Automatic switches - design and principle of operation. Categories of circuit breakers: A, B, C and D Types of electrical circuit breakers and their purpose

Circuit breakers are not at all like the usual ones that are installed in every room to turn the light on and off (Fig. 1). Their task is somewhat different. Circuit breakers are installed in switchboards and serve to protect the circuit from power surges and non-periodic power outages in certain sections of the power grid.

Rice. one.

Automata, as they are often called, are installed at the entrance to a house or apartment and are located in special boxes, metal or plastic (Fig. 2).

Rice. 2. Distribution board with automatic machines

There are many types of circuit breakers. Some of them serve only as circuit breakers and protect the network from overload. Such are, for example, the old AE type circuit breakers in a black carbolite case (Fig. 3).

Rice. 3. AE series circuit breaker

In most old shields in the entrances of residential buildings there are just such. However, they are quite reliable and are still in operation.
Modern variations allow additional functions, such as undercurrent protection.

According to the response time to an unacceptable voltage, the automata are divided into 3 types: selective, normal and high-speed. The response time of a normal machine ranges from 0.02 to 0.1 s. In selective circuit breakers, this time is the same. High-speed circuit breakers work faster - they have this value is only 0.005 s.

All circuit breakers are enclosed in a plastic unbreakable case with a special fastening (bar or rail) on the rear plane. Installing the machine on such a mount is very easy - just insert it on the rail until it clicks. You can remove it with a screwdriver by gently pulling on the special tab on top of the circuit breaker. This greatly simplifies the task of installing the machine in a cabinet (Fig. 4).

Rice. four.

Inside the case is the "stuffing" of the machine, its main safety devices, which can be 2 (Fig. 5).

Rice. 5. Internal

We are talking about electromagnetic and thermal releases - peculiar mechanisms for automatically breaking the circuit. A bimetallic plate, when heated by an unacceptably high current passing through it, straightens and opens the contacts - this is a thermal release. In terms of response time, it is the slowest.

The electromagnetic release operates according to the "dead hand" rule. The coil located in the center of the machine is continuously kept in place by a stable voltage. As soon as he jumps out of the nominal limits, the coil literally jumps out of its place, breaking the circuit. This way of breaking the chain is the fastest.
All circuit breakers have contacts for connecting incoming and outgoing wires (Fig. 6).

Rice. 6. Wires are connected to the contacts of the circuit breaker using screw terminals

Automata are distinguished by the degree of sensitivity to tripping. In the standard most common models, circuit breakers with a threshold value approximately equal to 140% of the nominal are most often used. With an increase in voltage by one and a half times, an electromagnetic (fast) release is triggered. With a slight excess of the rated voltage, the thermal release operates. The shutdown process can take hours, which is highly dependent on the ambient temperature. However, the machine will react to voltage changes in any case.

Circuit breakers are distinguished by the number of poles. What does it mean? In one machine there can be several electrical lines independent of each other, which are interconnected by a common shutdown mechanism (Fig. 7 and 8). Automatic machines are one-, two-, three- and four-pole (this applies to domestic use).

Rice. 7. in a plastic box in the off state

Rice. 8. : all lines are triggered at the same time when disconnected, they are connected together with one lever jumper

The circuit breaker has differences in other indicators. They differ in the threshold current strength that they pass through themselves. In order for the machine to work and turn off the power supply in an emergency, it must be set to a certain sensitivity threshold. This setting is made by the manufacturer, so the machine immediately writes the numerical value of this threshold. For domestic needs, machines with indicators of 6.3, 10, 16, 25, 32, 40, 63, 100 and 160 A are used (Fig. 9). There are machines with values of both 1000 and 2600 A, but they are not used in everyday life. These figures mean the total power of all consumers of electric current that will be connected to the circuit "guarded" by the machine.
Machine sensitivity it is necessary to calculate not only the total power of the proposed energy consumers, but also the wiring and electrical installation products - sockets and switches.
Table 1 shows the typology of automata.

