What is a capacitor used for? Electrolytic capacitors: application features. Purpose and use of capacitors

In electrical stores, capacitors can most often be seen in the form of a cylinder, inside of which there are many strips of plates and dielectrics.

Capacitor - what is it?

The capacitor is part electrical circuit, consisting of 2 electrodes that are capable of accumulating, focusing or transmitting current to other devices. Structurally, the electrodes are capacitor plates with opposite charges. In order for the device to work, a dielectric is placed between the plates - an element that prevents the two plates from touching each other.

The definition of condenser comes from the Latin word “condenso”, which means compaction, concentration.

Elements for soldering containers are used to transport, measure, redirect and transmit electricity and signals.

Where are capacitors used?

Every novice radio amateur often asks the question: what is a capacitor for? Beginners do not understand why it is needed and mistakenly believe that it can fully replace a battery or power supply.

All radio devices include capacitors, transistors and resistors. These elements make up a board or an entire module in circuits with static values, which makes it the basis for any electrical appliance, from a small iron to industrial devices.

The most common uses of capacitors are:

1. Filter element for HF and LF interference;
2. Levels sudden surges in alternating current, as well as for static and voltage on the capacitor;
3. Voltage ripple equalizer.

The purpose of the capacitor and its functions are determined by the purposes of use:

1. General purpose. This is a capacitor, the design of which contains only low-voltage elements located on small circuit boards, for example, devices such as a television remote control, radio, kettle, etc.;
2. High voltage. The capacitor in the DC circuit supports the production and technical systems under high voltage;
3. Pulse. Capacitive generates a sharp voltage surge and supplies it to the receiving panel of the device;
4. Launchers. Used for soldering in those devices that are designed to start, turn on/off devices, for example, a remote control or control unit;
5. Noise suppressing. The capacitor in the AC circuit is used in satellite, television and military equipment.

Types of capacitors

The design of the capacitor is determined by the type of dielectric. It comes in the following types:

1. Liquid. Dielectric in liquid form is rare; this type is mainly used in industry or for radio devices;
2. Vacuum. There is no dielectric in the capacitor, but instead there are plates in a sealed housing;
3. Gaseous. Based on interaction chemical reactions and is used for the production of refrigeration equipment, production lines and installations;
4. Electrolytic capacitor. The principle is based on the interaction of a metal anode and an electrode (cathode). The oxide layer of the anode is the semiconductor part, as a result of which this type of circuit element is considered the most productive;
5. Organic. The dielectric can be paper, film, etc. It is not able to accumulate, but only slightly level out voltage surges;
6. Combined. This includes metal-paper, paper-film, etc. Coefficient useful action increases if the dielectric contains a metal component;
7. Inorganic. The most common ones are glass and ceramic. Their use is determined by durability and strength;
8. Combined inorganic. Glass-film, as well as glass-enamel, which have excellent leveling properties.

Types of capacitors

The elements of the radio board differ in the type of capacitance change:

1. Permanent. The cells maintain a constant voltage capacity until the end of their shelf life. This type the most common and universal, as it is suitable for making any type of device;
2. Variables. They have the ability to change the volume of the container when using a rheostat, varicap or when changing temperature regime. The mechanical method using a rheostat involves soldering additional element to the board, while when using a varicond, only the amount of incoming voltage changes;
3. Trimmers. They are the most flexible type of capacitor, with which you can quickly and efficiently increase the throughput of the system with minimal reconstruction.

Operating principle of a capacitor

Let's look at how a capacitor works when connected to a power source:

1. Charge accumulation. When connected to the network, the current is directed to the electrolytes;
2. Charged particles are distributed on the plate according to their charge: negative ones - into electrons, and positive ones - into ions;
3. The dielectric serves as a barrier between the two plates and prevents particles from mixing.

The capacitance of a capacitor is determined by calculating the ratio of the charge of one conductor to its potential power.

Important! The dielectric is also capable of removing the resulting voltage on the capacitor during operation of the device.

