Main technical characteristics of automatic switches. Types and types of circuit breakers and their characteristics

In practical application, it is important not only to know the characteristics of circuit breakers, but also to understand what they mean. Thanks to this approach, you can decide on most technical issues. Let's look at what is meant by certain parameters indicated on the label.

Abbreviation used.

Device marking contains all the necessary information describing the main characteristics of circuit breakers (hereinafter AB). What they mean will be discussed below.

Time-current characteristic (VTH)

With this graphic display, you can get a visual representation under what conditions the circuit power-off mechanism will be activated (see Fig. 2). On the graph, the time required for AV activation is displayed as a vertical scale. The horizontal scale shows the I/In ratio.

Rice. 2. Graphical display of the time and current characteristics of the most common types of machines

Permissible excess of the nominal current, determines the type of time-current characteristics for releases in devices that perform automatic shutdown. In accordance with the current regulations (GOST P 50345-99), each type is assigned a specific designation (from Latin letters). Permissible excess is determined by the coefficient k=I/In, for each type the values ​​​​established by the standard are provided (see Fig. 3):

• "A" - maximum - three times the excess;
• "B" - from 3 to 5;
• "C" - 5-10 times more than regular;
• "D" - 10-20 times excess;
• "K" - from 8 to 14;
• "Z" - 2-4 more than regular.

Figure 3. Basic activation parameters for different types

Note that this graph fully describes the conditions for activation of the solenoid and thermoelement (see Fig. 4).

Considering all of the above, it can be summarized that the main protective characteristic of the AV is due to the time-current dependence.

List of typical time-current characteristics.

Having decided on the marking, let's move on to the consideration of various types of devices that correspond to a certain class, depending on the characteristics.

Characteristic type "A"

Thermal protection AB of this category is activated when the ratio of circuit current to nominal (I / I n) exceeds 1.3. Under these conditions, shutdown will occur after 60 minutes. As the rated current is further exceeded, the tripping time is reduced. The activation of electromagnetic protection occurs when the nominal value is doubled, the response speed is 0.05 sec.

This type is installed in circuits not subject to short-term overloads. As an example, we can cite circuits on semiconductor elements, in case of failure of which, the excess current is negligible. In everyday life, this type is not used.

Characteristic "B"

The difference between this type and the previous one lies in the operating current, it can exceed the standard one from three to five times. At the same time, the solenoid mechanism is guaranteed to be activated at a five-fold load (power-off time - 0.015 sec.), The thermoelement - three times (it will take no more than 4-5 seconds to turn off).

Such types of devices have found application in networks that are not characterized by high inrush currents, for example, lighting circuits.

Characteristic "C"

This is the most common type, and its allowed overload is higher than the previous two types. When the normal mode is exceeded five times, the thermoelement is triggered, this is a circuit that turns off the power supply within one and a half seconds. The solenoid mechanism is activated when the overload exceeds ten times the norm.

These AB are designed to protect the electrical circuit in which a moderate inrush current may occur, which is typical for a household network, which is characterized by a mixed load. When buying a device for the home, it is recommended to opt for this type.

Three-pole machine Legrand

Characteristic "D"

For AB of this type, high overload characteristics are characteristic. Namely, ten times the norm for the thermoelement and twenty times for the solenoid.

Such devices are used in circuits with high starting currents. For example, to protect starting devices of asynchronous electric motors. Figure 9 shows two devices of this group (a and b).

Figure 9. a) VA51-35; b) BA57-35; c) BA88-35

Characteristic "K"

For such ABs, activation of the solenoid mechanism is possible when the current load is exceeded by 8 times, and is guaranteed to occur when there is a twelvefold overload of the normal mode (eighteenfold for constant voltage). Load off time no more than 0.02 sec. As for the thermoelement, its activation is possible when 1.05 of the normal mode is exceeded.

Scope of application – circuits with inductive load.

