Main technical characteristics of automatic switches. What are the types and types of circuit breakers in electrical networks Electricity machines with 10 appointments

An electrical network is a system that includes inputs, wires, current consumers, as well as switching equipment. Installation of circuit breakers provides protection for the network as a whole and individual consumers in emergency situations when the current parameters go beyond normal values ​​(short circuit, voltage surges, change in current direction, etc.). In addition, they allow, if necessary, infrequent switching of consumers remotely or in manual mode (6-30 on / off cycles per day).

Care of electrical equipment

Evolution and basic design of circuit breakers

The history of electrical equipment began long before the advent of the first commercial power grids. So, the principle of operation of the circuit breaker was discovered back in 1836 by the American scientist C. G. Page, but the modern design was patented only in 1924 by the Swiss company Brown, Boveri & Cie. Since then, each machine has included the following elements:

• block of contacts;
• arc neutralization (extinguishing) chamber;
• release of the following types: thermal, electromagnetic, electronic, microprocessor;
• control mechanism: manual, spring or driven;
• free release mechanism.

At present, a lot of electrical equipment is being produced, which is illustrated by characteristics of circuit breakers, which provide reliable switching and protection of power networks and consumers of any complexity and power in any operating conditions. The number of models of these devices from different manufacturers is incalculable.

The Skat Technology catalogs contain products from the leading companies Siemens, Andeli, Schneider, whose products rightfully occupy leading positions in the electrical engineering market. Here you can see circuit breakers in the photo, as well as familiarize yourself with their main characteristics and installation methods. If you are not a professional in electrical engineering, we recommend using the help of our specialists, which can also be obtained online.

For those who are interested in how the circuit breaker works, we will give a short explanation. Each device has settings for certain parameters of current and heating of conductors. These settings are provided by the current sensitivity of the release solenoid and a thermal relay with screw adjustment (calibration). If during the operation of the network the parameters go beyond the established limits, the circuit breaks and the consumers are de-energized.

Classification of circuit breakers

For the classification of electrical appliances, there are regulatory documents that set out the technical and operational requirements for them. Breaker classes domestic and foreign production are determined in accordance with the following documents:

• GOST 9098-78;
• GOST 14255-69;
• GOST R 50345-2010;
• GOST R 50030.2-99;
• IEC 60898-95;
• EN 60947-2;
• EN 60898.

In accordance with domestic regulatory and technical documents, the classification of automatic machines is carried out according to 12 parameters, which take into account dozens of operational characteristics of the devices. The quantitative and qualitative values ​​of these parameters determine the purpose of the circuit breaker and the permissible conditions for its operation.

Main classification parameters of circuit breakers

The higher the level of power grid architecture, the more difficult it is to select protection and control equipment for it, since a large number of different operation parameters have to be taken into account. To achieve the desired result, it is necessary to carry out engineering calculations of all parameters so that the selection of a circuit breaker and other electrical devices ensures reliable and safe operation of the network. The list of the main characteristics of the machines is as follows:

• rated currents of the main circuit and releases - respectively 6.3-6300 (total 22 ratings) and 15-3200 amperes (total 12 ratings);
• design - air or ASV (800-6300 A), molded case or MCCB (10-2500 A), modular or MSV (0.5-125 A) automatic machines;
• the number of poles of the main circuit - from one to four;
• the presence or absence of current restrictions;
• types of releases: zero, minimum, independent, maximum;
• the presence or absence of contacts for connecting secondary circuits;
• input/output connection method: front, rear, combined, universal;
• mounting method: fixed, withdrawable (on a DIN rail), on connectors;
• cutoff type: normal, selective, instantaneous;
• type of drive: manual, spring, with propulsion (electromagnet, pneumatics, etc.);
• normal or protected execution.

The listed characteristics have their own designation or quantitative expression. For example, the tripping curve of a circuit breaker is a graphic representation of the tripping of a release. It indicates at what value of the rated current "In" the device trips. According to this parameter, foreign-made products are divided into 6 groups (types):

• A - 2-3 In;
• B - 3-5 In;
• C - 5-10 In;
• D - 10-20 In;
• Z - 2-4 In;
• K - 8-14 In.