Table 1. Types of machines

Type of	Purpose
A	For opening circuits with a large length of electrical wiring and protecting semiconductor devices
B	For lighting networks of general purpose
C	For lighting circuits and electrical installations with moderate starting currents (motors and transformers)
D	For circuits with active-inductive loads, as well as protection of electric motors with high starting currents
K	For inductive loads
Z	For electronic devices

Table 2. Two-core copper cable laid in a conduit

Section, mm2		Cable current/1.45, A	Automatic, A	Excess current, %
1,5	19	13,1	13	-
2,5	27	18,62	16	-
4	38	26,2	25	-
6	50	34,48	32	-
10	70	48,27	40(50)	3,5
16	90	62,06	50(63)	1,5

Table 3. Two-core copper wire laid in a box

Section, mm2	Maximum continuous cable current, A	Cable current/1.45, A	Automatic, A	Excess current, %
1	15	10,34	10	-
1,5	18	12,41	10(13)	4,7
2	23	15,86	13(16)	0,87
2,5	25	17,24	16	-
4	32	22,06	20	-
6	40	27,58	25	-
10	48	33,1	32	-
16	55	37,93	32(40)	5,4

The maximum continuous current of the cable is assumed for core temperature +65 and air +25 °C. The number of simultaneously laid conductors is up to 4. A number of automatic machines: 0.5 A, 1 A, 2 A, 3 A, 4 A, 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A and 63 A. Data in Table. 3 are also suitable for a three-core cable. In this case, the third core must be a protective earth or neutral wire.

Rice. 9. A row of 16 A single-pole automata. Let's say for a separate section in an apartment, for example, a kitchen, we have one 6.3 A automaton (it happens, too - electricians were joking). According to the well-known formula Watt \u003d Volt x Ampere, we calculate how many devices (and which ones) can be powered from our network. It turns out that this value is equal to 1386 W, since the default voltage is 220 V. This means that even a powerful kettle cannot be turned on in such a kitchen, not to mention a refrigerator or electric stove - the machine will work instantly and will not allow unacceptable, in its opinion, current to pass through controlled territory. In this case, it is urgent to change the circuit breaker to 25 or even 32 A.

Circuit breakers are devices whose task is to protect the electric line from the effects of a powerful current that can cause overheating of the cable with further melting of the insulating layer and fire. An increase in current strength can be caused by too much load, which occurs when the total power of the devices exceeds the value that the cable can withstand in its cross section - in this case, the machine does not turn off immediately, but after the wire heats up to a certain level. During a short circuit, the current increases many times over within a fraction of a second, and the device immediately reacts to it, instantly stopping the supply of electricity to the circuit. In this article we will tell you what types of circuit breakers are and their characteristics.

Automatic protective switches: classification and differences

In addition to residual current devices that are not used individually, there are 3 types of circuit breakers. They work with loads of different sizes and differ from each other in their design. These include:

Modular AV. These devices are mounted in household networks in which currents of insignificant magnitude flow. They usually have 1 or 2 poles and a width that is a multiple of 1.75 cm.

Cast switches. They are designed to work in industrial networks, with currents up to 1 kA. Made in a cast case, which is why they got their name.
Air electric machines. These devices are available with 3 or 4 poles and can withstand currents up to 6.3 kA. Used in electrical circuits with high power installations.

There is another type of circuit breaker - differential. We do not consider them separately, since such devices are ordinary circuit breakers, which include an RCD.

Release types

The releases are the main working components of the AB. Their task is to break the circuit when the permissible current value is exceeded, thereby stopping the supply of electricity to it. There are two main types of these devices, which differ from each other in the principle of decoupling:

Electromagnetic.
Thermal.

Electromagnetic type releases provide almost instantaneous operation of the circuit breaker and de-energize the circuit section when an overcurrent short circuit occurs in it.

They are a coil (solenoid) with a core drawn in under the influence of a large current and causing the tripping element to operate.

The main part of the thermal release is a bimetallic plate. When a current exceeding the rated value of the protective device passes through the machine, the plate begins to heat up and, bending to the side, touches the disconnecting element, which operates and de-energizes the circuit. The time for the thermal release to operate depends on the magnitude of the overload current passing through the plate.

Some modern devices are equipped as an option with minimum (zero) releases. They perform the function of turning off the AV when the voltage drops below the limit value corresponding to the technical data of the device. There are also remote releases, with which you can not only turn off, but also turn on the AB, without even approaching the switchboard.

The presence of these options significantly increases the cost of the device.

Number of poles

As already mentioned, the circuit breaker has poles - from one to four.

It’s not difficult to choose a device for a circuit according to their number, you just need to know where different types of AB are used:

Single terminals are installed to protect lines that include sockets and lighting fixtures. They are mounted on a phase wire without capturing zero.
A two-pole must be included in the circuit to which household appliances with a sufficiently high power are connected (boilers, washing machines, electric stoves).
Three-terminal networks are installed in semi-industrial scale networks, to which devices such as borehole pumps or car repair equipment can be connected.
Four-pole ABs allow you to protect electrical wiring with four cables from short circuits and overloads.

