horseshoe.

From the stator winding, current flows to the diode bridge, then it is “rectified” and supplied to the output contact on the back cover.

Current passes through diodes only in one direction, and currents of reverse polarity are cut off. The diode bridge can be located in the generator housing, or it can be placed outside the housing. But most often it is attached to the inside of the back cover.

The regulator maintains the generator voltage within certain limits. Modern models use semiconductor electronic voltage regulators. They are installed on top of the brush holder block.

Voltage regulator and brush assembly

When the engine operates at high speeds, the voltage on the stator winding can reach up to 16V. Such voltage should not be supplied to the on-board network. To eliminate this, the voltage regulator, receiving current from the battery, will reduce its value. A small current on the rotor winding will create an equally small magnetic field. This means that the voltage on the stator winding will decrease.

Brush unit

The brush assembly in modern generators is combined with a voltage regulator into one non-separable mechanism. It transfers the excitation current to the copper slip rings of the rotor. This is a simple design that consists of a brush holder, two graphite brushes and pressure springs.

How to increase?

A drop or too low voltage on the on-board network can be due to various reasons. Before increasing the network voltage from 5 to 12 Volts, you need to make sure that the car generator is functioning normally. If the energy loss is due to improper operation, then it is necessary to dismantle and repair the device, replacing the failed mechanisms with new ones.

Often this parameter drops due to a discharged battery, then perhaps it makes sense to diagnose it - check for cracks, replace the electrolyte, or charge it correctly. In terms of charging, certain points must be taken into account - the procedure must be carried out using only a working charger in compliance with all the rules and nuances. These points are described in detail in the article.

Installing a diode in the generator circuit

If the indicator in the electrical circuit drops, but this is not related to the operation of the generator or battery, then you can increase it on your own. The task is to “deceive” the generator regulator and make it “think” that the car’s on-board network has an even lower voltage than it actually is.

Before you increase the voltage that is falling, keep in mind that it is important to maintain polarity when installing the diode. If the polarity is reversed, nothing will happen, but the node will not be able to provide the required charge. Note that the diode must be designed for a current of at least 5 Amps. Since the diode will heat up during operation of the generator unit, it is optimal to mount it on a radiator.

When choosing a diode element, one nuance must be taken into account - for germanium parts, the voltage drop will be about 0.3-0.7 volts, and for silicon parts - from 0.8 to 1.2 volts. This is exactly the value by which the voltage in the electrical circuit will increase. Take this point into account when choosing, it will determine the final result.

When installing the diode element, it is necessary to ensure that the wire from it is not installed under tension; this will not be entirely convenient. The best option would be to increase the cable length by approximately 2 centimeters from the diode. This will make it easier to install it into the voltage relay connector of the generator device, and if dismantling is necessary, it will be easier to do.

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DC Characteristics

Direct Current or DC in English means a similar variety, which has the inherent property of not changing its parameters over any period of time. A small horizontal line or two parallel lines with a line drawing of one of them is a graphic representation of direct current.

Scope of application: most electronic devices, including computer equipment, TVs and gadgets, use in home networks and cars. To convert alternating current into direct current in the outlet area, voltage transformers with rectifiers or specialized power supplies are used.

A common example of DC consumption is almost all power tools that operate with batteries. The battery device remains in any case a constant power source. Conversion to variable is achieved, if necessary, with the help of inverters - special elements.

DC to AC converter

In this case, the process looks quite complicated. An inverter is a standard technique in everyday life; it is a generator of a periodic voltage obtained from a constant voltage close to a sine wave.

The high prices for such a device are due to the complexity of the design. The cost is largely determined by the maximum current output.

Used in rather rare situations. For example, if it is necessary to connect some kind of tool or devices to the car’s electrical network.

In our time, there is no sector of the national economy in which electricity is not used. And each of them places certain requirements on electrical machines and devices, which determine not only the design of these machines, but also the type of current used. Although both alternating and direct currents are widely used in technology and industry, their areas of application are very clearly delineated.