Capacitor Characteristics

The characteristics are conventionally divided into points:

1. The amount of deviation. IN mandatory Each capacitor goes through a series of tests on the production line before reaching the store. After testing each model, the manufacturer indicates the range of permissible deviations from the original value;
2. Voltage value. Mostly elements with a voltage of 12 or 220 Volts are used, but there are also 5, 50, 110, 380, 660, 1000 and more Volts. In order to avoid capacitor burnout and dielectric breakdown, it is best to purchase an element with a voltage reserve;
3. Permissible temperature. This parameter very important for small devices operating on a 220 Volt network. As a rule, the higher the voltage, the higher the level permissible temperature for work. Temperature parameters are measured using an electronic thermometer;
4. Availability of direct or alternating current. Perhaps one of the most important parameters, since the performance of the designed equipment completely depends on it;
5. Number of phases. Depending on the complexity of the device, single-phase or three-phase capacitors can be used. To connect an element directly, a single-phase one is sufficient, but if the board is a “city”, then it is recommended to use a three-phase one, as it distributes the load more smoothly.

What does capacity depend on?

The capacitance of the capacitor depends on the type of dielectric and is indicated on the case, measured in uF or uF. It ranges from 0 to 9,999 pF in picofarads, while in microfarads it ranges from 10,000 pF to 9,999 µF. These characteristics are specified in state standard GOST 2.702.

Note! The larger the electrolyte capacity, the longer the charging time, and the more charge the device can transfer.

The greater the load or power of the device, the shorter the discharge time. In this case, resistance plays an important role, since the amount of outgoing electrical flow depends on it.

The main part of the capacitor is the dielectric. It has the following number of characteristics that affect the power of the equipment:

1. Insulation resistance. This includes both internal and external insulation made from polymers;
2. Maximum voltage. The dielectric determines how much voltage the capacitor is capable of storing or transmitting;
3. The amount of energy loss. Depends on the configuration of the dielectric and its characteristics. Typically, energy dissipates gradually or in sharp bursts;
4. Capacity level. In order for a capacitor to store a small amount of energy for a short period of time, it needs to maintain a constant volume of capacitance. Most often, it fails precisely because of the inability to pass a given amount of voltage;

Good to know! The abbreviation “AC” located on the element body means AC voltage. The accumulated voltage on the capacitor cannot be used or transmitted - it must be extinguished.

Capacitor properties

The capacitor acts as:

1. Inductive coil. Let's take the example of a regular light bulb: it will light up only if you connect it directly to an AC source. This leads to the rule that the larger the capacity, the more powerful the luminous flux of the light bulb;
2. Charge storage. Properties allow it to quickly charge and discharge, thereby creating a powerful impulse with low resistance. Used for production various types accelerators, laser installations, electric flares, etc.;
3. The battery received charge. A powerful element is capable of maintaining the received portion of current for a long time, while it can serve as an adapter for other devices. Compared with battery, the capacitor loses some of its charge over time, and is also not able to accommodate a large volume of electricity, for example, for industrial scale;
4. Charging the electric motor. The connection is made through the third terminal (operating voltage of the capacitor is 380 or 220 Volts). Thanks to new technology, it became possible to use a three-phase motor (with a phase rotation of 90 degrees), using a standard network;
5. Compensator devices. It is used in industry to stabilize reactive energy: part of the incoming power is dissolved and adjusted at the output of the capacitor to a certain volume.

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• Translation

If you regularly create electrical diagrams, you probably used capacitors. It's a standard circuit component, just like resistor, that you just grab off the shelf without a second thought. We use capacitors to smooth out voltage/current ripple, to match loads, as a power source for low-power devices, and other applications.

But a capacitor is not just a bubble with two wires and a couple of parameters - operating voltage and capacitance. There is a huge array of technologies and materials with different properties, used to create capacitors. And although in most cases almost any capacitor of suitable capacity will do for any task, good understanding how these devices work can help you choose not just the right one, but the best fit. If you have ever had a problem with temperature stability or the task of finding the source of additional noise, you will appreciate the information in this article.