The use of machines of different poles - in the following video:

Characteristics of circuit breakers

There is another classification of machines - according to their characteristics. This indicator indicates the degree of sensitivity of the protective device to the excess of the rated current. The corresponding marking will show how quickly the device will react in the event of an increase in current. Some types of ABs work instantly, while others take time.

There is the following marking of devices according to their sensitivity:

A. Breakers of this type are the most sensitive and respond instantly to an increase in load. They are practically not installed in household networks, protecting circuits with high-precision equipment with their help.
B. These circuit breakers operate with a slight delay when the current increases. Usually they are included in lines with expensive household appliances (LCD TVs, computers, and others).
C. Such devices are the most common in household networks. Their shutdown does not occur immediately after the increase in current strength, but after a while, which makes it possible to normalize it with a slight difference.
D. The sensitivity of these devices to the increase in current is the lowest of all the listed types. They are most often installed in shields on the approach line to the building. They provide insurance for apartment machines, and if for some reason they do not work, they turn off the general network.

Features of the selection of machines

Some people think that the most reliable circuit breaker is the one that can handle the most current, which means it can provide the most circuit protection. Based on this logic, an air-type machine can be connected to any network, and all problems will be solved. However, this is not at all the case.

To protect circuits with different parameters, it is necessary to install devices with appropriate capabilities.

Mistakes in the selection of AB are fraught with unpleasant consequences. If you connect a high-power protective device to a normal household circuit, it will not de-energize the circuit, even when the current value is much higher than that which the cable can withstand. The insulating layer will heat up, then start to melt, but no shutdown will occur. The fact is that the current strength, which is destructive for the cable, will not exceed the AB rating, and the device will “think” that there was no emergency. Only when the melted insulation causes a short circuit will the machine turn off, but by that time a fire may already have started.

Here is a table that shows the ratings of machines for various electrical networks.

If the device is designed for less power than that which the line can withstand and which the connected devices have, the circuit will not be able to work normally. When the equipment is turned on, the AB will constantly knock out, and eventually, under the influence of high currents, it will fail due to “sticky” contacts.

Clearly about the types of circuit breakers in the video:

Conclusion

The circuit breaker, the characteristics and types of which we examined in this article, is a very important device that protects the electrical line from damage by powerful currents. The operation of networks that are not protected by automatic machines is prohibited by the Electrical Installation Rules. The most important thing is to choose the right type of AB that is suitable for a particular network.

From the very beginning of the emergence of electricity, engineers began to think about the safety of electrical networks and devices from current overloads. As a result, many different devices have been designed that are distinguished by reliable and high-quality protection. One of the latest developments has become electric machines.

This device is called automatic due to the fact that it is equipped with the function of turning off the power in automatic mode, in the event of short circuits, overloads. Conventional fuses after operation must be replaced with new ones, and the machines can be turned on again after the causes of the accident have been eliminated.

Such a protective device is necessary in any electrical network scheme. The circuit breaker will protect the building or premises from various emergencies:

Fires.
Electric shocks to a person.
Electrical faults.

Types and design features

It is necessary to know information about the existing types of circuit breakers in order to choose the right device at the time of purchase. There is a classification of electric machines according to several parameters.

Breaking capacity

This property determines the short circuit current at which the machine will open the circuit, thereby turning off the network and the devices that were connected to the network. According to this property, automata are divided into:

Automatic machines for 4500 amperes are used to prevent malfunctions in the power lines of old residential buildings.
At 6000 amperes, they are used to prevent accidents during short circuits in the network of houses in new buildings.
At 10,000 amperes, they are used in industry to protect electrical installations. A current of this magnitude can be formed in the immediate vicinity of the substation.

The operation of the circuit breaker occurs during short circuits, accompanied by the occurrence of a certain amount of current.

The machine protects the wiring from damage to the insulation by high current.

Number of poles

This property tells us about the largest number of wires that can be connected to the machine to provide protection. In the event of an accident, the voltage at these poles is turned off.

Features of machines with one pole

Such electric machines are the simplest in design, and serve to protect individual sections of the network. Two wires can be connected to such a circuit breaker: an input and an output.

The task of such devices is to protect electrical wiring from overloads and short circuits of wires. The neutral wire is connected to the neutral bus, bypassing the machine. Grounding is connected separately.

Electric machines with one pole are not introductory, since when it is turned off, the phase breaks, and the neutral wire still remains connected to the power supply. It does not provide 100% protection.

Properties of automata with two poles

In cases where an accident requires a complete disconnection from the electrical network, use circuit breakers with two poles. They are used as input. In emergency cases, or in case of a short circuit, all electrical wiring is turned off at the same time. This makes it possible to carry out repair and maintenance work, as well as work on connecting equipment, since complete safety is guaranteed.

Two-pole electric machines are used when it is necessary to have a separate switch for a device powered by a 220 volt network.

An automatic machine with two poles is connected to the device using four wires. Of these, two come from the power supply, and the other two come out of it.

Three-pole electric machines

In an electrical network with three phases, 3-pole machines are used. Grounding is left unprotected, and the phase conductors are connected to the poles.

A three-pole machine serves as an input device for any three-phase load consumers. Most often, this version of the machine is used in industrial conditions to supply electricity to electric motors.

6 conductors can be connected to the machine, three of which are the phases of the electrical network, and the remaining three are coming from the machine and provided with protection.

Using a four-pole machine

To provide protection for a three-phase network with a four-wire system of conductors (for example, an electric motor connected according to the “star” scheme), a 4-pole circuit breaker is used. It plays the role of an introductory device of a four-wire network.

It is possible to connect eight conductors to the device. On the one hand - three phases and zero, on the other hand - the output of three phases with zero.

Time-current characteristic

When devices that consume electricity and the electrical network are operating normally, normal current flow occurs. This phenomenon also applies to the electric machine. But, in the event of an increase in current strength for various reasons above the nominal value, the automatic release trips, and the circuit breaks.

The parameter of this operation is called the time-current characteristic of the electric machine. It is the dependence of the time of operation of the machine and the ratio between the real strength of the current passing through the machine and the nominal value of the current.

The importance of this characteristic lies in the fact that the least number of false positives is provided on the one hand, and current protection is carried out, on the other hand.

In the energy industry, there are situations when a short-term increase in current is not associated with an accident, and the protection should not work. It also happens with electric machines.

Time-current characteristics determine how long the protection will operate, and what current strength parameters will occur. The greater the overload, the faster the machine will work.

Electric machines marked "B"

Automatic switches of category "B" are able to turn off in 5 - 20 s. In this case, the current value is from 3 to 5 nominal current values ≅0.02 s. Such machines are used to protect household appliances, as well as all electrical wiring in apartments and houses.

Properties of machines marked "C"

Electric machines of this category can turn off in 1 - 10 s, at 5 - 10 times the current load ≅0.02 s. These are used in many areas, most popular for houses, apartments and other premises.

The meaning of the marking "D" on the machine

With this class, automata are used in industry and are made in the form of 3-pole and 4-pole versions. They are used to protect powerful electric motors and various three-phase devices. Their operation time is up to 10 seconds, while the operation current can exceed the nominal value by 14 times. This makes it possible to use it with the necessary effect to protect various circuits.

Electric motors with significant power are most often connected through electric machines with characteristic "D", because. starting current is high.

Rated current

There are 12 versions of automatic machines, which differ in the characteristics of the rated operating current, from 1 to 63 amperes. This parameter determines the speed at which the machine switches off when the current limit is reached.

The machine for this property is selected taking into account the cross-section of the conductors of the wires, the allowable current.

The principle of operation of electric machines

normal mode

During normal operation of the machine, the control lever is cocked, current flows through the power wire at the top terminal. Next, the current goes to the fixed contact, through it to the moving contact and through the flexible wire to the solenoid coil. After it, the current goes through the wire to the bimetallic release plate. From it, the current passes to the lower terminal and further to the load.

Overload mode

This mode occurs when the rated current of the machine is exceeded. The bimetallic plate is heated by a large current, bends and opens the circuit. The action of the plate requires time, which depends on the value of the passing current.

The circuit breaker is an analog device. There are certain difficulties in setting it up. The tripping current of the release is adjusted at the factory with a special adjusting screw. After the plate has cooled down, the machine can function again. The temperature of the bimetal strip depends on the environment.

The release does not act immediately, allowing the current to return to its nominal value. If the current does not decrease, the release trips. Overload can occur due to powerful devices on the line, or connecting several devices at once.

Short circuit mode

In this mode, the current increases very quickly. The magnetic field in the solenoid coil moves the core, which activates the release, and disconnects the contacts of the power supply, thereby removing the emergency load of the circuit and protecting the network from possible fire and destruction.

The electromagnetic release operates instantly, which is different from the thermal release. When the contacts of the working circuit are opened, an electric arc appears, the magnitude of which depends on the current in the circuit. It causes destruction of contacts. To prevent this negative effect, an arc chute is made, which consists of parallel plates. In it, the arc fades and disappears. The resulting gases are discharged into a special hole.