For the first time, people received electric current from galvanic cells. These elements created a flow of electrons in the electrical circuit, moving all the time in one specific direction. This current is called “constant”.

The first rotating generators, electric motors and appliances also ran on direct current. And when, at the end of the last century, the Russian electrical engineer M. O. Dolivo-Dobrovolsky proposed using three-phase alternating current, many scientists were distrustful of this. Even the famous American electrical engineer Edison considered alternating current an invention not worthy of attention. However, very soon alternating current began to be used in many areas of electrical engineering. Electric alternating current generators create a flow of electrons in an electrical circuit that continuously changes the direction of its movement. So, in the circuit of an electric light bulb that illuminates your room, electrons travel in one second

Change the direction of your movement 100 times: 50 times they move in one direction and 50 times in the opposite direction. Such a current is said to have a frequency of 50 cycles per second.

This feature of the movement of electrons gives alternating current a number of properties that determine its dominant position in modern electrical engineering.

One of the most important properties of alternating current is its ability to transform. As we know, the transmission of electrical energy over long distances is possible only at very high voltages, reaching 110, 220 and even 500-800 thousand V. Such a high voltage cannot be obtained directly from generators. At the same time, various electrical machines and devices require an electric current of several tens or hundreds of volts. This is where his transformation ability came in handy - it made it possible to change the alternating current voltage within any limits using transformers.

Little of. Connecting the generator windings into a three-phase system made it possible to obtain three-phase alternating current. This is a system of three alternating currents that have the same frequency, but differ in phase by one third of the period. Three-phase current has important advantages. Firstly, three-phase power lines are more profitable than single-phase ones: with the same cost of wires and insulation, more electrical energy can be transmitted through them than with single-phase alternating current. And secondly, thanks to the property of three-phase alternating current to create a rotating magnetic field, it was possible to build very simple and reliable asynchronous electric motors without a commutator and brushes.

These qualities of alternating current are the reason that today all industrial power plants produce only three-phase alternating current.

More than half of the electrical energy generated by these power plants is consumed by electric motors. So that they can perform a variety of work, they are made in different designs and sizes.

In addition to simple asynchronous motors, which are widely used to drive machine tools, there are motors with windings and slip rings on the rotor. They develop great forces when starting and are therefore successfully used on cranes. There are also synchronous motors that have a constant rotation speed. Electric motors can be as small as a spool of thread or as big as a carousel.

The use of several electric motors to drive machines made it possible to simplify the machine mechanisms, make them easier to control and make it possible to create automatic machine lines.

The small size of electric motors has made it possible to use electrical energy where previously only manual labor was used. Electric drills, saws, planes and other electrified tools made the work of workers much easier and made it more productive.

Electric floor polishers, vacuum cleaners, washing machines and refrigerators have come to the aid of housewives.

Alternating current is a good source of heat. Metal is melted and cooked in powerful electric arc furnaces. Electric resistance furnaces are widely used for air conditioning, heating ovens and various rooms.

Light bulbs produce light no matter how much current passes through their filaments. But since the transmission of alternating current is more economical, and transformers make it easy to maintain the voltage required for them, the entire lighting network of cities and villages is served by alternating current.

The continuous change in the direction of movement of electrons in alternating current, its ability to transform, opened a wide path for it in many areas of technology. But a current that constantly changes its direction is not always good. So you boarded a trolleybus, a metro train or an “electric train” car on the railway. Here you are in the domain of DC.

The fact is that simple and convenient AC electric motors do not allow smooth changes in their rotation speed over a wide range. And remember how many times the driver has to change the speed of the trolleybus; Only a DC motor can handle such hectic work well. These motors are powered from traction rectifier substations. The alternating current coming to them from power plants is converted into direct current using mercury rectifiers, and then fed into the contact network - into wires and rails.

The use of DC traction motors on transport vehicles has proven to be so beneficial that they can be found on diesel locomotives and motor ships.

