Types of circuit breakers. Types of releases of circuit breakers

Electricity is a very useful and at the same time dangerous invention. In addition to the direct impact of current on a person, there is also a high probability of fire if the electrical wiring is not connected. This is explained by the fact that the electric current passing through the conductor heats it up, and especially high temperatures occur in places with poor contact or in the event of a short circuit. To prevent such situations, machines are used.

What

These are specially designed devices, the main task of which is to protect the wiring from melting. In general, machines will not save you from electric shock and will not protect equipment. They are designed to prevent overheating.

The method of their work is based on opening the electrical circuit in several cases:

short circuit;
excess of the current flowing through the conductor is not intended for this.

As a rule, the machine is installed at the input, that is, it protects the section of the circuit following it. Since different wiring is used for dilution to different types of devices, it means that protection devices must be able to operate at different currents.

It may seem that it is enough to install just the most powerful machine and there are no problems. However, it is not. A high current that does not work can overheat the wiring and, as a result, cause a fire.

The installation of low power circuit breakers will break the circuit every time as soon as two or more powerful consumers are connected to the network.

What is the machine made of?

A typical machine consists of the following elements:

Platoon handle. With it, you can turn on the machine after it is triggered, or turn it off to de-energize the circuit.
Switching mechanism.
Contacts. Provide connection and break of the chain.
Terminals. Connect to a protected network.
Conditional mechanism. For example, a bimetallic thermal plate.
Many models may have an adjusting screw to adjust the current rating.
Arcing mechanism. Present at each of the poles of the device. It is a small chamber in which copper-plated plates are placed. On them, the arc is extinguished and disappears.

Depending on the manufacturer, model and purpose, the machines can be equipped with additional mechanisms and devices.

Trip mechanism device

The machines have an element that breaks the electrical circuit at critical current values. Their principle of operation can be based on different technologies:

Electromagnetic devices. Differ in the high speed of reaction to short circuit. Under the action of currents of an unacceptable value, a coil with a core is activated, which, in turn, disconnects the circuit.
Thermal. The main element of such a mechanism is a bimetallic plate, which begins to deform under the load of high currents. Bending, it has a physical effect on the element that breaks the chain. Approximately according to the same scheme, an electric kettle works, which is able to turn itself off when water boils in it.
There are also semiconductor open circuit systems. But in household networks they are used extremely rarely.

by current values

Devices differ in the nature of the response to an excessively high current value. There are 3 most popular types of automata - B, C, D. Each letter means the sensitivity coefficient of the device. For example, an automaton of type D has a value between 10 and 20 xln. What does it mean? Very simple - to understand the range at which the machine is able to work, you need to multiply the number next to the letter by the value. That is, a device marked D30 will turn off at 30 * 10 ... 30 * 20 or from 300 A to 600 A. But such machines are used mainly in places with consumers that have high starting currents, for example, electric motors.

Type B automaton has a value between 3 and 5 xln. Therefore, marking B16 means operation at currents from 48 to 80A.

But the most common type of machines is C. It is used in almost every home. Its characteristics are from 5 to 10 xln.

Conventions

Different types of machines are marked in their own way for quick identification and selection of the right one for a particular circuit or its section. As a rule, all manufacturers adhere to one mechanism, which allows unifying products for many industries and regions. Let's analyze in more detail the signs and numbers applied to the machine:

Brand. Usually, the manufacturer's logo is placed at the top of the machine. Almost all of them are stylized in a certain way and have their own corporate color, so it will not be difficult to choose a product of your favorite company.
indicator window. Shows the current status of the contacts. If there is a malfunction in the machine, then it can be used to determine whether there is voltage in the network.
Machine type. As already described above, it means the tripping characteristic at currents that are much higher than the rated current. C is used more often in everyday life and B is slightly less common. The differences between the types of electric machines B and C are not so significant;
Rated current. Shows the value of the current that can withstand a continuous load.
Rated voltage. Very often, this indicator has two values, written with a slash. The first is for a single-phase network, the second is for a three-phase network. As a rule, in Russia a voltage of 220 V is used.
Breaking current limit. It means the maximum allowable short-circuit current at which the machine will turn off without failure.
Current limiting class. Expressed in one digit or absent altogether. In the latter case, it is customary to consider the class number 1. This characteristic means the time for which the short-circuit current is limited.
Scheme. On the machine, you can even find a connection diagram for contacts with their designations. It is located almost always in the upper right part.

Thus, looking at the front of the machine, you can immediately establish what type of current it is intended for and what it is capable of.

