A two-pole switch is designed to control and compare the operation of two sections of the same electrical network. In the event of a short circuit, like other faults in any area, both lines are automatically disconnected. Its work can be compared with the action of two single-pole circuit breakers. But the fact is that the protection and blocking circuit of the machine is designed to compare the parameters of each device separately, so they cannot be replaced with single-pole switches.
Content
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Device device
- Electromagnetic protection mechanism
- Thermal release
- Connection diagrams
- Popular models
- Advantages and disadvantages of machines
Device device
A conventional machine protects and can disconnect only one line. Its design is based on this condition. The unit serving two lines has additional elements that allow you to disconnect zero and phase simultaneously in two circuits. That's what a two-pole machine is for.
Usually it is installed in a single-phase 220 V network, and three-pole and four-pole machines are used to protect electrical lines with three-phase voltage.
The important protection elements in a 2-pole circuit breaker are:- electromagnetic mechanism;
- thermal release.
Electromagnetic protection mechanism
The structural elements of this protection are triggered at the moment a short circuit appears in one of the lines. At the same time, currents of large magnitude appear in the circuit, which can exceed the permissible value by several thousand times.
To prevent cables and household equipment from burning out, the protection mechanism is triggered in a split second and breaks the supply network. Typically, each device has a response time designation.
Marking is applied to the machine body in the form of letters of the Latin alphabet, each of which corresponds to a specific response time. The structure of the mechanism consists of a core (solenoid), which is connected with a moving contact.
The solenoid is located inside a spring that connects the thermal release in series with the power contacts. The operating current is too small for the magnetic flux to draw in the core.
When the current increases sharply, the coil pulls in the solenoid, compressing the spring, and it disconnects the contacts. In the normal state, the spring is released and the contacts are connected again.
Thermal release
A distinctive feature of this protective mechanism is that it works much slower than the electromagnetic one. He is able to withstand the maximum load for some time, and if it does not fall to the operating value, it will disconnect the contacts. By the way, this mechanism does not react in any way to a short-term change in the current strength.
The release design includes:
- bimetallic plate;
- release lever;
- contacts.
At a normal current strength, the free part of the plate is next to the lever that turns off the mechanism. As the load increases, the plate will begin to heat up and bend. At the same time, it begins to act on the lever, and that, in turn, acts on the contacts and opens them.
Connection diagrams
Diagram and installation of the device directly depends on the presence of a ground loop. If only two wires (zero and phase) with a voltage of 220 V enter the house, then single-pole circuit breakers can be installed in the main panel. In this case, the phase is connected to the machine itself.
If there is also a third incoming wire (ground), then a two-pole device must be installed. Zero and phase are directly connected to the switch, and the ground wire is routed to the apartments through the terminal box. Then both wires from the machine are connected to the electricity meter and single-pole machines, which are distributed into control groups.
In the case of arranging a three-phase network, if there is no grounding, a three-pole switch is installed. In this case, wires of three phases are connected to the protective device, and zero is bred to consumers in a separate circuit.
If a grounding wire is present in the circuit, then a four-pole device is installed at the input, to which three phases and zero are connected, and the grounding is wired with a separate line according to the devices.
Popular models
Currently, there is a large selection of double-pole switches. Products of the Swedish-Swiss company ABB are especially popular. The following models are popular:
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2P 32A ABB SH 202LC32 is a circuit breaker designed for use inside houses and apartments. Due to its simplified design, it has a low price. It is possible to connect power to both the upper contacts and the lower ones. - 2P 06A ABB SH202LC6 is a device with a reduced module height, which greatly facilitates its installation. The switch is installed manually, without using a screwdriver. It is designed for a rated current of 6A.
- 32A Legrand TX3 is an automatic machine produced by Polish manufacturers and is characterized by excellent qualities. The device is used at a rated current of 32A. Such devices are used both in office buildings and in residential buildings.
And also the IEK brand is well known from Russian manufacturers, which occupies a leading place in the "Electrical" category.
Advantages and disadvantages of machines
These switches there are some shortcomings in operation. Although there are few of them, you should pay attention to them. If both lines are short-circuited, breakdown and failure of the two-pole machine are possible.
If one of the circuits is faulty, the device may sometimes not turn on. Failure of the thermal release is possible, although the entire electrical network will work properly. Unlike single-pole, double-pole machines are more likely to be mechanically damaged.
But nevertheless, despite the presence of these disadvantages, machines are popular, especially in apartments where powerful household appliances are installed on the same line. For example, they ensure safe operation of the washing machine and dishwasher on the same circuit.
If you install a three-pole switch, then it is allowed to connect to one line of the oven. It is best to distribute the connection of complex devices evenly before installing them. This option will ensure long-term and safe operation of double-pole switches and the entire electrical circuit.
