Automatic switches: selection, connection, service. Types and principle of operation of electrical machines Electricity cut-off machine

An electrical machine, or circuit breaker, is a mechanical switching device through which you can manually de-energize 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 electrical cable in the event of an emergency: for example, in the event of a short circuit or overload. The difference between such circuit breakers from conventional fuses is that after they have been triggered, they can be turned on again with a 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.

Do you need such a machine? An affirmative answer must be given. A properly working circuit breaker will protect your premises from various unpleasant situations, including:

fires;
electric shock;
damage to the wiring.

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

The main criteria for selection

Short-circuit current limit

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

4.5 kA;
6 kA;
10kA.

When choosing, one should be guided by the theoretical probability of a strong 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 electrical machine. To determine the operating current, you need to be guided by the power that is expected 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. It's just that 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 circuit breaker, you need to proceed from how it will be used.

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

A two-pole switch is used when you need to protect all wiring in an apartment or house with a single-phase power supply.

Three-phase wiring and load protection is provided by a three-pole circuit breaker, and four-pole ones are used to protect the four-wire power supply.

Machine characteristics

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 throughput of the cable, the operating current of the switch.

In the event that it is necessary to connect small inrush currents to the power supply line, i.e. electrical devices characterized by a small difference between the operating current and the current that occurs when switched on, the tripping characteristic B should be preferred.
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 stage of selection

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

obviously at the cost. Indeed, there is a difference. So, well-known European brands offer their circuit breakers at a price that is twice the cost of domestic counterparts and three times more than 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 specific manufacturer.

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

Modern power supply of private houses and apartments is not recommended to be done without protective circuit breakers. They provide safety and guarantee a long service life for the wiring. We will talk about the choice of a circuit breaker in this article.

The main task of the circuit breaker is to protect the wiring from overheating and the insulation from melting. And he does this by turning off the power supply at those moments when the conductor heats up to critical temperatures due to the connection of an excessively high power load. The second task of the bagger is to disconnect the line at short-circuit currents (short circuit). The goal is the same - to save the wiring from destruction.

Timely power off in case of problems is very important, as it prevents damage to wiring and fire. Therefore, the choice of a circuit breaker is a responsible task. It is necessary to choose according to the rules, and not according to the principle "so that it turns off less often." This method can lead to fire. In general, the choice of a circuit breaker is carried out according to three parameters:

face value;
breaking capacity (cut-off current);
type of electromagnetic splitter (time-current characteristic).

Each parameter is important and is selected depending on the load connected to a particular line, the location of the wiring relative to the distribution substations.

Types of circuit breakers

Circuit breakers are produced for single-phase and three-phase circuits. For a single-phase network, there are two types of packets - single-pole and double-pole. Only the phase conductor is connected to the single-pole and, when triggered, only the phase is disconnected. Such machines are recommended to be installed in houses and apartments in rooms with normal operating conditions. Usually they are installed on lighting lines, outlet groups that are located in living rooms, corridors, kitchens.

Circuit breakers - single pole, double pole and 3 pole

Both phase and neutral wires are connected to two-pole circuit breakers. He breaks both chains. The degree of protection is much higher here, since the shutdown is complete, not partial. Such an automatic machine will ensure safety even if, during an accident, the voltage hits the neutral conductor. Bipolar machines are recommended to be installed on dedicated lines to which powerful household appliances are connected. They are also placed in rooms with difficult operating conditions. These include a bathroom, pool, sauna.

For three-phase networks, three-pole and two-pole circuit breakers are used. On three-pole, all three phases are started. Accordingly, they turn off everything at the same time. Such bags are placed at the entrance to a house or apartment, as well as on the line to which three-phase consumers are connected - a hob, an oven and other similar equipment. For the same consumers, you can install four-pole circuit breakers. They will also disconnect the neutral wire.

On other power lines, which use one of the phases, two-pole packet bags are installed. Simultaneous disconnection of phase and zero is more preferable. And only on the lighting line, you can install single-pole devices.

Choice of circuit breaker for load current

When planning electrical wiring, the main task is to choose the correct rating of the circuit breaker. When current passes through the conductor, it begins to warm up. The more current flows through a conductor of the same cross-section, the more heat is generated. The purpose of the circuit breaker is to turn off the power until the current consumption is higher than allowed. Therefore, the rating of the circuit breaker must be less than the permissible wiring current.

