Marking of circuit breakers. Types and installation of circuit breaker releases Automatic power supply types and characteristics

Surely many of us have wondered why circuit breakers so quickly replaced outdated fuses from electrical circuits? The activity of their implementation is justified by a number of very convincing arguments, including the opportunity to buy this type of protection, which ideally matches the time-current data specific types electrical equipment.

Do you doubt which machine you need and don’t know how to choose it correctly? We will help you find the right solution - the article discusses the classification of these devices. And important characteristics, which you should pay close attention to when choosing a circuit breaker.

To make it easier for you to understand the machines, the article’s material is supplemented with visual photos and useful video recommendations from experts.

The machine almost instantly disconnects the line entrusted to it, which eliminates damage to the wiring and equipment powered from the network. After the shutdown has been completed, the branch can be restarted immediately without replacing the safety device.

If you have knowledge or experience performing electrical installation work please share it with our readers. Leave your comments about choosing a circuit breaker and the nuances of installing it in the comments below.

It is easier and cheaper to prevent the fire-hazardous consequences of destruction than to bitterly complain about measures not taken. Preventing electrical fires involves installing protective equipment. In the last century, the function of protection against short circuits and the danger of overload was entrusted to porcelain fuses with replaceable fuse links, then to automatic plugs. However, due to a significant increase in the load on power lines, the situation has changed. It's time to replace outdated devices with reliable machines. In order for the selection of a circuit breaker to result in the purchase of a device with the appropriate characteristics, information about a number of electrical technical nuances is required.

Why do we need machine guns?

Automatic circuit breakers are devices designed to protect the power cable, or more precisely, to insulate it from melting and loss of integrity. The machines do not protect equipment owners from impacts and do not protect the equipment itself. For these purposes, an RCD is equipped. The task of the machines is to prevent overheating that accompanies the flow of overcurrents to the entrusted section of the circuit. Thanks to their use, the insulation will not melt or be damaged, which means that the wiring will operate normally without the risk of fire.

Job circuit breakers consists of opening the electrical circuit in the event of:

the appearance of short circuit currents (hereinafter short circuit currents);
overload, i.e. the passage of currents through the protected section of the network, the strength of which exceeds the permissible operational value, but is not considered a TKZ;
noticeable reduction or complete disappearance of tension.

The machines guard the section of the chain that follows them. Simply put, they are installed at the input. They protect lighting lines and sockets, lines for connecting household equipment and electric motors in private homes. These lines are laid with cables of different sections, because equipment of different power is powered from them. Consequently, to protect network sections with unequal parameters, protection devices with unequal capabilities are needed.

If you want to learn how to install socket boxes, we recommend that you read the article

It would seem that you can, without unnecessary hassle, purchase the most powerful automatic shutdown devices for installation on each of the lines. The step is completely wrong! And the result will pave a direct “path” to the fire. Protection from the vagaries of electric current is a delicate matter. Therefore, it is better to learn how to choose a circuit breaker and install a device that breaks the circuit when there is a real need for it.

Attention. An overrated circuit breaker will carry currents that are critical to the wiring. It will not disconnect the protected section of the circuit in a timely manner, which will cause the cable insulation to melt or burn.

Automatic machines with reduced characteristics will also present many surprises. They will endlessly break the line when starting up the equipment and will eventually break due to repeated exposure to too much current. The contacts are soldered together, which is called “stuck”.

Design and principle of operation of the machine

It will be difficult to make a choice without understanding the circuit breaker design. Let's see what's hidden in a miniature box made of refractory dielectric plastic.

