Selection and installation of circuit breakers

A 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 enable or disable certain sections of the low-voltage electrical network.
2. Short circuit protection.
3. Protection of the electric circuit against overloads, which are caused by prolonged exceeding by the current of its rated value.
4. Protection against undervoltage or complete power failure.
5. Switches designed to operate with constant voltage react when a current changes its direction.

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

Requirements for AB

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 guidelines include: GOST R 50345-99, GOST R IEC 60898-2-2006, GOST R 50030.2-99.

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

The main indicators that all types of machines must meet, in accordance with the requirements of GOSTs, are:

1. The ability of the current-carrying circuit of a device to pass a rated current through itself for an unlimited time. This requirement applies equally to small 6A machines that protect lighting circuits, as well as more powerful devices having a rated current of 63 or 40A, which can be installed on the input electrical shield.
2. The ability of a circuit breaker to disconnect a circuit without shortening its operability when short-circuit currents occur in it.
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 disconnecting 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 during the passage of rated currents, as well as short-circuit currents. This parameter is important from the point of view of ensuring fire safety.
7. Short circuit disconnection time when short-circuit currents occur.
8. Selectivity of protection. Not all types of circuit breakers have this quality (as a rule, machines with a rated current of 40A, as well as 63, 80, 100A and above, can provide selectivity of protection). Selective machines 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 lower-level less powerful switches. Using this principle allows to disable 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, the circuit breakers are loaded. For this, special equipment is used to obtain experimental data on such characteristics, such as rated current, main contacts trip time, as well as trip current protection. Loading circuit breakers is not a one-time procedure; the frequency of its execution is determined by the manufacturer.

Construction AB

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, respectively, to the off state.
2. Terminals for connecting wires. In most AB models, the top terminal is for power supply, and the bottom is for connecting consumers.
3. Movable contact.
4. Fixed contact.
5. Thermal release. Includes bimetal plate.
6. Adjusting screw.
7. Electromagnetic release (coil with a pusher and a trip mechanism).
8. Arcing chamber.
9. Body. Made of dielectric material. The size and degree of protection of the housing from dust and moisture depends on the type and purpose of the AB. The front part of the product is marked with its main technical characteristics. The back is equipped with a mount 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 the model VA47 - 63 with a rated current of 16A.

Switches VA-47 - 63 have a fairly extensive lineup. To facilitate the selection of the required model, from which the following notation is taken:

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

Principle of operation

The ability of the VA47 - 63 product 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 along the winding of the solenoid sets in motion its core, which acts on the contact opening mechanism. It is only natural that the greater the value of the current passing through the main contacts of VA47 - 63, the faster the trip.

The thermal release opens the electric circuit during continuous flow of current exceeding the rated value 16A through it. The bimetallic plate, which is the main part of the thermal release, is able to bend when a current of a certain size passes through it. Curving, the plate drives the mechanical part of the device, which opens the power contacts. The response time of VA47 - 63 in this case substantially depends on 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 configure the circuit breaker in accordance with the requirements of consumers, such settings are made in the factory. After the thermal release is activated, the AB can be switched on again only after some time necessary for the bimetallic plate to cool.

The opening of the trip contacts is accompanied by the appearance of an electric arc. In the process of its burning, the breaker contacts are destroyed. The arc is especially dangerous for high-power circuit breakers rated for currents of 63, 100A or higher. In order to reduce the negative effect of the arc and extend the life of the device, an arcing chamber is used in which the electric arc is crushed and suppressed. This process is accompanied by the release of gases that are removed from the machine through a special hole.

Different models of circuit breakers can use different principles of suppression of the electric arc. The most popular technical solutions are:

1. The use of additional trip contacts, which are made of a special alloy. These contacts open later than the main ones, taking on the action of an electric arc.
2. The use of arcing gratings.
3. Using the rolling effect of the trip contacts. In this case, arc burning is carried out only in a certain section of them, which is made of especially durable and heat-resistant materials.
4. The 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 correct input single-pole AB for use in the electrical wiring of an apartment, one should take into account such parameters, such as rated and maximum currents, response time, overall dimensions, as well as the price of the device and its reputation manufacturer. The main characteristics are reflected on the device in the form of an appropriate designation.