The ratings of the circuit breakers are standardized: 6 A, 10 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A and 63 A. more and more and lines of small cross-section do not cope with the load.

Choice of denomination

A circuit breaker is chosen not for the load, not for the power of the connected devices or for the current. These parameters are taken into account when choosing a conductor cross-section. And the choice of the circuit breaker is made depending on the cross-section of the conductors. There is a special table in which the permissible load currents and the recommended rating of the circuit breaker are indicated. Using the table is simple: find the desired section, in this line look for the nominal value of the circuit breaker. Everything.

Cable cross-section	Recommended circuit breaker rating	Limiting operating current of the machine	Permissible continuous load current	Maximum load power	Application area
1.5 mm2	10 A	16 A	19 A	4.1 kW	Lighting and signaling
2.5 mm2	16 A	25 A	27 A	5.9 kW	Sockets, electric underfloor heating
4 mm2	25 A	32 A	38 A	8.3 kW	Water heaters, air conditioners, washing machines and dishwashers
6 mm2	32 A	50 A	46 A	10.1 kW	Electric stoves, ovens
10 mm2	50 A	63 A	70 A	15.4 kW	Entrances to the house, apartment

How does it work

Looking at the table, the question arises: why the rating of the machine is so much less than the maximum permissible current load. The answer lies in the mechanics of the circuit breaker. It turns off only when the current in the circuit is 13% higher than the pickup current.

For example, a 10 A machine will work when the current in the circuit is 16 A + 13% (2.08 A) = 18.08 A. That is, a small gap remains up to the permissible load. This gap is necessary to ensure the integrity of the insulation.

The modern power supply system of a house or apartment is not complete without automatic switches.

What happens if you put a 16 A machine on a wire with a cross section of 1.5 mm2. After all, its rating is lower than the permissible load current? Let's count. The current at which the bag will operate is 25 A + 3.25 A (13%) = 28.25 A. It is higher than the permissible continuous load current. Yes, it will rarely turn off, but after a while the insulation will melt and the wiring will have to be changed. Therefore, it is better to choose a circuit breaker according to this table, and not according to the long-term permissible current.

Load selection

If the power supply line is laid with a power reserve, and the load on it is far from the limit, you can put an automatic machine with a lower rating. In this case, it will protect not so much the line from overheating as the equipment from short-circuit currents.

Choosing a circuit breaker for load power is the wrong idea

The choice of the rating of the circuit breaker in this case can also be done according to the same table. We take the load power only as a starting point. But let's repeat it once more. This is in the event that the parameters of the line can withstand a much greater load than exists.

Type of electromagnetic splitter (trip curve)

The next parameter by which the choice of the circuit breaker is made is the type of electromagnetic splitter. He is responsible for the delay that occurs when triggered. It is necessary to avoid false shutdowns during the start of motors of various equipment.

When the motor of the refrigerator, dishwasher or washing machine is turned on, the current in the circuit rises for a short time. This phenomenon is called inrush currents, and they can exceed the operating consumption by 10-12 times, but they do not last very long. Such a short-term increase is not harmful. So, the electromagnetic splitter must have a delay that allows you to ignore these inrush currents. This characteristic is displayed in Latin letters B, C, D. This letter is placed in front of the rating of the circuit breaker (mi photo). The choice of a circuit breaker on this basis is not difficult. You just need to know the nature of the planned load:

Actually, the choice of a circuit breaker in this case is simple. It is enough to install category B machines on the lighting line, on the rest you can put C.

Choosing the degree of protection against short-circuit currents (cut-off current)

The second function of the protective circuit breaker is to turn off the power when overcurrents appear, which occur during a short circuit (SC). The circuit breakers are designed for different values of these currents, and the characteristic that reflects it is the breaking capacity or the cut-off current. It shows at what short-circuit current the machine will still remain in working condition. The fact is that the packet trap does not work instantly, because there is a response delay to ignore the starting overloads. During this delay, the contacts may melt and the device may become inoperative. So, the cut-off current or breaking capacity shows how much current the contacts can carry without affecting their performance.

In the household electrical network, circuit breakers are used with three degrees of protection against short-circuit currents: 4500 A, 6000 A, 10000 A. On the body of the device, these numbers are put in a frame just below the rating of the machine. In terms of price, the difference is quite tangible, but it is justified - in more "resistant" bags, refractory materials are used, and they are much more expensive.