Releases: their types and purpose

The main working parts of automatic circuit breakers are releases that break the circuit if the standard operating parameters are exceeded. Releases differ in the specificity of their action and in the range of currents to which they must respond. Their ranks include:

electromagnetic releases, which react almost instantly to the occurrence of a fault and “cut off” the protected section of the network in hundredths or thousandths of a second. They consist of a coil with a spring and a core, which is retracted from the effects of overcurrents. By retracting, the core strains the spring, and it causes the release device to work;
thermal bimetallic releases, acting as a barrier against overloads. They undoubtedly also respond to TKZ, but are required to perform a slightly different function. The task of thermal counterparts is to break the network if currents passing through it exceed the maximum operating parameters of the cable. For example, if a current of 35A flows through the wiring intended to transport 16A, the plate consisting of two metals will bend and cause the machine to turn off. Moreover, she will courageously “hold” 19A for more than an hour. But 23A won’t be able to “tolerate” for an hour, it will work earlier;
semiconductor releases are rarely used in household machines. However, they can serve as the working body of a protective switch at the input a private house or on the line of a powerful electric motor. Measurement and recording of abnormal current in them is carried out by transformers, if the device is installed on an alternating current network, or choke amplifiers, if the device is connected to the line direct current. The decoupling is carried out by a block of semiconductor relays.

There are also zero or minimum releases, most often used as a supplement. They disconnect the network when the voltage drops to a certain level. limit value specified in the technical passport. A good option are remote releases that allow you to turn the machine off and on without opening the control cabinet, and locks that fix the “off” position. It is worth considering that equipping with these useful additions significantly affects the price of the device.

Automatic machines used in everyday life are most often equipped with a smoothly working combination of an electromagnetic and thermal release. Devices with one of these devices are much less common and used. Still, combined type circuit breakers are more practical: two in one is more profitable in every sense.

Extremely Important Additions

There are no useless components in the design of the circuit breaker. All components work diligently in the name of overall safety, these are:

an arc extinguishing device mounted on each pole of the machine, of which there are from one to four pieces. It is a chamber in which, by definition, the electric arc that occurs when the power contacts are forced to open is extinguished. Copper-plated steel plates are located in parallel in the chamber, dividing the arc into small parts. The fragmented threat to the fusible parts of the machine in the arc extinguishing system cools down and completely disappears. Combustion products are removed through gas outlet channels. An addition is a spark arrester;
a system of contacts, divided into fixed ones, mounted in the housing, and movable ones, hingedly attached to the axle shafts of the levers of the opening mechanisms;
calibration screw, with which the thermal release is adjusted at the factory;
a mechanism with the traditional inscription “on/off” with a corresponding function and with a handle intended for implementation;
connection terminals and other devices for connection and installation.

This is what the arc extinguishing process looks like:

Let's linger a little on power contacts. The fixed version is soldered with electromechanical silver, which optimizes the electrical wear resistance of the switch. When an unscrupulous manufacturer uses a cheap silver alloy, the weight of the product decreases. Silver-plated brass is sometimes used. “Substitutes” are lighter than standard metal, which is why a high-quality device from a reputable brand weighs slightly more than its “left-hand” analogue. It is important to note that when replacing silver soldering of fixed contacts with cheap alloys, the service life of the machine is reduced. It will withstand fewer cycles of turning off and then turning on.

Let's decide on the number of poles

It has already been mentioned that the poles of this device protection can be from 1 to 4 pcs. Selecting the number of machine poles is as easy as shelling pears, because it all depends on its purpose of use:

A single-pole circuit breaker will do an excellent job of protecting lighting lines and sockets. Mounted only on a phase, no zeros!;
A two-pole switch will protect the cable that powers electric stoves, washing machines and water heaters. If there are no powerful household appliances in the house, they are placed on a line from the panel to the entrance to the apartment;
a three-pole device is required for three-phase wiring equipment. This is already on a semi-industrial scale. In everyday life there may be a workshop or well pump line. A three-pole device must not be connected to the ground wire. He must always be in full combat readiness;
Four-pole circuit breakers are used to protect four-wire wiring from fire.

If you plan to protect the wiring of an apartment, bathhouse, or house using two-pole and single-pole circuit breakers, first install a two-pole device, then a single-pole device with the maximum rating, then in descending order. The “ranking” principle: from the more powerful component to the weaker but sensitive one.

Labeling – food for thought

We figured out the structure and operating principle of the machines. We found out what and why. Now let’s boldly begin to analyze the markings affixed to each circuit breaker, regardless of the logo and country of origin.