Let's start simple

It's best to start simple and describe the basic principles of how capacitors work before moving on to the real devices. An ideal capacitor consists of two conducting plates separated by a dielectric. The charge collects on the plates, but cannot flow between them - the dielectric has insulating properties. This is how the capacitor accumulates charge.

Capacitance is measured in farads: a capacitor of one farad produces a voltage of one volt if it contains a charge of one coulomb. Like many other SI units, it's an impractical size, so unless you count supercapacitors, which we won't talk about here, you'll likely end up with micro-, nano-, and picofarads. The capacitance of any capacitor can be derived from its dimensions and dielectric properties - if interested, the formula for this can be found on Wikipedia. There is no need to memorize it unless you are studying for an exam - but it does contain one useful fact. The capacitance is proportional to the dielectric constant εr of the dielectric used, which has resulted in a variety of capacitors being commercially available using different dielectric materials to achieve larger capacitances or improve voltage characteristics.

Aluminum electrolytic

Aluminum electrolytic capacitors use an anodic oxidation layer on an aluminum sheet as one dielectric plate, and the electrolyte from an electrochemical cell as the other plate. The presence of an electrochemical cell makes them polar, that is, the DC voltage must be applied in one direction, and the anodized plate must be the anode, or positive.

In practice, their plates are made in the form of a sandwich of aluminum foil, wrapped in a cylinder and located in aluminum can. The operating voltage depends on the depth of the anodized layer.

Electrolytic capacitors have the largest capacitance among common ones, from 0.1 to thousands of microfarads. Due to the close packing of the electrochemical cell, they have a large equivalent series inductance (ESI, or effective inductance), which is why they cannot be used on high frequencies. They are typically used for power smoothing and decoupling as well as coupling at audio frequencies.

Tantalum electrolytic

Surface Mounted Tantalum Capacitor

Tantalum electrolytic capacitors are manufactured as a sintered tantalum anode with a large surface area on which a thick layer of oxide is grown and then a manganese dioxide electrolyte is placed as the cathode. The combination of the large surface area and dielectric properties of tantalum oxide results in high capacitance per volume. As a result, such capacitors are much smaller than aluminum capacitors of comparable capacity. Like the latter, tantalum capacitors have polarity, so direct current must flow in exactly one direction.

Their available capacitance varies from 0.1 to several hundred microfarads. They have much lower leakage resistance and equivalent series resistance (ESR), which is why they are used in testing, measuring instruments and high-quality audio devices – where these properties are useful.

In the case of tantalum capacitors, it is necessary to especially monitor the failure status; it happens that they catch fire. Amorphous tantalum oxide is a good dielectric, and in crystalline form it becomes a good conductor. Improper use of a tantalum capacitor - for example, applying too much inrush current - can cause the dielectric to change form, which will increase the current passing through it. It is true that earlier generations of tantalum capacitors had a reputation for fire problems, and improved manufacturing methods have led to more reliable products.

Polymer films

An entire family of capacitors uses polymer films as dielectrics, and the film is either sandwiched between twisted or interleaved layers of metal foil or has a metallized layer on the surface. Their operating voltage can reach up to 1000 V, but they do not have high capacitances - this is usually from 100 pF to a few microfarads. Each type of film has its pros and cons, but in general the entire family has lower capacitance and inductance than electrolytic ones. Therefore, they are used in high-frequency devices and for decoupling in electrically noisy systems, as well as in general purpose systems.

Polypropylene capacitors are used in circuits that require good thermal and frequency stability. They are also used in power systems, to suppress EMI, in systems using high voltage alternating currents.

Polyester capacitors, although they do not have the same temperature and frequency characteristics, are cheap and can withstand high temperatures when soldering for surface mounting. Because of this, they are used in circuits intended for use in non-critical applications.

Polyethylene naphthalate capacitors. They do not have stable temperature and frequency characteristics, but can withstand much higher temperatures and stresses compared to polyester ones.

Polyethylene sulfide capacitors have the temperature and frequency characteristics of polypropylene, and in addition can withstand high temperatures.

In old equipment you can come across polycarbonate and polystyrene capacitors, but now they are no longer used.

