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.

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.

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

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).

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.

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

When assembling a switchboard or connecting a new large household appliance, a home master will definitely face such a problem as the need to select circuit breakers. They provide electrical and fire safety, so the right choice of machine is the key to the safety of you, family and property.

What is the machine for?

In the power supply circuit, an automatic machine is installed to prevent overheating of the wiring. Any wiring is designed for the passage of a certain current. If the passed current exceeds this value, the conductor starts to heat up too much. If this situation persists for a sufficient period of time, the wiring begins to melt, which leads to a short circuit. A circuit breaker is installed to prevent this situation.

The second task of the circuit breaker is to turn off the power when a short circuit current (SC) occurs. When closing, the currents in the circuit increase many times and can reach thousands of amperes. So that they do not destroy the wiring and do not damage the equipment included in the line, the circuit breaker must turn off the power as soon as possible - as soon as the current exceeds a certain limit.

In order for the protective circuit breaker to perform its functions properly, it is necessary to correctly select the machine in all respects. There are not so many of them - only three, but each one must be dealt with.

What are automatic protection

To protect the conductors of a single-phase 220 V network, there are single-pole and two-pole disconnecting devices. Only one conductor is connected to single-pole - phase, to two-pole and phase and zero. Single-pole machines are installed on 220 V internal lighting circuits, on socket groups in rooms with normal operating conditions. They are also put on some types of load in three-phase networks, connecting one of the phases.

For three-phase networks (380 V) there are three and four poles. These circuit breakers (the correct name is a circuit breaker) are put on a three-phase load (ovens, hobs and other equipment that runs on a 380 V network).

In rooms with high humidity (bathroom, sauna, swimming pool, etc.), bipolar circuit breakers are installed. They are also recommended to be installed on powerful appliances - on washing machines and dishwashers, boilers, ovens, etc.

It's just that in emergency situations - during a short circuit or insulation breakdown - a phase voltage can get to the neutral wire. If a single-pole device is installed on the power line, it will disconnect the phase wire, and zero with a dangerous voltage will remain connected. So, there is a possibility of electric shock when touched. That is, the choice of the machine is simple - single-pole switches are placed on some of the lines, and two-pole switches on some. The exact amount depends on the network condition.

For a three-phase network, there are three-pole circuit breakers. Such an automatic machine is installed at the entrance and at consumers, to which all three phases are connected - an electric stove, a three-phase hob, an oven, etc. The remaining consumers are equipped with bipolar circuit breakers. They must necessarily disconnect both phase and neutral.

An example of a three-phase network wiring - types of circuit breakers

The choice of the circuit breaker rating does not depend on the number of wires connected to it.

Deciding on a denomination

Actually, from the functions of the circuit breaker, the rule for determining the rating of the circuit breaker follows: it must operate until the current exceeds the wiring capabilities. And this means that the current rating of the machine must be less than the maximum current that the wiring can withstand.

Based on this, the algorithm for choosing a circuit breaker is simple:

• for a specific area.
• See what maximum current this cable can withstand (there is in the table).
• Further, from all the denominations of circuit breakers, we select the nearest smaller one. The ratings of the machines are tied to the permissible continuous load currents for a particular cable - they have a slightly lower rating (there is in the table). The list of ratings looks like this: 16 A, 25 A, 32 A, 40 A, 63 A. From this list, choose the right one. There are denominations and less, but they are practically not used anymore - we have too many electrical appliances and they have considerable power.

Example

The algorithm is very simple, but it works flawlessly. To make it clearer, let's look at an example. Below is a table that indicates the maximum allowable current for conductors that are used for. There are also recommendations regarding the use of machines. They are given in the column "Rated current of the circuit breaker". It is there that we are looking for denominations - it is slightly less than the maximum allowable, so that the wiring works in normal mode.

In the table we find the selected wire section for this line. Let us need to lay a cable with a cross section of 2.5 mm 2 (the most common when laying to medium power devices). A conductor with such a cross section can withstand a current of 27 A, and the recommended rating of the machine is 16 A.

How will the chain work then? As long as the current does not exceed 25 A, the machine does not turn off, everything works in the normal mode - the conductor heats up, but not to critical values. When the load current begins to increase and exceeds 25 A, the machine does not turn off for some time - perhaps these are starting currents and they are short-lived. It turns off if the current exceeds 25 A by 13% for a sufficiently long time. In this case, if it reaches 28.25 A. Then the electric bag will work, de-energize the branch, since this current already poses a threat to the conductor and its insulation.