Which to choose?

When choosing a protective device, one of the main characteristics is considered to be the rated current. To do this, you need to determine what current strength is required by the totality of all consumer devices in the house.

And since electricity flows through wires, the current required for heating depends on its cross section.

The presence of poles also plays an important role. The most commonly used practice is:

One pole. Circuits with lighting fixtures and sockets to which simple appliances will be connected.
Two poles. It is used to protect wiring to electric stoves, washing machines, heaters, water heaters. It can also be installed as a protection between the shield and the room.
Three poles. It is mainly used in three-phase circuits. This is true for industrial or near-industrial premises. Small workshops, productions and the like.

The tactic of installing automata comes from largest to smallest. That is, it is first mounted, for example, a two-pole, then a single-pole. Next come devices with power decreasing at each step.

When choosing, it is worth focusing not on electrical appliances, but on wiring, since it will be protected by circuit breakers. If it is old, it is recommended to replace it so that you can use the most optimal version of the machine.
For premises such as a garage, or for the period of repair work, it is worth choosing an automatic machine with a larger rated current, since various machines or welding machines have rather large current strengths.
It makes sense to complete the entire set of protective mechanisms from the same manufacturer. This will help to avoid a mismatch in the rated currents between the devices.
It is better to buy vending machines in specialized stores. So you can avoid buying a low-quality fake, which can lead to disastrous consequences.

Conclusion

No matter how simple the wiring of the circuit around the room may seem, you should always remember about safety. The use of automatic machines largely helps to avoid overheating and, as a result, its ignition.

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.
With 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; sixteen; 20; 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.ru

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.
The 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 drop.
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.

yaelectric.ru

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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 (holding 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;
other.

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).

www.avtomats.com.ua

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. 4.

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 by the total power of the proposed energy consumers, but also by wiring and electrical installation products - sockets and switches.
Table 1 shows the typology of automata.

Table 1. Types of machines

Type	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 - the 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

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.
The 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 drop.
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

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Release definition

Releasers divide by two conditional groups:

circuit breakers;

Under overcurrent

Overload current
Short circuit current (short circuit)

Therefore, as soon as R→ to 0, then I→ to infinity.

Thermal release

The thermal release is a bimetallic plate, which, when heated, bends and acts on the mechanism of free disengagement.
A bimetallic plate is made by mechanically connecting two metal strips.

two materials with different coefficients of thermal expansion are taken and interconnected by soldering, riveting or welding.
Suppose the lower material in a bimetallic plate, when heated, elongates less than the upper metal, then the bend will occur downward.

The thermal release protects against overload currents and is configured for certain operating modes.

For example, for a product of the BA 51-35 series, the overload release is calibrated at a temperature of +30ºС to:

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.

The designation 1.05 In - means a multiple of the rated current. For example, with a rated current In = 100A, the conventional non-trip current is 105A.
On the time-current characteristics (graphs are always available in the factory catalogs), the dependence of the response time of the thermal and electromagnetic releases on the value of the flowing overcurrent is clearly shown.

Advantages:

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

Disadvantages:

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

It consists in principle of the same parts as a semiconductor release: an actuating electromagnet, measuring devices and a release control unit.

The operating current and holding time are set stepwise, guaranteeing protection in case of single-phase short circuit and inrush currents.
Example: products of the BA 88-43 series with an electronic release manufactured by the IEK company.

Advantages:

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.

Minuses:

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

Shunt release

With shunt trip(HP) carry out remote control specific circuit breaker. The independent release coil is energized from the control circuit, a magnetic field is created, the core moves, and it affects the free trip mechanism.
The shunt release can be designed for alternating or direct current (the manufacturer indicates the voltage range).
HP allows fluctuations in the operating voltage in the range from 0.7 to 1.2 of Un. Its mode of operation is short-lived.
After the independent release trips, you need to go to the switchboard and manually cock the circuit breaker, and then turn it on.
An alternative to HP can be an electromagnetic drive - it allows you to remotely turn off and turn on the circuit breaker.

Most common application– remote shutdown of the switching device that controls the ventilation system in the event of a fire. When a fire is detected, ventilation is turned off so that air (oxygen) is not injected into the building.

Electrodynamic forces

Electrodynamic forces act on a conductor with a current flowing through it, which is in a magnetic field with induction B.
When the rated current flows, the electrodynamic forces are insignificant, but when a short-circuit current appears, these forces can lead not only to deformation and breakage of individual parts of the switching device, but also to the destruction of the machine itself.
Special calculations are made for electrodynamic resistance, which are especially relevant when there is a tendency to reduce overall characteristics (distances between conductive parts are reduced).

A magnetic field

The magnetic field is one of the factors generating electrodynamic forces.
Magnetic fields adversely affect the operation of electrical equipment, especially measuring instruments and computers.

Thermal stress (overheating)

When any current with a force I flows through the conductor, its core heats up, which can lead to fires or damage to the insulation.
In the event of overcurrents, overheating is of current importance, if you do not block the short circuit, allowing you to reach maximum values.

Rated current

The rated current (denoted In) of the circuit breaker is understood as the current at which the device is designed for continuous operation and does not activate the protective operation. If the current indicated in the marking is exceeded, the machine, after a certain time, interrupts the supply to the network.

Small disclaimer:

rated current of the circuit breaker - the current for which conductive elements are calculated;
rated current of the thermal release - the current for which the release devices are adjusted (no tripping is caused by it).

In the following, by rated current we mean the rated current of the thermal release.
The rated current is one of the defining characteristics of the circuit breaker, since overcurrents are calculated relative to this value, at which the releases cause the contacts to open. For the correct choice of the circuit breaker, you need to know the rated current of the network.

The rated current of the network is calculated from the power consumption. It is certainly known which device consumes how much power. The total power is obtained and, as a first approximation, the ratio is used:
P \u003d U I, where P is the power consumption in watts, U is the mains voltage in volts, I is the mains current in amperes.

But this formula is true for a DC network, for an AC network everything is much more complicated.
Apparent power (S) is the vector sum of active power (P) and reactive power (Q):
S 2 \u003d P 2 + Q 2.
In its turn:

active power P = I U Cosϕ;
reactive power Q = I U Sinϕ.

Where ϕ is the angle at which the current lags or leads the voltage. Phase meters are used to measure the reactive power factor (Cosϕ).

Instantaneous trip current (protective characteristic B, C or D)

The circuit breaker is characterized by a current at which instantaneous tripping of the main contact group is caused. This occurs during a short circuit, which fixes and disables the electromagnetic release.

For modular and power circuit breakers, the instantaneous protection characteristic is specified in different ways:

modular automata are assigned a protective characteristic: B, C, D;
for circuit breakers, the current value is set in amperes or a multiple of the rated current.

Fast automata

Achieving a shutdown time of 0.002-0.008 s requires special measures and other principles of operation of drive electromagnets. In known designs, the following methods for obtaining speed are used:

1) according to the principle of flow displacement (speed 0.003-0.005 s). The machine is turned off not by turning off the coils of the holding electromagnet, but by displacing the flow from the core-armature section. In this case, the demagnetizing flux is created by a forced short-circuit current.

2) mechanical latches (locks) t o to 0.002 s. Switching on is also carried out by a short-term working electromagnet, and holding in the on position is carried out by a mechanical (electromechanical) latch. The latch is released by a tripping electromagnet operating in a forced mode, created by a short-circuit current.

3) systems with a shock electromagnet - an electromagnet working with a large force creates a "impact force" that exceeds the force of the holding electromagnet and "tear off" the anchor, i.e. turns off the switch.

4) a switch with an explosive release - a trip time of 0.001 s - has not received distribution due to its complexity.

5) vacuum circuit breakers providing arc extinguishing t0=0.003-0.007s. Examples of execution of some switches are shown below.

a) Switch BVP-5. Built on the principle of magnetic field displacement. It is designed to protect the power circuit of DC electric locomotives. U nom =4000 V, U max=4000 V, I nom=1850 A, own tripping time 0.003 s.

b) DC vacuum circuit breaker type VPTV-15-5/400 on the

U nom=15 kV, I nom = 400 A, I off =5 kA.

c) Automatic series VAB - 28 the most versatile I nom = 1.5-6 kA, U\u003d 825-3300 V.

HIGH VOLTAGE SWITCH

high voltage circuit breaker- a switching device designed for operational switching and emergency switching in power systems, for performing operations of switching on and off individual circuits or electrical equipment with manual or automatic control.

The high-voltage circuit breaker consists of: a contact system with an arcing device, current-carrying parts, a housing, an insulating structure and a drive mechanism (for example, an electromagnetic drive, a manual drive).

