Selection and installation of circuit breakers

The circuit breaker (AB) is one of the most common relay protection and automation devices.

The use of circuit breakers in electrical networks pursues several goals at once, the main of which are:

1. Providing the ability to manually turn on or turn off certain sections of the low-voltage electrical network.
2. Short circuit protection.
3. Protection of the electrical circuit against overloads, which are caused by a prolonged current exceeding its rated value.
4. Protection against reduction or complete loss of mains voltage.
5. Switches designed for operation with constant voltage react when the current changes its direction.

Important! The circuit breaker is not designed to be used for permanent opening and closing of a circuit. A large number of switching, especially under load, after a while will lead to wear and failure of the device contacts.

Requirements for AV

Before choosing a circuit breaker for your own apartment, you should familiarize yourself with the basic requirements for these devices. There are several GOSTs that define such requirements. The main governing documents include: GOST R 50345-99, GOST R IEC 60898-2-2006, GOST R 50030.2-99.

The marking of circuit breakers, applied to the body of each product, contains information about its main technical characteristics.

The main indicators that all types of machines must comply with, according to the requirements of GOSTs, are:

1. The ability of the current-carrying circuit of the device to pass through itself the rated current for an unlimited time. This requirement applies equally to small 6A circuit breakers that protect lighting circuits, as well as to more powerful devices with a rated current of 63 or 40A that can be installed on the input electrical panel.
2. The ability of a circuit breaker to disconnect a circuit when short-circuit currents occur in it without degrading its performance.
3. The type of time-current characteristic of the circuit breaker, which must meet the needs of the consumers connected to it.
4. The possibility of self-diagnosis of the tripping mechanism provided by the electronic protection unit.
5. Small overall dimensions and weight of the device. This parameter is extremely important when installing the product in small junction boxes or electrical panels.
6. Low heat generation during the passage of rated currents, as well as short-circuit currents. This parameter is important from the point of view of fire safety.
7. Short circuit disconnection time in the event of short-circuit currents.
8. selectivity of protection. Not all types of switches have this quality (as a rule, automatic devices with a rated current of 40A, as well as 63, 80, 100A and above, can provide protection selectivity). Selective automata have an additional current path equipped with their own contacts. This additional circuit allows you to respond to changes in the design of the electrical network that occur as a result of the operation of downstream less powerful circuit breakers. Using this principle allows you to achieve disconnection of only those sections of the wiring in which an emergency has occurred.
9. Electrical safety of users.

To check the compliance of the device parameters with the requirements of GOST, automatic switches are loaded. For this, special equipment is used, which allows obtaining experimental data on such characteristics as the rated current, the time of disconnection of the main contacts, as well as the protection operation current.Loading circuit breakers is not a one-time procedure, the frequency of its implementation is determined by the manufacturer.

AB design

The main structural elements of the circuit breaker are:

1. Control lever. Its upper position corresponds to the on state of the main contacts AB, the lower one, respectively, to the off state.
2. Terminals for connecting wires. In most AB models, the upper terminal is used to supply electricity, and the lower terminal is used to connect consumers.
3. moving contact.
4. fixed contact.
5. Thermal release. Includes bimetal plate.
6. Adjusting screw.
7. Electromagnetic release (coil with pusher and release mechanism).
8. Arc chamber.
9. Frame. Made from dielectric material. The size and degree of protection of the housing against dust and moisture depends on the type and purpose of the AB. On the front of the product, symbols are applied that display its main technical characteristics. The rear part is equipped with a mounting that allows the circuit breaker to be mounted on a DIN rail.

The design of the circuit breaker can be considered on the example of model VA47 - 63 with a rated current of 16A.

Switches VA-47 - 63 have a fairly extensive range. To facilitate the selection of the required model, from which the following designations are adopted:

1. VA - automatic switch.
2. 47 - 63 - product series number.
3. After the general designation, two numbers and a letter are used to indicate the number of poles, the rated current and the characteristic type of the circuit breaker.

Principle of operation

The ability of the product BA47 - 63 to respond to the action of a short circuit current is provided by an electromagnetic release. The principle of its operation is based on the phenomenon of electromagnetic induction. A large current flowing through the solenoid winding drives its core, which acts on the contact opening mechanism. It is quite natural that the greater the value of the current passing through the main contacts VA47 - 63, the faster such a release operates.