The main reference point is the denomination

Because The purpose of purchasing and installing a machine is to protect the wiring, so first of all you need to focus on its characteristics. The current flowing through the wires heats the cable in proportion to the resistance of its current-carrying core. In short, the thicker the vein, the greater value current can pass through it without melting the insulation.

In accordance with the maximum value of the current transported by the cable, the rating of the automatic shutdown device is selected. There is no need to calculate anything; the interdependent values of electrical installation devices and wiring by caring electricians have long been summarized in the table:

The tabular information should be slightly adjusted according to domestic realities. The predominant number of household sockets are designed to connect a wire with a 2.5 mm² core, which, according to the table, suggests the possibility of installing a machine with a rating of 25A. The actual rating of the outlet itself is only 16A, which means you need to buy a circuit breaker with a rating equal to the rating of the outlet.

A similar adjustment should be made if there are doubts about the quality of the existing wiring. If there are suspicions that the cable cross-section may not correspond to the size specified by the manufacturer, it is better to play it safe and take a machine whose nominal value is one position lower than the table value. For example: according to the table, an 18A machine is suitable for cable protection, but we’ll take a 16A one, because we bought the wire from Vasya at the market.

Calibrated characteristic of the device rating

This characteristic is the operating parameters of a thermal release or its semiconductor analogue. It is a coefficient by which we multiply to obtain the overload current that the device may or may not hold for a certain period of time. The value of the calibrated characteristic is established during the production process and cannot be adjusted at home. They select it from the standard range.

The calibrated characteristic indicates how long and what kind of overload the machine can withstand without disconnecting the circuit section from the power supply. Usually these are two numbers:

the lowest value indicates that the machine will pass current with parameters exceeding the standard for more than an hour. For example: a 25A circuit breaker will pass a current of 33A for more than an hour without disconnecting the protected section of wiring;
the highest value is the limit beyond which shutdown will occur in less than an hour. The device indicated in the example will quickly turn off at a current of 37 amperes or more.

If the wiring runs in a groove formed in a wall with impressive insulation, the cable will practically not cool during overload and the accompanying overheating. This means that in an hour the wiring can suffer quite a bit. Maybe no one will immediately notice the result of the excess, but the service life of the wires will be significantly reduced. Therefore, for hidden wiring We will look for a switch with minimal calibration characteristics. For the open version, you don’t have to focus too much on this value.

Setting – instantaneous response indicator

This number on the body is a characteristic of the operation of the electromagnetic release. It denotes the maximum value of abnormal current, which during repeated shutdowns will not affect the performance of the device. It is standardized in units of current, and is indicated in numbers or Latin letters. With numbers, everything is extremely simple: this is the face value. Here's the hidden meaning letter designations It's worth finding out.

Letters are stamped on machines made according to DIN standards. They indicate the multiple of the maximum current that occurs when the equipment is turned on. A current that is several times greater than the operating characteristics of the circuit, but does not cause a shutdown and does not render the device unusable. Simply, how many times the equipment switching current can exceed the rating of the device and cable without dangerous consequences.

For circuit breakers used in everyday life, these are:

IN– designation of machines capable of reacting without self-damage to currents exceeding the nominal value in the range from 3 to 5 times. Very suitable for equipping old buildings and rural areas. They are not used often, therefore they are most often a custom item for retail chains;
WITH– designation of these protective equipment, the response range of which is from 5 to 10 times. The most common option, in demand in new buildings and new country houses with autonomous communications;
D- designation of switches that instantly break the network when a current is supplied with a force exceeding the nominal value from 10 to 14, sometimes up to 20 times. Devices with such characteristics are needed only to protect the wiring of powerful electric motors.

There are variations abroad, both higher and lower, but the average owner of domestic property should not be interested in them.

Current limiting class and its meaning

Let's talk about this briefly, because most of the devices offered by trade belong to the 3rd class of current limitation. Occasionally there is a second one. This is an indicator of the speed of the device. The higher it is, the faster the device will respond to TKZ.

There is a lot of information, but without it it will be difficult to choose the right circuit breaker and protect property from unwanted fires. Information is also needed for those who will order the installation of protection devices. After all, not every electrician who positions himself as a great specialist should be trusted unconditionally.