Options

In accordance with GOST R 52565-2006, switches are characterized by the following parameters:

rated voltage Unom (mains voltage in which the circuit breaker operates);
rated current In (current through the switched on switch, at which it can work for a long time);
rated breaking current Iо.nom - the highest short-circuit current (effective value) that the circuit breaker is able to disconnect at a voltage equal to the highest operating voltage under given conditions of recovering voltage and a given cycle of operations;
permissible relative content of aperiodic current in the tripping current;
if the circuit breakers are intended for automatic reclosing (AR), then the following cycles must be provided:

Cycle 1: O-tbp-BO-180 s-BO; Cycle 2: О-180 s-VO−180 s-VO, where О is the opening operation, VO is the closing and immediate opening operation, 180 is the time interval in seconds, tbp is the minimum dead time guaranteed for circuit breakers during automatic reclosure (time from extinguishing arc until the current appears at the next turn-on) For circuit breakers with automatic reclosure it should be within 0.3-1.2 s, for circuit breakers with BAPV (high-speed) 0.3 s.

stability with through short-circuit currents, which is characterized by thermal resistance currents It and limiting through current
rated making current - short-circuit current, which the circuit breaker with the appropriate drive is able to turn on without welding of contacts and other damages at Unom and a given cycle.
proper tripping time - the period of time from the moment the command to turn off is given until the moment the arcing contacts begin to diverge.
recovery voltage parameters at rated trip current - recovery voltage rate, normalized curve, peak-to-peak ratio and recovery voltage.

Automatic breakers. Operating principle. Design and types of releases.

Release definition

Releasers divide by two conditional groups:

circuit breakers;
releases performing auxiliary functions.

Releaser (first group), in relation to a circuit breaker, a device is called that is capable of recognizing a critical situation (the appearance of overcurrent) and preventing its development in advance (causing a divergence of the main contacts).

To the second group of releases additional devices can be distinguished (they do not complete the basic versions of the machines, but only supply custom versions):

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

Under overcurrent is understood as the current strength exceeding the rated (working) current. This definition includes short-circuit current and overload current.

Overload current- overcurrent acting in the functional network (prolonged exposure to overloads can cause damage to the circuit).
Short circuit current (short circuit)– overcurrent, which is caused by the shorting of two elements with a very low impedance between them, while in normal operation these elements are endowed with different potential (short circuit can be caused by incorrect connection or damage). For example, mechanical stress or aging of insulation causes contact of conductive wires and a short circuit.
The high value of the short circuit current is recognized from the formula:
I \u003d U / R (current strength is equal to the ratio of voltage to resistance).
Therefore, as soon as R→ to 0, then I→ to infinity.

The rated current flows through the main contacts in the circuit breaker during normal use. The free tripping mechanism of the switching device has sensitive elements (eg rotary tripping bar). The impact of the release on these elements contributes to the instantaneous automatic operation, that is, the disengagement of the contact system.

Overcurrent release (MRT)- a release that causes the opening of the main contacts with or without maintaining a certain period of time, as soon as the effective value of the current exceeds a given threshold.
MRT with inverse time delay - the maximum current release, initiating the release of contacts after the expiration of a specified time, which is inversely dependent on the current strength.
MRT of direct action is the maximum current release that initiates operation directly from the operating overcurrent.

The definitions of the overcurrent release, short circuit current and overload are taken (rephrased without loss of meaning) from the GOST R 50345 standard.

cyberpedia.su

Varieties of switches

All machines are divided according to the type of releases. They are divided into 6 types:

thermal;
electronic;
electromagnetic;
independent;
combined;
semiconductor.

They are very quick to recognize emergencies such as:

the occurrence of overcurrents - an increase in the current strength in the electrical network that exceeds the rated current of the circuit breaker;
voltage overload - short circuit in the circuit;
voltage fluctuations.

At these moments, the opening of contacts occurs in the automatic releases, which prevents serious consequences in the form of damage to wiring, electrical equipment, which very often leads to fires.

Thermal switch

It consists of a bimetallic strip, one of the ends of which is located next to the release device of the automatic release. The plate is heated by the current passing through it, hence the name. When the current strength begins to increase, it bends and touches the trigger bar, which opens the contacts in the "machine".

The operation of the mechanism occurs even with slight excesses of the rated current and an increased operating time. If the load increase is short-term, the circuit breaker does not work, so it is convenient to install it in networks with frequent, but short overloads.

Advantages of a thermal release:

lack of contacting and rubbing surfaces;
vibration resistance;
budget price;
simple design.

The disadvantages include the fact that its work largely depends on the temperature regime. It is better to place such machines away from heat sources, otherwise there will be numerous false alarms.

