How to connect a circuit breaker

Content:

Circuit breakers, called automata or switches in everyday life, refer to the means of switching and are intended to supply electric current to an object. The main function of these devices is to automatically turn off the power supply in the event of an emergency and network problems. The machine protects the electrical circuit from short circuits, overloads and voltage drops beyond the permissible value.

In old houses, in the power supply system, the neutral wire was not only a working one, but also performed a protective function at the same time. In modern buildings, a clear separation of the purpose of working and protective conductors is provided. In this regard, the question often arises of how to connect a circuit breaker, since all European-style electrical installation products are equipped with terminals for connecting a ground wire. In addition, the fastening of the machines themselves in the switch cabinet can be done by mounting on a DIN rail or on a special mounting panel.

Device and principle of operation

Before connecting the machine, it is necessary to understand the features of its design and the principle of operation. The circuit breaker consists of a body, a switching device, a control mechanism in the form of a button or a handle, an arc chute and screw terminals located at the top and bottom.

For the manufacture of the body and the control mechanism, durable plastic is used that does not support combustion. The switching device consists of moving and fixed contacts. Each pole of the machine consists of a pair of these contacts and is equipped with its own arc chute.

The purpose of the arc chute is to extinguish the electric arc that appears when the contacts are broken under the action of the load. The chamber itself is made in the form of a set of steel plates with a profile of a certain shape. They are isolated from each other and located at the same distance relative to each other. It is to these plates that the arc is attracted, which here cools down and dies out. The number of pairs of contacts in different models of machines ranges from 1 to 4. The devices have position indicators. Red indicates on, green indicates off. In this way, the current state of the circuit breaker can be determined very quickly.

All parts are hidden inside the case, only the upper and lower screw clamps, control handle and indicator are visible from the outside. There is a latch on the case that allows you to quickly install the machine on and just as easy to dismantle it.

To turn off the machine, there is a special mechanism called a release. Each type of release has its own design. For example, in conventional machines, the function of a disconnecting device is performed by a coil with a winding and a core. For winding, copper insulated wire is used. The inclusion of the coil in the electrical circuit is carried out in series with the contacts, since it is through it that the load current moves. If this current exceeds the set permissible value, then under the influence of the magnetic field of the coil, the core moves and exerts a mechanical effect on the disconnecting device. As a result, the contacts of the circuit breaker open.

The design of the thermal release has its own characteristics. It includes a special bimetallic plate. For its manufacture, two types of metals are used, heterogeneous in composition and with different coefficients of linear expansion. The plate is connected to the circuit in series with the load. During the operation of the machine, it is heated by the current passing through it. In case of overload, the plate bends towards the metal with the lowest expansion coefficient. The trigger mechanism comes into action, turning off the machine. The greater the current exceeds the rated value, the faster the thermal release trips.

Installation of circuit breakers

The connection of circuit breakers in the switch cabinet is carried out in a certain sequence. From above, a cable is connected to an external current source, and through the output holes located below, the wiring is routed to its objects, in accordance with the electrical circuit.

At the beginning of the installation, an introductory machine is connected. If there are several lines in the circuit that are isolated from each other, they are separated from the introductory circuit breaker. Its power must not be less than the total power of the machines connected to separate lines. For this purpose, two- or four-pole devices of group D are selected that are resistant to the inclusion of power tools and other powerful equipment.

The most widely used, suitable for any power supply schemes for apartments and private houses. Modular circuit breakers are mounted on a DIN rail and connected by conductors with a current carrying capacity exceeding the operating current of the circuit breaker. A more convenient connection of several machines in one row can be performed using a special connecting bus. A piece of the required length is cut off from it and fixed in the terminals. Such a connection is possible due to the distance between the bus contacts, corresponding to the standard width of the modular machines. The switch is installed on the phase, and the neutral conductor is supplied from the input device directly to the devices.