The operation class of domestic circuit breakers is designated by the letters B, C and D, since our industry does not produce other types of products. In turn, according to the speed of the cut-off, the automata are divided into normal (0.02-1 sec.) And high-speed or instantaneous (less than 0.005 seconds). Selectivity of circuit breakers means the possibility of setting different cut-off times with a shutter speed of 0.25-0.6 seconds for slave electric devices.

Automatic machines of this type have a main and additional working circuits, which makes it possible to turn off the emergency section of the power supply network controlled by the slave device and save the current supply to the remaining consumers. The time range of the speed and selection processes also reflect circuit breakers curves. The protection devices are triggered not only by the current, but also by the heating of the wires, which is provided by a thermal relay. Simply put, the electromagnetic release responds to current consumption, and the thermal relay responds to heating of the wiring.

It is from the setting of the latter that the time-current characteristic of the circuit breaker depends. The value of the thermal load should not exceed the nominal value for wires of a certain section by more than 1.45 times. It is determined taking into account the method of laying wires and the total load. Depending on the setting, the thermal relay can operate instantly or keep the network operational for a certain time, but not more than an hour.

On the importance of timely operation of protection equipment

From the above data, it is clear how important the tripping time of the circuit breaker is. The minimum value of this indicator is necessary for powerful industrial equipment. Here, class D devices with instantaneous tripping are usually used. For domestic needs, with a margin, there are enough automata of class C of normal tripping.

The exception is worn-out networks and particularly sensitive current consumers, where class A and B devices should be used, in which the minimum tripping time of the circuit breaker in case of short circuit not only provides protection, but also prevents the ignition of the wiring. By the way, the state of the latter is often of decisive importance when choosing electrical equipment. If the size of the wires does not correspond to the load on the network, the thermal response of the circuit breaker will prevent its normal operation.

Reflection of the characteristics of electrical equipment in its marking

For electrical products, it is typical to use the most important operational characteristics in the marking of products. For lighting lamps, this is the power consumption and the luminous flux. Marking of circuit breakers much more complicated, a minimum of information can be squeezed into the name of the product. This is usually the rated operating voltage. Therefore, the marking symbols are applied to the body of the machine:

• the current limit class is indicated by a number placed inside the square; the number of poles is displayed with an icon;
• the class or category of use of the circuit breakers is displayed together with the value of the rated current - for example, "C16";
• the maximum allowable value of the tripping current, at which the risk of damage to the machine is excluded, is indicated in a rectangular frame.

The listed information in the product labeling is enough for a specialist to decide how to select / select a circuit breaker in full accordance with the parameters of the mains. However, when purchasing the device on your own, it is easy to make a mistake if you do not take into account the characteristics of the wiring and the magnitude of the loads. For example, the operating parameters of open and closed wiring, copper and aluminum wires are noticeably different.

If you are wondering how to choose / select a circuit breaker for power, it should be borne in mind that a copper wire with a cross section of 4 mm, laid in an open way, can withstand a load of 9 kW. The same wire with closed wiring will withstand 5.9 kW. It is clear that the power of the current consumer should not exceed the capabilities of the wiring.

Similarly ratings of circuit breakers must be less than the corresponding network parameters. Otherwise, there is a risk of overloading the electrical network, up to the ignition of the wiring, to which the machine simply will not react. In order to avoid this situation, preliminary calculations are necessary that will ensure a balance between current consumers, wiring, and protection and control equipment. For those who are interested in the question how to choose a circuit breaker for your home, we will give advice: choose the nominal value of the device according to the bandwidth of the wiring (the cross section and material of the wires, as well as the method of laying them).

Basic rules for connecting a circuit breaker

A competent arrangement of the architecture of power networks allows to increase their reliability by an order of magnitude. Currently, we use a lot of household appliances and equipment, including those with significant power. The old Soviet-style wiring was not designed for such loads, so consumers often face the question of how to calculate the circuit breaker current in order to ensure the safe operation of the home electrical network.

Based on its experience, Skat Technology concluded that with a significant increase in the load on the network (for example, installing an electric stove), old wiring should not be used. The correct choice of the circuit breaker for the load current will not help either, since the wiring is not designed for it. It is best to completely reconstruct or replace the network with the distribution of current consumers into groups.