Electronic switch

Its components include:

measuring devices (current sensors);
Control block;
electromagnetic coil (transformer).

Each pole of the electronic automatic release has a transformer that measures the current passing through it. The electronic module that controls the trip processes this information by comparing the received result with the specified one. In the case when the received indicator is more than the programmed one, the "machine" will open.

There are three trigger zones:

Long delay. Here, the electronic release serves as a thermal release, protecting the circuits from overloads.
Short delay. Provides protection against minor short circuits, which usually occur at the end of the protected circuit.
The work area "instantaneously" provides protection against high-intensity short circuits.

Pluses - a large selection of settings, the maximum accuracy of the device to a given plan, the presence of indicators. Cons - sensitivity to an electromagnetic field, high price.

Electromagnetic

This is a solenoid (a coil with a wound wire), inside of which there is a core with a spring that acts on the release mechanism. This is an instant device. During the flow through the overcurrent winding, a magnetic field is formed. It moves the core and, exceeding the force of the spring, acts on the mechanism, turning off the "automatic".

Pros - resistance to vibration and shock, simple design. Cons - forms a magnetic field, instantly works.

This is an additional device to automatic releases. With it, you can turn off both a single-phase and a three-phase machine located at a certain distance. To activate the shunt release, the coil must be energized. To return the machine to its original position, you must manually press the "return" button.

Important! The phase conductor must be connected from one phase from under the lower terminals of the switch. If it is connected incorrectly, the independent switch will fail.

Basically, independent machines are used in automation panels in highly branched power supply devices of many large facilities, where control is displayed on the operator's console.

Combination switch

It has both thermal and electromagnetic elements and protects the generator from overloads and short circuits. For the operation of the combined automatic release, the current of the thermal "automatic device" is indicated and selected: the electromagnet is designed for 7-10 times the current, which corresponds to the operation of heating networks.

Electromagnetic elements in the combination switch serve as instantaneous protection against short circuits, and thermal protection against overloads with a time delay. The combined machine turns off when any of the elements is triggered. With short-term overcurrents, none of the types of protection works.

Semiconductor switch

It consists of AC transformers, magnetic amplifiers for DC, control unit and electromagnet, which performs the functions of an independent automatic release. The control unit helps to set the selected contact release program.

Its settings include:

regulation of the rated current in the device;
time setting;
operation at the moment of occurrence of a short circuit;
protective switches against overcurrents and single-phase short circuit.

Pluses - a large selection of regulation for different power supply schemes, ensuring selectivity to series-connected machines with fewer amperes.

Cons - high cost, fragile control components.

Installation

Many homegrown electricians find that installing an automatic machine is not difficult. This is fair, but certain rules must be followed. The circuit breaker releases, as well as plug fuses, must be connected to the network so that when the plug of the machine is turned out, its screw sleeve is without voltage. The connection of the supply conductor with one-sided power supply to the machine must be made to fixed contacts.

Installation of an electric single-phase two-pole machine in an apartment consists of several stages:

fixing the switched off device in the electrical panel;
connecting wires without voltage to the meter;
connection to the machine from above the voltage wires;
turning on the machine.

Fastening

In the electrical panel we mount a din rail. We cut off the desired size and fasten it with self-tapping screws to the electrical panel. We snap the automatic circuit breaker onto the DIN rail using a special lock, which is located on the back of the machine. Make sure the device is in shutdown mode.

Connection to the electricity meter

We take a piece of wire, the length of which corresponds to the distance from the counter to the machine. We connect one end to the electric meter, the other to the release terminals, observing the polarity. We connect the supply phase to the first contact, and the neutral supply wire to the third. The cross section of the wire is 2.5 mm.

Connecting voltage wires

From the central distribution electrical panel, the supply wires go to the apartment panel. We connect them to the terminals of the machine, which should be in the “off” position, observing the polarity. The cross section of the wire is calculated depending on the energy consumed.

energomir.biz

It is impossible to imagine a modern electrical network without the necessary means of protection, in particular, a circuit breaker. Unlike obsolete fuses, it is designed for reusable protection of the network and electrical equipment. At the same time, the circuit breaker protects against short circuit currents, excessive overloads, and some models even against unacceptable voltage drops. And in the center of this whole structure, the most significant element is the circuit breaker release. It is on him that the reliability and speed of response depend, so it is worth comparing all the currently existing varieties.