Their main engines are diesel engines, which drive generators that produce direct current. And he, in turn, makes electric motors work, turning wheels or propellers.

However, the high cost and complexity of converter substations have forced scientists and engineers to think about the use of alternating current in transport. Now there are already sections of railways that use single-phase alternating current. It is also successfully used on many diesel-electric ships.

Further electrification of railways in our country will be carried out mainly using alternating current with a voltage of 25 thousand V. This current will be converted into direct current directly on electric locomotives using rectifier devices.

The good adjustment capabilities of DC electric motors have made it possible to successfully use them also on lifting and transport mechanisms. Conventional cranes you see on construction sites are powered by AC motors. But on powerful cranes of large metallurgical plants, DC motors are installed. After all, here you need to smoothly lift and carry huge ladles with molten metal, pour it into molds or feed red-hot ingots to rolling mills.

These engines also drive the mechanisms of giant walking excavators.

DC motors can reach very high rotation speeds - up to 25 thousand rpm. This allows you to get more power from a very small engine size. Therefore, they are indispensable as control motors used on airplanes for turning rudders, ailerons and flaps, for raising and lowering landing gear and other mechanisms.

The constant direction of electron movement in a direct current circuit has determined a large and important area of its application, in which alternating current cannot compete with it. We are talking about electrolysis - a process associated with the passage of current through liquid solutions - electrolytes. Under the influence of direct current passing through the electrolyte, it decomposes into individual elements, which are deposited on certain electrodes - the anode or cathode. This property is widely used in non-ferrous metallurgy - for the production of aluminum, magnesium, zinc, copper, and manganese. In the chemical industry, fluorine, chlorine, hydrogen and other substances are produced using electrolysis.

In electroplating, electrolysis is used to deposit metal onto the surface of various products. In this way, protective coatings are applied to metal products (nickel plating, chrome plating), metal monuments, printed forms, etc. are made. Galvanization is used in medicine to treat certain diseases.

The constant direction of electron flow helps direct current compete with alternating current in welding and some types of lighting. When welding with direct current, metal particles are transferred from the electrode to the product more correctly and the seam is of better quality than when welding with alternating current.

Go to the film studio. Powerful arc film projectors flood the filming pavilion with light. With alternating current, the arc burns less steadily, produces less light, and produces a hum that interferes with sound recording during filming. Therefore, film projectors are powered by direct current, which produces a silent, stable arc. High-power military searchlights and arc film projection machines also use direct current.

To obtain alternating current, you need to continuously rotate an alternating current generator, and direct current can be provided by stationary batteries or galvanic cells. These properties of the electric current source also in some cases determine the scope of application of direct current.

The car is standing still. How to start its engine? A rechargeable battery is at your service. You press the starter button and the DC motor, drawing power from the battery, starts the engine. And when the motor is running, it rotates the generator, which charges the battery and restores expended energy. Such a reversible process is not possible with alternating current.

What would happen if train lighting was powered by alternating current? If the train stopped, the wheels of the cars would stop rotating, and along with it the electric generators would stop and the lights in the cars would go out. But this does not happen because DC generators are installed under the cars, operating in parallel with batteries. The train is moving - the generators rotate, provide energy for lighting and at the same time charge the battery. When the train stops, the battery sends current to the lighting network.

Imagine that there was an accident at a power plant: all the turbo or hydrogen generators stopped and the power lines connecting it to other power plants were disconnected. In such cases, direct current obtained from large batteries comes to the rescue. With its help, auxiliary mechanisms are set in motion, switches that have been turned off are turned on, and the main turbo or hydrogen generators are put back into operation. Battery power is very reliable, so all control, automation and alarm protection circuits in large power plants operate on direct current.

Can a submarine sail without DC current? On the surface of the water maybe. In this case, its propellers are rotated by diesel engines. But under water, diesel engines stop - there is not enough air. It runs a DC motor that receives energy from batteries. When the boat floats to the surface again and the diesel engines are turned on, the electric motor turns into a generator and recharges the batteries.