Definition and types of releases, their advantages and disadvantages; examples of circuit breakers with thermal, electromagnetic, semiconductor and electronic tripping devices; processes occurring at supercurrents

Definition of release

Releases divide by two conditional groups:

main releases for circuit protection;
auxiliary releases for increased functionality.

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

Auxiliary releases- additional devices (they are not included with the basic versions of the machines, but are supplied only with custom-made special versions):

independent release (remote shutdown of the circuit breaker based on a signal from the auxiliary circuit);
minimum voltage release (turns off the circuit breaker when the voltage drops below the permissible level);
zero voltage release (causes contacts to trip when there is a significant voltage drop).

Definitions of terms

Under overcurrent understand the current strength exceeding the rated (operating) current. This definition includes short circuit current and overload current.

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

The main contacts in the circuit breaker carry the rated current during normal operation. The free release mechanism of the switching device has sensitive elements (for example, a rotary trip bar). The action of the release on these elements contributes to instantaneous automatic operation, that is, the release of the contact system.

Overcurrent release (MRT)- a release that causes the main contacts to open, with or without a certain period of time, as soon as the effective current value exceeds a specified threshold.
Inverse time MRT is an overcurrent release that initiates tripping of the contacts after a specified time has elapsed, which is inversely dependent on the current strength.
MRI direct action- maximum current release, which initiates operation directly from the current overcurrent.

Definitions of maximum current release, short-circuit current and overload are taken (paraphrased without loss of meaning) from the GOST 50345 standard.

Types of releases, used in circuit breakers

In circuit breakers install one or a combination of the following releases:

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

one of the ones proposed below replaces the first two; during operation, adjustment is allowed (holding time at overcurrent to ensure selectivity, which current is considered an overload, which is a short circuit):
- semiconductor release;
- electronic release;

additional tripping devices to expand functionality:
- independent release;
- undervoltage release;
- zero voltage release.

It should be taken into account that cheap devices are electromagnetic and thermal releases. Automatic switches equipped with a semiconductor or electronic release (they functionally replace a combination of a thermal and electromagnetic release) cost from $1200 and above, so they are used as input devices for rated currents from 630 A (there are rare exceptions of lower amperage).

Briefly in the video describes the design of the circuit breaker, in particular about thermal and electromagnetic releases:

Thermal release

The thermal release is a bimetallic plate, which bends when heated and affects the free release mechanism.
A bimetallic plate is made by mechanically joining two metal strips. Two materials with different coefficients of thermal expansion are selected and connected to each other by soldering, riveting or welding.
Suppose the lower material in a bimetallic plate, when heated, elongates less than the upper metal, then the bending 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 releases are calibrated at a temperature of +30 °C to:

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

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

Advantages:

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

Flaws:

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

Electromagnetic release

An electromagnetic (abbreviated as EM) release is an instantaneous device. It is a solenoid, the core of which acts on the free release mechanism. When a supercurrent flows through the solenoid winding, a magnetic field is generated that moves the core, overcoming the resistance of the return spring.

The EM release is configured to operate at short-circuit currents ranging from 2 to 20·In. The setting error varies within ±20% of the set value.

For power circuit breakers The short-circuit setpoint (the current value at which tripping is initiated) can be indicated either in amperes or as a multiple of the rated current. There are settings:

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

For example, with the rated current of the machine In = 200 A, with a setting of 7 In, tripping will occur when the overcurrent reaches a value of 7 200 = 1400 A.

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

The limit values from rated current In, at which contact divergence will occur.

Advantages:

simplicity of design;

Flaws:

creates a magnetic field;
triggers instantly, without delay.

Time delay means ensuring selectivity. Selectivity or selectivity is achieved when the input circuit breaker recognizes a short circuit and passes it for a specified time. This time is enough for the downstream to trigger protective device. In this case, not the entire object is disabled, but only the damaged branch.

Devices with a time delay or selective - application category B (all automatic devices with an electronic or semiconductor release).
Instantaneous or non-selective devices - application category A (virtually all circuit breakers with an electromagnetic tripping device).

