Automatic switches. Types, characteristics, calculation of circuit breaker

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Overloads in electrical circuits are common. To protect electrically powered devices from such voltage surges, circuit breakers were invented. Their task is simple - to break the electrical circuit if the voltage exceeds the nominal limits.

The first such devices were the familiar traffic jams, which are still installed in some apartments. As soon as the voltage jumps above 220 V, they are knocked out. Modern types circuit breakers are not only plugs, but also many other varieties. Their great feature is that they can be reused.

Classification

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

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

Types (species)

GOST R 50345-2010 divides circuit breakers into the following types (the division is based on sensitivity to overloads), marked with letters of the Latin alphabet:

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

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

Distinctive design features

Automatic devices consist of the following components:

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

The contact system can be multi-stage (one-, two- and three-stage). It consists of arc extinguishing, main and intermediate contacts. Single-stage contact systems are mainly made from cermets.

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

For anyone circuit breaker the limiting current is found. Thanks to the protection of the machine, it cannot cause damage. With huge overloads of such current, the contacts can either burn out or even weld to each other. For example, for the most common household appliances with an operating current from 6 A to 50 A, the maximum current can range from 1000 A to 10,000 A.

Modular designs

Designed for low currents. Modular circuit breakers consist of separate sections (modules). The entire structure is mounted on a DIN rail. Let's take a closer look at the design of a modular switch:

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

BA series – industrial switches

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

Among the important characteristics of this series are:

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

AP series

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

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

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

When the air humidity is 90%, the temperature should not exceed 20 degrees.
The operating temperature ranges from -40 to +40 degrees.
Vibration at the mounting location should not exceed 25 Hz.

It is strictly prohibited to work in an explosive environment that contains gases that destroy metal and windings, near the pure energy of heating devices, water flows and splashes, in places with conductive dust.

The variety of automatic switches allows you to easily select a device for an apartment or house. It is best to invite a specialist to install it.

Circuit breakers are devices whose task is to protect an electrical line from exposure to 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 material we will tell you what types of circuit breakers are and their characteristics.

Automatic protective switches: classification and differences

Beyond Devices protective shutdown, 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 AB. 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 different types of AVs are used:

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 household appliances with sufficiently high power are connected (boilers, washing machines, electric stoves).
Three-terminal networks are installed in semi-industrial networks, to which devices such as well pumps or auto repair shop equipment can be connected.
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 connected to 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 different parameters, it is necessary to install devices with the 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 there wasn't. Only when the melted insulation causes a short circuit will the machine turn off, but by then a fire may have already 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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Definition of release

Releases divide by two conditional groups:

circuit protection releases;

Under overcurrent

Overload current
Short circuit current (SC)

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

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 taken 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 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 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 = 100A, the conditional non-trip current is 105A.
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.

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

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

Advantages:

a varied selection of settings needed by the user;
high accuracy of execution of a given program;
performance indicators and reasons for operation;
logic selectivity with upstream and downstream switches.

Cons:

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

Shunt release

Using an independent release(NR) carry out remote control specific circuit breaker. Voltage from the control circuit is applied to the independent release coil, a magnetic field is created, the core moves, and affects the free release mechanism.
The independent release can be designed for alternating or direct current (the manufacturer indicates the voltage range).
HP allows operating voltage fluctuations in the range from 0.7 to 1.2 from Un. Its operating mode is short-term.
After the independent release has tripped, you need to go to the switchboard and manually reset 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 use– remote shutdown of the switching device that controls the ventilation system in the event of a fire. When a fire is detected, the ventilation is turned off so that air (oxygen) is not forced 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 (the distances between conductive parts are reduced).

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.

Rated current

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

A small disclaimer:

rated current of a circuit breaker - the current for which the current-carrying elements are designed;
rated current of a thermal release - the current to which the release devices are adjusted (it does not cause operation).

In what follows, by rated current we mean the rated current of the thermal release.
The rated current is one of the defining characteristics of a circuit breaker, since overcurrents are calculated relative to this value, at which the releases cause the contacts to open. To select the correct 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 known which device consumes how much power. The total power is obtained and, as a first approximation, the following relation is used:
P = U · I, where P is the power consumption in watts, U is the network voltage in volts, I is the network 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 = P 2 + Q 2 .
In turn:

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

Where ϕ is the angle with which the current lags behind or advances the voltage. To measure the reactive power factor (Cosϕ), phase meters are used.

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

A circuit breaker is characterized by a current that causes instantaneous tripping of the main contact group. This occurs when there is a short circuit that latches and trips the electromagnetic release.

For modular and power circuit breakers, the instantaneous protection characteristic is indicated differently:

modular machines are assigned a protective characteristic: B, C, D;
For power switches, the current value is set in amperes or a multiple of the rated current.

High-speed machines

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

1) according to the principle of flow displacement (performance 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 flow is created by a forced short-circuit current.

2) mechanical latches (locks) t o up to 0.002 s. Switching on is also carried out by a short-term operating 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 forced mode, generated by current KZ.

3) systems with an impact electromagnet - an electromagnet working with high force creates " impact force", exceeding the force of the holding electromagnet and "tears off" the armature, i.e. turns off the switch.

4) a switch with an explosive release - shutdown time 0.001 s - has not become widespread due to its complexity.

5) vacuum switches providing arc extinction t0=0.003-0.007s. Examples 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 time shutdown 0.003s.

b) DC vacuum switch type VPTV-15-5/400 on

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

c) VAB series automatic machine - 28 the most versatile I nom =1.5-6 kA, U=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 on and off of individual circuits or electrical equipment under manual or automatic control.

A high-voltage circuit breaker consists of: a contact system with an arc extinguishing device, current-carrying parts, a housing, an insulating structure and a driving 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 (voltage of the network in which the switch operates);
rated current Inom (current through the switched-on switch, at which it can operate for a long time);
rated interruption current Iо.nom - the highest short-circuit current (rms value) that the switch is capable of disconnecting at a voltage equal to the highest operating voltage under given conditions of recovery voltage and a given cycle of operations;
permissible relative content of aperiodic current in the shutdown current;
If the circuit breakers are designed for automatic reclosing (AR), then the following cycles must be provided:

Cycle 1: O-tbp-VO-180 s-VO; Cycle 2: O-180 s-VO−180 s-VO, where O is the shutdown operation, VO is the operation of switching on and immediate shutdown, 180 is the time period in seconds, tbp is the minimum dead-time pause guaranteed for switches during automatic reclosure (time from extinguishing arc until current appears upon subsequent switching on) For circuit breakers with autorecloser it should be within 0.3-1.2 s, for circuit breakers with autorecloser (high-speed) 0.3 s.

stability under through short-circuit currents, which is characterized by thermal stability currents It and maximum through current
rated switching current - short-circuit current that a switch with a corresponding drive is capable of switching on without welding contacts and other damage at Unom and a given cycle.
own shutdown time - the time interval from the moment the shutdown command is given until the moment the arc-extinguishing contacts begin to diverge.
parameters of recovery voltage at rated shutdown current - speed of recovery voltage, normalized curve, coefficient of excess amplitude and recovery voltage.

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

Definition of release

Releases divide by two conditional groups:

circuit protection releases;
releases performing auxiliary functions.

Trip 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).

To the second group of releases can be distinguished additional devices(they are not included with basic versions of machines, but are supplied only with custom 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 found below

Under overcurrent refers to 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.
Direct action MRI is a maximum current release that 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 R 50345 standard.

cyberpedia.su

Types of switches

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

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

They very quickly recognize emergency situations, 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 contacts in the automatic releases open, which prevents serious consequences in the form of damage to wiring and electrical equipment, which very often leads to fires.