In mines, it is not possible to hang a contact wire for electric locomotives everywhere. How can they get around? And here the battery comes to the rescue again. In many mines, mine battery electric locomotives deliver coal from the most remote faces. You often see electric trolleys with batteries - electric cars - at train stations. They are also found in the workshops of large plants and factories.

Notice how the cameraman films some important event. He has a light film camera in his hands and a battery on his belt. I pressed the button and the device started working. Such lightweight batteries are widely used for portable radios, signaling devices, and electrical measuring instruments.

Of course, the examples listed here do not exhaust all areas of application of electrical energy. We did not say anything about its use for telegraph and telephone communications, for radio and television and other purposes - you will read about this in the relevant articles on our website.

5.1. WHY IS ALTERNATING CURRENT NEEDED?

In the first electrical installations, only direct current was used. However, it soon became clear that it was much more profitable to use alternating rather than direct current, that is, one that periodically changes its value and direction.

First of all, alternating current is more convenient to generate at power plants. AC generators are simpler and cheaper than similar DC generators.

It also turned out that transmitting electric current through wires is more profitable at high voltage. Changing the AC voltage is very simple - you just need to use a transformer. This is much more difficult to do with direct current.

Simple and reliable AC electric motors have been designed and are widely used in industry.

But these are all applications where alternating current can compete with direct current. Generators, transmission lines and electric motors can be made on both direct and alternating current. However, there are physical phenomena that appear only when the current changes.

These phenomena are widely used in radio engineering, automation, electronics, etc.

It can be said that if there were no alternating current, many of these branches of electrical engineering would not exist.

Radios, televisions, and tape recorders use alternating currents and it is fundamentally impossible to replace them with direct current.

Many technological processes in industry are also based on alternating current.

Instructions

First, let's figure out what electric current is. The directed movement (flow) of charged particles is called electric current. In an alternating electric current, different numbers of charged particles pass through the cross-section of a conductor over equal periods of time. In a constant, the number of these particles at equal time intervals is always equivalent.

Alternating current constantly changes its strength, magnitude or direction. And these changes always occur periodically, that is, they are repeated at regular intervals. For example, using AC

the battery cannot be charged or cannot be used for such technical purposes.

Unlike DC

, the variable has several additional meanings: - period - the temporary value of completing a full cycle of alternating
current
;
half-cycle and frequency (number of cycles for a specific period of time); - amplitude - the highest value of alternating current
; - instantaneous value - the value
of the current
at a given moment in time.

Alternating current is more common and widely used. It is easier to convert it into alternating current of a different voltage, to change the voltage in electrical networks depending on the necessary needs. This can be done using a transformer. Transformer - a device that converts alternating current of one voltage into the same current, but of a different voltage at the same frequency

Lobar pneumonia begins acutely, most often after severe hypothermia. The temperature rises sharply to 39-40 degrees, the patient suffers from severe chills. Pain immediately appears when breathing and coughing from the affected lung. The cough is accompanied by the release of purulent, viscous sputum streaked with blood. The patient's condition is serious. Breathing is shallow, rapid, with flaring of the wings of the nose. The affected side of the chest noticeably lags behind the healthy side when breathing.

On planet Earth today, 98% of all electricity is generated by alternating current generators. Such current is quite easy to produce and transmit over long distances. In this case, the current and voltage can be repeatedly increased and decreased - transformed. Work is done not by voltage, but by current. Therefore, the lower its value, the lower the losses in the wires.

Many users believe that at home only alternating current with a voltage of 220V and a frequency of 50Hz is used. This is only true for incandescent lamps, electric motors in vacuum cleaners, and refrigerators.

In any complex household device powered by an alternating current network, there are components that operate at constant voltage with different values. It is virtually impossible to predict what these values might be. Therefore, all consumers in the outlet have alternating current of the same frequency and voltage.