How to choose a circuit breaker in this case? The choice depends on the location of the network in relation to the substation. If a house or apartment is located nearby, the short-circuit currents can be very large, therefore the breaking capacity must be at least 10,000 A. In all other cases, set at 6000 A.

Enclosure protection

The degree of protection of the case is in the characteristics. It is designated by the Latin letters IP and two numbers. The first figure shows how protected the device is from the ingress of dust and foreign objects. The lowest protection (none) is 0, the highest level is 6 (full protection against long-term exposure). The second number represents moisture protection. Without protection - 0, it may be in the water for some time - 8. The decoding of the numbers is given in the table.

If the electrical panel is installed in an apartment, in a dry room, the IP20 degree of protection is sufficient. On staircases, a higher degree of protection is desirable. At least IP32. If the machine is installed on the street, it should be set at least IP55.

Expensive or cheap?

There are two price categories of automatic circuit breakers in shops and markets. One part is produced by well-known brands and has a very solid price tag. These are Schneider Electric (Schneider Electric), ABB, LeGrand and others. These brands have been on the market for a long time, have European roots and an established reputation. The quality of their products is always at their best, so those who do not like to take risks and can afford to spend a lot of money on assembling the switchboard prefer to buy products from these manufacturers.

Next to them are usually the same machines, but they cost 2-5 times less. These are IEK (IEK), EKF (EKF), TDM (TDM), DEKRAFT (Derkaft), etc. These are Chinese machines, but manufactured at factories. Some brands (the same Dekraft) have European roots (in this case Germany), but production facilities in China. These brands are also considered good and show stable results. So for those who are trying not to spend extra money, this is a good option. Affordable and good quality.

What you shouldn't do is buy products from unknown manufacturers. Even if their price is very attractive and the seller praises you very much.

There are also pitfalls when buying well-known brands: there are too many fakes. Moreover, they are sold at almost the same price as the original, and it is very difficult to distinguish them by their appearance. The only thing you can focus on is less weight. There is less metal in fakes, some elements may be missing. Due to this, the weight is less. There may also be errors in the application of inscriptions, sometimes paints of other shades are used. To notice all this, you must first study well all the nuances of the originals on the official sites, and even better to hold them in your hands.

The main difference between these switching devices from all other similar devices is the complex combination of capabilities:

1. to maintain the rated load in the system for a long time due to the reliable transmission of powerful flows of electricity through its contacts;

2. to protect the operating equipment from accidental faults in the electrical circuit by quickly removing power from it.

Under normal operating conditions of the equipment, the operator can manually switch the loads with the circuit breakers, providing:

different power schemes;

changing the network configuration;

withdrawal of equipment from work.

Emergency situations in electrical systems occur instantly and spontaneously. A person is not able to quickly respond to their appearance and take measures to eliminate them. This function is assigned to automatic devices built into the circuit breaker.

In the power industry, the division of electrical systems by type of current is accepted:

constant;

alternating sinusoidal.

In addition, there is a classification of equipment according to the magnitude of the voltage for:

low voltage - less than a thousand volts;

high voltage - everything else.

For all types of these systems, their own circuit breakers are created, designed for repeated operation.

AC circuits

According to the power of the transmitted electricity, automatic switches in alternating current circuits are conventionally divided into:

1.modular;

2. in a molded case;

3. power air.

Modular designs

A specific design in the form of small standard modules with a width of multiples of 17.5 mm determines their name and design with the possibility of mounting on a Din-rail.

The internal structure of one of these circuit breakers is shown in the picture. Its body is completely made of durable dielectric material, excluding.

The supply and outgoing wires are connected to the upper and lower terminal clamp, respectively. For manual control of the state of the switch, a lever with two fixed positions is installed:

the upper one is designed to supply current through a closed power contact;

bottom - provides a break in the power supply circuit.

Each of these machines is designed for long-term operation at a certain value (In). If the load becomes larger, then the power contact breaks. For this, two types of protections are placed inside the case:

1. thermal release;

2.current cutoff.

The principle of their operation makes it possible to explain the time-current characteristic, which expresses the dependence of the protection operation time on the load current or failure passing through it.

The graph shown in the picture is for one specific circuit breaker, when the cut-off operating zone is selected at 5 ÷ 10 times the rated current.

At the initial overload, a thermal release is made, which, with an increased current, gradually heats up, bends and acts on the disconnecting mechanism not immediately, but with a certain time delay.