Thermal switch

It consists of a bimetallic plate, 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 begins to increase, it bends and touches the trigger bar, which opens the contacts in the “machine”.

The mechanism operates even with slight excesses of the rated current and an increased response time. If the load increase is short-term, the switch does not trip, so it is convenient to install it in networks with frequent but short-term overloads.

Advantages of a thermal release:

absence of contacting and rubbing surfaces;
vibration stability;
budget price;
simple design.

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

Electronic switch

Its components include:

measuring devices (current sensors);
control unit;
electromagnetic coil (transformer).

At each pole of the electronic circuit breaker there is a transformer that measures the current passing through it. The electronic module that controls the trip processes this information, comparing the obtained result with the specified one. In the event that the resulting indicator is greater 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 that usually occur at the end of the protected circuit.
The working area “instantly” provides protection against high-intensity short circuits.

Pros - a large selection of settings, maximum accuracy of the device to a given plan, the presence of indicators. Cons: sensitivity to electromagnetic fields, high price.

Electromagnetic

This is a solenoid (a coil of wound wire), inside of which there is a core with a spring that acts on the release mechanism. This is an instant action device. As the supercurrent flows through the winding, a magnetic field is generated. It moves the core and, exceeding the force of the spring, acts on the mechanism, turning off the “automatic machine”.

Pros: resistance to vibration and shock, simple design. Cons – forms a magnetic field, triggers instantly.

This is an additional device to automatic releases. With its help, you can turn off both single-phase and three-phase circuit breakers located at a certain distance. To activate the independent release, voltage must be applied to the coil. 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 circuit breakers are used in automation panels in highly ramified power supply devices of many large objects, where control is transferred to the operator's console.

Combination switch

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

The electromagnetic elements in the combination switch provide instantaneous protection against short circuits, and the thermal elements protect against overloads with a time delay. The combined machine is switched off when any of the elements is triggered. During short-term overcurrents, none of the types of protection are triggered.

Semiconductor switch

It consists of alternating current transformers, magnetic amplifiers for direct current, a control unit and an electromagnet that performs the functions of an independent automatic release. The control unit helps set the selected contact release program.

Its settings include:

regulation of the rated current in the device;
setting the time;
triggered when a short circuit occurs;
protective switches against overcurrent and single-phase short circuit.

Pros - a wide choice of regulation for different schemes power supply, ensuring selectivity to series-connected circuit breakers with fewer amperes.

Cons: high cost, fragile control components.

Installation

Many home-grown electricians believe that installing a machine is not difficult. This is fair, but certain rules must be followed. Circuit breaker releases, as well as plug fuses, must be connected to the network so that when the plug of the circuit breaker is turned out, its screw sleeve is without voltage. The connection of the supply conductor for one-way power supply to the machine must be made to the fixed contacts.

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

securing the switched-off device to the electrical panel;
connecting wires without voltage to the meter;
connecting voltage wires to the machine from above;
turning on the machine.

Fastening

We install a DIN rail in the electrical panel. Cutting off right 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 that 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 meter to the machine. We connect one end to the electric meter, the other to the terminals of the release, observing the polarity. We connect the supply phase to the first contact, and the neutral supply wire to the third. Wire cross-section – 2.5 mm.

Connecting voltage wires

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

energomir.biz

Modern electrical network It is impossible to imagine without the necessary means of protection, in particular, a circuit breaker. Unlike outdated fuses, it is designed for reusable protection of networks 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 at the center of this entire structure, the most significant element is the circuit breaker release. The reliability and speed of operation depends on it, so it’s worth comparing all the currently existing varieties.

Comparison

So, one of the first can be called a thermal release. Due to its design, the thermal release operates with a time delay. The greater the current excess, 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 type is classified as instantaneous releases. We are talking about such a concept as an electromagnetic release. It operates in a fraction of a second, which compares favorably with thermal releases. However, the electromagnetic release also has its own peculiarity - operation occurs when the rated current is significantly higher than 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 circuit breaker release. The fast response 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 higher currents.

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

Operating principle

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 connected to it. The circuit breaker release, 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 opens.

Design

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

The design of an electromagnetic release 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 retracted, affecting the opening mechanism.

But the electronic trip unit of the circuit breaker is not based on mechanical impact 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 established characteristics, and if the specified current parameters are exceeded, it gives a signal to shut down. Thus, the electronic release has more flexible settings, allowing you to configure the parameters of the circuit breaker to meet the specific requirements of power network protection.

chint-electric.ru

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 common 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 this type of circuit breaker can operate with. Some can operate on 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 cope well with higher rates.

By ability to limit the flow of electricity

According to this characteristic, the following are distinguished:

Current-limiting - immediately eliminates 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 release switch – 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 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 all electrical devices, also have different varieties, which 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.

The design of various types of circuit breakers usually includes 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 an 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 protective 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 AB. 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

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 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 different types of AVs are used:

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 household appliances with sufficiently high power are connected (boilers, washing machines, electric stoves).
Three-terminal networks are installed in semi-industrial networks, to which devices such as well pumps or auto repair shop equipment can be connected.
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 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 connected to 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 an air-type machine to any network, and all problems will be solved. However, this is not at all true.

To protect circuits with different parameters, it is necessary to install devices with the 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 there was no emergency. Only when the melted insulation causes a short circuit will the machine turn off, but by then a fire may have already started.

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

Visually about the types of circuit breakers in the video:

Conclusion

yaelectrik.ru

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Definition of release

circuit protection releases;
releases performing auxiliary functions.

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 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 or short-circuit release;

one of the ones proposed below replaces the first two; during operation, adjustment is allowed (holding time at overcurrent for РѕР±РµСЃРїРµС‡РµРЅРёСЏ СЃРµР»РµРєС‚РёРІРЅРѕСЃС‚Рё, 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.

Thermal release

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

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

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

Electromagnetic release

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

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

simplicity of design;

creates a magnetic field;
triggers instantly, without delay.

Thermomagnetic or combined release

Semiconductor release

adjustment of the rated current of the machine;
setting the dwell time in the short circuit zone, as well as overload;
response setting when a short circuit occurs;
protection switches against switching currents, against single-phase short circuit;
switch that turns off the time delay during a short circuit (transition from selectivity mode to instantaneous mode).

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

high price;
fragile controls.

Electronic release

a varied selection of settings needed by the user;
high accuracy of execution of a given program;
performance indicators and reasons for operation;
logic selectivity with upstream and downstream switches.

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

Shunt release

Undervoltage release

turns off the switched-on circuit breaker without a 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 restarting when the mains voltage is lower than 0.85 Un.

After the device is triggered, the free release mechanism must be cocked manually if an electromagnetic drive is not installed.

Zero voltage release

causes tripping of the main contacts at a voltage from 0.35 to 0.1 of the rated voltage;
does not turn off the switched-on circuit breaker when the voltage exceeds 0.55 Un;
allows restarting when the voltage is restored to more than 0.85 of the rated voltage.

As in the case of the minimum voltage release, the machine must be manually cocked and then turned on.

Read more about the design of an independent release device, zero and minimum voltage release С‡РёС‚Р°Р№ Р·РґРµСЃСЊ.

Phenomena caused by overcurrents

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

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

www.avtomats.com.ua

Circuit breakers They are not at all like the usual ones, which are installed in each room to turn the lights on and off (Fig. 1). Their task is somewhat different. Circuit breakers are installed in distribution boards and serve to protect the circuit from power surges and non-periodic power outages in certain sections of the electrical network.

Rice. 1.

Slot machines, as they are more 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. Switchboard with automatic machines

There are many types of circuit breakers. Some of them serve only as circuit breakers and protect the network from overload. These 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 panels in the entrances of residential buildings, there are exactly these. However, they are quite reliable and are still in use today.
Modern variations allow additional functions, such as protection against underload currents.