The thermal release opens the electrical circuit when a current flows through it for a long time, exceeding the nominal value of 16A. The bimetallic plate, which is the main part of the thermal release, is able to bend when a current of a certain amount passes through it. Curving, the plate activates the mechanical part of the device, which opens the power contacts. The response time of VA47 - 63 in this case depends significantly on the magnitude of the current flowing through it.

For many models of circuit breakers, a prerequisite is the ability to work with overload for some time. Due to the presence of an adjusting screw, it is possible to adjust the parameters of the switch in accordance with the requirements of consumers, such settings are made in the factory. After the thermal release has been triggered, the AB can be switched on again only after some time, necessary for the cooling of the bimetallic plate.

The opening of the release contacts is accompanied by the appearance of an electric arc. In the process of its burning, the contacts of the switch are destroyed. The arc is especially dangerous for powerful switches rated for currents of 63, 100A or higher. In order to reduce the negative impact of the arc and extend the life of the device, an arc chute is used in which the electric arc is crushed and suppressed. This process is accompanied by the release of gases, which are removed from the body of the machine through a special hole.

Different models of circuit breakers may use different arc suppression principles. The most popular technical solutions in this case are:

1. The use of additional release contacts, which are made of a special alloy. These contacts open later than the main ones, taking on the action of the electric arc.
2. The use of arcing grids.
3. Using the effect of rolling the contacts of the release. In this case, the burning of the arc is carried out only in a certain area of ​​them, which is made of especially durable and heat-resistant materials.
4. Use of "double break". It is one of the most promising technical solutions actively used in modern models of circuit breakers.

Classification

In order to choose the right input single-pole AB for use in the electrical wiring of an apartment, one should take into account such parameters as rated and maximum currents, response time, overall dimensions, as well as the price of the device and the reputation of its manufacturer. The main characteristics are reflected on the body of the device in the form of an appropriate designation.

Depending on the operating time, the following types of circuit breakers are distinguished:

1. Fast acting. As a rule, DC switches have such characteristics (operating time is less than 0.008 s). The requirements for these devices are described in GOST 2585-81.
2. Normal speed (0.02 - 0.005 s).
3. Reduced speed (response time is greater than 0.02 s).
4. Selective automatic switch.

According to the number of independent electrical lines switched off by one release mechanism, the machines can be divided into one-, two-, three- and four-pole ones. The three-pole circuit breaker is widely used in low-voltage three-phase networks. A two-pole switch can be used to organize reliable protection of single-phase networks, as well as DC circuits.

Depending on the purpose, the circuit breaker may have a different value of the rated current and the type of time-current characteristic. Currently, GOST has established the following ratings of circuit breakers for current:

1. Up to 25 A. Such switches are used to protect household electrical wiring. 3A and 6A devices are mainly used to protect lighting circuits. Automatic machines for 6A, 10A or 16A can be used for separate connection of more powerful consumers.
2. Automatic machines for 32A, 40A and 50A are used as input devices.
3. Switches with a rated current above 63 A (100A, 160A) are three-pole devices designed for installation in three-phase networks.

The type of time-current characteristic is indicated on the body of the product in the form of a letter designation and shows for which type of load this type of machine is suitable.

Type B. The characteristic of this type has an automatic light switch with a small rated current (3A and 6A).

Type C. Such machines are the most popular. Their installation is recommended when arranging home electrical wiring, which may contain both lighting devices (3 - 6A), as well as low-power motors or transformers (up to 40A). An example is the ABB S231 C 16A or AE246M 40A automatic machines.

Automatic switches manufactured by ABB (Germany):

Single-pole machine ABB S201 C3 3A

Two-pole machine ABB SH202-C6 6A

ABB S231 C 16A

Like other products of the ABB brand, automatic protection devices are distinguished by high reliability and workmanship.

Type D. Switches with a similar time-current characteristic are used to connect three-phase electric motors with high starting currents, as well as other inductive loads.

Features of selection and installation

When choosing a circuit breaker, you should first of all pay attention to the following characteristics.

Rated voltage

Depends on the mains voltage (220 or 380 V).

Rated current

An extremely important parameter, which is determined by the total power of all devices connected through the machine. In order to calculate the required rated current, you need to divide the total power of consumers by the voltage of the electrical network. After that, you should choose the nearest higher value of the rated current from the standard range defined by GOST.