Power calculation

Is it possible to choose an automatic machine according to the load power? If only one device is connected to the power line (usually it is a large household appliance with a large power consumption), then it is permissible to make a calculation based on the power of this equipment. Also in terms of power, you can choose an introductory machine, which is installed at the entrance to a house or apartment.

If we are looking for the value of the introductory machine, it is necessary to add up the power of all devices that will be connected to the home network. Then the found total power is substituted into the formula, the operating current for this load is found.

After you have found the current, select the value. It can be either a little more or a little less than the found value. The main thing is that its tripping current does not exceed the maximum allowable current for this wiring.

When can this method be used? If the wiring is laid with a large margin (this is not bad, by the way). Then, in order to save money, you can install automatic switches corresponding to the load, and not to the cross section of the conductors. But once again we pay attention that the long-term permissible current for the load must be greater than the limiting current of the circuit breaker. Only then will the choice of circuit breaker be correct.

Choosing a breaking capacity

The selection of a packet box for the maximum allowable load current is described above. But the circuit breaker should also turn off when a short circuit (short circuit) occurs from the network. This characteristic is called the breaking capacity. It is displayed in thousands of amperes - this order can be reached by currents during a short circuit. The choice of a machine for breaking capacity is not very difficult.

This characteristic shows at what maximum value of the short circuit current the machine remains operational, that is, it can not only turn off, but will also work after being turned on again. This characteristic depends on many factors and for accurate selection it is necessary to determine the short-circuit currents. But for wiring in a house or apartment, such calculations are made very rarely, but are guided by the distance from the transformer substation.

If the substation is located near the entrance to your house / apartment, they take an automatic circuit breaker with a breaking capacity of 10,000 A, for all other city apartments, 6,000 A is enough. and a breaking capacity of 4,500 A. The networks here are usually old and short-circuit currents are not large. And since the price increases significantly with increasing breaking capacity, the principle of reasonable economy can be applied.

Is it possible to install bags with a lower breaking capacity in city apartments. In principle, it is possible, but no one guarantees that after the first short circuit you will not have to change it. He may have time to turn off the network, but will be inoperable at the same time. In the worst case, the contacts will melt and the machine will not have time to turn off. Then the wiring will melt and a fire may occur.

Type of electromagnetic release

The machine should operate when the current rises above a certain mark. But the network periodically experiences short-term congestion. They are usually associated with inrush currents. For example, such overloads can be observed when turning on the refrigerator compressor, washing machine motor, etc. The circuit breaker should not trip during such temporary and short-term overloads, because they have a certain delay in operation.

But if the current has increased not because of an overload, but because of a short circuit, then during the time that the circuit breaker “waits”, its contacts will melt. That's why there is an electromagnetic automatic release. It works at a certain current value, which can no longer be an overload. This indicator is also called the cut-off current, since in this case the circuit breaker cuts off the line from the power supply. The magnitude of the tripping current can be different and is displayed by the letters that precede the numbers indicating the rating of the machine.

There are three most common types:

With what characteristic to choose a package? In this case, the choice of a circuit breaker is also based on the remoteness of your household from the substation and the state of the power grid, the choice of a circuit breaker is carried out using simple rules:

• With the letter "B" on the case, they are suitable for summer cottages, houses in villages and towns that receive power through air ducts. They can also be installed in apartments of old houses in which the reconstruction of the house electrical network has not been carried out. These circuit breakers are not always on sale, they cost a little more than category C, but they can be delivered to order.
• Bags with a "C" on the body are the most widely used variant. They are installed in networks with a normal state, suitable for apartments in new buildings or after major repairs, in private houses near the substation.
• Class D is put in enterprises, in workshops with equipment that has high starting currents.

That is, in fact, the choice of a circuit breaker in this case is simple - type C is suitable for most cases. It is available in stores in a large assortment.

Which Manufacturers Should You Trust?

And finally, let's pay attention to manufacturers. The choice of a machine cannot be considered complete if you have not thought about what brand of circuit breakers you will buy. You definitely shouldn’t take unknown firms - an electrician is not an area where you can experiment. Details about choosing a manufacturer in the video.

The main difference between these switching devices and all other similar devices is a complex combination of abilities:

1. maintain nominal loads in the system for a long time due to the reliable transmission of powerful electricity flows through their contacts;

2. to protect the operating equipment from accidental malfunctions in the electrical circuit by quickly removing power from it.