Thermomagnetic or combined release

A series connection of a thermal and electromagnetic release is often used. Depending on the manufacturer, this linking of two devices is called combined or thermomagnetic release. The phrase “thermomagnetic release” is often used in foreign catalogs and literature.

Phenomena caused by overcurrents

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

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

In case of overload, the determining factor remains overheating of the conductive parts.

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 breakdown individual parts 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 (the distances between the conductive parts of the poles are reduced).

A magnetic field

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

Thermal stress (overheating)

When any current with strength I flows through a conductor, its core heats up, which can lead to fires or damage to the insulation.
When overcurrents occur, overheating is of current importance if the short circuit is not blocked, allowing it to reach maximum values.

To ensure that all equipment in the home or workplace is protected from voltage surges electric current you need to install special circuit breakers. They will be able to detect a surge and quickly react to it by disconnecting the entire system from the electricity supply. A person cannot do this on his own, but a certain type of machine 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. This indicator will indicate how quickly the device will respond to a power surge. It has several markings:

A– used for super sensitive types of machines. They instantly detect a surge in the network and also react to it instantly. Most often they are used in production to protect expensive equipment. They are practically not suitable for household purposes.

IN– such markings are applied to those types of circuit breakers that respond with a slight delay. Manufacturers of expensive household appliances install them to protect the device itself. If a minor failure occurs, the device reacts to it itself and does not turn off the entire network in the house.
WITH The markings are those machines that are capable of turning off the household network when the voltage increases or decreases significantly. If the jump is small, the device may turn off for a while, but then return to normal operation.
Machine with markings D installed only in the panel that connects the house or apartment to the general system. Its sensitivity to voltage surges is minimal, so it is exclusively a backup option. If the voltage drop is very large, then the entire house or apartment is disconnected from the electrical network.

Classification of machines

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

Current type

In relation to this characteristic, machines are divided into:

For operation on AC power;
For operation in a DC network;
Universal models.

Everything is clear here and no additional explanation is needed.

Based on rated current

The value of this characteristic will determine in the network what maximum value the circuit breaker can operate with. 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 what voltage it can work with this type automatic switches. Some can operate on a network with a voltage of 220 or 380 Volts - these are the most common options for household use. But there are machines that will cope well with higher rates.

By ability to limit the flow of electricity

According to this characteristic, the following are distinguished:

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

Other characteristics

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

By structure they are distinguished:

Air;
Modular;
Molded case circuit breakers.

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

Automatic machines also have a drive, which can be manual, connected to a motor or a spring. Switches differ in the presence of free contacts and in the method of connecting conductors.

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

IP protection;
From mechanical impact;
Current conductivity 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, using a lever, latch, spring or rocker, can instantly disconnect the network from the supply of electricity. Types of circuit breakers are distinguished by the type of release. There are:

Automatic switch with magnetic release - responds to surges instantly. Well suited for networks where short circuits occur frequently. The release is represented by a solenoid with a movable core. During the jump, the core is retracted and the circuit opens. Reacts in a split second.
Thermal switch – protects against overload electrical network. 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 supply of electricity. These types of machines are capable of responding from a few seconds or up to 1 minute to excess voltage. It all depends on what indicators the device is designed for.

Circuit breakers are much more cost effective 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 replacing it may take a long time.

infoelectrik.ru

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

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

Electric tomatoes combine two devices: a regular switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit if the threshold current value is exceeded. Circuit breakers, like everyone else electrical devices, also have different varieties what divides them into certain types. Let's take a look at the main classifications of circuit breakers.

1" Classification of machines by number of poles:

a) single-pole circuit breakers

b) single-pole circuit breakers with neutral

c) two-pole circuit breakers

d) three-pole machines

e) three-pole circuit breakers with neutral

e) four-pole machines

2" Classification of automatic machines according to the type of releases.

In design various types Automatic circuit breakers usually include 2 main types of releases (breakers) - electromagnetic and thermal. Magnetic circuit breakers are used for electrical protection against short circuits, while thermal circuit breakers are intended mainly to protect electrical circuits against a certain overload current.