Electrical engineering is an exact applied science, therefore the production of electrical goods is carried out according to certain standards. This is clearly seen in the example of what kind of circuit breakers are, the design of which is designed for specific operating conditions. The division of consumers into groups has long been practiced in industrial networks. At the household level, this approach looks like this:

• for lighting fixtures, the rating of the machine should not exceed 10 A;
• for ordinary sockets - 16 A;
• for power sockets for electric stoves, boilers and other things, a circuit breaker is selected according to the power of consumers.

To implement this approach to the construction of networks, manufacturers offer a sufficient selection of automata with a different number of poles, differential type and other units. For domestic purposes, devices in molded cases should be used, in which all current-carrying parts are protected, which excludes accidental electric shock. In order to install a universal circuit breaker, distribution devices (cabinets, assemblies, etc.) are required.

The variety of electrical appliances is also explained by the fact that their design provides for all kinds of installation conditions. In other words, a device with identical parameters can have several versions. So circuit breaker connection diagram is a must for every product. It indicates the number of poles, the points of connection of phases and neutrals, the methods of preparing wires for connection, and other features of a particular model.

If a person has a minimal understanding of electrical engineering, he will not think for a long time about how to connect a single-phase circuit breaker on the panel of his apartment. Just look at the diagram, in which there is nothing complicated. The only warning: if you change the machine, in no case put a switch with a higher power than the previous one. First you need to make sure that the wiring is able to withstand the increased load.

Care of electrical equipment

Electrical equipment, like any other appliances, needs care. Maintenance of circuit breakers is carried out according to a certain procedure with strict frequency. Users are often unaware of this need, but it is there. Electrical engineering is subject to wear, contacts are gradually oxidized, insulation is aging, moving parts are worn out and other changes occur. Therefore, the calculation of the circuit breaker in terms of power, performed 5 years ago, may not correspond to the real state of affairs.

Probably, many of you have experienced situations when a perfectly working network starts to act up. An obvious manifestation of this is the fact that, for no apparent reason, the circuit breaker often trips. The reason may be in the device itself, but most often this happens due to wiring problems and hidden defects in the electrical circuits of household appliances and equipment.

To detect and prevent such situations, there is loading circuit breakers. It is carried out every three years using special equipment and is carried out in order to verify that the actual condition of the machine meets the requirements for the safe operation of electrical networks. The method for checking circuit breakers provides for checking the condition of the insulation, the response time of overcurrent and heating protection, the condition of the contacts, and other parameters.

Regular maintenance ensures that problems are detected early, prevent more serious consequences, and ensure the safe operation of networks for the foreseeable future. Detected malfunctions of circuit breakers are eliminated if possible, but most often in such cases a complete replacement of electrical devices is required, especially in the case of their small sizes.

Manufacturers of electrical products produce many spare parts for powerful industrial machines. For household or low-power equipment, only spare contact groups are usually produced. So replacement of circuit breakers- a typical action in the repair of electrical networks. Regular maintenance of electrical equipment is a completely easy procedure, including in terms of money. Its main goal is prevention.

Among the technical characteristics of the machines, the guaranteed number of on / off cycles is also indicated. According to these indicators, circuit breakers have a service life measured in decades, provided that the devices are properly installed and maintained in a timely manner. They must fully comply with the network parameters. In addition, to extend their service life, you should not use faulty electrical appliances that provoke frequent power outages.

Professional services from the company "Scat technology"

Our company specializes in works on engineering communications, including electrical networks. Our specialists are ready to give recommendations on the choice of circuit breakers and perform network design, including load calculations and their distribution, taking into account all safety standards. Experienced engineers will answer any practical questions, including how to connect a circuit breaker for different categories of current consumers, taking into account installation conditions, wiring conditions and other factors.

Our catalogs contain a wide selection of electrical products from leading manufacturers. Our range will allow you to easily carry out a complete set of works on the arrangement of electrical networks. If it bothers you cost of circuit breakers with logos of famous brands, we remind you that high-quality products cannot be frankly cheap. In addition, the service life of such electrical equipment is an order of magnitude higher than that of products of dubious origin.

