Circuit breaker categories: A, B, C and D

Circuit breakers are devices that are responsible for protecting an electrical circuit from damage caused by exposure to large currents. Too strong a flow of electrons can damage household appliances, as well as cause overheating of the cable, followed by melting and fire of the insulation. If you do not de-energize the line in time, this can lead to a fire. Therefore, in accordance with the requirements of the PUE (Electrical Installation Rules), operation of a network in which electrical circuit breakers are not installed is prohibited. AVs have several parameters, one of which is the time-current characteristic of the automatic protective switch. In this article we will tell you how circuit breakers of categories A, B, C, D differ and what networks they are used to protect.

Rated current of the machine

The time has come to figure out what the rated current of the machine actually means and what the protection operation current will be.
For those who understand the difference between effective and instantaneous values, I clarify that all parameters of machines associated with current or voltage are effective values, unless otherwise specified. According to GOST R 50345-2010 (clause 3.5.1), the rated current of a circuit breaker is the current value that determines the operating conditions for which it is designed and built. Brief and precise. A common mistake is that people often think that the rated current is the tripping current. In fact, a working circuit breaker will never trip at its rated current. Moreover, it will not work even at 10% overload. With a higher overload, the machine will turn off, but this does not mean that it will turn off quickly. A conventional modular circuit breaker has 2 releases: a slow thermal one and a fast-reacting electromagnetic one.

The thermal release basically contains a bimetallic plate, which is heated by the current passing through it. When heated, the plate bends and, at a certain position, acts on the latch and the switch turns off. The electromagnetic release is a coil with a retractable core, which, at high current, also acts on the latch that turns off the circuit breaker. If the purpose of a thermal release is to turn off the circuit breaker during overloads, then the task of an electromagnetic release is to quickly turn off during short circuits, when the current value is several times higher than the rated value.

Range of rated currents

I had to install circuit breakers with a rating of 0.2A. In general, I have come across modular machines of the following denominations: 0.2, 0.3, 0.5, 0.8, 1, 1.6, 2, 2.5, 3, 3.15, 4, 5, 6, 6.3, 8, 10, 13, 16, 20, 25, 32 , 40, 50, 63, 80, 100, 125 Ampere. The maximum rating of a machine designed to operate in 0.4 kV networks that I have seen is 6300A. This corresponds to a transformer with a capacity of 4 MVA, but we don’t make more powerful transformers for this voltage, this is the limit. I cannot say that the ratings strictly correspond to any single standard series, such as E6, E12 for radio elements. It seems that they are sculpting whatever they want. With machines above 100A the situation is approximately the same. Nevertheless, the GOST 8032-84 standard “Preferred numbers and series of preferred numbers” exists and is still in force today. According to this standard, denominations must correspond to certain ranges of values. The main row is R5, which defines the following scale of nominal values: 1, 1.6, 2.5, 4, 6.3, 10, 16, 25, 40, 63, 100, 160, etc. As you can see, the series consists of five repeating values; the decimal point simply moves after each cycle. If there is a demand for a more accurate selection, GOST provides for rows R10 (1, 1.25, 1.6, 2, 2.5, 3.15, 4, 5, 6.3, and R20 (1, 1.12, 1.25, 1.4, 1.6, 1.8, 2, 2.24, 2.5 , 2.8, 3.15, 3.55, 4, 4.5, 5, 5.6, 6.3, 6.3, 7.1, 8, 9). However, in justified cases, some rounding is allowed (for example, 3.2 instead of 3.15 or 6 instead of 6.3). I think not If you need to describe the standard in more detail, anyone can find it and read it.

But that's not all. In the same GOST R 50345-2010 there is chapter 5.3 entitled “Standard and preferred values”. According to it, the preferred values ​​of the rated current of modular circuit breakers are: 6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125 A.

Types of protective devices

There are several types of AVs that are connected to the network in order to monitor the condition of the wiring and, if necessary, stop the current supply. They may be as follows:

• Mini models (small in size).
• Air (open type).
• Residual current devices (abbreviated name - RCD).
• Closed (device elements are housed in a molded housing).
• Differential (circuit breakers combined with RCD).

Mini models

These devices are designed to operate in circuits where the load is low. They usually do not have additional adjustment functions. This series includes devices that can withstand a misfire current of 4.5 - 15A. They are not suitable for factory power, since the current strength in enterprises is much higher than their nominal value. Therefore, they are usually connected to household wiring.