In order for all equipment in the house or at work to be protected from power surges, special automatic switches must be installed. They will be able to fix the jump and quickly respond to it by turning off the entire system from the electricity supply. A person cannot do this on his own, but a machine of a certain type can do it in a few seconds.

Device sensitivity

Before you get acquainted with the types of machines, you need to find out with what sensitivity the devices are suitable for home use, and which ones will be inappropriate. Such an indicator will indicate how quickly the device will respond to a power surge. It has several markings:

BUT- used for super sensitive types of machines. They instantly detect a jump in the network and also instantly respond to it. Most often they are used in production to protect expensive equipment. Practically not suitable for domestic purposes.

AT- such marking is applied to those types of circuit breakers that react with a slight delay. Manufacturers of expensive household appliances install them to protect the device itself. If a small failure occurs, then the device reacts to it itself and at the same time does not turn off the entire network in the house.
FROM those machines that are able to turn off the household network with a significant increase or decrease in voltage have the marking. If the jump is small, then the device may turn off for a while, but then return to normal operation.
Marking machine D installed only in a shield that connects a house or apartment to a common system. Its sensitivity to power surges is minimal, so it is only a fallback option. If the voltage drop is very large, then the entire house or apartment is disconnected from the electrical network.

Classification of automata

There are different types of machines in relation to the type of current, rated voltage or current indicator and other technical characteristics. Therefore, you need to specifically understand each item separately.

Current type

In relation to this characteristic, the machines are divided into:

For work in the alternating current network;
For work in a network of a direct current;
Universal models.

Everything is clear here and no further explanation is needed.

In terms of rated current

The value of this characteristic will depend on the network with what maximum value the circuit breaker can operate. There are devices that can operate from 1 A to 100 A and more. The minimum value with which machines can be found on sale is 0.5 A.

Rated voltage indicator

This characteristic indicates with what voltage this type of circuit breakers can operate. Some can work in a network with a voltage of 220 or 380 volts - these are the most common options for domestic use. But there are machines that will do just fine with higher rates.

The ability to limit the flow of electricity

According to this characteristic, there are:

Current limiting - immediately eliminate the access of electric current to the device. Therefore, during a short circuit, neither the device nor the electrical network wiring is damaged.
Non-limiting - work much slower.

Other characteristics

The number of poles can be from one to four. Accordingly, they are called single-pole, two-pole, and so on.

According to the structure, they distinguish:

Air;
Modular;
Molded case circuit breakers.

According to the drop rate, high-speed, normal and selective devices are produced. They can be set with a time delay function that can be inversely dependent on the current or independent of it. The time delay may or may not be set.

Automatic machines also have a drive, which can be manual, connected to an engine or a spring. The switches differ both in the presence of free contacts and in the method of connecting the conductors.

An important characteristic will be protection from environmental influences. Here you can highlight:

IP protection;
From mechanical impact;
Current conduction of the material.

All characteristics can be combined in various combinations. It all depends on the model and manufacturer.

Switch types

The machine inside contains a release, which, with the help of a lever, latch, spring or rocker, is able to instantly disconnect the network from the supply of electricity. Types of circuit breakers and are distinguished by the type of release. There are:

Circuit breaker with magnetic release - responds to surges instantly. Well suited for networks where short circuits often occur. The release is a moving core solenoid. During the jump, the core is drawn in and the circuit is opened. Responds in a split second.
Thermal circuit breaker - protects the electrical network from excessive load. The release is represented by a bimetallic plate. Under the influence of a current with an increased value, the plate heats up and bends, thereby turning off the electricity supply. These types of machines are able to respond from a few seconds or up to 1 minute to overvoltage. It all depends on what indicators the device is designed for.

Circuit breakers are much more profitable than fuses. This is because after cooling, the machine can already be turned on, and it will work as it should if the cause of the overload is eliminated. The fuse needs to be replaced. It may not be available and replacement may take a long time.

infoelectric.ru

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

The circuit breaker is an electrical device, the main purpose of which is to switch its operating state when a certain situation occurs.

electric tomatoes combine two devices, this is a conventional switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit in case the threshold value of the current is exceeded. Circuit breakers, like all electrical devices, also have different varieties, which divides them into certain types. Let's get acquainted with the main classifications of circuit breakers.

1 "Classification of machines by the number of poles:

a) single-pole machines

b) single-pole machines with neutral

c) bipolar machines

d) three-pole machines

e) three-pole circuit breakers with neutral

e) four-pole machines

2» Classification of automata according to the type of releases.

