A circuit breaker is a switching device that conducts permissible electric current and cuts off power when the rating is exceeded. It serves to protect against overloading of electrical circuits. A single-pole circuit breaker provides protection for only one wire.
Device and principle of operation
The main characteristics of the circuit breaker are the rating and trip speed. A single-pole circuit breaker is triggered by two mechanisms: thermal and electromagnetic releases. The first disconnects the circuit in case of increased load for a long time, and the second instantly, with a short circuit.
The thermal protection device is a bimetal plate. When a current passes through it above the maximum permissible, it gradually warms up and bends, pushing the lever that turns off the machine. After cooling, the plate returns to its place and the switch is ready for operation again. To enter the operational state, you must connect it manually.
An electromagnetic device consists of a coil with a core located inside it. When a short circuit current passes through the winding, an electromagnetic field appears that moves the core, which turns off the machine. At the same time, the power contacts open, disconnecting the circuit. Since a large current passes through them, an arc arises. It enters the interrupter chamber, where parallel metal plates are located. With their help, the arc breaks up and decays.
The machine is also used as a switch by manually turning the control handle.
Application of a single pole circuit breaker
The electrical wiring in the apartment branches into several groups. The connection of a single-pole circuit breaker is made to break the phase wire. It is mounted on a DIN rail, and a power wire is inserted into its upper clamp. The shielded wire connects to the bottom terminal. If the wires are pressed with screws, they must be tightened with a little effort.
As a rule, the upper terminals of single-pole circuit breakers are connected to the power supply through the comb, and the lower ones are wired into groups. You can install multiple backup devices.
Marking
Circuit breakers are standardly labeled and read from top to bottom.
The values of its main parameters are marked on the body of the device:
- trademark - EKF;
- series number - BA47-29;
- characteristic "C" and the rated current for a single-pole machine - 25A;
- rated supply voltage - 230/415 V;
- maximum permissible short-circuit breaking currents - 4500 A;
- current limitation class - 3.
By brand you can determine the manufacturer. It is advisable to choose automatic machines from well-known brands: Legrand, ABB, IEK, EKF, etc.
The inscription on the machine 230/415 V means that the device is capable of working in single-phase and three-phase networks. Most devices in household wiring have this capability.
The rated current is the amount of current at which the machine will not work for a long time. If it is increased by 13%, it will turn off after an hour. The larger the value of the continuously flowing current, the faster the response. The main goal of the machine is to prevent overheating of the wiring when connecting the load. It is important that the current allowed for the conductor is greater than the nominal value of the device, and not vice versa.
The time-current characteristic “C” means that the tripping of both tripping mechanisms will occur after a five-fold increase in the rated current. It is suitable for lighting and most household appliances. If there is an automatic machine with such a characteristic at the entrance, then in the apartment panel an apparatus with characteristic “B” should be installed on the main entrance. This means that with all other identical characteristics, it will work faster. Then you do not have to run into the porch and turn on the machine there. Choosing the right device with the right characteristic ensures the right selectivity.
The maximum permissible tripping current shows its maximum value at which the machine is able to trip at least once.
Number of poles
If you choose a single-pole or two-pole machine, it is important where to install it. At the main entrance of the apartment shield, a two-terminal should be installed. This will reliably de-energize the house wiring during repairs, when the phase should be disconnected together with the neutral. When 2 wires are inserted into the house, you can install a machine with one pole. In the presence of a grounding conductor, a two-pole input circuit breaker is installed.
On each branch of the home network, a single-pole machine is connected together with an RCD.
If the apartment is supplied with power according to a three-phase circuit, a four-pole circuit breaker should be installed on the main input.
Automatic single-pole: price
A single-pole machine is cheaper among the others in the line with a large number of poles. Domestic products can be bought for 40-50 rubles., And imported brands are already 150-200 rubles. It is important to choose devices according to the quality-price ratio, and not those that are cheaper.
Errors when choosing machines
When choosing circuit breakers, users make a number of mistakes.
- They focus on the total power consumption instead of protecting the wiring from overload. Installing a powerful machine on weak wiring leads to its overheating. It is important to select the device according to the cross section of the wire.
- Often the same machines are installed on all lines, which is why some of them are overloaded. For sockets, protection is required at 25 A, and for lighting - 16 A. The line leading to the garage can be heavily loaded with powerful power tools. It is advisable to install the machine on 32 A.
- Do not choose machines for the price. It is better to purchase products of well-known brands where quality is guaranteed.
Conclusion
In order to select the correct single-pole circuit breaker without errors, you should understand the markings on the front of the case. The characteristics of the device are selected depending on the type of connected load and the wiring section.