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

1. High-speed. As a rule, DC circuit breakers have such characteristics (response 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 more than 0.02 s).
4. Selective circuit breaker.

By the number of independent electric lines that are switched off by one trip mechanism, the machines can be divided into one-, two-, three- and four-pole. A three-pole circuit breaker is widely used in low-voltage three-phase networks. To organize reliable protection of single-phase networks, as well as DC circuits, a two-pole switch can be used.

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 installed the following ratings of current circuit breakers:

1. Up to 25 A. Such switches are used to protect household wiring. Devices on 3A and 6A are mainly used to protect lighting circuits. Automatic machines on 6A, 10A or 16A can be used for separate connection of more powerful consumers.
2. Automatic machines on 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 product body in the form of an alphabetic designation and shows what type of load this type of machine is suitable for.

Type B. This type of characteristic 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, in which simultaneously present lighting fixtures (3 - 6A), as well as low-power engines or transformers (up to 40A). As an example, automatic machines ABB S231 C 16A or AE246M 40A.

Automatic circuit breakers manufactured by ABB (Germany):

Single-pole automatic machine ABB S201 C3 3A

Bipolar automatic machine ABB SH202-C6 6A

ABB S231 C 16A

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

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

Features of selection and installation

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

Rated voltage

Depends on the voltage of the electrical network (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, it is necessary to divide the total power of consumers by the voltage of the electric network. After that, you should choose the nearest larger value of the rated current from the standard series defined by GOST.

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

Maximum short circuit current

According to GOST, this parameter characterizes the maximum switching capacity of the circuit breaker. The value of the maximum current is applied to the device case in the form of a figure showing what maximum current in amperes or kiloamperes is able to turn off such an automatic machine. The necessary breaking capacity of the circuit breaker is determined by conducting fairly complex mathematical calculations or measuring 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 (АВВ SH201L). In most cases, the maximum short circuit current in such electrical networks does not exceed 1000 A.
2. 6000 A. (For example, АВВ SH200). Switches of this type are used to connect powerful consumers.
3. 10000 A and higher. These devices include powerful three-phase circuit breakers (ABB T7 series). Such devices are used in most cases for use as input switches. In this case, there is a certain risk of a short circuit in the immediate vicinity of the input electrical panel. Such a situation can cause the appearance of large short-circuit currents.

Security Selectivity

System selectivity means its selectivity, that is, the ability to automatically turn off only damaged elements in which abnormal operating modes occur. To ensure this quality, machines having a small rated current (3A or 6A) and located closer to the load according to the scheme power supply must have a shorter response time than the opening switches (whose rated current is 40A - 100A).

The most common series of domestic and foreign models of AB

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

Features of c60n circuit breakers:

1. C60n machines comply with the requirements of domestic and international standards.
2. C60n devices are designed for single-phase and three-phase networks.
3. C60n machines have a wide range of capacities, which includes products with a rated current of 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 a unique status indication.
6. The time and current characteristics of c60n devices can be of 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 machines is 6 kA.

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

Features of switches ae series:

1. Automata ae are used in three-phase AC networks.
2. The main function of ae type machines is to protect consumers such as asynchronous motors.
3. The circuit breakers of the ae series provide a large selection of trip parameters, which include the value of the setpoint 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 = 480 A.
4. The maximum switching capacity of ae 2046M automatic machines is 4500A.

Circuit breaker 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 it is worth paying 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 performed using an ordinary tester. To do this, check the resistance between the upper and lower terminals of its poles in the on state of the device.

In order to distinguish a fake from the original product of reliable manufacturers, you should carefully inspect the machine case, paying attention to the quality of its manufacture. The circuit breakers are marked by the machine, so all designations are distinguished by high clarity and precise location.

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

1. The choice of device in terms of size and technical specifications.
2. Power failure on the upstream switchboard.
3. Installing the switch on a DIN rail.
4. Connecting the incoming phase wire (or wires in the case of installing the three-phase model AB) to the upper terminals of the switch.
5. Connecting the phase wire supplying the load to the bottom terminal of the device.
6. Power on from the upstream machine.
7. Connect the load and check the operability of the installed circuit breaker.

The correct choice of circuit breaker allows you to reliably protect electrical installations from emergency modes, and also to achieve the necessary level of electrical safety during operation and maintenance of home electrical wiring.