Comparison

So, among the first can be called a thermal release. Due to its design, the thermal release trips with a time delay. The greater the excess current, the faster the thermal release operates. So the response time can vary from a few seconds to an hour. That is why the sensitivity of the machine, where the thermal release is installed, is always determined by the time-current characteristic and corresponds to class B, C or D.

The next variety is among the instantaneous releases. We are talking about such a thing as an electromagnetic release. It works in a fraction of a second, which compares favorably with thermal releases. However, the electromagnetic release also has its own peculiarity - operation occurs at a significantly higher excess of the rated current. Based on this, the electromagnetic release also has a certain sensitivity and belongs to one of the classes - A, B, C or D.

Perhaps the most effective is the electronic release of the circuit breaker. Fast operating speed and high sensitivity make the electronic trip unit ideal for protection against overloads and short-circuit currents. For this reason, this instantaneous release is used for more currents.

It is the electronic release that is often mounted on both air circuit breakers and molded case circuit breakers. Air circuit breakers imply an open design (usually in a metal case) and are designed for currents up to several thousand amperes. As already mentioned, the electronic release is ideal for power networks due to the instantaneous response speed. As for the molded case circuit breakers, they are distinguished by their compact dimensions and closed design in a housing made of thermosetting plastic. It is convenient to mount them on a DIN rail, but the closed case implies increased requirements for the reliability of the release. This again is an electronic release, where there are no moving mechanical elements.

Principle of operation

Regardless of the type of release, the principle of its operation is based on opening the circuit in case of exceeding the current characteristics. Any release is an integral part of the circuit breaker, built into it or mechanically associated with it. The release of the circuit breaker, under the influence of short circuit currents or when the load is exceeded, initiates the release of the holding device in the circuit breaker housing. As a result, the electrical circuit is opened.

Design

The design largely depends on the type of release. So, the basis of the thermal release is a bimetallic plate - a metal tape of two strips with different coefficients of thermal expansion. When currents exceeding the permissible value pass through it, the bimetallic plate is deformed, thereby triggering the trip mechanism.

For an electromagnetic release, the design is a solenoid (cylindrical winding) with a movable core. The current passes through the solenoid winding, and if the current characteristics are exceeded, the core is drawn in, acting on the opening mechanism.

But the electronic release of the circuit breaker is not based on mechanical action and is a slightly different design. It consists of a controller and current sensors. The controller compares the values of the current sensors with the set characteristics, and if the set current parameters are exceeded, it gives a shutdown signal. Thus, the electronic release has more flexible settings, allowing you to adjust the parameters of the circuit breaker to the specific requirements of protecting the mains.

chint-electric.com

Circuit breakers are devices that provide wiring protection under short circuit conditions, when a load is connected with indicators exceeding the set values. They should be chosen with special care. It is important to consider the types of circuit breakers, their parameters.

Automatic machines of different types

Characteristics of machines

When choosing a circuit breaker, it makes sense to focus on the characteristics of the device. This is an indicator by which you can determine the sensitivity of the device to a possible excess of current values. Different types of circuit breakers have their own marking - it is easy to understand from it how quickly the equipment will respond to excess current values to the network. Some switches respond instantly, while others are activated over a period of time.

A - marking, which is affixed to the most sensitive models of equipment. Automatic machines of this type immediately register the fact of overload and quickly respond to it. They are used to protect equipment characterized by high accuracy, but in everyday life they are almost impossible to meet.
B - characteristic, which have switches that operate with an insignificant delay. In everyday life, switches with the appropriate characteristics are used together with computers, modern LCD TVs and other expensive household appliances.
C - a characteristic of automata, which are most widely used in everyday life. The equipment begins to function with a slight delay, which is enough for a delayed response to registered network congestion. The network is turned off by the device only if it has a fault that really matters
D is a characteristic of switches that have a minimum sensitivity to exceeding current indicators. Basically, such devices are used as part of the supply of electricity to the building. They are installed in shields, almost all networks are under their control. Such devices are selected as a fallback option, since they are activated only if the machine does not turn on in time.

All parameters of circuit breakers are written on the front

Important! Experts believe that the ideal performance of circuit breakers should vary within certain limits. Maximum - 4.5 kA. Only in this case, the contacts will be under reliable protection, and current discharges will be discharged in any conditions, even if the established indicators are exceeded.