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

3 "Classification of automata by tripping current: B, C, D, (A, K, Z)

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

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

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

C) type "D" - over 10 In to 20 In inclusive

Machine manufacturers 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 automata according to 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, automatic machines for the rated currents of the main electrical circuits of automatic machines are also produced: 1500; 3000; 3200 A.

5 "Classification by the presence of current limitation:

a) current limiting

b) non-limiting

6 "Classification of machines by types of releases:

a) with overcurrent release

b) with independent release

c) with minimum or zero voltage release

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

a) no 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 these characteristics

8" Classification by the presence of free contacts: with contacts 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 type of drive: with manual, with motor and with spring.

electrohobby.com

Automatic protective switches: classification and differences

Modular AV. These devices are mounted in household networks in which currents of insignificant magnitude flow. They usually have 1 or 2 poles and a width that is a multiple of 1.75 cm.

Cast switches. They are designed to work in industrial networks, with currents up to 1 kA. Made in a cast case, which is why they got their name.
Air electric machines. These devices are available with 3 or 4 poles and can withstand currents up to 6.3 kA. Used in electrical circuits with high power installations.

There is another type of circuit breaker - differential. We do not consider them separately, since such devices are ordinary circuit breakers, which include an RCD.

Release types

Electromagnetic.
Thermal.

Electromagnetic type releases provide almost instantaneous operation of the circuit breaker and de-energize the circuit section when an overcurrent short circuit occurs in it.

They are a coil (solenoid) with a core drawn in under the influence of a large current and causing the tripping element to operate.

The presence of these options significantly increases the cost of the device.

Number of poles

As already mentioned, the circuit breaker has poles - from one to four.

It’s not difficult to choose a device for a circuit according to their number, you just need to know where different types of AB are used:

Single terminals are installed to protect lines that include sockets and lighting fixtures. They are mounted on a phase wire without capturing zero.
A two-pole must be included in the circuit to which household appliances with a sufficiently high power are connected (boilers, washing machines, electric stoves).
Three-terminal networks are installed in semi-industrial scale networks, to which devices such as borehole pumps or car repair equipment can be connected.
Four-pole ABs allow you to protect electrical wiring with four cables from short circuits and overloads.

The use of machines of different poles - in the following video:

Characteristics of circuit breakers

There is the following marking of devices according to their sensitivity:

A. Breakers of this type are the most sensitive and respond instantly to an increase in load. They are practically not installed in household networks, protecting circuits with high-precision equipment with their help.
B. These circuit breakers operate with a slight delay when the current increases. Usually they are included in lines with expensive household appliances (LCD TVs, computers, and others).
C. Such devices are the most common in household networks. Their shutdown does not occur immediately after the increase in current strength, but after a while, which makes it possible to normalize it with a slight difference.
D. The sensitivity of these devices to the increase in current is the lowest of all the listed types. They are most often installed in shields on the approach line to the building. They provide insurance for apartment machines, and if for some reason they do not work, they turn off the general network.

Features of the selection of machines

To protect circuits with different parameters, it is necessary to install devices with appropriate capabilities.

Here is a table that shows the ratings of machines for various electrical networks.

Clearly about the types of circuit breakers in the video:

Conclusion

yaelectric.ru

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- С‚РµСЂРјРѕРјР°РіРЅРёС‚РЅС‹Р№ СЂР°СЃС†РµРїРёС‚РµР»СЊ
- РїРѕР»СѓРїСЂРѕРІРѕРґРЅРёРєРѕРІС‹Р№ СЂР°СЃС†РµРїРёС‚РµР»СЊ
- СЌР»РµРєС‚СЂРѕРЅРЅС‹Р№ СЂР°СЃС†РµРїРёС‚РµР»СЊ
- PSPµR P°PIRёSЃRёRјS‹Р№ СЂР°СЃС†РµRїРёС‚РµR»СЊ
- СЂР°СЃС†РµРїРёС‚РµR»СЊ РјРёРЅРёРјР°Р»СЊРЅРѕРіРѕ РSR°РїСЂСЏР¶РµРЅРёСЏ
- СЂР°СЃС†РµRїРёС‚РµР»СЊ РЅСѓР»РµРІРѕРіРѕ РSP°РїСЂСЏР¶РµРЅРёСЏ
РЇРІР»РµРЅРёСЏ, РІС‹Р·С‹РІР°РµРјС‹Рµ СЃРІРµСЂС…С‚РѕРєР°РјРё (short-circuit and overload currents)

Release definition

circuit breakers;
releases performing auxiliary functions.

independent release (remote shutdown of the circuit breaker by a signal from the auxiliary circuit);
undervoltage release (turns off the machine when the voltage drops below the permissible level);
zero voltage release (causes tripping of contacts with a significant voltage drop).