Those who are wondering which circuit breakers are better should decide what meaning you put into it. For us, the determining factor is reliability and safety at adequate costs? We offer electrical products at the most fair prices, so we are convinced that our customers do not overpay. Dimensions of circuit breakers are far from always the equivalent of prices, therefore, if you want to get a normal result of arranging the power grid, use the services of Skat Technology professionals.

The development of power grid security tools has become relevant since their inception. Various overloads led not only to cable damage, but also to fires.

To date, the most popular devices of this type are circuit breakers.

They help prevent events such as fires, damage to electrical wiring. Since they are automatic, the operation occurs without human intervention. Choosing the right switch will help protect the room from accidents.

Design and principle of operation

Understanding the circuit breaker's automatic tripping mechanism will help you select the right model. Structurally, the machine includes the following key elements:

• terminals;
• toggle switch;
• electromagnetic release;
• bimetallic plate.

Depending on the type of overload, one of two mechanisms is triggered.

When an overload of the circuit occurs with a current that exceeds the nominal value by several times, the bimetallic plate is triggered. It heats up within a few seconds, resulting in its thermal expansion. When a certain size is reached, its significant bending is carried out and the chain opens. The setting of the plate parameters is carried out by the manufacturer. For switches used in everyday life, the operating time takes 5–20 s. They are usually marked with the letters: B, C, D.

The short circuit mode (short circuit) is characterized by an avalanche-like increase in current, which exceeds not only the nominal value, but also its maximum permissible loads. There is no time left to heat the plate during the jump, otherwise the wiring may melt. In such a situation, an electromagnetic release is triggered. The magnetic field drives the core, which opens the circuit. Instant operation allows you to protect the premises from the consequences of a short circuit.

Classification

Electric machines differ in the following key characteristics:

• number of poles;
• time current characteristic;
• operating current;
• breaking capacity.

Number of poles

This characteristic corresponds to the number of electrical wiring lines that can be directly connected to the machine. All output wires will be disconnected at the same time when the machine is triggered.

Single pole machine. This is the simplest type of circuit protection devices. Only 2 wires are connected to it: one goes to the load, the second is power. It mounts on a standard 18mm din rail. The power wire is fed from above, and the load to the bottom terminal. It can work in single, two or three phase power lines. In addition to the power and load wires, it has a neutral and ground, which are connected to the corresponding busbars. Such machines are not installed at the input, since the circuit will open only along the phase line. The zero wiring remains closed and, in case of failures, potential may remain on it.

A two-pole machine, its difference from a single-pole one. This type of circuit breakers allows you to completely de-energize the electrical wiring of the room. It allows you to synchronize the moment of turning off two of its output lines. The latter leads to a higher level of safety during electrical work. It can be used as a separate toggle switch for appliances such as a water heater or a washing machine. The connection is made using 4 cables: a pair at the input and output.

A simple question is logical: is it possible to connect two single-pole machines instead of one two-pole one? Of course no. After all, when the shutdown is automatically triggered, all output lines are turned off at the two-terminal network. For a pair of independent automata, overload may not occur on one of the lines and the de-energization will be partial. In ordinary apartments, you can connect a phase and neutral line to this machine. When opened, a complete deenergization of the entire group of devices that are powered from it will occur.

Three and four-pole machines. All three or four phase conductors are connected to the poles of the corresponding circuit breaker. They are used when connected by a star, when the phase wires are protected from overloads, and the middle wire remains switched all the time, or by a triangle, when there is no middle central cable, and the phase wires are protected.

If an overload occurs on one of the lines, a shutdown occurs immediately on all the others. 6 (three-phase machine) or 8 wires are connected to these machines. 3-4 at the output and the same number of lines at the output. They are mounted on din rails with a length of 54 (three-phase machine) and 72 mm, respectively. They are used most often in industrial installations, when connecting powerful electric motors.

Time current parameter

The power consumption patterns of different devices vary even if the power values ​​are the same. Uneven dynamics of consumption during correct operation, a surge in load during turn-on - all these phenomena lead to significant changes in such a parameter as current consumption. Power dissipation can lead to false tripping of the circuit breaker.