In this way, it allows small overloads associated with short-term connection of consumers to self-eliminate and eliminate unnecessary shutdowns. If the load provides critical heating of the wiring and insulation, then the power contact breaks.

When an emergency current arises in the protected circuit, capable of burning equipment with its energy, then an electromagnetic coil comes into operation. With an impulse, due to the surge of the load that has arisen, it throws the core onto the disconnecting mechanism in order to instantly stop the out-of-limit mode.

The graph shows that the higher the short-circuit currents, the faster they are disconnected by the electromagnetic release.

The household automatic steam fuse works according to the same principles.

When large currents are broken, an electric arc is created, the energy of which can burn out the contacts. To eliminate its effect, an arc-extinguishing chamber is used in circuit breakers, which divides the arc discharge into small flows and extinguishes them due to cooling.

Multiplicity of cutoffs of modular structures

Electromagnetic releases are tuned and matched to work with certain loads because they create different transients when they start. For example, during the switching on of various luminaires, the short-term inrush current due to the changing resistance of the filament can approach three krats of the nominal value.

Therefore, for the socket group of apartments and lighting circuits, it is customary to choose automatic switches with a time-current characteristic of the "B" type. It is 3 ÷ 5 In.

Asynchronous motors, when spinning a rotor with a drive, cause higher overload currents. For them, select machines with the characteristic "C", or - 5 ÷ 10 In. Due to the created margin in time and current, they allow the engine to spin up and it is guaranteed to enter the operating mode without unnecessary shutdowns.

In industrial production, on machine tools and mechanisms, there are loaded drives connected to motors, which create more increased overloads. For such purposes, automatic switches of characteristic "D" with a rating of 10 ÷ 20 In are used. They have proven themselves well when working in circuits with active-inductive loads.

In addition, the machines have three more types of standard time-current characteristics that are used for special purposes:

1. "A" - for long wiring with an active load or protection of semiconductor devices with a value of 2 ÷ 3 In;

2. "K" - for pronounced inductive loads;

3. "Z" - for electronic devices.

In the technical documentation from different manufacturers, the cutoff rate for the last two types may differ slightly.

This class of devices is capable of switching higher currents than modular designs. Their load can reach values up to 3.2 kiloamperes.

They are manufactured according to the same principles as modular structures, but, taking into account the increased requirements for the transmission of the increased load, they are trying to give them relatively small dimensions and high technical quality.

These machines are designed for safe operation in industrial facilities. By the value of the rated current, they are conventionally divided into three groups with the ability to switch loads up to 250, 1000 and 3200 amperes.

Constructive design of their case: three- or four-pole models.

Power air switches

They work in industrial installations and handle very heavy currents up to 6.3 kiloamperes.

These are the most complex devices for switching devices of low-voltage equipment. They are used for the operation and protection of electrical systems as input and output devices for high power distribution plants and for connecting generators, transformers, capacitors or powerful electric motors.

A schematic representation of their internal structure is shown in the picture.

Here, a double break of the power contact is already used and arc extinguishing chambers are installed with gratings on each side of the disconnection.

The operation algorithm involves the closing coil, the closing spring, the motor-drive of the spring charging and the automation elements. To monitor the flowing loads, a current transformer with a protective and measuring winding is integrated.

Circuit breakers for high-voltage equipment are very complex technical devices and are made strictly individually for each voltage class. They are usually used.

Requirements are imposed on them:

high reliability;

security;

performance;

ease of use;

relative noiselessness during operation;

optimal cost.

Loads that break during a fault trip are accompanied by a very strong arc. Various methods are used to extinguish it, including breaking the circuit in a special environment.

This switch includes:

contact system;

arc extinguishing device;

live parts;

insulated housing;

drive mechanism.

One of these switching devices is shown in the photograph.

For high-quality operation of the circuit in such structures, in addition to the operating voltage, take into account:

the rated value of the load current for its reliable transmission in the on state;

maximum short-circuit current at rms value that the tripping mechanism can withstand;

the permissible component of the aperiodic current at the moment of circuit rupture;

automatic reclosing capabilities and two AR cycles.

According to the methods of extinguishing the arc during tripping, the switches are classified into:

oil;

vacuum;

air;

SF6 gas;

autogas;

electromagnetic;

auto-pneumatic.