Definitions of terms found below

Types of releases used in circuit breakers

provide basic overcurrent protection, factory settings do not change during operation:
- thermal release or overload release;
- electromagnetic release or short circuit release;

one of the proposed below replaces the first two, adjustment is allowed during operation (hold time at overcurrent for РѕР±РµСЃРїРµС‡РµРЅРёСЏ СЃРµР»РµРєС‚РёРІРЅРѕСЃС‚Рё, which current is considered an overload, which short circuit):
- semiconductor release;
- electronic release;

additional trip units for extending the functionality:
- independent release;
- undervoltage release;
- zero voltage release.

Thermal release

conditional non-trip current 1.05 In (time 1 hour for In ≤ 63A and 2 hours for In ≥ 80A);
conditional tripping current 1.3 In for AC and 1.35 In for DC.

no rubbing surfaces;
have good vibration resistance;
easily tolerate pollution;
simplicity of design → low price.

constantly consume electrical energy;
sensitive to changes in ambient temperature;
when heated from third-party sources, they can cause false alarms.

Electromagnetic release

3.5 In;
7 In;
10 In;
12 In;
and others.

B(3-5);
C(5-10);
D(10-50).

simplicity of design;

creates a magnetic field;
works instantly, without time delay.

Thermal magnetic or combined release

Semiconductor release

adjustment of the rated current of the machine;
setting the exposure time in the short circuit zone, as well as overload;
operation setting in the event of a short circuit;
switches for protection against switching currents, from single-phase short circuit;
a switch that disables the time delay in case of short circuit (transition from the selectivity mode to the instantaneous mode).

a wide range of adjustments for the most complex power supply schemes;
ensuring selectivity (selectivity), relative to series-connected automata with lower amperages.

high price;
fragile controls.

Electronic release

a variety of settings for the user;
high accuracy of execution of a given program;
health indicators and causes of operation;
logic selectivity with upstream and downstream switches.

high price;
fragile control unit;
exposure to electromagnetic fields.

Shunt release

Undervoltage release

disconnects the switched on circuit breaker without time delay when the voltage drops from 0.7 to 0.35 from Un;
if the voltage is higher than 0.7 Un, no shutdown is performed;
prevents reclosing if the mains voltage is lower than 0.85 Un.

After the device has tripped, manual cocking of the free trip mechanism is required, unless a solenoid drive is installed.

Zero voltage release

causes disengagement of the main contacts at a voltage of 0.35 to 0.1 of the nominal;
does not turn off the switched on machine at a voltage of more than 0.55 Un;
allows re-closing when the voltage is restored more than 0.85 of the nominal.

As in the case of the undervoltage release, manual cocking of the machine is required, and then turning it on.

More about the device of an independent trip device, zero and undervoltage release С‡РёС‚Р°Р№ Р·РґРµСЃСЊ.

Phenomena caused by overcurrents

When a short circuit current occurs, the following phenomena occur:

electrodynamic forces;
a magnetic field;
thermal stress (overheating).

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Rice. one.

Automata, as they are often called, are installed at the entrance to a house or apartment and are located in special boxes, metal or plastic (Fig. 2).

Rice. 2. Distribution board with automatic machines

Rice. 3. AE series circuit breaker

Rice. four.

Inside the case is the "stuffing" of the machine, its main safety devices, which can be 2 (Fig. 5).

Rice. 5. Internal

Rice. 6. Wires are connected to the contacts of the circuit breaker using screw terminals

Rice. 7. in a plastic box in the off state

Rice. 8. : all lines are triggered at the same time when disconnected, they are connected together with one lever jumper

Table 1. Types of machines

Type of	Purpose
A	For opening circuits with a large length of electrical wiring and protecting semiconductor devices
B	For lighting networks of general purpose
C	For lighting circuits and electrical installations with moderate starting currents (motors and transformers)
D	For circuits with active-inductive loads, as well as protection of electric motors with high starting currents
K	For inductive loads
Z	For electronic devices

Table 2. Two-core copper cable laid in a conduit

Section, mm2		Cable current/1.45, A	Automatic, A	Excess current, %
1,5	19	13,1	13	—
2,5	27	18,62	16	—
4	38	26,2	25	—
6	50	34,48	32	—
10	70	48,27	40(50)	3,5
16	90	62,06	50(63)	1,5