Under normal operating conditions of the equipment, the operator can manually switch the loads with circuit breakers, providing:

different power schemes;

changing the network configuration;

decommissioning equipment.

Emergency situations in electrical systems occur instantly and spontaneously. A person is not able to quickly respond to their appearance and take measures to eliminate them. This function is assigned to automatic devices built into the switch.

In the energy sector, the division of electrical systems by types of current is accepted:

constant;

alternating sinusoidal.

In addition, there is a classification of equipment according to the magnitude of the voltage on:

low voltage - less than a thousand volts;

high voltage - everything else.

For all types of these systems, their own circuit breakers are created, designed for repeated operation.

AC circuits

According to the power of the transmitted electricity, circuit breakers in AC circuits are conventionally divided into:

1. modular;

2. molded case;

3. power air.

Modular designs

Specific execution in the form of small standard modules with a width multiple of 17.5 mm determines their name and design with the possibility of mounting on a DIN rail.

The internal structure of one of these circuit breakers is shown in the picture. Its body is completely made of durable dielectric material, excluding .

The supply and outgoing wires are connected to the upper and lower terminal clamp, respectively. For manual control of the circuit breaker state, a lever with two fixed positions is installed:

the upper one is designed to supply current through a closed power contact;

lower - provides a break in the power circuit.

Each of these automata is designed for long-term operation at a certain value (In). If the load becomes greater, then the power contact breaks. For this, two types of protection are placed inside the case:

1. thermal release;

2. current cutoff.

The principle of their operation makes it possible to explain the time-current characteristic, which expresses the dependence of the protection response time on the load or accident current passing through it.

The graph shown in the picture is for one specific circuit breaker, when the cut-off operating zone is selected to be 5÷10 times the rated current.

During the initial overload, a thermal release operates, made of which, with increased current, gradually heats up, bends and acts on the tripping mechanism not immediately, but with a certain time delay.

In this way, it allows small overloads associated with short-term connection of consumers to self-eliminate and eliminate unnecessary disconnections. If the load provides critical heating of the wiring and insulation, then the power contact breaks.

When an emergency current arises in the protected circuit, capable of burning the equipment with its energy, then the electromagnetic coil comes into operation. It impulse due to the surge of the load that has arisen throws the core onto the tripping mechanism in order to instantly stop the transcendental mode.

The graph shows that the higher the short-circuit currents, the faster they are turned off by the electromagnetic release.

According to the same principles, a household automatic steam fuse works.

When high currents break, an electric arc is created, the energy of which can burn out the contacts. To exclude its action in circuit breakers, an arc chute is used, which divides the arc discharge into small flows and extinguishes them due to cooling.

Multiplicity of cut-offs of modular structures

Electromagnetic releases are configured and selected to work with certain loads because they create different transients at start-up. For example, during the switching on of various lamps, a short-term inrush current due to the changing resistance of the filament can approach three times the nominal value.

Therefore, for the outlet group of apartments and lighting circuits, it is customary to choose circuit breakers with a time-current characteristic of type "B". It is 3÷5 In.

Asynchronous motors, when spinning the rotor with the drive, cause higher overload currents. For them, automatic machines with the characteristic “C” are selected, or - 5 ÷ 10 In. Due to the created time and current margin, they allow the motor to spin up and guarantee to reach the operating mode without unnecessary shutdowns.

In industrial production, on machines and mechanisms, there are loaded drives connected to engines that create more increased overloads. For such purposes, circuit breakers of characteristic "D" with a rating of 10 ÷ 20 In are used. They have proven themselves well when working in circuits with active-inductive loads.

In addition, automata have three more types of standard time-current characteristics that are used for special purposes:

1. "A" - for long wiring with an active load or protection of semiconductor devices with a value of 2 ÷ 3 In;

2. "K" - for pronounced inductive loads;

3. "Z" - for electronic devices.

In the technical documentation for different manufacturers, the cutoff actuation ratio for the last two types may differ slightly.

This class of devices is capable of switching higher currents than modular designs. Their load can reach up to 3.2 kiloamperes.

They are manufactured according to the same principles as modular structures, but, taking into account the increased requirements for the transmission of increased loads, they are trying to give them relatively small dimensions and high technical quality.

These machines are designed for safe operation in industrial facilities. By the value of the rated current, they are conditionally divided into three groups with the possibility of switching loads up to 250, 1000 and 3200 amperes.

The design of their housing: three- or four-pole models.