To exclude such situations, dynamic operation parameters are introduced, called time-current characteristics of circuit breakers. Automata according to this parameter are divided into several types. Each group has its own response time. The front panel of the switch is marked with the corresponding letter from the list: A, B, C, D, K, Z.

Rated current

The differences of automata depending on the nominal values ​​of the current are divided into several groups (12 current levels). It is directly related to the response time when the power consumption is exceeded. The operating value can be determined purely theoretically by adding up the sums of the currents consumed by each of the devices separately. In this case, a small margin should be taken. Also, do not forget about the possibilities of electrical wiring.

Machines are designed primarily to prevent damage to it. Depending on the metal of the wires and their cross section, the maximum load is calculated. The ratings of the circuit breakers for current allow such a separation.

Breaking capacity

This parameter depends on the maximum current in the event of a short circuit, provided that the machine performs a network shutdown. According to the magnitude of the short-circuit current, all automata are divided into three groups.

• The first includes devices with a nominal value of 4.5 kA. They are used in private houses intended for human habitation. The current limit is approximately 5 kA. This is due to the fact that the resistance of the system of conductive cables leading to the house from the substation is 0.05 ohms.
• The second group has rated 6 kA. This level is already used in residential apartment buildings and public places. The current limit can reach 5.5 kA (wiring resistance 0.04 Ohm). In this case, models of types are used: B, C, D.
• In industrial plants the nominal value is 10 kA. The limit value of the current that can occur in the circuit near the substation has the same value.

How to choose the right machine

Until recently, porcelain fuses with fusible elements were widely used. They were well suited for the same type of load of Soviet apartments. Now the number of household appliances has become much larger, as a result of which the probability of getting a fire with old fuses has increased. To prevent this, it is necessary to carefully approach the choice of a machine with the correct characteristics. Excess power reserves should be avoided. The final choice is made after a few simple steps.

Determining the number of poles

When determining this switch parameter, a simple rule should be followed. If you plan to secure sections of the circuit with devices that have low power consumption (for example, lighting devices), then it is better to leave your choice on a single-pole machine (usually class B or C). If you plan to connect a complex household device with significant power consumption (washing machine, refrigerator), then you should install a two-pole machine (class C, D). If a small production workshop or a garage with multi-phase propulsion systems is being equipped, then it is worth choosing a three-pole option (class D).

Power consumption calculation

As a rule, by the time it is planned to connect the machine, the wiring to the room has already been connected. Based on the cross section of the cores and the type of metal (copper or aluminum), you can determine the maximum power. For example, for a copper core of 2.5 mm 2, this value is 4–4.5 kW. But the wiring is often summed up with a large margin. Yes, and the calculation should be done before the start of all installation work.

In this case, you will need a value about what the total power will be used by all devices. It is always possible to turn them on at the same time. So, in an ordinary kitchen, the following appliances are often used:

• fridge- 500 W;
• Electric kettle- 1700 W;
• microwave– 1800 W

The total load is 4 kW and a 25 A machine is enough for it. But there are always consumers who turn on sporadically and can create factors that contribute to the operation of the switch. Such devices can be a combine or a mixer. Therefore, you should take the machine with a margin of 500-1200 watts.

Rated current calculation

Since the power in single-phase networks is equal to the product of voltage and current, it is easy to determine the current as a quotient of power and voltage. For the above example, this value is easy to calculate, knowing that the mains voltage is 220 V. The current consumption is 18.8 A. With a margin of 500-1200 V, it will be 20.4-23.6 A.

In order for the work not to stop even with such short-term excess loads, the rated current for the machine can be taken equal to 25 A. Approximately the same value corresponds to the rating, based on a copper cable with a cross section of 2.5 mm 2, which is enough with a margin for such loads. A machine with a rated current of 25 A will work before it starts to heat up.

Determination of the current characteristic time

This parameter is determined by a special table that lists the starting currents and their flow time. For example, for a household refrigerator, the starting current ratio is 5. With a power of 500 W, the operating current is 2.2 A. The starting current will be 2.2 * 7 \u003d 15.4 A. Data on the frequency is also taken from a special table.