The machines included in the product line of the French company Schneider Electric are very popular. The ratings of the AVs produced by this company can be 2 - 125A, so you can choose a package for home lines of various powers.

Air (open) devices

If the total power of the devices connected to the network is large, and the ratings of the machines mentioned above are insufficient, air protective devices should be chosen. The rated cut-off current of open-type bags is an order of magnitude higher than that of mini-models. Most often they are three-pole, but recently many companies have started producing four-pole machines.

Open type protective devices should be installed in distribution cabinets equipped with special DIN rails on the inside.

If the cabinet's protection class is IP55, then it can be placed outside the building. The body of this equipment is made of refractory metal and is reliably protected from moisture penetration, which ensures a high level of safety for the machines located inside it.

Airborne ABs have a great advantage over miniature ones. It lies in the ability to customize their nominal characteristics using special inserts that are placed on the active contact.

Enclosed circuit breakers

The body of these devices is cast from refractory metal, which ensures their perfect tightness and makes them suitable for use in harsh conditions. The maximum voltage that such machines can withstand is 750V, and the current is 200A. Closed AVs are classified according to the type of action into the following groups:

• Adjustable.
• Thermal.
• Electromagnetic.

The optimal type should be selected based on the tasks being solved.

The highest accuracy is achieved by electromagnetic closed circuit breakers, which determine with a minimum error the root mean square indicator of the active electric current and instantly de-energize the network in the event of a short circuit, avoiding serious consequences.

Electromagnetic machines are successfully used to control the functioning of motors in factory machines, as well as other powerful equipment, since they can withstand currents of up to 70 kA. The number indicating the current rating of the circuit breaker is printed on its body.

All types of enclosed switches can have two to four poles. Thanks to this, they can be used to protect electrical networks of any residential and non-residential buildings and structures.

Residual current devices

Residual current devices should not be used as independent protective devices, since their main task is to protect people from sudden electric shock. Therefore, it is recommended to install them together with the automatic circuit breaker, or to purchase a differential circuit breaker that already includes an RCD. In the first case, you need to take into account that the residual current device should be installed first, and then the circuit breakers.

If you change the installation order, a short circuit will lead to failure of the RCD as a result of too high a load.

TOP 5 machine gun models on the market this year

When choosing an AB, it is necessary to take into account the ratings of manufacturers of such devices.

The best machines (more precisely, their manufacturers) today:

• Schneider Electric. French company. The machines produced by it have long been tested in Russian conditions, serve for a long time and are reliable.
• General Electric. The disadvantage is the high price, but the reliability and workmanship are also excellent. The American manufacturer produces excellent AVs for three-phase networks.
• Siemens. Low price, but the quality is worse than the two leaders presented above. It's hard to find devices for sale. Initially, the brand was German, then it was acquired by Americans. AB's reliability and average cost make the company so popular.
• Contactor. The best Russian brand, but the prices are steep. It is better to purchase machines made in Europe, although Contactor is a good solution for lightly loaded networks.

Briefly the principle of operation and purpose of circuit breakers

In the event of a short circuit, the circuit breaker is triggered almost instantly thanks to the electromagnetic splitter. At a certain excess of the rated current value, the heating bimetallic plate will turn off the voltage after some time, which can be found out from the current characteristic time graph.

This safety device protects the wiring from short circuits and overcurrents exceeding the calculated value for a given wire cross-section, which can heat the conductors to the melting point and cause the insulation to ignite. To prevent this from happening, you need not only to choose the right protective switch that matches the power of the connected devices, but also to check whether the existing network can withstand such loads.

Appearance of a three-pole circuit breaker

Wires must match the load

It often happens that in an old house a new electric meter, automatic machines, and RCDs are installed, but the wiring remains old. A lot of household appliances are bought, the power is summed up and an automatic machine is selected for it, which regularly holds the load of all switched on electrical appliances.

Everything seems to be correct, but suddenly the wire insulation begins to emit a characteristic odor and smoke, a flame appears, and the protection does not work. This can happen if the wiring parameters are not designed for such current.