Power air circuit breakers

They work in industrial installations and operate with very high currents up to 6.3 kiloamperes.

These are the most complex devices of switching devices of low-voltage equipment. They are used for the operation and protection of electrical systems as incoming and outgoing devices of high-power switchgear and for connecting generators, transformers, capacitors or large electric motors.

A schematic representation of their internal structure is shown in the picture.

Here, a double break of the power contact is already used and arc chute chambers with gratings are installed on each side of the disconnection.

The switching coil, the closing spring, the motor drive for charging the spring and the automation elements are involved in the operation algorithm. To control the flowing loads, a current transformer with a protective and measuring winding is built in.

Circuit breakers of high-voltage equipment are very complex technical devices and are manufactured strictly individually for each voltage class. They are usually used.

They are required to:

high reliability;

security;

speed;

ease of use;

relative noiselessness during operation;

optimal cost.

Loads that break during emergency shutdown are accompanied by a very strong arc. To extinguish it, various methods are used, including breaking the circuit in a special environment.

This switch includes:

contact system;

arc extinguishing device;

live parts;

insulated body;

drive mechanism.

One of these switching devices is shown in the photograph.

For high-quality operation of the circuit in such designs, in addition to the operating voltage, take into account:

the nominal value of the load current for its reliable transmission in the on state;

the maximum short-circuit current in terms of the effective value that the tripping mechanism can withstand;

permissible component of the aperiodic current at the moment of circuit break;

the possibility of automatic reclosing and the provision of two AR cycles.

According to the methods of extinguishing the arc during shutdown, the circuit breakers are classified into:

oil;

vacuum;

air;

SF6;

autogas;

electromagnetic;

autopneumatic.

For reliable and convenient operation, they are equipped with a drive mechanism that can use one or more types of energy or combinations thereof:

cocked spring;

lifted load;

compressed air pressure;

electromagnetic pulse from the solenoid.

Depending on the conditions of use, they can be designed to operate under voltage from one to 750 kilovolts inclusive. Naturally, they have a different design. dimensions, automatic and remote control capabilities, protection settings for safe operation.

Auxiliary systems of such circuit breakers can have a very complex branched structure and be placed on additional panels in special technical buildings.

DC circuits

These networks also have a huge number of circuit breakers with different capabilities.

Electrical equipment up to 1000 volts

Here, modern modular devices that can be mounted on a Din-rail are being massively introduced.

They successfully complement the classes of old automata such as , AE and other similar ones, which were fixed on the walls of the shields with screw connections.

Modular DC designs have the same design and operating principle as their AC counterparts. They can be performed by one or several blocks and are selected according to the load.

Electrical equipment above 1000 volts

High-voltage circuit breakers for direct current operate at electrolysis plants, metallurgical industrial facilities, railway and urban electrified transport, and energy enterprises.

The main technical requirements for the operation of such devices correspond to their analogues on alternating current.

hybrid switch

Scientists from the Swedish-Swiss company ABB managed to develop a high-voltage DC switch that combines two power structures in its device:

1. SF6;

2. vacuum.

It is called hybrid (HVDC) and uses the technology of sequential arc extinguishing in two environments at once: sulfur hexafluoride and vacuum. For this, the following device is assembled.

Voltage is applied to the top busbar of the hybrid vacuum circuit breaker, and the voltage is removed from the bottom busbar of the SF6 circuit breaker.

The power parts of both switching devices are connected in series and controlled by their individual drives. In order for them to work simultaneously, a synchronized coordinate operations control device was created, which transmits commands to a control mechanism with independent power supply via a fiber optic channel.

Through the use of high-precision technologies, the design developers managed to achieve consistency in the actions of the actuators of both drives, which fits into a time interval of less than one microsecond.

The circuit breaker is controlled by a relay protection unit built into the power line through a repeater.

The hybrid circuit breaker made it possible to significantly increase the efficiency of composite SF6 and vacuum structures by using their combined characteristics. At the same time, it was possible to realize advantages over other analogues:

1. the ability to reliably turn off short-circuit currents at high voltage;

2. the possibility of a small effort for switching power elements, which made it possible to significantly reduce the dimensions and. respectively, the cost of equipment;

3. the availability of various standards for the creation of structures operating as part of a separate circuit breaker or compact devices at one substation;

4. ability to eliminate the consequences of a rapidly increasing restoring voltage;

5. the possibility of forming a basic module for working with voltages up to 145 kilovolts and above.

