Classification of automatic machines according to tripping current. Circuit breakers. Types, characteristics, calculation of circuit breaker. Class A devices

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. Electrical circuit breakers combine two devices: a regular switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit if the threshold current value is exceeded. Circuit breakers, like everyone else electrical devices, also have different varieties, 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.

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

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

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

A) type “B” - over 3 In to 5 In inclusive (In is the rated current)

b) type “C” - over 5 In up to 10 In inclusive

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

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

4" Classification of machines according to the type of current in the circuit: constant, variable, both.

Rated electric currents for the main circuits of the release are selected from: 6.3; 10; 16; 20; 25; 32; 40; 63; 100; 160; 250; 400; 630; 1000; 1600; 2500; 4000; 6300 A. Automatic machines are also additionally produced with rated currents of the main electrical circuits of the automatic machines: 1500; 3000; 3200 A.

5" Classification according to the presence of current limitation:

a) current-limiting

b) non-current limiting

6" Classification of automatic machines by types of releases:

A) with overcurrent release

b) with independent release

c) with minimum or zero voltage release

7" Classification of machines according to time delay characteristics:

A) without time delay

b) with a time delay independent of current

c) with a time delay inversely dependent on the current

d) with a combination of the specified characteristics

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

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

A) with rear connection

b) with front connection

c) with combined connection

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

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

P.S. Everything has its own varieties. After all, if there was only one thing in its only copy, it would be, at a minimum, simply boring and too limited! The good thing about the variety is that you can choose exactly what best suits your needs.

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 machine guns

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 of the old shields in the entrances residential buildings These are exactly what they cost. However, they are quite reliable and are still in use today.
Modern variations allow additional functions, for example, 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 automatic switches 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 eyelet on top 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

It's about about electromagnetic and thermal releases - unique mechanisms for automatically interrupting the circuit. When heated by an unacceptably high current passing through it, a bimetallic plate 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 can be one-, two-, three- and four-pole (this applies to household 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 household needs they use machines with indicators of 6.3, 10, 16, 25, 32, 40, 63, 100 and 160 A (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 electric current, which will be connected to the circuit “guarded” 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 must be a protective grounding or grounding wire.

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 in this case It is urgent to change the circuit breaker to 25 or even 32 A.

Circuit breakers are devices that provide protection for wiring in short circuit conditions when connecting a load with values exceeding the established values. They should be selected from special attention. It is important to consider the types of circuit breakers and their parameters.

Vending 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 possible excess current values. Different types circuit breakers have their own marking - it is easy to understand how quickly the equipment will respond to excess current values to the network. Some switches respond instantly, while others activate over a period of time.

A is a marking that is affixed to the most sensitive equipment models. Automatic machines of this type immediately register the fact of overload and promptly respond to it. They are used to protect equipment characterized by high accuracy, but it’s almost impossible to meet them in everyday life
B is a characteristic possessed by 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 is a characteristic of machines that are most widely used in everyday life. The equipment begins to function with a slight delay, which is sufficient for a delayed response to registered network overloads. The network is switched off by the device only if it has a fault that really matters
D - characteristic of switches with minimal sensitivity to excess current. Basically, such devices are used to supply electricity to a building. They are installed in panels and control almost all networks. Such devices are chosen as a backup 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 part

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 under any conditions, even if the established values are exceeded.

Types of machines

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

Rated breaking capacity - we are talking about the resistance of the switch contacts to the effects of high currents, as well as to conditions in which deformation of the circuit occurs. Under such conditions, the risk of burning increases, which is neutralized by the appearance of an arc and an increase in temperature. The higher quality and durable the equipment is made of, the higher its corresponding capabilities are. Such switches are more expensive, but their characteristics fully justify the price. Switches last a long time and 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 production stage of the equipment, and are not regulated during its use. This characteristic allows you to understand how strong overloads the device can withstand, the period of time it operates in such conditions
Setpoint - usually this indicator is displayed as a marking on the equipment body. We are talking about maximum current values in non-standard conditions, which, even if switched off frequently, will not have any effect on the functioning of the device. The setting is expressed in current units, marked in Latin letters and digital values. The numbers, in this case, reflect the denomination. Letters can be seen in the markings of only those machines that are manufactured in accordance with DIN standards

Installation of protective equipment is an important stage in the construction of electrical networks. In the event 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 current value is associated with a short circuit that occurs during the operation of faulty equipment.

To avoid the risk of fire and damage to wires, various types of electrical circuit breakers are used, depending on the parameters of the electrical devices used in conjunction with them.

Operating principle and varieties

The operating principle 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. Electrical 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.

Based on their type and parametric values, automata are divided into:

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

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

Regardless of their characteristics, the operating principle of all switches is identical. To connect the machine to electrical network it is necessary to set the control switch to the “on” position. The current entering the switch is supplied 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 linear thermal expansion. The current from the plate arrives at the output terminal and then enters the electrical circuit. The plate and solenoid are called releases.

Current release - important element designs, it can be:

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

There are two conditions under which the electrical switch will trip to disconnect 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. As the power on the line increases, the current flowing through the electrical machine increases, exceeding the operating 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 stops. The amount of current at which the plate breaks the contact is adjusted at the factory using an adjustment screw. After the plate cools, it returns to its previous shape and contact appears again.

In short circuit mode, the current increases very quickly, and the magnetic field it creates in the solenoid sets the core in motion. The core acts on the release, and the electrical circuit is broken, and an arc appears. The appearance of an arc has a negative impact on internal parts machine, so they use a device to extinguish it. The arcing chamber is made of plates located parallel to each other, through which the arc is dissipated.