Ceramics

The history of ceramic capacitors is quite long - they have been used from the first decades of the last century to the present day. Early capacitors were a single layer of ceramic, metallized on both sides. Later ones are also multilayer, where plates with metallization and ceramics are interspersed. Depending on the dielectric, their capacitances vary from 1 pF to tens of microfarads, and voltages reach kilovolts. In all electronics industries where low capacitance is required, both single-layer ceramic disks and multi-layer surface-mount stack capacitors can be found.

The easiest way to classify ceramic capacitors is by dielectrics, since they are what give the capacitor all its properties. Dielectrics are classified according to three-letter codes, which encrypt their operating temperature and stability.

C0G has better stability in capacitance with respect to temperature, frequency and voltage. Used in high-frequency circuits and other high-speed circuits.

X7R do not have such good characteristics by temperature and voltage, therefore they are used in less critical cases. This usually includes decoupling and various universal applications.

Y5V have much higher capacity, but their temperature and voltage characteristics are even lower. Also used for decoupling and in various general purpose applications.

Since ceramics often also have piezoelectric properties, some ceramic capacitors also exhibit a microphonic effect. If you have worked with high voltages and frequencies in the audio range, for example, in the case of tube amplifiers or electrostatics, you could hear the capacitors “singing”. If you used a piezoelectric capacitor to provide frequency stabilization, you might find that its sound is modulated by the vibration of its surroundings.

As we already mentioned, this article does not aim to cover all capacitor technologies. Taking a look at the electronics catalog you will find that some of the technologies available are not covered here. Some offers from catalogs are already outdated, or have such a narrow niche that you most often will not come across them. We only hoped to dispel some of the mystery about popular models capacitors, and help you select the right components when designing your own devices. If we've whetted your appetite, you may want to check out our article on inductors.

Please write about any inaccuracies or errors you find via

Constant voltage and set the voltage on his crocodiles to 12 Volts. We also take a 12 Volt light bulb. Now we insert a capacitor between one probe of the power supply and the light bulb:

Nope, it doesn't burn.

But if you do it directly, it lights up:

This begs the conclusion: DC current does not flow through the capacitor!

To be honest, at the very initial moment of applying voltage, the current still flows for a fraction of a second. It all depends on the capacitance of the capacitor.

Capacitor in AC circuit

So, to find out whether AC current is flowing through the capacitor, we need an alternator. I think this frequency generator will do just fine:

Because Chinese generator I have a very weak one, then instead of a light bulb load we will use a simple 100 Ohm. Let’s also take a capacitor with a capacity of 1 microfarad:

We solder something like this and send a signal from the frequency generator:

Then he gets down to business. What is an oscilloscope and what it is used for, read here. We will use two channels at once. Two signals will be displayed on one screen at once. Here on the screen you can already see interference from the 220 Volt network. Do not pay attention.

We will apply alternating voltage and watch the signals, as professional electronics engineers say, at the input and output. Simultaneously.

It will all look something like this:

So, if our frequency is zero, then this means constant current. As we have already seen, the capacitor does not allow direct current to pass through. This seems to have been sorted out. But what happens if you apply a sinusoid with a frequency of 100 Hertz?

On the oscilloscope display I displayed parameters such as signal frequency and amplitude: F is the frequency Ma – amplitude (these parameters are marked with a white arrow). The first channel is marked in red, and the second channel in yellow, for ease of perception.

The red sine wave shows the signal that the Chinese frequency generator gives us. The yellow sine wave is what we already get at the load. In our case, the load is a resistor. Well, that's all.

As you can see in the oscillogram above, I supply a sinusoidal signal from the generator with a frequency of 100 Hertz and an amplitude of 2 Volts. On the resistor we already see a signal with the same frequency (yellow signal), but its amplitude is some 136 millivolts. Moreover, the signal turned out to be somewhat “shaggy”. This is due to the so-called ““. Noise is a signal with small amplitude and random voltage changes. It can be caused by the radio elements themselves, or it can also be interference that is caught from the surrounding space. For example, a resistor “makes noise” very well. This means that the “shaggyness” of the signal is the sum of a sinusoid and noise.