A distinctive feature of the design is the ability to break the electrical circuit in 5 milliseconds, which is almost impossible to perform with power devices of other designs.

The hybrid circuit breaker device was named one of the top ten designs of the year by the MIT (Massachusetts Institute of Technology) Technology Survey.

Other manufacturers of electrical equipment are also engaged in similar studies. They also achieved certain results. But ABB is ahead of them in this matter. Its management believes that large losses occur during the transmission of AC electricity. They can be significantly reduced by using high voltage DC circuits.

From the very beginning of the emergence of electricity, engineers began to think about the safety of electrical networks and devices from current overloads. As a result, many different devices have been designed that are distinguished by reliable and high-quality protection. One of the latest developments has become electric machines.

This device is called automatic due to the fact that it is equipped with the function of turning off the power in automatic mode, in the event of short circuits, overloads. Conventional fuses after operation must be replaced with new ones, and the machines can be turned on again after the causes of the accident have been eliminated.

Such a protective device is necessary in any electrical network scheme. The circuit breaker will protect the building or premises from various emergencies:

• Fires.
• Electric shocks to a person.
• Electrical faults.

Types and design features

It is necessary to know information about the existing types of circuit breakers in order to choose the right device at the time of purchase. There is a classification of electric machines according to several parameters.

Breaking capacity

This property determines the short circuit current at which the machine will open the circuit, thereby turning off the network and the devices that were connected to the network. According to this property, automata are divided into:

• Automatic machines for 4500 amperes are used to prevent malfunctions in the power lines of old residential buildings.
• At 6000 amperes, they are used to prevent accidents during short circuits in the network of houses in new buildings.
• At 10,000 amperes, they are used in industry to protect electrical installations. A current of this magnitude can be formed in the immediate vicinity of the substation.

The operation of the circuit breaker occurs during short circuits, accompanied by the occurrence of a certain amount of current.

The machine protects the wiring from damage to the insulation by high current.

Number of poles

This property tells us about the largest number of wires that can be connected to the machine to provide protection. In the event of an accident, the voltage at these poles is turned off.

Features of machines with one pole

Such electric machines are the simplest in design, and serve to protect individual sections of the network. Two wires can be connected to such a circuit breaker: an input and an output.

The task of such devices is to protect electrical wiring from overloads and short circuits of wires. The neutral wire is connected to the neutral bus, bypassing the machine. Grounding is connected separately.

Electric machines with one pole are not introductory, since when it is turned off, the phase breaks, and the neutral wire still remains connected to the power supply. It does not provide 100% protection.

Properties of automata with two poles

In cases where an accident requires a complete disconnection from the electrical network, use circuit breakers with two poles. They are used as input. In emergency cases, or in case of a short circuit, all electrical wiring is turned off at the same time. This makes it possible to carry out repair and maintenance work, as well as work on connecting equipment, since complete safety is guaranteed.

Two-pole electric machines are used when it is necessary to have a separate switch for a device powered by a 220 volt network.

An automatic machine with two poles is connected to the device using four wires. Of these, two come from the power supply, and the other two come out of it.

Three-pole electric machines

In an electrical network with three phases, 3-pole machines are used. Grounding is left unprotected, and the phase conductors are connected to the poles.

A three-pole machine serves as an input device for any three-phase load consumers. Most often, this version of the machine is used in industrial conditions to supply electricity to electric motors.

6 conductors can be connected to the machine, three of which are the phases of the electrical network, and the remaining three are coming from the machine, and provided with protection.

Using a four-pole machine

To provide protection for a three-phase network with a four-wire system of conductors (for example, an electric motor connected according to the “star” scheme), a 4-pole circuit breaker is used. It plays the role of an introductory device of a four-wire network.

It is possible to connect eight conductors to the device. On the one hand - three phases and zero, on the other hand - the output of three phases with zero.

Time-current characteristic

When devices that consume electricity and the electrical network are operating normally, normal current flow occurs. This phenomenon also applies to the electric machine. But, in the event of an increase in current strength for various reasons above the nominal value, the automatic release trips, and the circuit breaks.

The parameter of this operation is called the time-current characteristic of the electric machine. It is the dependence of the time of operation of the machine and the ratio between the real strength of the current passing through the machine and the nominal value of the current.

The importance of this characteristic lies in the fact that the least number of false positives is provided on the one hand, and current protection is carried out, on the other hand.

In the energy industry, there are situations when a short-term increase in current is not associated with an accident, and the protection should not work. It also happens with electric machines.