3" Classification of automatic machines according to tripping current: B, C, D, (A, K, Z)

GOST R 50345-99, according to instantaneous tripping current, automatic machines 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 up to 10 In inclusive

B) type “D” - over 10 In to 20 In inclusive

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

4" Classification of machines 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; 10; 16; 20; 25; 32; 40; 63; 100; 160; 250; 400; 630; 1000; 1600; 2500; 4000; 6300 A. Automatic machines are also additionally produced with rated currents of the main electrical circuits of the automatic machines: 1500; 3000; 3200 A.

5" Classification according to the presence of current limitation:

a) current-limiting

b) non-current limiting

6" Classification of automatic 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 time delay characteristics:

a) without time delay

b) with a time delay independent of current

c) with a time delay inversely dependent on the current

d) with a combination of the specified characteristics

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

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

a) with rear connection

b) with front connection

c) with combined connection

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

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

electrohobby.ru

Automatic safety switches: classification and differences

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

Modular AV. These devices are installed in household networks in which negligible currents flow. Typically have 1 or 2 poles and a width that is a multiple of 1.75 cm.

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

There is another type of circuit breaker for protecting the electrical network - differential. We do not consider them separately, since such devices are ordinary circuit breakers that include an RCD.

Types of releases

Releases are the main operating components of the automatic circuit breaker. 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, differing from each other in the principle of tripping:

Electromagnetic.
Thermal.

Electromagnetic type releases ensure almost instantaneous operation of the circuit breaker and de-energization of a section of the circuit when a short circuit overcurrent occurs in it.

They are a coil (solenoid) with a core that is drawn inward under the influence of a large current and causes 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 circuit breaker, the plate begins to heat up and, bending to the side, touches the disconnecting element, which trips and de-energizes the circuit. The time it takes 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 addition 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 the help of which you can not only turn off, but also turn on the AV, without even going to the distribution board.

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.

Selecting a device for a circuit based on their number is not at all difficult; you just need to know where they are used Various types AB:

Single-pole circuits are installed to protect lines that include sockets and lighting fixtures. They are mounted on the phase wire without touching the neutral wire.
The two-terminal network must be included in the circuit to which it is connected Appliances with sufficiently high power (boilers, washing machines, electric stoves).
Three-terminal networks are installed in semi-industrial networks, to which devices such as borehole pumps or auto repair shop equipment.
Four-pole AVs allow you to protect electrical wiring with four cables from short circuits and overloads.

The use of machines of different polarities is shown 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 exceeding 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 AVs work instantly, while others will take some time.

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

A. Switches of this type are the most sensitive and react instantly to increased load. They are practically not installed in household networks, using them to protect circuits that include high-precision equipment.
B. These machines operate when the current increases with a slight delay. They are usually included in lines with expensive household appliances (LCD TVs, computers and others).
C. Such devices are the most common in household networks. They are turned off not immediately after increasing the current strength, but after some time, which makes it possible to normalize it with a slight difference.
D. The sensitivity of these devices to increasing current is the lowest of all types listed. They are most often installed in shields at the line approach to the building. They provide security for apartment automatic 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, and therefore can provide the most protection to the circuit. Based on this logic, you can connect a machine to any network air type, and all problems will be solved. However, this is not at all true.

To protect circuits with various parameters It is necessary to install devices with appropriate capabilities.

Errors in the selection of AB are fraught with unpleasant consequences. If you connect a high-power protective device to a regular household circuit, it will not de-energize the circuit, even when the current significantly exceeds what the cable can withstand. The insulating layer will heat up and then begin to melt, but no shutdown will occur. The fact is that the current strength destructive to the cable will not exceed the AB rating, and the device will “consider” that emergency situation did not have. Only when the melted insulation causes a short circuit will the machine turn off, but by then a fire may already have started.

We present a table that shows the ratings of machines for various electrical networks.

If the device is designed for less power than what the line can withstand and which the connected devices have, the circuit will not be able to operate normally. When you turn on the equipment, the AV will constantly knock out, and ultimately, under the influence of high currents, it will fail due to “stuck” contacts.

Visually about the types of circuit breakers in the video:

Conclusion

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

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