Based on the response time to unacceptable voltage, automatic machines 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 more quickly - for them 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 surface. It is very easy to install the machine on such a mount - just insert it onto the rail until it clicks. You can remove it using a screwdriver by lightly pulling the special tab on top of the circuit breaker. This greatly simplifies the task of installing the machine in the cabinet (Fig. 4).

Rice. 4.

Inside the case is the “filling” of the machine, its main safety devices, of which there can be 2 (Fig. 5).

Rice. 5. Internal

We are talking about electromagnetic and thermal releases - unique mechanisms for automatically interrupting the circuit. A bimetallic plate when heated by a current passing through it is unacceptable high value 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 maintained in place by a stable voltage. As soon as it jumps beyond the nominal limits, the coil literally jumps out of its place, breaking the chain. This method 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

Automatic machines 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 value are most often used. When the voltage increases by one and a half times, the electromagnetic (fast) release is triggered. When the rated voltage is slightly exceeded, the thermal release operates. The shutdown process can last for hours, which greatly depends on the temperature. external environment. However, the machine will react to a change in voltage in any case.

Automatic switches are distinguished by the number of poles. What does it mean? One machine may have several electrical lines independent from each other, which are connected to each other by a common shutdown mechanism (Fig. 7 and 8). Automatic machines come in one-, two-, three- and four-pole types (this applies to domestic use).

Rice. 7. in a plastic box when turned off

Rice. 8. : All lines are triggered simultaneously when tripping, they are connected together using one lever jumper

The circuit breaker has differences in other respects. They differ in the threshold current strength that they pass through themselves. In order for the machine to operate and turn off the power supply in an emergency, it must be configured to a certain sensitivity threshold. This setting is made by the manufacturer, so the numerical value of this threshold is immediately written on the machine. For domestic needs, machines with ratings 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 numbers mean the total power of all electrical consumers that will be connected to the circuit “protected” by the machine.
Machine sensitivity it is necessary to calculate not only the total power of the expected energy consumers, but also the wiring and electrical installation products - sockets and switches.
Table 1 presents the typology of machines.

Table 1. Types of machines

Type	Purpose
A	For breaking long-distance circuits and protecting semiconductor devices
B	For general purpose lighting networks
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 box

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 cable current is assumed for a core temperature of +65 and air temperature of +25 °C. The number of simultaneously laid conductors is up to 4. A number of 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. Table data. 3 are also suitable for three-core cable. In this case, the third core should be a wire protective grounding or zeroing.

Rice. 9. A row of single-pole 16 A circuit breakers. Let’s say that for a separate area in an apartment, for example a kitchen, we have one 6.3 A circuit breaker (it happens, the electricians joked). Using the well-known formula Watt = 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 in such a kitchen it is impossible to turn on even a powerful kettle, not to mention a refrigerator or electric stove - the machine will work instantly and will not allow, in its opinion, unacceptable current to pass through the controlled territory. In this case, it is urgent to change the circuit breaker to 25 or even 32 A.

Every person in general outline knows what the circuit breaker installed in the electrical panel is. Most the population knows at the genetic level when the light in the apartment goes out, gently go and check whether the circuit breaker in the floor switchboard has turned off, and if necessary, turn it on. However, not everyone has an idea about the technical characteristics of these devices, and by what criteria they need to be selected to maintain high performance qualities switchboard operation.

I welcome all friends to the “Electrician in the House” website. Today we will look at a very important, in my opinion, topic, which directly affects the normal operating conditions of automatic protection devices, namely - . Not everyone knows what the symbols and designations on the body of the circuit breaker mean, so let’s decipher the markings and look in detail at what each inscription on the body of the circuit breaker means.