Let's say the cross-section of the old cable core is 1.5mm², with a maximum permissible current limit of 19A. We assume that several electrical appliances were connected to it at the same time, making up a total load of 5 kW, which in current equivalent is approximately 22.7 A; it corresponds to a 25 A circuit breaker.

The wire will heat up, but this machine will remain on all the time until the insulation melts, which will lead to a short circuit, and the fire can already flare up in full swing.

NYM power cable

Protect the weakest link in the electrical wiring

Therefore, before choosing a machine according to the load being protected, you need to make sure that the wiring will withstand this load.

According to PUE 3.1.4, the machine must protect the weakest section of the electrical circuit from overloads, or be selected with a rated current corresponding to the currents of the connected electrical installations, which again implies their connection with conductors with the required cross-section.

If you ignore this rule, you should not blame an incorrectly designed machine and curse its manufacturer if a weak link in the electrical wiring causes a fire.

Melted wire insulation

Calculation of the machine's nominal value

We assume that the wiring is new, reliable, correctly calculated, and meets all requirements. In this case, the selection of a circuit breaker comes down to determining a suitable rating from a typical range of values, based on the calculated load current, which is calculated by the formula:

where P is the total power of electrical appliances.

This means active load (lighting, electric heating elements, household appliances). This calculation is completely suitable for a home electrical network in an apartment.

Let's say the power calculation is made: P = 7.2 kW. I=P/U=7200/220=32.72 A. Select a suitable 32A machine from a range of values: 1, 2, 3, 6, 10, 16, 20, 25, 32, 40, 63, 80, 100.

This rating is slightly less than the calculated value, but it is practically impossible for all electrical appliances in the apartment to be turned on at the same time. It is also worth considering that in practice, the operation of the machine begins with a value 1.13 times greater than the nominal value, due to its time-current characteristics, that is, 32 * 1.13 = 36.16 A.

To simplify the selection of a circuit breaker, there is a table where the ratings of the circuit breakers correspond to the power of single-phase and three-phase loads:

Current circuit breaker selection table

The denomination found using the formula in the above example is closest in terms of power value, which is indicated in the red highlighted cell. Also, if you want to calculate the current for a three-phase network, when choosing a machine, read the article about calculating and choosing the wire cross-section

The selection of circuit breakers for electrical installations (electric motors, transformers) with reactive loads, as a rule, is not made based on power. The rating and type of current characteristics of the circuit breaker are selected according to the operating and starting current specified in the passport of this device.

Table for selecting wire cross-section by power

What wire cross-section is needed for 3 kW

Formula for finding current power

Smooth start of an asynchronous electric motor with a squirrel-cage rotor

New Year's greetings with humor

Selecting the breaking capacity

The selection of a packager based on the maximum permissible load current is described above. But the network circuit breaker must also turn off when a short circuit (short circuit) occurs in the network. This characteristic is called breaking capacity. It is displayed in thousands of amperes - this is the order currents can reach during a short circuit. Selecting a machine based on its breaking capacity is not very difficult.

This characteristic shows at what maximum value of the short-circuit current the circuit breaker remains operational, that is, it will not only be able to turn off, but will also work after being turned on again. This characteristic depends on many factors and for accurate selection it is necessary to determine the short-circuit currents. But for wiring in a house or apartment, such calculations are done very rarely, and are based on the distance from the transformer substation.

Breaking capacity of automatic protective switches

If the substation is located close to the entrance to your house/apartment, take a circuit breaker with a breaking capacity of 10,000 A; for all other city apartments, 6,000 A is sufficient.

If the house is located in a rural area or you are choosing an electrical circuit breaker for your dacha, a breaking capacity of 4,500 A may well be enough. The networks here are usually old and the short-circuit currents are not large. And since the price increases significantly with increasing breaking capacity, the principle of reasonable savings can be applied.

Is it possible to install bags with a lower breaking capacity in city apartments? In principle, it is possible, but no one guarantees that after the first short circuit you will not have to change it. He may have time to turn off the network, but will be inoperative. In the worst case scenario, the contacts will melt and the machine will not have time to turn off. Then the wiring will melt and a fire may occur.

What is the rated current of the machine

Rated current is the maximum permissible value of electric current that the circuit breaker allows without disconnecting the network.