Important! It is not recommended to install circuit breakers, the rated current of which significantly exceeds the total current of the network, since such a solution will significantly reduce the level of electrical safety of the system.

Maximum short circuit current

According to GOST, this parameter characterizes the limiting switching capacity of the circuit breaker. The value of the maximum current is applied to the body of the device in the form of a figure showing what maximum current in amperes or kiloamperes such a machine can turn off. The necessary breaking capacity of the circuit breaker is determined by carrying out rather complex mathematical calculations or measurements of the resistance of the phase-zero loop. In practice, such actions are rarely resorted to, much more often they use the approximate classification of circuit breakers according to the maximum short-circuit current:

1. 4500 A. This type of device is suitable for installation in private apartments or houses (ABV SH201L). In most cases, the maximum short-circuit current in such electrical networks does not exceed 1000 A.
2. 6000 A. (For example, ABB SH200). Switches of this type are used to connect powerful consumers.
3. 10000 A and above. These devices include powerful three-phase machines (ABV T7 series). Such devices are used in most cases to be used as introductory switches. In this case, there is a certain risk of a short circuit in the immediate vicinity of the introductory electrical panel. This situation can cause the appearance of large short-circuit currents.

Selectivity of the protection system

The selectivity of the system means its selectivity, that is, the ability to automatically turn off only damaged elements in which abnormal operating modes occur. To ensure this quality, automata with a small rated current (3A or 6A) and located closer to the load according to the power supply circuit should have a shorter response time than the introductory switches (the rated current of which is 40A - 100A).

The most common series of domestic and foreign AB models

One of the most demanded series of circuit breakers on the market, presented by foreign manufacturers, is the c60n series.

Features of c60n circuit breakers:

1. The c60n machines meet the requirements of domestic and international standards.
2. The c60n devices are designed for operation in single-phase and three-phase networks.
3. C60n machines have a wide range of capacities, which includes products with a rated current from 0.5 to 125A.
4. Depending on the purpose, c60n machines can have from one to four poles.
5. Unlike most similar devices, c60n machines have an unambiguous status indication.
6. The c60n time-current characteristics can be type B, C and D.
7. Breaking capacity up to 20 kA (depending on the type of machine marked c60n).
8. The maximum breaking capacity of c60n circuit breakers is 6 kA.

The most popular types of domestic circuit breakers include devices of the ae series, which include devices of the ae 2036, ae 2043, ae 2046, and ae 2056 types.

Features of ae series circuit breakers:

1. Automata ae are used in three-phase AC networks.
2. The main function of automata type ae is to protect consumers such as asynchronous motors.
3. The ae series circuit breakers provide a wide range of tripping parameters, which include the setting value for the operating current. For example, for an automaton ae with a rated current value of 40A and a setting of 12, the operation current will be 40X12 \u003d 480 A.
4. The maximum switching capacity of automatic machines ae 2046M is 4500A.

Switch installation

Choosing a circuit breaker for installation in your own apartment is an important task. You need to purchase such products in specialized stores, while you should pay attention to the products of proven and well-established manufacturers. The most famous companies producing electrical equipment include Schneider Electric, ABB, IEK, Legrand.

Checking circuit breakers directly in the store can be done using an ordinary tester. To do this, check the resistance between the upper and lower terminals of its poles when the device is on.

In order to distinguish a fake from an original product from reliable manufacturers, you should carefully examine the body of the machine, paying attention to the quality of its workmanship. Circuit breakers are marked by machine, so all markings are highly legible and accurately positioned.

Installing circuit breakers at the entrance to the apartment is a fairly simple operation, which includes only a few steps:

1. The choice of the device according to the sizes and technical characteristics.
2. Power outage at the upstream switchboard.
3. Installing the switch on a DIN rail.
4. Connecting the incoming phase wire (or wires in case of installing a three-phase AB model) to the upper terminals of the circuit breaker.
5. Connecting the phase wire supplying the load to the lower terminal of the device.
6. Turning on the power from the higher machine.
7. Connecting the load and checking the operability of the installed circuit breaker.

The correct choice of a circuit breaker allows you to reliably protect electrical installations from emergency conditions that occur in them, as well as achieve the required level of electrical safety during the operation and maintenance of home electrical wiring.