Time-current characteristics determine how long the protection will operate, and what current strength parameters will occur. The greater the overload, the faster the machine will work.

Electric machines marked "B"

Automatic switches of category "B" are able to turn off in 5 - 20 s. In this case, the current value is from 3 to 5 nominal current values ​​≅0.02 s. Such machines are used to protect household appliances, as well as all electrical wiring in apartments and houses.

Properties of machines marked "C"

Electric machines of this category can turn off in 1 - 10 s, at 5 - 10 times the current load ≅0.02 s. These are used in many areas, most popular for houses, apartments and other premises.

The meaning of the marking "D" on the machine

With this class, automata are used in industry and are made in the form of 3-pole and 4-pole versions. They are used to protect powerful electric motors and various three-phase devices. Their operation time is up to 10 seconds, while the operation current can exceed the nominal value by 14 times. This makes it possible to use it with the necessary effect to protect various circuits.

Electric motors with significant power are most often connected through electric machines with characteristic "D", because. starting current is high.

Rated current

There are 12 versions of automatic machines, which differ in the characteristics of the rated operating current, from 1 to 63 amperes. This parameter determines the speed at which the machine switches off when the current limit is reached.

The machine for this property is selected taking into account the cross-section of the conductors of the wires, the allowable current.

The principle of operation of electric machines

normal mode

During normal operation of the machine, the control lever is cocked, current flows through the power wire at the top terminal. Next, the current goes to the fixed contact, through it to the moving contact and through the flexible wire to the solenoid coil. After it, the current goes through the wire to the bimetallic release plate. From it, the current passes to the lower terminal and further to the load.

Overload mode

This mode occurs when the rated current of the machine is exceeded. The bimetallic plate is heated by a large current, bends and opens the circuit. The action of the plate requires time, which depends on the value of the passing current.

The circuit breaker is an analog device. There are certain difficulties in setting it up. The tripping current of the release is adjusted at the factory with a special adjusting screw. After the plate has cooled down, the machine can function again. The temperature of the bimetal strip depends on the environment.

The release does not act immediately, allowing the current to return to its nominal value. If the current does not decrease, the release trips. Overload can occur due to powerful devices on the line, or connecting several devices at once.

Short circuit mode

In this mode, the current increases very quickly. The magnetic field in the solenoid coil moves the core, which activates the release, and disconnects the contacts of the power supply, thereby removing the emergency load of the circuit and protecting the network from possible fire and destruction.

The electromagnetic release operates instantly, which is different from the thermal release. When the contacts of the working circuit are opened, an electric arc appears, the magnitude of which depends on the current in the circuit. It causes destruction of contacts. To prevent this negative effect, an arc chute is made, which consists of parallel plates. In it, the arc fades and disappears. The resulting gases are discharged into a special hole.

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

The circuit breaker is an electrical device, the main purpose of which is to switch its operating state when a certain situation occurs. Electric automata combine two devices, this is a conventional switch and a magnetic (or thermal) release, the task of which is to timely break the electrical circuit in case the threshold value of the current is exceeded. Circuit breakers, like all electrical devices, also have different varieties, which divides them into certain types. Let's get acquainted with the main classifications of circuit breakers.

1 "Classification of machines by the number of poles:

A) single-pole machines

b) single-pole machines with neutral

c) bipolar machines

d) three-pole machines

e) three-pole circuit breakers with neutral

e) four-pole machines

2» Classification of automata according to the type of releases.

The design of various types of circuit breakers usually includes 2 main types of releases (openers) - electromagnetic and thermal. Magnetic breakers are used for electrical protection against short circuits, and thermal breakers are mainly designed to protect electrical circuits for a certain overload current.

3 "Classification of automata by tripping current: B, C, D, (A, K, Z)

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

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

b) type "C" - over 5 In to 10 In inclusive

C) type "D" - over 10 In to 20 In inclusive

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

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

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

5 "Classification by the presence of current limitation:

a) current limiting

b) non-limiting

6 "Classification of machines by types of releases:

A) with overcurrent release

b) with independent release

c) with minimum or zero voltage release

7 "Classification of machines according to the time delay characteristic:

A) no time delay

b) with a time delay independent of the current

c) with a time delay inversely dependent on current

d) with a combination of these characteristics

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

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

A) with rear connection

b) with front connection

c) with combined connection

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

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

P.S. Everything has its varieties. After all, if there were only one thing in its single copy, it would be at least just boring and too limited! The diversity is good because you can choose exactly what best suits your needs.