Thus, the main structural parts can be noted:

current terminals;
release:
control lever;
release adjusting screw;
arc suppression 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 pins from one to four. The design of a single-pole switch is no different from a multi-pole one, only in the second case, when 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 phase wire break; the neutral one is connected directly through the block; its use as an input circuit breaker is not recommended. For installation at the input, two-pole circuit breakers are used; the phase and neutral wires are simultaneously connected to them. For use in a three-phase network, a three-pole circuit breaker is used as an input circuit breaker. To protect a four-phase electrical network, for example, a star-connected motor, a four-phase circuit breaker is used. In this case, three phase and one neutral wires are connected.

The usual scheme for constructing a defense on electrical switches comes down to installing an input circuit breaker with the required number of poles. After it, single-pole ones are installed - one for each group. In this case, the rated current of a single-pole circuit breaker is 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 passed through the machine to the rated value. Depending on the value of the ratio, the sensitivity of the machine is determined, which is characterized by the number of false positives. There are various types of slot machines. They are marked with letters of the Latin alphabet. The most widely used switches are those marked B, C and D.

Electrical machines with characteristic B switch off within 5-20 seconds. In this case, the current value can exceed the rated value by five times. These models have become widespread in household premises. Marking C means shutdown interval 1−10 seconds, with a tenfold load. Class D circuit breakers are used to protect engines. The operating current exceeds the rated current by 14–20 times.

Rated current

Indicates the amount of current that can pass through an electrical circuit breaker without tripping it. Available in strictly defined values 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 amount of power 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 circuit breakers for use are 6A, 10A and 16A. Automatic machines with a nominal value of 20A, 25A, 32A are used in apartments as input ones, that is, two-pole.

Location and accommodation

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

The most popular is the DIN rail mounting. Typically, such a rail is installed in the shield. Electrical switches Structurally, they have special grooves into which the rail is inserted.

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

Inscriptions are made on the control lever 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:

This famous brands, producing any type of automatic machines. They differ high quality housing, long service life and high mechanical strength. Often, protective covers are additionally installed on them. These manufacturers make their devices from high-quality materials. Their quality is confirmed by certificates and the warranty period provided by manufacturers for their products.

At 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 determine the majority technical issues. Let's look at what is meant by certain parameters indicated on the label.

Abbreviation used.

Device markings contain all the necessary information describing the main characteristics of circuit breakers (hereinafter referred to as AB). What they mean will be discussed below.

Time-current characteristic (VTC)

Using this graphical display, you can get a visual representation of the conditions under which the circuit power-off mechanism will be activated (see Fig. 2). On the graph, the time required to activate the AB is displayed as a vertical scale. The horizontal scale shows the I/In ratio.

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

The permissible excess of the standard current determines the type of time-current characteristics for releases in devices that perform automatic shutdown. In accordance with current regulations (GOST P 50345-99), each type is assigned a specific designation (from Latin letters). The 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 excess;
“B” - from 3 to 5;
“C” - 5-10 times more than standard;
“D” - 10-20 times excess;
"K" - from 8 to 14;
"Z" - 2-4 more than standard.

Figure 3. Basic activation parameters for various types

notice, that this schedule fully describes the conditions for activation of the solenoid and thermoelement (see Fig. 4).

Taking into account all of the above, we can summarize that the main protective characteristic of an AV is due to the time-current dependence.

List of typical time-current characteristics.

Having decided on the labeling, let's move on to considering the various types of devices that meet a certain class depending on the characteristics.

Characteristic type "A"

AB thermal protection of this category is activated when the ratio of the circuit current to the rated current (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 becomes shorter. Activation of electromagnetic protection occurs when the nominal value is doubled, the response speed is 0.05 seconds.

This type is installed in circuits not subject to short-term overloads. As an example, we can cite circuits based on semiconductor elements, when they fail, the excess current is insignificant. This type is not used in everyday life.

Characteristic "B"

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

These 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, its permissible overload is higher than that of the two previous types. When the normal operating mode is exceeded five times, the thermocouple 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 the norm by ten times.

These AVs are designed to protect an 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 your home, it is recommended to choose this type.

Legrand three-pole circuit breaker

Characteristic "D"

ABs of this type are characterized by high overload characteristics. Namely, ten times the norm for the thermoelement and twenty times for the solenoid.

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

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

Characteristic "K"

For such AVs, activation of the solenoid mechanism is possible when the current load is 8 times higher, and is guaranteed to occur when there is a twelve-fold overload of the normal mode (eighteen-fold for constant voltage). Load disconnection time is no more than 0.02 seconds. As for the thermoelement, its activation is possible when it exceeds 1.05 from the standard mode.

Scope of application: circuits with inductive loads.

Characteristic "Z"

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

This subtype is used for connecting electronic devices.

Characteristics "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 circuits, this is quite enough to connect Electrical engine. Figure 9 shows such a device (c).

Normal operation current

This parameter describes the maximum permissible 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 products as an example).

Thermal parameters

This term refers to the operating conditions of the thermoelement. This data can be obtained from the corresponding time-current graph.

Ultimate breaking capacity (UCC).

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

Rice. 5. Device from Schneider Electric

Current limiting categories

This term is used to describe the ability of an AV to trip a circuit before the short-circuit current in it reaches its maximum. The devices are produced with current limiting of three categories, depending on the load disconnection time: