A circuit breaker or circuit breaker is a switching device that conducts currents under normal conditions in the circuit and automatically cuts off the supply of electricity from the mains to the consumer in the event of a short circuit or during overload; you can also turn the circuit on and off manually.
The main difference between a bipolar automaton and a unipolar one is the presence of an automaton both at phase and at zero, that is, at two poles. Moreover, when disconnected, both phase and zero are simultaneously disconnected, thanks to the common cocking handle. Used for mounting a single-phase circuit. For a three-phase circuit, 3- and 4-pole circuit breakers must be used.
Application area
- As introductory circuit breakers. This is the most popular use. When phase and zero are switched off at the same time, maximum safety is ensured when working in the circuit, because there is a complete blackout. In addition, according to the new rules of the Electrical Installation Device (clause 6.6.28, clause 3.1.18), the operation of single-pole circuit breakers at the input is prohibited.
- To protect a separate group of consumers of electricity. Disconnecting a two-pole circuit breaker will prevent the operation of an RCD (residual current device - designed to protect against differential currents) in the event of a false contact of zero and phase during repair work in circuits under load. It also facilitates the search for a branch with a malfunction when an RCD trips from leakage of currents to the ground.
- To protect and control circuits while simultaneously connecting power. For example, when connecting a heat gun through one pole of the machine, a phase is supplied to the heaters, and through another pole a phase is supplied to the fan motor. If one equipment shuts down, the other switches off too, which will prevent the likelihood of Tenes working without cooling.
Advantages of application over single-pole machines
Consider a situation where someone mixed up the phase with zero. Then, when disconnecting a single-pole circuit breaker, the zero line disconnects, and the phase remains in the circuit. A man, thinking that he has secured himself by turning off the machine, begins to work and receives an electric shock. To avoid this, after disconnecting the single-pole circuit breaker, it is necessary to check the absence of voltage in the circuit with an indicator. But it is still more reliable to use a bipolar circuit breaker, which will completely disconnect the circuit.
In the event that an RCD tripped, it is necessary to find a malfunction in the circuit. First of all, all electrical appliances from outlets are turned off. If this does not work, the chain branches are switched off sequentially, but both zero and phase must be disconnected. A single-pole machine does not provide such an opportunity. It is necessary to tilt the zero on the bus, which is problematic, since it requires dialing to find the desired wire. The bipolar automatic machine perfectly copes with this task.
Thus, the advantages:
- Safety - the whole circuit is broken.
- Ease of troubleshooting.
Disadvantages of using in front of single-pole machines
In fact, there are very few drawbacks:
- Cost - bipolar more expensive than unipolar.
- Ergonomics - take up twice as much space in the switchboard.
- Labor costs during installation - zero wires are not combined into a bus, and each is wound up in its own machine.
- The inability to use standard distribution buses is a "comb", instead of them you will have to use jumpers.
Machine device
The circuit breaker is a plastic case with contacts and an on / off handle. Inside is the working part. A stripped wire is inserted into the terminals and clamped with a screw. When cocked, the power contacts are closed - the position of the handle is "On". The handle is connected to the platoon mechanism, which, in turn, moves the power contacts. Electromagnetic and thermal splitters provide automatic shutdown in case of abnormal circuit conditions. The arcing chamber prevents combustion and quickly extinguishes the arc. The exhaust channel removes combustion gases from the housing.
Wiring diagram
It is proposed to consider the connection scheme of a bipolar machine.
Here VA 47-63 2 / 50A is an introductory two-pole machine. It completely de-energizes the entire circuit if necessary. Behind it, a counter and an RCD are connected. Next, the connection diagram of a number of single-pole circuit breakers is applied . They are installed only on phase wires, and zero conductors are distributed via a bus.
There is a scheme for connecting a number of bipolar machines that protect each branch.
The first to connect is an RCD, then two rows of bipolar switches. Blue indicates the neutral wire, red - phase, and yellow - grounding distributed using the grounding bus. Thus, each branch of the circuit is protected.
Mounting
How to mount circuit breakers in an electrical panel? At first, the din-rails are screwed in with self-tapping screws - these are metal plates, onto which then all automatic machines and RCDs are attached. The length of the din rail can be adjusted using a hacksaw. In addition, distribution terminal blocks are attached to the shield. They can be for neutral wires and separately for grounding. The modern configuration of the tires allows you to mount them directly on the din rail.
It is very simple to install a bipolar automatic machine on a din rail. Use a flat-blade screwdriver to pull out the latching bracket on the top of the case, place the machine on the din-rail, and release the mount. Removal is also carried out. According to the rules, the introductory machine is installed in the upper left corner.
Next you need to connect the wires. It should strictly adhere to the scheme. The input wires of the phase and zero are suitable for a bipolar circuit breaker from above, and from the bottom the conductors are assigned to the circuit. It is important not to confuse: the input is from above, the output is from below, otherwise the machine may fail and will not perform its functions.
Automata can be combined using jumpers made of copper wire of the same cross section as that of a circuit wire. Jumpers are required to connect bipolar circuit breakers in a row. And also with the help of combs - these are insulated tires, used to connect single-pole machines.
The ends of the wires are stripped using a special stripper tool or a sharp knife. Then crimp the cable ends with a hand tool with a crimper. If there is no such equipment, then you can simply irradiate the ends with a soldering iron using rosin and tin. When connecting wires to the machines, it is necessary to tighten the bolts firmly with a screwdriver so that poor contact does not cause heating and damage to conductive materials.
The ground wire always passes by machines directly from the ground bus. Zero wires are connected to the zero bus.
Marking
Particular attention should be paid to the marking of machines.
On the case of automatic machines there are special designations:
- Rated current of the device (in amperes).
- Overload current group (trip current range).
- Maximum tripping current or short circuit current (in amperes).
- Current limiting class (the higher the class, the higher the response speed with a short circuit).
- Graphic designation or circuit diagram of the device.
- A series of apparatus.
- The rated voltage at which you want to use the machine.
Machine selection
First you need to calculate the value of the rated current for your network. You can do this by the formula (Ohm's law):
I = P / U, where:
I - rated current in amperes "A".
P - power of all devices (total power) in watts "W".
U is the network voltage in volts "V" (mainly 220 V). Choose a machine with the nearest large value of the rated current.
Also, the choice of the machine according to the value of the long permissible current should be made, depending on the characteristics of the wiring cable. The rules of the electrical installation are given calculation tables. The larger the cable cross section, the higher the permissible continuous current.