A circuit breaker or circuit breaker is a switching device that conducts currents under normal conditions in a circuit and automatically cuts off the supply of electricity from the mains to the consumer in the event of a short circuit or overload, you can also turn the circuit on and off manually.
The main difference between a bipolar machine and a single-pole machine is the presence of an automaton both in phase and at zero, that is, at two poles. Moreover, when disconnected, both the phase and zero are simultaneously disconnected, thanks to the common cocking handle. It is used for installation of a single-phase circuit. For a three-phase circuit, 3- and 4-pole circuit breakers must be used.
Scope of application
- As introductory circuit breakers. This is the most popular application. With the simultaneous disconnection of the phase and zero, 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 automatic machines at the input is prohibited.
- To protect a separate group of electricity consumers. Disabling a two-pole machinewill prevent the operation of the RCD (residual current device - designed to protect against differential currents) in case of erroneous contact of zero and phase during repair work in circuits under load. It also facilitates the search for a branch with a malfunction when the RCD is triggered from leakage currents to the ground.
- For protecting and controlling circuits while connecting power. For example, when a heat gun is connected, a phase is supplied to the heating elements through one pole of the machine, and a phase is supplied to the fan motor through the other pole. If one equipment shuts down, the other will shut down as well, preventing the heaters from running without cooling.
Advantages over single-pole machines
Let's consider a situation where someone mixed up the phase with zero. Then, when the single-pole machine is turned off, the zero line is disconnected, and the phase remains in the circuit. A person, thinking that he has secured himself by turning off the machine, begins to work and receives an electric shock. To prevent this from happening, after turning off the single-pole machine, you need to check the absence of voltage in the circuit with an indicator. But still it is more reliable to use a two-pole machine, which will completely de-energize the circuit.
In the case when the RCD has tripped, it is necessary to find a fault in the circuit. First of all, all electrical appliances from the sockets are turned off. If this does not work, the circuit branches are switched off in sequence, but both zero and phase must be disconnected. A single-pole machine does not provide such an opportunity. You will have to drop zero on the bus, which is problematic, as it requires a dial tone to find the right wire. A two-pole circuit breaker does an excellent job of this.
So the benefits:
- Safety - the electrical circuit is completely broken.
- Ease of troubleshooting.
Disadvantages of using before single-pole machines
In fact, there are very few shortcomings:
- Cost - double-pole is more expensive than single-pole.
- Ergonomic - take up twice as much space in the electrical panel.
- Labor costs during installation - neutral wires are not combined into a bus, but each starts up in its own machine.
- The impossibility of using standard distribution busbars - "combs", instead of them you will have to use jumpers.
Automatic 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 cocking mechanism, which, in turn, moves the power contacts. Electromagnetic and thermal splitters provide shutdown of the machine in case of abnormal circuit conditions. The arc chute prevents burning and extinguishes the arc quickly. The exhaust duct leads combustion gases out of the housing.
Connection diagram
It is proposed to consider the connection diagram of a two-pole machine.
Here BA 47-63 2/50A is an introductory two-pole machine. It completely de-energizes the entire circuit if necessary. A meter and an RCD are connected behind it. Next, a connection diagram for a number of single-pole circuit breakers is applied. They are installed only on the phase wires, and the neutral conductors are distributed via the bus.
There is a scheme for connecting a number of two-pole automata, each protecting its own branch.
First, the RCD is connected at the input, then two rows of two-pole switches. The neutral wire is marked in blue, the phase wire is red, and the ground wire, distributed using a ground bus, is yellow. Thus, each branch of the circuit is protected.
Installation
How to properly mount circuit breakers in the electrical panel? First, din-rails are screwed into it with self-tapping screws - these are metal plates, on which all automatic machines and RCDs are then attached. The length of the DIN rail can be adjusted with a hacksaw. In addition, distribution terminals-tires are attached to the shield. They can be for neutral wires and separately for ground wires. The modern busbar configuration allows you to mount them directly on the din rail.
Installing a two-pole machine on a DIN rail is very simple. With a flat screwdriver, you need to pull out the snap-in bracket on the top of the case, attach the machine to 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. You should strictly adhere to the scheme. The input wires of the phase and zero are connected to the two-pole machine from above, and the wires are led into the circuit from below. It is important not to confuse: the entrance is from above, the exit is from below, otherwise the machine may fail and will not perform its functions.
You can combine machines using jumpers made of copper wire of the same cross section as the circuit wire. Jumpers are required to connect two-pole machines 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 they are crimped with cable lugs with a crimper hand tool. If there is no such equipment, then you can simply tin the ends with a soldering iron using rosin and tin. When connecting wires to machines, it is necessary to firmly tighten the bolts with a screwdriver so that weak contact does not cause heating and damage to conductive materials.
The ground wire always goes past the machines straight from the ground bus. Neutral wires are connected to the zero bus.
Marking
Particular attention should be paid to marking machines.
Special markings are applied on the body of the machines:
- Rated current of the device (in amps).
- Overload current group (operating current range).
- Maximumoperating current or short-circuit current (in amps).
- Current limiting class (the higher the class, the faster the response speed in case of a short circuit).
- Graphic designation or circuit diagram of the device.
- Machine series.
- Rated voltage at which the machine should be used.
Selecting machine
First you need to calculate the value of the rated current for your network. This can be done using the formula (Ohm's law):
I=P/U where:
I - rated current in amperes "A".
P - power of all devices (sum of power) in watts "W".
U - mains voltage in volts "V" (mainly 220 V). You need to choose an automatic machine with the nearest large value of the rated current.
Also, the choice of the machine according to the value of the long-term permissible current should be made, depending on the characteristics of the wiring cable. The rules for the installation of electrical installations contain tables of calculations. The larger the cable section, the higher the permissible continuous current.