Characteristic "Z"

This type is distinguished by a small allowable excess of the nominal current, the minimum limit is two times the standard one, the maximum is four times. The thermoelement response parameters are the same as for AB with characteristic K.

This subspecies is used to connect electronic devices.

Characteristic "MA"

A distinctive feature of this group is that a thermoelement is not used to disconnect the load. That is, the device only protects against short circuit, this is quite enough to connect an electric motor. Figure 9 shows such a device (c).

Normal operation current

This parameter describes the maximum allowable value for normal operation, if it is exceeded, the load shedding system will be activated. Figure 1 shows where this value is displayed (using IEK as an example).

Thermal parameters

This term refers to the conditions for the operation of a thermoelement. These data can be obtained from the corresponding time-current graph.

Ultimate breaking capacity (PKS).

This term refers to the maximum allowable load value at which the device can open the circuit without loss of performance. In Figure 5, this marking is indicated by a red oval.

Rice. 5. Schneider Electric device

Categories of current limiting

This term is used to describe the ability of an AB to break a circuit before the short circuit current in it reaches its maximum. Devices are produced with current limiting of three categories, depending on the load off time:

1. 10 ms. and more;
2. 6 to 10 ms;
3. 2.5-6ms.

Note that ABs belonging to the first category may not have the appropriate marking.

A small life hack on how to choose the right switch for your home

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

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

Classification

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

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

Types (kinds)

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

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

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

Distinctive design features

Automatic devices consist of the following units:

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

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

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

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

Modular designs

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

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

VA series - industrial switches

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

Important features of this series include:

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

AP series

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

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

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

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

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

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

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

Rice. one.

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

Rice. 2. Distribution board with automatic machines

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

Rice. 3. AE series circuit breaker

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

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

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

Rice. 4.

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

Rice. 5. Internal

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

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

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

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

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

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

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

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

Table 1. Types of machines

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

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

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

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

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

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

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

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

Automatic machines of different types

Characteristics of machines

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

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

All parameters of circuit breakers are written on the front

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

Types of machines

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

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

Installation of protective equipment is an important stage in the construction of electrical networks. In the event of the occurrence of large currents, heating occurs, causing the melting of the insulating layer of the conductor. This situation leads to a fire. A sharp increase in the magnitude of the current is associated with a short circuit that occurs during the operation of faulty equipment.

In order to avoid the threat of fire and damage to wires, various types of electric machines are used, depending on the parameters used in conjunction with electrical devices.

Principle of operation and varieties

The principle of operation of electrical switches is to break the electrical circuit when a short circuit occurs. Or exceeding the permissible power for which the electrical network is designed. Electric circuit breakers are always located at the beginning of the protected section of the circuit. In this case, the type of connected load does not matter.

According to their form and parametric values, automata are divided into:

• by the number of poles;
• according to the time-current characteristic;
• by rated current.

It is also necessary to note the current limiting class. This value is characterized by the speed of the device's response to an emergency situation. The division is into three classes. For domestic use, the third class is used.

Regardless of their characteristics, the principle of operation for all switches is identical. To connect the machine to the electrical network, it is necessary to set the control switch to the "on" position. The current flowing to the switch is fed through the input terminal to the solenoid coil, and from it to the bimetallic plate. The plate is a strip of two pressed metals with different coefficients of thermal linear expansion. The current from the plate comes to the output terminal and then enters the electrical circuit. The plate and solenoid are called releases.

Current release- an important design element, it can be:

• electromagnetic (solenoid);
• thermal (bimetallic plate);
• combined (combination of thermal and electromagnetic);
• independent (remotely acting on the switch, it turns off).

There are two conditions under which the electrical switch will trip to open the line: overload mode and short circuit mode.