Table No. 1. Starting currents and pulse durations for household appliances

For the selected device, this characteristic does not exceed 3 s. The choice becomes obvious: for such a consumer, it is necessary to take a type B circuit breaker. It is permissible to make a choice of the machine according to the load power. You can skip the last step by opting for a class B switch. For domestic needs, the characteristics of class B and C electrical switches are most often sufficient.

The topic of our today's article is the rating of manufacturers of automatic switches in the domestic and foreign markets. Next, we will tell you which company is better to give preference to when choosing a machine, and also provide readers of the site with leading brands that produce automation for domestic and industrial use. A brief overview of the best economy class AVs that are most often used in a house and apartment will also be provided.

Brand Overview

So, to begin with, we will briefly talk about the main manufacturers of circuit breakers. As for foreign brands, the most famous are:

• ABB. The Swedish-Swiss company, which is rightfully considered a leader in the production of electrical products. To date, ABB circuit breakers are the highest quality, durable and safe to use. As you understand, you will have to pay more money for such foreign products than for a domestic model. At the same time, the difference in price is small, therefore, for a house and an apartment, we recommend buying automatic machines from the manufacturer ABB.
  
• Legrand. Country of origin - France. Legrand circuit breakers are not inferior in quality to the ABB brand, therefore it is also preferable to choose Legrand products for electrical work. In terms of cost, the machines are about the same, in fact, as in terms of reliability.
  
• Schneider Electric. Another French company that closes the TOP-3 of the best manufacturers specializing in the production of reliable circuit breakers. Schneider Electric has long settled in the Russian market of electrical products and has many positive reviews from experienced electricians.
  
• General Electric. An American manufacturer of power machines and other electrical products, which can also be called one of the best in quality. To date, there are many discussions on the forums about which is better: GE or Legrand. Here we can say that both brands produce good quality circuit breakers, but in fact, there is more demand for Legrand in the Russian market.
  
• Siemens. Siemens company specializes not only in the production of automation, but still has a wide range of models for industrial and domestic use. The quality is already a little worse than that of the top three, but still very high. The price is also slightly lower compared to manufacturers such as ABB, Legrand and Schneider Electric.
• Moeller. A German company that successfully competes with such a global giant as ABB. Despite the fact that in 2007 Moeller was bought out by the American Eaton Corporation, this did not affect the quality and reliability of the products for the worse. Moeller circuit breakers meet all international standards and are very popular.

Among domestic manufacturers of automatic machines, the best quality is from brands such as:

I would also like to say a few words about products from China. Chinese circuit breakers EKF electrotechnica, whose direct competitors are IEK circuit breakers. Both companies have about the same price and similar quality. Oddly enough, China gives a guarantee on its product for a period of 5 years.

Our rating

So, we have listed all the most popular domestic and foreign companies that are engaged in the production of these devices. Now I would like to provide my own rating of manufacturers of circuit breakers for 2019:

1. ABB, in particular the S200 series. A detailed overview of ABB machines is available at the link:. Slightly inferior to SH200.
2. Legrand, TX3 or DX3 series.
3. Schneider Electric, Acti9 iC or iK series. More budget option Easy 9.
4. Siemens, 5SX, 5SY, 5SP, 5SL series.
5. General Electric, DMS LINE.
6. Moeller, PL6 or PL7.
7. Hager, MS series.
8. KEAZ, OptiDin BM63.
9. Eaton, xPole Home. By the way, we did a review of the machine of this series in a separate article:.
10. DEKraft, VA-103.

The only thing I would like to clarify is that this rating of manufacturers of electric machines is not entirely convenient, so that on its basis by company. Here, you must first decide how much money you can allocate for protective automation for your home. Even companies like ABB have their own series of low cost budget models. If you need to buy an economy-class machine, we recommend that you still give preference to reliability - the brands Legrand, ABB and Schneider Eletric. For supporters of Russian products, we can advise DEKraft, because. On the forums, we did not meet a lot of negative reviews about this company!

That's all I wanted to tell you about companies specializing in the production of protective automation. We hope that you make the right choice and take advantage of our rating of circuit breakers!