Marking of electrical machines - designations on the body

All circuit breakers have certain technical characteristics. To familiarize yourself with them when choosing a machine, markings are applied to the body, which includes a set of diagrams, letters, numbers and other symbols. Friends will agree that appearance the machine will not be able to say anything about itself and all its characteristics can be recognized only by the applied markings.

The marking is applied on the front (front) side of the machine body with durable, indelible paint, so you can familiarize yourself with the parameters even when the machine is in operation, that is, installed in a distribution panel on a DIN rail and wires are connected to it (no need to disconnect the wires and pull them out). it from the shield to read the markings).

In the picture below you can see several examples, how electrical machines are marked different manufacturing plants. Each of them is clearly marked with different letters and numbers. In this article we will not disassemble industrial protection devices, but will only touch on ordinary household modular circuit breakers. But in any case, the article will be of interest not only to beginners, but also to professionals, “bisons” who deal with this every day, and will also be interested in remembering the basics of their profession.

Decoding the machine markings

To choose the right circuit breaker when purchasing, you should pay attention not only to the appearance and brand of the device, but also to its characteristics. Let's look in order at what characteristics the manufacturer displays on the body of the circuit breaker for its the right choice. Automatic marking provides the following information about yourself for review.

1. Manufacturer (brand) of the circuit breaker

The marking of circuit breakers begins with the logo or name of the manufacturer. The pictures show machines from the most popular brands hager, IEK, ABB, Schneider Electric.

These brands have been represented to the world public for a long time and have proven themselves to be producing quality products throughout their existence. On the case, the manufacturer's name is applied at the very top and is difficult to miss.

2. Linear series of machines (model)

The circuit breaker model usually reflects the device series in the manufacturer's line and represents alphanumeric designation, for example, the SH200 and S200 series machines belong to the manufacturer ABB, and Schneider Electric has Acti9, Nulti9, and Domovoy.

An example of how circuit breakers from Schneider Electric, Hager and IEK are marked.

Often, a series is assigned to a machine to distinguish models by technical characteristics or price category, for example, SH200 are designed for short circuits up to 4.5 kA, less expensive to manufacture and cheaper in cost than S200, designed for 6 kA.

3. Time-current characteristics of the machine

This characteristic is denoted by a Latin letter. In total, there are 5 types of time-current characteristics: “B”, “C”, “D”, “K”, “Z”. But the most common of them are the first three: “B”, “C” and “D”.

Circuit breakers with characteristics of type “K” and “Z” are used to protect consumers where an actively inductive load and electronics are used, respectively.

The most universal, suitable for use in everyday life - characteristic type "C". Most electricians use it to protect electrical wiring. Narrow-profile machines with technical specifications “B” or “D” can only be found in specialized stores and, often, upon request.

Friends, I have a separate article on the topic of current characteristics of machines, please come, read, and get acquainted.

4. Rated current of the machine

After literal meaning there is a number that determines the rating of the circuit breaker. The rating determines the maximum value of current that can continuously flow without tripping the circuit breaker. Moreover, the rated current value is indicated for a certain ambient temperature + 30 degrees.

For example, if rated current of the machine is 16A, then the machine will hold this load and not turn off at an ambient temperature of no higher than +30 degrees. If the temperature is above +30, then the machine can operate at a current of less than 16 A.

If overloads occur in the network, that is, a situation when the load current exceeds the rated current, it reacts to this thermal release circuit breaker. Depending on the frequency of the overload, the time during which the machine will turn off will range from several minutes to seconds. The current at which the thermal release will operate must exceed the nominal value of the machine by 13% - 55%.

When a short circuit occurs in the network, an overcurrent occurs, to which the electromagnetic release circuit breaker. In the event of a short circuit, a working machine must operate within 0.01 - 0.02 seconds, otherwise the electrical wiring insulation will begin to melt with the risk of further ignition.

5. Rated voltage

Immediately below marking on the time-current characteristic machine there is a designation of the rated voltage for which this machine is designed. The rated voltage is displayed in Volts (V/V), and can be constant (“-”) or variable (“~”).