To understand and make a choice of a circuit breaker, you need to proceed from two factors:

1. 1. Electrical cable cross-section - the cross-sectional area of ​​an electrical wiring cable that is capable of withstanding a certain load power without heating.
2. 2. Maximum load - the power of all electrical appliances connected to a given line at maximum operating mode.

When choosing a circuit breaker, you should not install a protective device with a current rating higher than the installed power cable can withstand. Such a machine will not protect the electrical wiring and the line overheating field will trigger.

In any case, the cross-section of the electrical cable, the rating of the machine and the load power are very closely related. The power cable can carry a current limited by its cross-section.

Therefore, the ideal option for installing an electrical network would be the following sequence: calculating the power of all consumers on the power line, calculating the cross-sectional area of ​​the installed cable based on the maximum power of all devices, calculating the circuit breaker based on the selected cable.

Criterias of choice

It is necessary for its owner to select a circuit breaker based on power for a long and long service, based not only on him. You also need to take into account the brand, price, cable cross-section, current, long-term permissible conductor charge, total power of household equipment, amperage. Be sure to take into account the manufacturer's rated current value with selectivity in the calculation. As a rule, all the necessary information is presented on the unit itself with markings.

Brand and price as criteria for choosing a circuit breaker

By load power

Load power is the amount of energy consumed by all electrical appliances that are connected to the same line. To determine this number, you need to calculate the current load and select a higher current rating or equal to the resulting value.

It should be noted that the value of the electric current in a single-phase network is 5 times higher, and in a three-phase network 2 times higher. That is, each electrical appliance in kilowatts must be multiplied by 5 or 2, and then converted to amperes. The result will be the correct value. You can also use the formula I=P/U*cos φ or special online software that works like a calculator. Often such coefficients are presented in tables on the Internet.

Load power as a selection criterion

By cable cross-section

The cross-section of an electrical cable is the cable cross-sectional area that is capable of withstanding a specific load power without heating. This is a very important parameter, since if the cross section is calculated incorrectly, the entire power line can come out. To calculate this, it is enough to use a special table that shows the cross-section and power for connecting to a network with one, two and three phases. The cross section can also be determined using Ohm's law and summing the maximum power of all equipment.

Note! As a rule, a 3*4 section is chosen for a house

It is important to summarize all electrical appliances, even those that are turned on for a short time

By short circuit current (SC)

To select a machine based on short-circuit current, it is important to strictly follow the rules of the PUE. At the moment, it is prohibited to use a device with 6 kiloamps. Therefore, today systems with 10 kiloamperes are especially common.

Therefore, systems with 10 kiloamperes are especially common today.

According to the long-term permissible current of the conductor

Non-shutdown current is an important parameter when choosing a circuit breaker, since the safe operation of the electrical network will depend on this parameter

It is important to note that it can operate and not turn off when the rated current value exceeds a certain number specified in its technical characteristics. That is, when selecting a device, you need to calculate the power line and take the value with a margin. It takes a certain amount of time for the circuit breaker to operate when the load is exceeded.

It is regulated by the existing guest from 2010. For example, the average response time is 50 seconds

It takes a certain amount of time for the circuit breaker to operate when the load is exceeded. It is regulated by the existing guest from 2010. For example, the average response time is 50 seconds.

In general, a circuit breaker is equipment whose main task is to ensure the safety of the electrical network from overcurrent with short circuits and overloads. You need to select it according to the power criterion, cable cross-section, minimum and maximum permissible conductor current.

Current ratings of circuit breakers

The limit value of the nominal value is determined by the formula Ir ≤ Ipr/1.45, where Ipr is the permissible current in long-term mode for a certain wiring. If you plan to install a network, proceed as follows:

• clarify the consumer connection diagram;
• collect passport data of equipment, measure voltage;
• according to the presented diagram, they are calculated separately, the currents in individual circuits are summed up;
• for each group it is necessary to select a machine that will withstand the appropriate load;
• determine cable products with a suitable conductor cross-section.

Rules for choosing denomination

An example of choosing the machine's nominal value for each line

For correct conclusions, it is necessary to take into account the characteristics of the connected equipment. If the total current is calculated to be 19 amperes, users prefer to buy a 25A device. This solution assumes the possibility of applying additional loads without significant restrictions.

However, in some situations it is better to choose a 20A circuit breaker. This ensures a relatively shorter time for power outages when the current increases (temperature increases) with a bimetallic disconnector

This precaution will help maintain the integrity of the electric motor windings when the rotor rotation is blocked by a jammed drive.