Related content:

An electric machine, or circuit breaker, is a mechanical switching device, by means of which it is possible to manually achieve a de-energization of the entire electrical network or a specific section of it. This can be done in a house, apartment, country house, garage, etc. Moreover, such a device is equipped with the function of automatically turning off the electric cable in case of emergency: for example, in the event of a short circuit or overload. The difference between such circuit breakers and conventional fuses is that after operation they can be turned on again with the button.

Let's talk about how to choose machines: electric machines exist in a wide variety, which requires taking into account a number of factors at once when buying them.

Is such a machine necessary? It is necessary to give an affirmative answer. A properly functioning circuit breaker will protect your premises from various unpleasant situations, including:

• fires;
• electric shock;
• wiring damage.

So, when choosing a machine, as we noted, several indicators should be taken into account at once. Let's consider them in order.

Main selection criteria

Limiting short-circuit current

This indicator must be taken into account immediately. It means the maximum current value at which the electric machine will work and open the circuit. Here the choice is not great, since there are only three options:

• 4.5 kA;
• 6 kA;
• 10kA.

When choosing, one should be guided by the theoretical probability of a high short-circuit current. If there is no such probability, then it will be enough to purchase a 4.5 kA automatic machine.

Machine current

Accounting for this indicator is the next step. We are talking about the required nominal value of the operating current of the electric machine. To determine the operating current, you need to be guided by the power that is supposed to be connected to the wiring, or by the value of the allowable current (the level that will be maintained in normal mode).

What do you need to know when determining the parameter in question? It is not recommended to use machines with an overestimated operating current. Just in this case, the machine will not turn off the power during overload, and this can cause thermal destruction of the wiring insulation.

This is perhaps the simplest indicator. To choose the number of poles for a switch, you need to proceed from how it will be used.

So, a single-pole machine is your choice if you need to protect the wiring that goes from the electrical panel to sockets and lighting circuits.

A bipolar switch is used when it is necessary to protect all wiring in an apartment or house with single-phase power.

Protection of three-phase wiring and load is provided by a three-pole circuit breaker, and four-pole ones are used to protect four-wire power.

Characteristics of the machine

This is the last indicator that you need to pay attention to. The time-current characteristic of the circuit breaker is determined by the loads that are connected to the protected line. When choosing a characteristic, the following are taken into account: the operating current of the circuit, the rated current of the machine, the cable capacity, the operating current of the switch.

• In the event that it is necessary to connect small starting currents to the power supply line, i.e. electrical appliances characterized by a small difference between the operating current and the current that occurs when switched on, preference should be given to the operation characteristic B.
• Finally, there is one more characteristic - D. You should stop your choice on it if you intend to connect powerful devices with high starting points. What devices are we talking about? For example, about the electric motor.

The final selection stage

These are the main indicators that should be considered when choosing a circuit breaker. Accordingly, if you know all the necessary data, then the choice will not be difficult. It remains only to take into account the latest criterion - the manufacturer of the machine. What does it affect?

• obviously at a cost. Indeed, there is a difference. Thus, well-known European brands offer their circuit breakers at a price that is twice the cost of domestic counterparts and three times the price of devices from the South-Eastern countries;
• also, the presence or absence of a switch with clearly defined indicators in the warehouse depends on the choice of a particular manufacturer.

Another useful way to choose an electric machine is offered in the video below:

In practical application, it is important not only to know the characteristics of circuit breakers, but also to understand what they mean. Thanks to this approach, you can decide on most technical issues. Let's look at what is meant by certain parameters indicated on the label.

Abbreviation used.

Device marking contains all the necessary information describing the main characteristics of circuit breakers (hereinafter AB). What they mean will be discussed below.

Time-current characteristic (VTH)

With this graphic display, you can get a visual representation under what conditions the circuit power-off mechanism will be activated (see Fig. 2). On the graph, the time required for AV activation is displayed as a vertical scale. The horizontal scale shows the I/In ratio.

Rice. 2. Graphical display of the time and current characteristics of the most common types of machines

Permissible excess of the nominal current, determines the type of time-current characteristics for releases in devices that perform automatic shutdown. In accordance with the current regulations (GOST P 50345-99), each type is assigned a specific designation (from Latin letters). Permissible excess is determined by the coefficient k=I/In, for each type the values ​​​​established by the standard are provided (see Fig. 3):

• "A" - maximum - three times the excess;
• "B" - from 3 to 5;
• "C" - 5-10 times more than regular;
• "D" - 10-20 times excess;
• "K" - from 8 to 14;
• "Z" - 2-4 more than regular.

