To conduct currents under normal conditions and automatically turn off the voltage in cases of overload or short circuit, a special switching device is used. A bipolar machine is an electrical appliance with an automatic phase and zero, i.e., two poles. At the time of disconnection, the separation of neutral and phase occurs simultaneously. The equipment is used for a single-phase network.
Features of the operation of unipolar and bipolar AB
The difference between a single-pole device and a two-pole circuit breaker is the number of monitored networks. Single pole models are designed to turn off current on a single line. Two-terminal systems are responsible for two lines, comparing the electron flux and establishing the correspondence of values for the normal functioning of the network.
The devices will also differ in the design of the release. On bipolar, a trip element is installed, which immediately turns off the zero and phase in both automatic and manual mode. Another difference is the ability to use together with sophisticated equipment. A single-pole can be connected to a single-circuit power network, a two-terminal can be connected to household appliances that cannot be thrown on one line.
PUE rules prohibit the operation of single-pole models at the input.
Device and principle of operation
The bipolar circuit breaker is made in the form of a plastic case, equipped with contacts on the outside and a handle for turning it off / on. The handle is connected to the platoon, which provides the movement of power contacts. They are closed by turning the knob to "On". The sealed enclosure prevents dust and moisture from seeping in.
Work units are located inside. These are two splitters - electromagnetic and thermal, which are responsible for stopping the device in case of network damage. The elimination of fires is provided by the arcing chamber. Combustion gases are removed from the inside through a special channel. To connect, you need to put protected wires in the terminals and tighten them with a screw.
Principle of operation
Difavtomat with two poles operates on the principle of electromagnetic induction. The measuring transformer-sensor responds to differences in currents that have an input and output cable. Thus, the device controls the flow of differential current, turning off the circuit at abnormal values.
The transformer windings are designed according to the type of on-switching, and each generates its own magnetic flux in the core. If the flow is equal, the secondary current will be zero. The presence of a magnetic flux in the core activates the appearance of a secondary current, which contributes to the operation of the protection mechanism.
When the protective node is active, the contracts of the machine open.
Marking Circuit Breakers
On electrical circuits, a double circuit breaker is marked with unified designations. The icons on the device’s body allow the consumer to get complete information about the model:
- Manufacturer - brand name is indicated.
- Series - alphanumeric designation depends on the manufacturer's line.
- Time-current characteristic - the most common are B, C, D. Under conditions of active inductive load and working electronics, models K and Z are used. A universal household appliance is C.
- Rated current - the maximum current value at which the device will not turn off the network. For example, at a temperature of +30 degrees, models of 16 A are used, with an increase in the temperature regime, the rated current can be less than 16 A.
- Rated voltage - marked as V / V, it is constant ("-") or variable ("~").
- The shutdown current limit is the limit of short-circuit currents in Amperes, which can withstand a difavtomat.
- The current limitation class is class 1 (no marker, 10 ms), class 2 (6-10 ms), class 3 (2.5-6 ms). The marker looks like a number in a black square.
- The wiring diagram is another difference between single-pole and two-terminal. In the first case, the numbers 1 (top) and 2 (bottom) are used to indicate contacts. In the second - 1 and 3 (top), 2 and 4 (bottom);
- Article - a bar code or a QR code provide a choice of a specific model in the manufacturer's catalog.
By marking the voltage, you can find out which network the device is suitable for. 230 / 400V ~ - for single-phase type, 400 / 400V ~ - for three-phase.
Opportunities and purpose of multi-pole machines
The two-pole AB installation is designed to provide control:
- independent lines - in case of malfunctions, they are simultaneously turned off;
- indicators of each of the lines - if there are malfunctions, both are turned off;
- DC networks - similar disconnection reasons.
The introductory device will turn off the voltage in the entire apartment or house if failures appear in at least one area. The bag is convenient in that de-energizing can be done manually.
Device assignment
For a single-circuit circuit with single-phase wiring (grounded zero, the neutrals are shorted on neutral buses), the two-terminal circuit is not suitable. In this case, a single pole switch is mounted.
If it is not possible to connect several devices to a common network, use a two-terminal device. The machine is installed, because at the output of the transformer there is no neutral and phase. The electric current, cutting off on one wire, may remain on the other. The bipolar device replaces the differential protection and RCD systems, which eliminates the cost of acquiring discrete devices.