For reliable and convenient operation, they are equipped with a drive mechanism that can use one or several types of energies or their combinations:

cocked spring;

lifted load;

compressed air pressure;

electromagnetic pulse from the solenoid.

Depending on the conditions of use, they can be created with the ability to operate under voltage from one to 750 kilovolts inclusive. Naturally, they have a different design. dimensions, automatic and remote control capabilities, protection settings for safe operation.

The auxiliary systems of such circuit breakers can have a very complex branched structure and be located on additional panels in special technical buildings.

DC circuits

A huge number of circuit breakers with different capabilities also operate in these networks.

Electrical equipment up to 1000 volts

Modern modular devices with the ability to mount on a Din-rail are massively introduced here.

They successfully complement the classes of old automatic machines such as, AE and other similar ones, which were fixed on the walls of the panels with screw connections.

DC modular designs have the same structure and principle of operation as their alternating voltage counterparts. They can be performed by one or several units and are selected according to the load.

Electrical equipment above 1000 volts

High-voltage circuit breakers for direct current are used in electrolysis plants, metallurgical industrial facilities, railway and urban electrified transport, and energy enterprises.

The main technical requirements for the operation of such devices correspond to their alternating current counterparts.

Hybrid breaker

Scientists from the Swedish-Swiss company ABB managed to develop a high-voltage DC circuit breaker that combines two power structures in its device:

1. SF6 gas;

2. vacuum.

It was named hybrid (HVDC) and uses the technology of sequential arc quenching in two environments at once: sulfur hexafluoride and vacuum. For this, the following device is assembled.

Voltage is applied to the upper busbar of the hybrid vacuum circuit breaker, and voltage is removed from the lower busbar of the SF6 circuit breaker.

The power parts of both switching devices are connected in series and controlled by their individual drives. In order for them to work simultaneously, a synchronized coordinate operations control device was created, which transmits commands to the control mechanism with independent power supply via a fiber-optic channel.

Due to the use of high-precision technologies, the designers managed to achieve the coordination of actions of the actuators of both drives, which fits into a time interval of less than one microsecond.

The circuit breaker is controlled from a relay protection unit built into the power line through a repeater.

The hybrid circuit breaker has made it possible to significantly increase the efficiency of composite SF6 and vacuum structures through the use of their combined characteristics. At the same time, it was possible to realize the advantages over other analogues:

1.the ability to reliably disconnect short-circuit currents at high voltage;

2. the possibility of a small effort to carry out the switching of the power elements, which made it possible to significantly reduce the dimensions and. accordingly, the cost of equipment;

3. the availability of implementation of various standards for the creation of structures operating as part of a separate circuit breaker or compact devices at one substation;

4. the ability to eliminate the effects of rapidly increasing recovery stress;

5. Possibility of forming a basic module for working with voltages up to 145 kilovolts and above.

A distinctive feature of the design is the ability to break an electrical circuit in 5 milliseconds, which is almost impossible to perform with power devices of other designs.

The hybrid circuit breaker device was ranked among the top ten developments of the year according to the MIT (Massachusetts Institute of Technology) Technology Review.

Other manufacturers of electrical equipment are engaged in similar research. They also achieved certain results. But ABB is ahead of them in this matter. Its management believes that the transmission of AC power is causing its great losses. They can be significantly reduced by using high voltage direct voltage circuits.

Topic: what types are divided into electric machines, their types and classification.

A circuit breaker is an electrical device, the main purpose of which is to switch its operating state when a certain situation occurs. Electrical machines combine two devices in themselves, this is a conventional switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit in case of exceeding the threshold value of the current strength. Circuit breakers, like all electrical devices, also have various varieties, which divides them into certain types. Let's take a look at the main classifications of circuit breakers.

1 "Classification of machines by the number of poles:

A) single-pole machines

b) single-pole circuit breakers with neutral

c) two-pole machines

d) three-pole machines

e) three-pole circuit breakers with neutral

f) four-pole machines

2 "Classification of automatic machines by type of release.

The design of various types of circuit breakers usually includes 2 main types of releases (breakers) - electromagnetic and thermal. Magnetic ones are used for electrical protection against short circuits, and thermal breakers are intended mainly for protecting electrical circuits at a certain overload current.