Different response times are useful to ensure selective operation of protective equipment. Devices with lower latency are installed on the lines. In an emergency, only the damaged part is disconnected from electricity. The input machine will not have time to turn off. Power supply through other circuits is useful for maintaining lighting, alarms, and other engineering systems in working order.

Weak link protection

Each individual line must have its own circuit breaker. In addition to the cross-section, when choosing suitable cable products, pay attention to the actual operating conditions. Standardized values ​​are given for heating to a temperature not exceeding +60°C

When installing the line on a site near a country house, it is necessary to provide protection from humidity and other adverse external influences.

Carefully check all parts of the electrical network. The basic rule is reliable protection, taking into account the performance of the area with the worst parameters. It should be taken into account that copper is designed with the same cross-section for greater loads compared to aluminum. The purity of the metal is of certain importance. As impurities increase, conductivity deteriorates and losses due to useless and dangerous heating increase.

Indoor wiring device

In such real estate objects, the following standard solutions are used to create a high-quality power supply system:

• the introductory machine must be placed before the counter;
• a general residual current device (RCD) is installed behind the control device;
• Next, separate lines are equipped with automatic switches (AB).

The RCD prevents accidents that provoke leakage currents. In some situations, it prevents electric shock. However, complex protective measures are carried out using circuit breakers. Effective grounding must be used.

Ratings of automatic devices for kitchen wiring

As a rule, it is convenient to install several groups in the kitchen to evenly distribute the loads. It is recommended to carefully select the distribution of powerful consumers:

• hobs;
• ovens;
• heating boilers, boilers, flow heaters;
• electric convectors, heat guns;
• air conditioners.

How does a circuit breaker work?

The main task of a circuit breaker (circuit breaker) is to capture excessive currents in the electrical network and instantly de-energize it

No matter what category the circuit breaker belongs to, it must be able to quickly de-energize the electrical network and thereby prevent damage to cables

Therefore, the main function of the circuit breaker is:

• Triggered in case of power overload. Everything here is quite simple, and if there is an excessively large load on the network, for example, due to a large number of connected electrical appliances in the house, the circuit breaker should trip and de-energize the home electrical network. If this does not happen, and the machine does not cope with its task, then the electrical wiring in the house may catch fire;
• React to overcurrent caused by a short circuit in the electrical wiring. Everything here is also clear. In the event of a short circuit, the electrical wiring is subjected to strong heating, and where it is thin, as is known, it breaks, therefore, if the machine does not work, the electrical wiring may be damaged and caught fire.

You should know that each circuit breaker is rated for a different amperage. The response time of the machine depends on the magnitude of the power supply overload. If this is a short circuit, then the circuit breaker will operate instantly, literally in a matter of seconds. If the overload is not too large, then the machine and electrical wiring can heat up for hours.

As for the design of the circuit breaker and its operating principle, it is based on a bimetallic plate through which electric current passes. If it is too large, for which the machine is not designed, then the plate begins to heat up, which ultimately leads to the operation of the circuit breaker.

Circuit breakers “B” and “C” - what is the difference, categories of circuit breakers

Those people who are upgrading their home electrical network are often interested in the question of how exactly circuit breakers of categories “B” and “C” differ, because they are most often installed in household networks. The main difference between the machines “B” and “C” is the sensitivity of the electromagnetic release.

The letters A, B, C, D and K, Z indicate the characteristics of the release installed in the circuit breaker:

A - circuit breakers of this category have the highest sensitivity. If the rated current on the line where the category “A” circuit breaker will be installed exceeds 30%, the circuit breaker will turn off.

B - machines of this category are triggered when the rated current load is 3-5 times higher. Category “B” circuit breakers are designed for installation in electrical networks with no or minimal starting current (electric motors, etc.). In simple words, category “B” machines are more sensitive to passing current, and can work when starting powerful electric motors.

C - standard type automatic circuit breakers with an even greater overload capacity than class “B” circuit breakers. They are switched off if the rated current passing through the machine becomes 5-10 times higher. The response time of a category “C” machine is about 1.5 seconds. Such machines are designed to provide protection for general-purpose electrical networks.