The amplitude of the yellow signal has become smaller, and even the graph of the yellow signal shifts to the left, that is, it is ahead of the red signal, or in scientific language, it appears phase shift. It is the phase that is ahead, not the signal itself. If the signal itself was ahead, then we would have the signal on the resistor appear in time earlier than the signal applied to it through the capacitor. The result would be some kind of time travel :-), which, of course, is impossible.

Phase shift- This difference between the initial phases of two measured quantities. In this case, tension. In order to measure the phase shift, there must be a condition that these signals same frequency. The amplitude can be any. The figure below shows this very phase shift or, as it is also called, phase difference:

Let's increase the frequency on the generator to 500 Hertz

The resistor has already received 560 millivolts. The phase shift decreases.

We increase the frequency to 1 KiloHertz

At the output we already have 1 Volt.

Set the frequency to 5 Kilohertz

The amplitude is 1.84 Volts and the phase shift is clearly smaller

Increase to 10 Kilohertz

The amplitude is almost the same as at the input. The phase shift is less noticeable.

We set 100 Kilohertz:

There is almost no phase shift. The amplitude is almost the same as at the input, that is, 2 Volts.

From here we draw profound conclusions:

The higher the frequency, the less resistance the capacitor has to alternating current. The phase shift decreases with increasing frequency to almost zero. On indefinitely low frequencies its value is 90 degrees orπ/2 .

If you plot a slice of the graph, you will get something like this:

I plotted voltage vertically and frequency horizontally.

So, we have learned that the resistance of a capacitor depends on frequency. But does it only depend on frequency? Let's take a capacitor with a capacity of 0.1 microfarad, that is, a nominal value 10 times less than the previous one, and run it again at the same frequencies.

Let's look and analyze the values:

Carefully compare the amplitude values ​​of the yellow signal at the same frequency, but with different capacitor values. For example, at a frequency of 100 Hertz and a capacitor value of 1 μF, the amplitude of the yellow signal was 136 millivolts, and at the same frequency, the amplitude of the yellow signal, but with a capacitor of 0.1 μF, was already 101 millivolts (in reality, even less due to interference ). At a frequency of 500 Hertz - 560 millivolts and 106 millivolts, respectively, at a frequency of 1 Kilohertz - 1 Volt and 136 millivolts, and so on.

From here the conclusion suggests itself: As the value of a capacitor decreases, its resistance increases.

Using physical and mathematical transformations, physicists and mathematicians have derived a formula for calculating the resistance of a capacitor. Please love and respect:

Where, X C is the resistance of the capacitor, Ohm

P - constant and equals approximately 3.14

F– frequency, measured in Hertz

WITH– capacitance, measured in Farads

So, put the frequency in this formula at zero Hertz. A frequency of zero Hertz is direct current. What will happen? 1/0=infinity or very high resistance. In short, a broken circuit.

Conclusion

Looking ahead, I can say that in this experiment we obtained (high-pass filter). Using a simple capacitor and resistor, and applying such a filter to the speaker somewhere in the audio equipment, we will only hear squeaky high tones in the speaker. But the bass frequency will be dampened by such a filter. The dependence of capacitor resistance on frequency is very widely used in radio electronics, especially in various filters where it is necessary to suppress one frequency and pass another.