3 "Classification of automatic devices for trip current: B, C, D, (A, K, Z)

GOST R 50345-99, according to the instantaneous release current, the machines are divided into the following types:

A) type "B" - over 3 In up to 5 In inclusive (In is the rated current)

b) type "C" - over 5 In up to 10 In inclusive

B) type "D" - over 10 In up to 20 In inclusive

Manufacturers of automatic machines in Europe have a slightly different classification. For example, they have an additional type "A" (over 2 In to 3 In). Some manufacturers of circuit breakers also have additional tripping curves (ABB has circuit breakers with K and Z curves).

4 "Classification of machines by the type of current in the circuit: constant, variable, both.

Rated electric currents for the main circuits of the release are selected from: 6.3; ten; 16; twenty; 25; 32; 40; 63; 100; 160; 250; 400; 630; 1000; 1600; 2500; 4000; 6300 A. Also, in addition to produce machines for rated currents of the main electrical circuits of machines: 1500; 3000; 3200 A.

5 "Classification by the presence of current limitation:

a) current-limiting

b) non-current limiting

6 "Classification of automatic machines by type of release:

A) with overcurrent release

b) with a shunt release

c) with undervoltage release or zero voltage release

7 "Classification of machines according to the time delay characteristic:

A) without time delay

b) with a time delay independent of the current

c) with a time delay, inversely dependent on current

d) with a combination of the specified characteristics

8 "Classification by the presence of free contacts: with and without contacts.

9 "Classification of machines according to the method of connecting external wires:

A) with rear connection

b) with front connection

c) with combined connection

d) with universal connection (both front and rear).

10 "Classification by drive type: with manual, motor and spring.

P.S. Everything has its own varieties. After all, if there was only one thing in its single copy, it would be at least just boring and too limited! So the diversity and good that in it you can choose exactly what the maximum meets your needs.

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

Maintenance of electrical equipment

Evolution and basic structure of circuit breakers

The history of electrical equipment began long before the appearance of the first commercial power grids. Thus, the principle of operation of a 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:

contact block;
arc neutralization (extinguishing) chamber;
release of the following types: thermal, electromagnetic, electronic, microprocessor;
control mechanism: manual, spring or with a drive;
free release mechanism.

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

In the catalogs of "Skat Technology" are presented the products of the leading companies Siemens, Andeli, Schneider, whose products rightfully occupy the 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 be obtained, including 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 conductor heating. These settings are provided by the sensitivity of the current release solenoid and by a screw-regulated thermal relay (calibration). If, during the operation of the network, the parameters go beyond the established limits, the circuit is broken and the consumers are de-energized.

Classification of circuit breakers

For the classification of electrical devices, there are regulatory documents that set out the technical and operational requirements for them. Classes of circuit breakers 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 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.

The main classification parameters of circuit breakers

The higher the level of the power grid architecture, the more difficult it is to select protection and control equipment for it, since a large number of different operating 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 would ensure 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 ACB (800-6300 A), in a molded case or MCCB (10-2500 A), modular or MCB (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;
release types: zero, minimum, independent, maximum;
presence or absence of contacts for connecting secondary circuits;
way of connecting inputs / outputs: front, rear, combined, universal;
mounting method: stationary, withdrawable (on a DIN rail), on connectors;
cutoff type: normal, selective, instant;
type of drive: manual, spring, with a propeller (electromagnet, pneumatics, etc.);
regular or protected execution.

The listed characteristics have their own designation or quantitative expression. For example, the trip curve of a circuit breaker is a graphical representation of the trip of the trip unit. It indicates at what value of overshoot of the rated current "In" the device is triggered. 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 trip 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 cut-off response speed, the automatic machines 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 delay of 0.25-0.6 seconds for slave electrical devices.

Automatic devices of this type have main and additional working circuits, which allows you to turn off the emergency section of the power grid, controlled by the slave device, and keep the current supply to the remaining consumers. The time range of the speed and selection processes also reflect circuit breaker 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 reacts to current consumption, and the thermal relay reacts to heating of the wiring.

The time-current characteristic of the circuit breaker depends on the setting of the latter. The magnitude of the heat 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 wiring and the total load. Depending on the installed setting, the thermal relay can be triggered instantly or keep the network operational for a certain time, but not more than an hour.