Category D machines are rarely used in everyday life. Most often, these circuit breakers are used in electrical networks with large starting loads. Well, the last categories of machines are “K” and “Z”, they are used for special purposes, for example, to protect lines to which electronic devices are connected.

Circuit breaker power dissipation

Dissipation is the loss of electricity that is released into the environment in the form of heat. As an example, I will give the nameplate power dissipation values ​​for VA 47-63 automatic machines (for new automatic machines at current values ​​equal to the rated one):

As you can see, the circuit breaker also wants to eat. Therefore, you should not get carried away and stick machine guns wherever possible. Where do the losses occur? The main part falls on the thermal release. But there is no need to overdramatize the situation. These losses are proportional to the current flowing. Therefore, if, for example, the load is 2 times less than the rated load, then the losses will be correspondingly 4 times less, and in the absence of load there will be no losses. If they are presented as a percentage, then the values ​​will be on the order of 0.05-0.5%, with the smallest percentage for the most powerful machines. In the contacts themselves, while the machine is new, losses are insignificant. But during operation, the contacts will burn out, the contact resistance will increase, and with it the losses will increase. Therefore, with an old machine, losses may be noticeably greater. How to measure losses -

Current limiting class

Let's move on. An electromagnetic release, although called instantaneous, also has a certain response time, which reflects such a parameter as the limitation class. It is indicated by one number and for many models this number can be found on the device body. Basically, machines with current limiting class 3 are now produced - this means that from the time the current reaches the trigger value until the circuit is completely broken, no more than 1/3 of the half-cycle will pass. With our standard frequency of 50 Hertz, this turns out to be about 3.3 milliseconds. Class 2 corresponds to a value of 1/2 (about 5 ms). According to some sources, the absence of marking of this parameter is equivalent to class 1. The highest class that I came across is 4th for OptiDin machines manufactured by KEAZ.

Application of measuring instruments

To determine the diameter of the cores of wires and cables, various measuring instruments are widely used, showing the most accurate results. Basically, the use of micrometers and calipers is practiced for these purposes. Despite their high efficiency, a significant drawback of these devices is their high cost, which is of great importance if the tool is planned to be used only 1-2 times.

As a rule, professional electricians who are constantly engaged in electrical installation work use special devices. With the right approach, it becomes possible to measure the diameter of wire cores even on working lines. After obtaining the necessary data, all that remains is to use a special formula:

Unacceptable mistakes when purchasing

There are several mistakes that novice electricians can make when choosing a circuit breaker based on current strength and load. If you choose an automatic protective device incorrectly, even slightly missing the rating, this can lead to many unfavorable consequences: the circuit breaker will trip when the electrical appliance is turned on, the electrical wiring will not withstand current loads, the service life of the circuit breaker will be quickly reduced, etc.

The first and most important thing you should know is that when concluding a contract, new subscribers order the energy capacity of their connection. From this, the technical department makes calculations and selects where the connection will take place and whether the equipment, lines, TP can withstand the load

Also, based on the declared power, the cable cross-section and the rating of the circuit breaker are calculated. For residential subscribers, an unauthorized increase in the input load without upgrading it is unacceptable, since the power has already been declared according to the project and the supply cable has already been laid. In general, the nominal value of the introductory machine is chosen not by you, but by the technical department. If you end up choosing a larger circuit breaker, everything must line up. Always focus not on the power of household appliances, but on the electrical wiring. You should not select a machine only based on the characteristics of electrical appliances if the wiring is old. The danger is that if, for example, to protect an electric stove you choose a 32A model, and the cross-section of the old aluminum cable can only withstand a current of 10A, then your wiring will not withstand it and will quickly melt, which will cause a short circuit in the network. If you need to choose a powerful switching device for protection, first of all replace the electrical wiring in the apartment with a new, more powerful one. If, for example, when calculating the appropriate rating of the machine for the operating current, you came up with an average value between two characteristics - 13.9A (not 10 or 16A), give preference to the larger value only if you know that the wiring will withstand the current load 16A. For a dacha and a garage, it is better to choose a more powerful circuit breaker, because a welding machine, a powerful submersible pump, an asynchronous motor, etc. can be used here. It is better to provide for the connection of powerful consumers in advance, so as not to overpay later on the purchase of a switching device of a higher rating. As a rule, 40A is quite enough to protect the line in domestic use. It is advisable to select all automation from one, high-quality manufacturer. In this case, the likelihood of any discrepancy is minimized. Buy products only in specialized stores, or even better, from an official distributor. In this case, you are unlikely to choose a fake and, moreover, the cost of products from a direct supplier is, as a rule, slightly lower than from intermediaries.