The rated voltage value determines which networks the device is intended for. Voltage marking provides two values for single-phase and three-phase networks. For example, the marking 230/400V~ means that 230 Volts are the voltage of a single-phase network, 400 Volts are the voltage of a three-phase network. The "~" symbol indicates alternating mains voltage.

6. Trip current limit

The next parameter is the limiting shutdown current or as it is also called circuit breaker breaking capacity. This parameter characterizes the short circuit current that the machine can pass through and turn off without losing its functionality (without the risk of failure).

The electrical network is a complex system in which overcurrents often occur due to short circuits. Overcurrents are short-term, but are characterized by large magnitude. Each circuit breaker has a maximum switching capacity that determines the ability to withstand overcurrents and trip.

For modular circuit breakers, the maximum shutdown current value is 4500, 6000 or 10000. The values are indicated in Amperes.

7. Current limiting class

Immediately below the value of the limiting shutdown current on the housing, the so-called current limiting class. The occurrence of overcurrents is dangerous because when they occur, thermal energy is released. As a result, the insulation of the electrical wiring begins to melt.

The circuit breaker will trip when the short circuit current reaches its maximum value. And for the short-circuit current to reach its maximum, it takes some time, and the longer this time, the greater the damage caused to the equipment and insulation of the electrical wiring.

The current limiter promotes accelerated shutdown of the circuit breaker, thereby preventing the short-circuit current from reaching its maximum value. Essentially, this parameter limits the short circuit time.

There are three classes of current limiter, which are marked in a black square. The higher the class, the faster the machine will turn off.

- class – 1 there is no marking, or in other words, machines that do not have a current limiting class on the body belong to the first class. The limit time is more than 10 ms;
- class – 2 limits the time of passage of the short-circuit current within 6-10 ms;
- class – 3 limits the time of passage of the short-circuit current within 2.5-6 ms (the fastest).

8. Connection diagram and terminal designation

Some manufacturers put a connection diagram for the machine on the body to inform the consumer. The connection diagram is an electrical circuit with the designation of thermal and electromagnetic releases. The diagram also shows contacts indicating where the wires are connected.

On single-pole circuit breakers contacts are marked as “1” - upper and “2” - lower. As a rule, the power wire is connected to the upper contact, and the load is connected to the lower contact. By the way, there is a separate article on this topic on how to properly connect the machine. On two-pole circuit breakers, the contacts are marked “1”, “3” - the top one; “2”, “4” - bottom.

And this is what the designation of the circuit and contacts for connecting to a two-pole circuit breaker looks like

Also on two- and four-pole circuit breakers, near the connection diagram you can find a designation in the form of the Latin letter “N”, indicating the terminal for connecting the neutral working conductor. This is important, since not all poles of multi-pole circuit breakers have releases (thermal and electromagnetic).

9. Article

On any side of the machine body there is also information about the product (article number, QR code) provided by the manufacturer, which helps you easily find a specific model in the store catalog.

After reading the above information, it will not be a problem for you, and you can easily choose a security device with the characteristics that suit you.

Friends, if this article was interesting for you, I would be grateful if you share it on social networks. If you have any questions or suggestions, do not hesitate to ask them in the comments, I will try to answer everyone.

Automatic protective switches: classification and differences

Modular AB. 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

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 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 different types of AVs are used:

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 household appliances with sufficiently high power are connected (boilers, washing machines, electric stoves).
Three-terminal networks are installed in semi-industrial networks, to which devices such as well pumps or auto repair shop equipment can be connected.
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 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 connected to 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 an air-type machine to any network, and all problems will be solved. However, this is not at all true.

To protect circuits with different parameters, it is necessary to install devices with the 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 there was no emergency. Only when the melted insulation causes a short circuit will the machine turn off, but by then a fire may have already started.

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

Visually about the types of circuit breakers in the video:

Conclusion

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