Types of machines

The classification of circuit breakers is based on their types and features. As for the types, we can distinguish the following:

Rated breaking capacity - this is the resistance of the contacts of the switch to the effects of currents with high rates, as well as to the conditions in which the circuit is deformed. Under such conditions, the risk of burning increases, which is neutralized by the appearance of an arc and an increase in temperature. The higher the quality and durability of the equipment material, the higher are its corresponding abilities. Such switches are more expensive, but their characteristics fully justify the price. Switches have a long service life, do not require regular replacement
Rating calibration - we are talking about the parameters in which the equipment operates in normal mode. They are installed at the stage of equipment production, and are not regulated already in the process of its use. This characteristic allows you to understand how strong overloads the device can withstand, the period of time of its operation in such conditions
Setpoint - usually this indicator is displayed as a marking on the equipment case. We are talking about the maximum current values in non-standard conditions, which, even with frequent shutdowns, will not have any effect on the functioning of the device. The setting is expressed in current units, marked with Latin letters, digital values. The numbers, in this case, display the face value. Latin letters can be seen in the marking of only those machines that are made in accordance with DIN standards

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

Automata (automatic switches) are what came to replace conventional traffic jams, i.e. fuses in a ceramic case, where the overcurrent protection was a blown nichrome wire.

Unlike cork, machine - reusable device, and its protection functions are separated. Firstly, protection against overcurrents (short circuit currents or short circuits), and secondly, protection against overload, i.e. the mechanism of the machine breaks the load circuit when the operating current of the machine is slightly exceeded.

According to these functions, the circuit breaker contains two types of breakers. Magnetic quick release short circuit protection with arc quenching system (response time in milliseconds) and slow thermal disconnect with a bimetallic plate (its reaction time is from several seconds to several minutes, depending on the load current).

Classification of electric machines

There are several typical circuit breakers: A, B, C, D, E, K, L, Z

BUT– for breaking long circuits and for protecting electronic devices.
B- for lighting networks.
With- for lighting networks and electrical installations with moderate currents (current overload capacity is twice that of B).
D– for circuits with inductive loads and electric motors.
K– for inductive loads.
Z– for electronic devices.

Main criteria for choosing a circuit breaker

Limiting short-circuit current

This indicator must be taken into account immediately. It means the maximum current value at which the electric machine will work and open the circuit. Here the choice is not great, since there are only three options: 4.5 kA; 6 kA; 10kA.

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

Machine current

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

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

The pole of the machine

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

So, a single-pole machine is your choice if you need to protect the wiring that goes from the electrical panel to sockets and lighting circuits. A bipolar switch is used when it is necessary to protect all wiring in an apartment or house with single-phase power. Protection of three-phase wiring and load is provided by a three-pole circuit breaker, and four-pole ones are used to protect four-wire power.

Characteristics of the machine

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

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

RCD classification

The RCD responds to differential current, i.e. the difference between the currents flowing in the forward and reverse wires. A differential current appears when a person touches a protected circuit and a grounded object. RCDs to protect people are selected for current 10-30 mA , fire RCDs - for a current of 300 mA. The latter protects the entire wiring system, and in case of fire, leakage currents usually occur earlier than short-circuit currents.

Residual current devices protect people from electric shock.

The choice of RCD is difficult because it is a more complex device than an automatic machine. For example, there is difavtomatami- devices that combine an automatic machine and an RCD. RCDs are also subdivided according to the type of execution into electronic and electromechanical. Experience has shown that it is better to use electromechanical RCDs. They are better protected from false positives and from breakdowns.

By number of poles RCDs are divided into:

bipolar for 220 V circuits;
four-pole for 380 V circuits.

According to the terms of operation on the:

AC- responding only to alternating sinusoidal differential current.
BUT- responding both to alternating sinusoidal differential current and to direct pulsating differential current.
AT- reacting to alternating sinusoidal differential current, to direct pulsating differential current and to direct differential current.

By the presence of a delay on RCDs without delay for general use and with a time delay of type S. According to the current characteristic (difavtomatov) for B, C, D. And, finally, according to the rated current.

You should be aware that if the conventional Residual Current Device and the machine are in series in the same circuit, then the machine must be at a lower current than the RCD. Otherwise, the RCD may be damaged, because. the machine breaks the load circuit with a delay.

In conclusion, it must be said that you should choose devices from well-known companies: ABB abb, GE POWER, siemens siemens, LEGRAND and others at least certified in Russia. It is better to choose electromechanical RCDs, because. they are much more reliable than electronic ones. Instead of a tandem of an RCD and an automatic machine, it is better to choose a difavtomat, this will make the design of the shield more compact and reliable. The current characteristics must be selected depending on the wiring used. The operation current of automata and difavtomatov must be less than the maximum allowable cable currents.

