Single-pole automatic device: device, specifications and connection features

A circuit breaker is a switching device that conducts an admissible electric current and cuts off the power when the rating is exceeded. It serves to protect against overload of electrical circuits. A single-pole circuit breaker provides protection for only one wire.

The device and the principle of operation

The main characteristics of the circuit breaker are the rating and the tripping speed. A single-pole automatic device is triggered by two mechanisms: thermal and electromagnetic releases. The first disconnects the circuit in the event of an increased load for a long time, and the second - instantly, with a short circuit.

The thermal protection device is a plate made of bimetal. When it passes a current above the maximum permissible, it gradually warms up and flexes, pushing the lever that turns off the machine. After cooling, the plate returns to its place, and the switch is again ready for operation. To enter the operational state, you must connect it manually.

The electromagnetic device consists of a coil with a core inside it. When an short-circuit current passes through the winding, an electromagnetic field arises that moves the core, which turns off the machine. In this case, the power contacts are disconnected, de-energizing the circuit. Since a large current passes through them, an arc arises. It enters the arc chute chamber, where parallel metal plates are located. With their help, the arc is crushed and disintegrates.

The automaton is also used as a switch by turning manually the control handle.

Use of a single-pole circuit breaker

Electrical wiring in the apartment branched into several groups. The connection of a single-pole circuit breaker is made by breaking the phase wire. It is mounted on the DIN rail, and the power cable is inserted into its upper terminal. The cable to be protected is connected to the lower 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 automata are connected to the power supply through the comb, and from the bottom one is routed in groups. Multiple standby units can be installed.


The circuit breakers are standard-labeled, which is read from top to bottom.

The body of the device shows the values of its main parameters:

  • The trade mark is EKF;
  • Number of the series - BA47-29;
  • The characteristic "C" and the rated current for a single-pole machine is 25A;
  • The rated supply voltage is 230/415 V;
  • Maximum permissible short-circuit breaking currents - 4500 A;
  • Class of current limitation - 3.

By brand, you can identify the manufacturer. Automatic machines should be chosen from well-known brands: Legrand, ABB, IEK, EKF, etc.

The inscription on the 230/415 V machine means that the device is capable of operating in single-phase and three-phase networks. Most of the devices in household wiring have this capability.

The rated current is the magnitude of the current strength at which the machine does not operate for a long time. If you increase it by 13%, it will turn off after one hour. The larger the value of the continuously flowing current, the faster the operation. The main purpose of the machine is to prevent overheating of the wiring when the load is connected. It is important that the current allowed for the conductor is greater than the nominal value of the apparatus, and not vice versa.

Time-current characteristic "C" means that the operation of both trip 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 in the entrance, then the apparatus with the characteristic "B" should be installed in the main panel. This means that with all the other identical characteristics it will work faster. Then do not have to run into the porch and turn on the gun there. The correct choice of a device with a suitable characteristic ensures the desired selectivity of operation.

The maximum permissible breaking current shows its maximum value, at which the machine can be turned off at least once.

Number of poles

If you choose a single-pole or two-pole machine, here it is important where to install it. At the main input of the housing flap, a two-terminal network should be installed. This will reliably disconnect the wiring at home during repairs, when you should turn off the phase together with the neutral. When two wires are entered into the house, it is possible to install an automaton with one pole. In the presence of a grounding conductor, a two-pole input automaton is placed.

At each branch of the home network, a single-pole machine is connected with the RCD.

If the apartment is powered by a three-phase circuit, you should install a four-pole machine at the main input.

Automatic single-pole: price

A single-pole automatic is cheaper than the rest in a line with a large number of poles. Products of domestic manufacturers can be bought for 40-50 rubles. And imported brands are already 150-200 rubles. It is important to choose the devices in terms of quality-price ratio, and not those that are cheaper.

Errors in the selection of automata

Choosing automatic switches, users make a number of mistakes.

  1. 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 on the wire cross-section.
  2. Often, the same machines are installed on all lines, which causes some of them to be overloaded. For outlets need protection at 25 A, and for lighting - 16 A. The line leading to the garage can be heavily loaded with powerful power tools. Here it is expedient to establish an automaton for 32 A.
  3. Do not choose the vending machines for the price. It is better to buy products of famous brands, where quality is guaranteed.


In order to select the required single-pole automatic machine without errors, it is necessary to understand the marking applied to the housing from the front side. The characteristics of the device are selected depending on the type of load to be connected and the section of the wiring.

Similar articles





Trending Now






Copyright © 2018 Theme powered by WordPress.