Table 3. Two-core copper wire laid in a box

Section, mm2	Maximum continuous cable current, A	Cable current/1.45, A	Automatic, A	Excess current, %
1	15	10,34	10	—
1,5	18	12,41	10(13)	4,7
2	23	15,86	13(16)	0,87
2,5	25	17,24	16	—
4	32	22,06	20	—
6	40	27,58	25	—
10	48	33,1	32	—
16	55	37,93	32(40)	5,4

Electrical overloads are common. To protect appliances powered by electricity from such voltage drops, circuit breakers were invented. Their task is simple - to break the electrical circuit if the voltage exceeds the nominal limits.

The first such devices were plugs familiar to everyone, which are still in some apartments. As soon as the voltage jumps above 220 V, they are knocked out. Modern types of circuit breakers are not only plugs, but also many other varieties. Their remarkable feature is the possibility of repeated use.

Classification

Modern GOST 9098-78 distinguishes 12 classes of circuit breakers:

This classification of circuit breakers is very convenient. If you wish, you can figure out which of the devices to install in the apartment, and which for production.

Types (kinds)

GOST R 50345-2010 divides circuit breakers into the following types (division occurs according to sensitivity to overloads), marked with Latin letters:

These are the main circuit breakers used in residential buildings and apartments. In Europe, the marking begins with the letter A - the most sensitive circuit breakers to overloads. They are not used for domestic needs, but are actively used to protect the power supply circuits of precision instruments.

There are also three more markings - L, Z, K.

Distinctive design features

Automatic devices consist of the following units:

main contact system;
arc chute;
the main drive of the release device;
various types of release;
other auxiliary contacts.

The contact system can be multistage (one-, two- and three-stage). It consists of arcing, main and intermediate contacts. Single-stage contact systems are mainly made from sintered metal.

In order to somehow protect parts and contacts from the destructive force of an electric arc, reaching 3,000 ° C, an arc chute is provided. It consists of several arc quenching grids. There are also combined devices that can extinguish a high current electric arc. They contain slit chambers along with a grille.

For any circuit breaker, there is a current limit. Due to the protection of the machine, it can not lead to breakage. With huge overloads of such a current, the contacts can either burn out or even weld to each other. For example, for the most common household appliances with a trip current from 6 A to 50 A, the current limit can be from 1000 A to 10,000 A.

Modular designs

Designed for small currents. Modular automatic switches consist of separate sections (modules). The whole structure is mounted on a DIN rail. Let's consider in more detail the device of the modular switch:

On / off is made by a lever.
The terminals to which the wires are connected are screw.
The device is fixed to the DIN rail with a special latch. This is very convenient, because such a switch can be easily dismantled at any time.
The connection of the entire electrical circuit is made due to the movable and fixed contacts.
Disconnection occurs with the help of some kind of release (thermal or electromagnetic).
Contacts are specially placed next to the arc chute. This is due to the occurrence of a powerful electric arc during the disconnection of the connection.

VA series - industrial switches

Representatives of these machines are primarily intended for use in AC circuits of 50-60 Hz, with an operating voltage of up to 690 V. They are also used for direct current of 450 V and current strength of up to 630 A. Such switches are designed for very rare operational use ( no more than 3 times per hour) and protection of lines from short circuit and electrical overload.

Important features of this series include:

high breaking capacity;
a wide range of electromagnetic releases;
button for testing the device with free tripping;
load break switches with special protection;
remote control through a closed door.

AP series

Automatic circuit breaker ap is able to protect electrical installations, motors from sudden voltage surges and short circuits within the network. The launches of such mechanisms are not intended to be very frequent (5-6 times per hour). Automatic switch ap can be two-pole and three-pole.

All structural elements are located on a plastic base, which is closed with a lid on top. In case of large overloads, the free tripping mechanism is activated, and the contacts open automatically. At the same time, the thermal release withstands the operating time, and the electromagnetic release provides instantaneous disconnection in the event of a short circuit.

When operating the machine, it is desirable to adhere to the following conditions:

With air humidity of 90%, the temperature should not exceed 20 degrees.
The operating temperature ranges from -40 to +40 degrees.
Vibration at the attachment point should not exceed 25 Hz.

It is strictly forbidden to work in an explosive atmosphere containing gases that destroy metal and winding, near the pure energy of heating devices, water flows and splashes, in places with conductive dust.

The variety of circuit breakers allows you to easily choose a device for an apartment or house. It is best to invite a specialist to install it.