That’s the whole method for choosing the right machine for your own home, apartment or cottage! We hope that now you know how to choose a circuit breaker based on current, load and other equally important characteristics, as well as what mistakes should not be made when purchasing!

We recommend reading:

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Which manufacturers should you trust?

And finally, let’s pay attention to the manufacturers. The choice of a circuit breaker cannot be considered complete if you have not thought about which brand of circuit breakers you will buy. You definitely shouldn’t take on unknown companies - electrical engineering is not a field where you can conduct experiments. Learn more about choosing a manufacturer in the video.

Sources

• https://220.guru/elektrooborudovanie/avtomaty-uzo/nominaly-avtomatov.html
• https://sovet-ingenera.com/elektrika/uzo-schet/vybor-avtomata-po-moshhnosti-nagruzki.html
• https://sovet-ingenera.com/elektrika/uzo-schet/nominaly-avtomaticheskix-vyklyuchatelej-po-toku.html
• https://rusenergetics.ru/oborudovanie/nominaly-avtomaticheskikh-vyklyuchateley-po-toku
• https://www.calc.ru/Tablitsa-Dlya-Vybora-Avtomaticheskikh-Vyklyuchateley.html
• https://stroychik.ru/elektrika/vybor-avtomata

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Types of slot machines

Classification of circuit breakers occurs according to the following parameters:

• number of poles;
• rated and limit currents;
• the type of electromagnetic release used;
• maximum power switching capacity.

Let's look at it in order.

Number of poles

The number of poles is the number of phases that the machine is capable of protecting. Depending on the number of poles, machines can be:

1. Single pole. Protection is provided for one output wire, one phase.
2. Bipolar. As a rule, these are two combined single-pole circuit breakers with one common control knob. In a situation where the current of one of the machines exceeds the permitted load, both devices are switched off. Two-pole circuit breakers are used to completely disconnect the load (one phase), turning off the working phase and the working zero.
3. Three-pole. They are used with three-phase circuits; if the load is exceeded, three phases are switched off simultaneously. Such machines also have one common circuit breaker.
4. Four-pole. Similar to two-pole, but designed to work with three-phase circuits. When the load is exceeded, three phases and the working zero are opened simultaneously.

Rated and limiting currents

Everything is simple here - such a current strength at which the machine will open the circuit. At the rated current and even a little more than stated, work will be carried out, but only when the limit current is exceeded by 10–15% will a shutdown occur. This is due to the fact that quite often the starting currents exceed the maximum possible currents for a short period of time, so the machine has a certain reserve of time, after which the circuit will open.

Type of electromagnetic release

This is a part of the machine that allows you to open the circuit in the event of a short circuit, as well as in the event of an increase in current (overload) by a certain number of times. Releases are divided into several categories, let's look at the most popular:

• B - opening when the rated current is exceeded by 3–5 times;
• C - when exceeded by 5–10 times;
• D - when exceeded by 10–20 times.

Maximum power switching capacity. This is the value of the short circuit current (determined in thousands of amperes) at which the machine will remain operational after the circuit opens due to a short circuit.

Marking

All circuit breakers, regardless of the manufacturer and their type, are marked according to a single scheme, including the main parameters:

• manufacturer's name or logo;
• type indication, according to the manufacturer's series number and catalogue;
• operating voltage value: designation of alternating current is a wavy line, direct current is a straight line, combined is two lines at once;
• the value of the operating current (indicated without the measurement value in amperes), the type of time-current characteristic is indicated before the current value;
• operating frequency (in the case when only the set frequency is used);
• short circuit switching capacity (in Amperes);
• the degree of protection is indicated in the form of IP;
• The current limit class is indicated in a rectangle (value from 1 to 3);
• designation of the terminals: for connection to the neutral conductor - N, for connecting the protective line - grounding symbol.

The lever itself contains a status designation: “off”, “on” or “1”, “0”. While turning off occurs automatically, turning on can only be done manually.

A circuit breaker reduces the risks caused by short circuits or sudden blackouts to a minimum.