For copper three-wire cables, you can give the following data on the correspondence of the cross section of the cable conductors in square millimeters and the currents of the machines:

3 x 1.5mm 2 - 16 Amps;
3 x 2.5 mm 2 - 25 A;
3 x 4 mm 2 - 32 Amps;
3 x 6mm 2 - 40 A;
3 x 10 mm 2 - 50 Amps;
3 x 16 mm 2 - 63 A.

We hope that after reading all the material it will be easier for you to understand the design and construction of electrical wiring.

The history of the creation of the RCD

The first residual current device (RCD) was patented by the German company RWE in 1928, when the principle of current differential protection, previously used to protect generators, lines and transformers, was applied to protect a person from electric shock.

In 1937 Schutzapparategesellschaft Paris & Co. manufactured the first operating device based on a differential transformer and a polarized relay, which had a sensitivity of 0.01 A and a speed of 0.1 s. In the same year, with the help of a volunteer (an employee of the company), an RCD was tested. The experiment ended successfully, the device worked well, the volunteer experienced only a mild electric shock, although he refused to participate in further experiments.

All subsequent years, with the exception of the war and the first post-war years, intensive work was carried out to study the effect of electric current on the human body, the development of electrical protective equipment and the improvement and implementation of protective shutdown devices.

In our country, the problem of using residual current devices first arose in connection with the electrical and fire safety of schoolchildren about 20 years ago. It was during this period that they developed and put into production UZOSH (UZO school) for the equipment of school buildings. Interestingly, RCDs of this type are still installed in school buildings, although due to outdated technologies, these devices no longer fully meet modern electrical and fire safety requirements.

Another event that exacerbated the problem of installing an RCD was the reconstruction of the Rossiya Hotel in Moscow after the infamous fire, which was caused by the most ordinary short circuit. The fact is that the principles of power supply were violated during the construction of this hotel complex. Several tragic incidents that led to the death of service personnel forced the hotel management to schedule the installation of residual current devices in order to ensure electrical and fire safety.

At that time, such installations were produced only for industrial use. One of the defense enterprises was entrusted with developing a protective shutdown installation for domestic purposes. But they did not have time to prevent the tragedy, and the fire that arose as a result of a short circuit in the Rossiya Hotel led to numerous victims. After the fire, during the restoration of the building, work was carried out to install an RCD in each room. Since domestic RCDs were manufactured in a very short time and had flaws, they gradually began to be replaced by devices from SIEMENS (Germany).

By this time, our electrical engineering enterprises also began to think about the problem of producing household protective shutdown devices. So, the Gomel plant "Electroapparatura" and the Stavropol electrical plant "Signal" developed and began to produce household protective shutdown devices. And since 1991-1992, the mass introduction of protective shutdown devices in housing construction began, at least in Moscow.

In 1994, the standard “Power supply and electrical safety of mobile (inventory) buildings made of metal or with a metal frame for street trading and consumer services was adopted. Technical requirements". In the same year, a decree of the Moscow government was issued on the introduction of an RCD, which prescribed the mandatory equipping of new buildings in Moscow with protective shutdown devices.

In 1996 came out Letter of the Main Directorate of Civil Service of the Ministry of Internal Affairs of Russia dated 05.03.96 No. 20 / 2.1 / 516 « On the use of residual current devices (RCD)". And the Moscow government made another decision to improve the reliability of power supply to the entire housing stock, regardless of the year of construction. We can say that from that moment the legalized mass introduction of RCDs in housing construction began.

At present, the areas of application of RCDs are already clearly defined, a number of regulatory documents are in force that regulate the technical parameters and requirements for the use of RCDs in electrical installations of buildings. Today, the RCD is an indispensable element of any switchboard, all mobile objects are equipped with these devices without fail (residential trailer houses on camping sites, shopping vans, catering vans, small temporary outdoor electrical installations, arranged on the squares during the festive festivities), hangars , garages.

An RCD connection option that provides the safest operation of electrical wiring. In addition, RCDs are built into socket blocks or plugs through which power tools or household electrical appliances are connected, operated in especially dangerous, humid, dusty, with conductive floors, etc., rooms.

When assessing the risk that determines the sum insured, insurance companies must take into account the presence of RCDs on the insurance object and their technical condition.

Currently, there are an average of two RCDs for every inhabitant of developed countries. Nevertheless, dozens of companies over the years have consistently produced these devices of various modifications in significant quantities, constantly improving their technical parameters.

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

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