Figure 3. Basic activation parameters for different types

Note that this graph fully describes the conditions for activation of the solenoid and thermoelement (see Fig. 4).

Considering all of the above, it can be summarized that the main protective characteristic of the AV is due to the time-current dependence.

List of typical time-current characteristics.

Having decided on the marking, let's move on to the consideration of various types of devices that correspond to a certain class, depending on the characteristics.

Characteristic type "A"

Thermal protection AB of this category is activated when the ratio of circuit current to nominal (I / I n) exceeds 1.3. Under these conditions, shutdown will occur after 60 minutes. As the rated current is further exceeded, the tripping time is reduced. The activation of electromagnetic protection occurs when the nominal value is doubled, the response speed is 0.05 sec.

This type is installed in circuits not subject to short-term overloads. As an example, we can cite circuits on semiconductor elements, in case of failure of which, the excess current is negligible. In everyday life, this type is not used.

Characteristic "B"

The difference between this type and the previous one lies in the operating current, it can exceed the standard one from three to five times. At the same time, the solenoid mechanism is guaranteed to be activated at a five-fold load (power-off time - 0.015 sec.), The thermoelement - three times (it will take no more than 4-5 seconds to turn off).

Such types of devices have found application in networks that are not characterized by high inrush currents, for example, lighting circuits.

Characteristic "C"

This is the most common type, and its allowed overload is higher than the previous two types. When the normal mode is exceeded five times, the thermoelement is triggered, this is a circuit that turns off the power supply within one and a half seconds. The solenoid mechanism is activated when the overload exceeds ten times the norm.

These AB are designed to protect the electrical circuit in which a moderate inrush current may occur, which is typical for a household network, which is characterized by a mixed load. When buying a device for the home, it is recommended to opt for this type.

Three-pole machine Legrand

Characteristic "D"

For AB of this type, high overload characteristics are characteristic. Namely, ten times the norm for the thermoelement and twenty times for the solenoid.

Such devices are used in circuits with high starting currents. For example, to protect starting devices of asynchronous electric motors. Figure 9 shows two devices of this group (a and b).

Figure 9. a) VA51-35; b) BA57-35; c) BA88-35

Characteristic "K"

For such ABs, activation of the solenoid mechanism is possible when the current load is exceeded by 8 times, and is guaranteed to occur when there is a twelvefold overload of the normal mode (eighteenfold for constant voltage). Load off time no more than 0.02 sec. As for the thermoelement, its activation is possible when 1.05 of the normal mode is exceeded.

Scope of application – circuits with inductive load.

Characteristic "Z"

This type is distinguished by a small allowable excess of the nominal current, the minimum limit is two times the standard one, the maximum is four times. The thermoelement response parameters are the same as for AB with characteristic K.

This subspecies is used to connect electronic devices.

Characteristic "MA"

A distinctive feature of this group is that a thermoelement is not used to disconnect the load. That is, the device only protects against short circuit, this is quite enough to connect an electric motor. Figure 9 shows such a device (c).

Normal operation current

This parameter describes the maximum allowable value for normal operation, if it is exceeded, the load shedding system will be activated. Figure 1 shows where this value is displayed (using IEK as an example).

Thermal parameters

This term refers to the conditions for the operation of a thermoelement. These data can be obtained from the corresponding time-current graph.

Ultimate breaking capacity (PKS).

This term refers to the maximum allowable load value at which the device can open the circuit without loss of performance. In Figure 5, this marking is indicated by a red oval.

Rice. 5. Schneider Electric device

Categories of current limiting

This term is used to describe the ability of an AB to break a circuit before the short circuit current in it reaches its maximum. Devices are produced with current limiting of three categories, depending on the load off time:

1. 10 ms. and more;
2. 6 to 10 ms;
3. 2.5-6ms.

Note that ABs belonging to the first category may not have the appropriate marking.

A small life hack on how to choose the right switch for your home