Four- and three-phase models function similarly.
PUE are allowed to install a 2-pole circuit breaker at the input, but it is impossible to connect a grounding cable to it.
Cons of bipolar circuit breakers
Multipole power line protection devices have several disadvantages:
- breakdown of a cable by an electric current with a simultaneous closure of two networks;
- power failure throughout the wiring in case of failure of the thermal release;
- the inability to turn on the power after fixing the AB in the event of an emergency breakdown along one line;
- sensitivity to mechanical damage.
Despite the list of negative properties, models for providing control on two lines are popular. They ensure the safety of the common network in case of breakdowns on the line to which high-power equipment is thrown.
Installation and wiring diagrams
The bipolar circuit breaker is installed in accordance with the electrification plan. The device body is checked for damage and deformation before installation. The shutdown knob should work qualitatively at manual start. Installation is carried out only on a flat surface.
In the process of work take into account:
- type of connection of copper conductors with a cross section of 16-25 mm2 - by means of cable lugs (GOST 9688-82);
- features of connecting aluminum cables with end parts similar to TAM-7 (GOST 9581-80);
- connecting the conductors from the power source to the upper group of stationary switches without effort on the automatic terminals;
- termination of conductors - carried out using insulating tubes and protective tape;
- the minimum distance from the metal nodes of the distribution equipment is from above from 30 to 50 mm, from the side from 5 to 10 mm;
- the possibility of location in an additional box - a shield without a cover, the entry of the drive unit is checked.
After installation, check the bipolar for on and off quality.
Used circuits
The machine is installed on a din rail. The latch bracket at the top of the case is removed with a flat screwdriver, then put the device on the rail and release the fasteners.
During installation, a standard scheme is used:
- An input switch is placed in front of the counter.
- After the counter with the input to one phase, a bipolar device is mounted.
- From above, the input of zero and phase is connected, from the bottom the wires are taken into the circuit.
To combine several devices using jumpers from a copper wire. Their ends are cleaned with a sharp object, crimped with a crimper. The second option - tin and tin rosin ends with a soldering iron.
Tighten the bolts tightly so that when heating the wiring is not damaged.
How to choose a two-terminal
To choose a good protective device, you should focus on the cross-sectional area of the connection wire. To do this, you need to calculate the value.
First, you should calculate the power and current of the equipment on the power line from the machine. For the current in the circuit, the formula I = P / 220 is used, where 220 is the rated voltage, I is the current (A), P is the power (W).
Next, select the type of wire, focusing on the table.
| Current strength, A | Network power, W | Copper wire cross section | Cross section of aluminum wire |
| 1 | 0,2 | 1 | 2,5 |
| 2 | 0,4 | 1 | 2,5 |
| 3 | 0,7 | 1 | 2,5 |
| 4 | 0,9 | 1 | 2,5 |
| 5 | 1,1 | 1 | 2,5 |
| 6 | 1,3 | 1 | 2,5 |
| 8 | 1,7 | 1 | 2,5 |
| 10 | 2,2 | 1,5 | 2,5 |
| 16 | 3,5 | 1,5 | 4 |
| 20 | 4,4 | 2,5 | 6 |
Focusing on the data obtained, it is possible to choose an automatic machine taking into account thermal inertia during heating.
The current in the wires should be greater than the current of the difavtomat, and the latter should be greater than the current load.
Security measures when installing bipolar circuit breakers
Install a two-pole circuit breaker in accordance with the safety instructions:
- Work together with an assistant to control the process.
- Mount the device only after permission from the Housing Office, Energy Supervision.
- Protect hands with rubber gloves, stand on a rubberized mat.
- Installation is made on a din rail or a guard.
- The mounting location must not be damaged.
- Fix the power cable to the protection device to the fixed contacts.
- Before installation, turn off the electricity in the apartment, check the voltage with a multimeter or a screwdriver.
The bipolar circuit breaker provides reliable protection for the power line, equipment in case of overcurrent during short circuit. Understanding the purpose, design features and adhering to the installation diagram, you can secure household appliances and sophisticated industrial equipment.