The principle of operation in overload mode is based on the ability of a bimetallic strip to bend under the influence of heat. With an increase in power to the line, the current flowing through the electric machine increases, exceeding the working value switch. As a result, the release heats up, its plate bends, and the contact breaks. Accordingly, the electrical circuit is broken. The current supply is stopped. The amount of current at which the plate breaks the contact is set at the factory with an adjustment screw. After the plate has cooled, it returns to its previous shape, and the contact appears again.

In the short circuit mode, the current increases very quickly, the magnetic field formed by it in the solenoid drives the core. The core acts on the release, and the electrical circuit breaks, and an arc appears. The appearance of an arc negatively affects the internal parts of the machine, therefore, a device for extinguishing it is used. The arc chute is made of plates parallel to each other, passing through which the arc dissipates.

Thus, the main structural parts can be noted:

• current terminals;
• release:
• control lever;
• release adjusting screw;
• arc chamber.

Number of poles

The number of poles indicates how many wires can be passed through the switch at the same time. There are devices with the number of outputs from one to four. The device of a single-pole switch is no different from a multi-pole one, only in the second case, when the passage of electric current several chains are broken at the same time.

Single-pole devices are more often used in domestic conditions and are placed in a break in the phase wire, the zero one is connected directly through the block, as an introductory machine, its use is not recommended. For installation at the entrance, two-pole circuit breakers are used, the phase and neutral wires are connected to them at the same time. For use in a three-phase network, a three-pole machine is already used as an input. To protect a four-phase electrical network, for example, a star-connected motor, a four-phase automatic machine is used. In this case, three phase and one neutral wire are connected.

The usual scheme for building protection on electrical switches comes down to installing an input automaton of the required number of poles. After it, single-pole ones are installed - one for each group. In this case, the value of the rated current of a single-pole machine is already calculated based on the parameters of the group to which it is connected. Its value is chosen less than the input value.

Time-current characteristic

This parameter indicates the ratio of the actual current flowing through the machine to the nominal value. Depending on the value of the ratio, the sensitivity of the automaton is determined, which is characterized by the number of false positives. There are different types of machines. They are marked with letters of the Latin alphabet. The most common switches are labeled B, C and D.

Electric machines with characteristic B are switched off within 5-20 seconds. In this case, the current value can exceed the nominal value by five times. These models are widely used in domestic premises. Marking C means switching off interval 1-10 seconds, while the load is ten times the value. Class D circuit breakers are used to protect engines. The operating current exceeds the nominal by 14−20 times.

Rated current

Indicates the amount of current that can pass through an electric machine without it tripping. Strictly defined values ​​\u200b\u200bare produced from 1 to 63 amperes. There are 12 values ​​in total: 1A, 2A, 3A, 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A.

The choice of rated current depends on the power value that the wiring can withstand without damage. This value is determined by the cross section of the wire and the material of its manufacture. In homes, the most popular machines for use are 6A, 10A and 16A. Automatic machines with a nominal value of 20A, 25A, 32A are used in apartments as introductory, i.e., two-pole.

Location and accommodation

The method of placement (whether it is a single-phase electric machine or another type) is strictly vertical. The fixed part of the control lever must be on top, i.e. the device is switched on by switching from bottom to top. Devices are placed in accessible places, and the possibility of their mechanical damage is excluded.

DIN rail mounting is the most popular. Usually such a rail is installed in the shield. Electrical switches structurally have special grooves into which the rail is inserted.

What are the machines, how are they marked - you need to know this information in order to choose the right device. Regardless of the manufacturer and type of electric machines, they are always marked on the front side. Marking is carried out according to a single scheme. It includes an indication of all the main parameters:

On the control lever, inscriptions are made indicating the set position - “on.” and "off" or "1" and "0".

Leading brands and manufacturers

The leaders in the production of circuit breakers are the following brands:

These are well-known brands that produce any kind of electric machines. They are characterized by high quality housing, long service life and high mechanical strength. Often, protective covers are additionally installed on them. These manufacturers produce their devices from solid materials. Their quality is confirmed by certificates and a warranty period given by manufacturers for their products.