• single pole the switch is used in the installation of sockets and lighting systems.
• Bipolar the machine is suitable for high power appliances, such as an electric stove or a boiler. In case of overloads, it is guaranteed to break the circuit. The connection diagram of such switches is practically no different from single-pole models. For more efficient use, it is recommended to connect them to a separate line.
• Three-pole the circuit breaker should be installed only in cases where it is planned to use electrical appliances operating at a voltage of 380 V. In order to exclude, the load is connected according to the "triangle" scheme. This connection does not require a neutral conductor, and the consumer is connected to his own switch.
• four-pole the circuit breaker is most often used as an input. The main condition for connection is the uniform distribution of the load on all phases. When connecting equipment according to the “star” scheme or three separate single-phase wires, excess current will flow through the neutral conductor.

With a uniform distribution of all loads, the neutral wire begins to perform a protective function in case of unforeseen power imbalances. To ensure a normal connection, only high-quality materials should be used. All connections must be securely fastened to the terminals. If several cables are connected at once, their contacts must be carefully cleaned and tinned.

The procedure during connection can be considered using the example of a two-pole circuit breaker installed in a shield. First of all, the electricity is turned off in order to completely de-energize the network. The absence of electricity is checked with an indicator screwdriver or a multimeter. Then the machine must be installed on a DIN rail and snapped into place. The absence of a mounting rail can create certain inconveniences. After that, the cores of the incoming and outgoing wires are cleaned to a distance of 8-10 mm.

Introductory wires are connected to two clamps located on top -. In the lower clamps, similar outgoing conductors are fixed, distributed to sockets, switches and electrical appliances. All wires are qualitatively clamped in the terminals with screws. The connections must be checked manually. To do this, the conductors must be gently moved from side to side. In the event of a poor-quality connection, the core will stagger in the terminal and may even jump out of it. In this case, the terminal screw must be tightened.

Upon completion of installation, voltage is applied to the network and the operability of the circuit breaker is checked.

How to choose the right machine

The correct choice of the circuit breaker is of great importance. Each device is distinguished by its own parameters, such as rated current, mains operating voltage, number of poles, maximum short-circuit current, time-current characteristic and other important values.

The operating time of the device has a digital designation indicating at what current the normal operation of the circuit breaker is maintained. In home electrical networks, machines with numbers 4500, 6000 and 10000 amperes are most often used. All technical characteristics are indicated by manufacturers directly on the device case. This also includes the connection diagram, as well as the symbol of the machine.

The main criteria for choosing a circuit breaker is the load power and the cross section of the wires used. In addition, the overload current and short-circuit breaking current are taken into account. As a rule, overloads in the network occur when devices and devices with a total power are turned on at the same time, causing excessive heating of conductors and contacts. Therefore, the tripping current of the machine installed in the circuit must be greater than or equal to the calculated one. Its value is defined as the sum of the capacities of all devices used, divided by 220.

The short-circuit tripping current also causes the machine to trip. It is selected by calculation for a specific circuit and depends on the loads used most often. In order to improve protection, they can be included in the electrical circuit.

Errors when installing the circuit breaker

When performing electrical work, serious mistakes are sometimes made that can lead to negative consequences in the course of further operation.

1. The power cable is connected from below. Although this is not prohibited by the PUE, such a scheme will be inconvenient, since the installation and placement of machines in the shield is designed specifically for the top connection.
2. A common mistake is to over-tighten the pins with the set screws. This can lead not only to damage to the core, but also to deformation of the body of the product.
3. Sometimes the wires are connected incorrectly. It is necessary to pay attention to the marking, connect the phase and neutral wires located on top with the same wires located below.
4. In some cases, one two-pole machine is replaced by two single-pole ones. This is absolutely impossible to do, since they do not provide simultaneous separation of the phase and zero.
5. Often, during the fixation of the core in contact, the insulation enters the seat. This leads to a weakening of the contact, resulting in overheating of the core and other negative consequences. Therefore, it is imperative to protect the wire in accordance with the technical requirements of a particular model of the machine. This operation must be carried out using a stripping tool.

A negative role can be played by the wrong choice of the circuit breaker, which subsequently is not able to withstand the planned loads. Therefore, it is recommended that you first perform all the necessary calculations, especially. It should be remembered that when calculating the value of the automaton should be rounded down. For example, with a current load of 20 A, the circuit breaker should be selected at 16 A, which will significantly increase the life of the wiring.