Functions of electrolytic capacitors

Precautions when using aluminum electrolytic capacitors

1. When used in applications where DC voltage is applied to them, correct polarity must be observed. Otherwise, if the capacitor is installed in reverse polarity, its service life may be reduced or even the capacitor may be damaged. In circuits with unknown polarity or if there is a possibility of changing the polarity in the circuit, non-polarized capacitors should be used. Also, polar electrolytic capacitors cannot be used in tasks where alternating voltage is applied to them.
2. Do not apply voltage to the capacitor for a long time exceeding the rated voltage. This will damage the capacitor due to increased leakage current.
3. Use an electrolytic capacitor if the current ripple through it is within acceptable limits.
4. Use electrolytic capacitors within the permitted operating temperature range. Operating capacitors at room temperature will ensure a longer service life.
5. Electrolytic capacitors are not suitable for circuits with repeated charge and discharge cycles. Their use in circuits in which the capacitor is repeatedly deeply discharged and charged can lead to a decrease in capacitance or even damage to the capacitor. If it is necessary to use an electrolytic capacitor for such a task, please contact our engineering department for technical advice.
6. If electrolytic capacitors have been stored in a discharged state for a long time, use them only after preliminary training. Long-term storage without feeding DC voltage may increase capacitor leakage current. In such cases, before use, it is necessary to perform a preliminary “preforming” procedure for the capacitor by applying a constant voltage of a given value.
7. Should be paid Special attention to comply with the temperature conditions and duration of operations when soldering aluminum electrolytic capacitors. If the soldering temperature is too high or the lead dipping time is too long, degradation may occur. electrical characteristics capacitors and damage to the insulating shell covering the housing. When soldering small-sized aluminum electrolytic capacitors by dipping into solder, its temperature should not exceed 260°C, and the duration of the operation should not exceed 10 seconds.
8. Cleaning printed circuit boards after soldering. It is not recommended to use halogenated hydrocarbon solvents to clean boards containing aluminum electrolytic capacitors with exposed terminal seals. If halogenated hydrocarbon solvents must be used to clean printed circuit boards, capacitors with epoxy-coated end seals should be used.
9. Do not apply excessive force to the terminals of an aluminum electrolytic capacitor. This may lead to breakage of its terminals or internal connections. (To determine the permissible mechanical loads on terminals, please refer to the guidelines JIS C5102 and JIS C5141.)
10. Ensure sufficient clearance between the capacitor housing and the wall of the device housing (Fig. 19).

Rice. 19. Minimum permissible distance between the housing of an aluminum electrolytic capacitor and the wall of the equipment housing

Do not obstruct the operation of ventilation systems unless otherwise specified in catalogs or technical specifications equipment. Too small a gap between the capacitor body and the device body can negatively affect the operation of the ventilation system and lead to an explosion of the capacitor.

Attention!

• The information contained in this article is subject to change to improve product quality without prior notice. Therefore, please check the latest specifications before ordering electrolytic capacitors.

• The general characteristics, reliability data and other parameters of aluminum electrolytic capacitors given in this article should not be considered as guaranteed values ​​- they are standard, typical values ​​only.
• For correct use electrolytic capacitors, please first carefully read the application recommendations given in this article.

They are used in timers because resistors allow for slow charging and discharging. Inductors along with capacitors are present in the circuits of oscillatory circuits of receiving and transmitting devices. IN various designs power supplies, they effectively smooth out voltage ripples after the rectification process.

It passes through capacitors easily, but is delayed. This makes it possible to produce filters for various purposes. In electrical and radio electronic circuits, capacitors help slow down processes such as voltage increases or decreases.

Capacitor: principle of operation

The basic principle of operation of a capacitor is its ability to store electric charge. That is, it can be charged or discharged at the right time. This property is most clearly manifested when a capacitor is connected in parallel or in series with an inductor in transmitter or radio receiver circuits.

This connection allows you to obtain a periodic change in polarity on the plates. First, the first plate is charged with a positive charge, and then the second plate takes on a negative charge. After complete discharge, charging occurs in reverse direction. Instead of a positive charge, the plate receives a negative charge and, conversely, the negative plate becomes positively charged. This polarity change occurs after each charge and discharge. This operating principle is the basis for generators installed in analog transceiver devices.

The main characteristic is electrical capacitance

When considering the principle of operation of a capacitor, one should not forget about such a characteristic as electrical capacitance. First of all, it lies in the ability of a capacitor to retain an electrical charge. That is, the higher the capacity, the higher value charge can be saved.

The electrical capacitance of a capacitor is measured in farads and is designated by the letter F. However, one farad is a very large capacitance, so in practice smaller units such as micro-, nano- and picofarads are used.

It presents a certain complexity due to different labeling options.