The importance of timely triggering of protection equipment

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

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

Reflection of characteristics of electrical equipment in its marking

For electrical products, it is characteristic to use the most important performance characteristics in product labeling. For lighting lamps, this is the power consumption and the luminous flux. Circuit breaker marking much more difficult, a minimum of information can be squeezed into the name of the product. This is usually the nominal operating voltage. Therefore, the marking symbols are applied to the machine body:

the current limiting class is indicated by a number inside the square; the number of poles is indicated by the pictogram;
the class or utilization category of the circuit breakers is displayed together with the rated current - eg "C16";
the maximum permissible operating current value, 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 choose / select a circuit breaker in full accordance with the parameters of the electrical network. However, when purchasing the device yourself, 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 differ significantly.

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 wiring capability.

Likewise ratings of circuit breakers must be less than the corresponding network parameters. Otherwise, there is a risk of overloading the power grid up to the point of fire of the wiring, to which the machine simply will not react. In order to avoid such a situation, preliminary calculations are necessary, which will provide a balance between current consumers, wiring and protection and control means. For those who are interested in the question, how to choose a circuit breaker for home, we will give advice: choose the nominal value of the device according to the throughput of the wiring (cross-section and material of the wires, as well as the method of laying them).

Basic rules for connecting a circuit breaker

A competent design of the architecture of power grids makes it possible 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 current of the circuit breaker in order to ensure the safe operation of the home electrical network.

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

Electrical engineering is an exact applied science, so the production of electrical goods is carried out 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 conventional sockets - 16 A;
for power outlets for electric stoves, boilers and other things, a circuit breaker is selected according to the power of consumers.

To implement this approach to the arrangement of networks, manufacturers offer a sufficient selection of machines with different numbers of poles, differential type and other units. For domestic purposes, use devices in molded cases, in which all live parts are protected, which excludes accidental electric shock. In order to install a universal circuit breaker, switchgears (cabinets, assemblies, etc.) are required.

The variety of electrical devices 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. That's why circuit breaker connection diagram is a mandatory supplement for every product. It indicates the number of poles, connection points of phases and neutral, 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 long about how to connect a single-phase circuit breaker on the dashboard of his apartment. Just look at the diagram, which is not complicated. The only warning: if you are changing 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.

Maintenance of electrical equipment

Electrical equipment, like any other device, needs care. Maintenance of circuit breakers is carried out according to a specific procedure with strict intervals. Users are often unaware of this need, but it is there. Electrical equipment is subject to wear and tear, contacts oxidation, insulation aging, wear of moving parts and other changes occur gradually. 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 had situations when a perfectly working network starts to fail. 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 problems with wiring and hidden defects in the electrical circuits of household appliances and equipment.

To identify and prevent such situations, there is loading circuit breakers... It is carried out every three years using special equipment and is performed in order to check the compliance of the actual state of the machine with the requirements for safe operation of power grids. The method for testing circuit breakers provides for checking the state of insulation, the response time of the overcurrent and heating protection, the state of the contacts and other parameters.

Regular maintenance ensures that problems are identified early, prevents more serious consequences, and ensures that your networks are safe for the foreseeable future. The detected malfunctions of the circuit breakers are eliminated as far as possible, but most often in such cases a complete replacement of electrical devices is required, especially in the case of their small standard sizes.

Manufacturers of electrical products manufacture many spare parts for powerful industrial machines. For household or low-power equipment, only spare contact groups are usually produced. That's why replacement of circuit breakers- a typical activity in the repair of electrical networks. Regular maintenance of electrical equipment is a completely easy procedure, including for the 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, the circuit breakers have a service life measured in decades, provided that the devices are correctly installed and properly maintained. They must fully comply with the parameters of the network. In addition, to extend their service life, you should not use faulty electrical appliances that provoke frequent network outages.

Professional services from the company "Skat Technology"

Our company specializes in works on engineering communications, including power grids. Our experts are ready to give recommendations on the selection of circuit breakers and design networks, including calculations of loads and their distribution, taking into account all the norms of safe operation. Experienced engineers will answer any practical questions, including how to connect a circuit breaker for different categories of current consumers, taking into account the installation conditions, the state of the wiring and other factors.

Our catalogs contain a wide selection of electrical products from leading manufacturers. Our assortment will allow you to easily carry out a complete complete set of works on the arrangement of power grids. If confuses you cost of circuit breakers with logos of famous brands, we remind you that 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 are putting into it. Is reliability and safety at the right cost the determining factor for us? We offer electrical products at the most fair prices, therefore we are convinced that our customers do not overpay. Dimensions of circuit breakers They are far from always equivalent to prices, therefore, if you want to get a normal result of arranging the power grid, use the services of Skat Technology professionals.