The most common protective electrical device is a single-phase circuit breaker breaking one line.
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The circuit is disconnected when the current exceeds the rated value. The larger it is, the higher the response speed. In addition, the circuit breaker is turned off during a short circuit, when a very large current arises in the protected circuit. Here the cutoff occurs instantly.
As an example, consider a block of outlets connected to a loop, to which several powerful consumers are connected at the same time. The current exceeds the nominal value, and the power wires begin to heat up. So that they do not melt, the machine disconnects the circuit in time.
The response of the device is selected so that the wires do not overheat. The circuit breaker also protects connected loads. But he does not save a person from direct exposure to electric current. To do this , protective shutdown devices are used .
Operating principle
Despite its simple appearance, a single-phase circuit breaker is a complex device. It may be electronic, but the most common classic electromechanical design.
The input terminal is always on top of the device. It is connected to a fixed contact. The lower output terminal is connected to the upper via a movable contact and a thermal release in the form of a bimetallic plate. An electromagnetic disconnecting device is also connected to them.
The movable contact is fixed by the spring in two stable positions - in the on and off states. The machine is set into operation only manually through the lever. Disabling is done automatically. The device can also be used as a switch.
In normal mode, electric current flows through a closed contact group of the machine. If the rating is exceeded, the circuit is overloaded. If this happens for a long time, the bimetallic plate gradually heats up and bends, pushing the lever of the release mechanism. The machine then triggers, the contacts open and the circuit breaks.
If a short circuit occurs, the electromagnetic tripping mechanism is activated, instantly turning off the power. In this case, a spark discharge arises between the contacts, forming an electric arc, which is extinguished between the plates in a special chamber.
Over time, the contacts begin to burn. The machine is designed primarily to protect wiring and it is often not recommended to use it as a switch. For switching, knife switches are used.
How to choose the right machine?
A single - phase circuit breaker is selected according to the cross-section of the wire and the load characteristics indicated on the marking on the front of the device.
According to the specified parameters, you can select the desired machine.
- E.NEXT - trademark (above) indicates the manufacturer. It is recommended to choose well-known brands. In this case, it should be guided by the fact that the level of the device is not much different from other electrical equipment.
- 220/400 V - 50 Hz - the inscription means that the machine is applicable in single-phase and three-phase networks with a frequency of 50 Hz.
- 4500 - current limit value in A, at which the circuit breaker trips at least once (current limitation class - 3).
- C16 - time-current characteristic (C) means that the shutdown mechanism will work with a five-fold increase in the rated current. It is best suited for household appliances and lighting. The number 16 indicates the face value. A single - phase circuit breaker 16A will not work for a long time with a current of 16 amperes. If it is increased by 13%, the circuit will disconnect in an hour. The larger the value, the faster the response.
In apartment wiring, class B devices are often used, where the cut-off current is 3 times higher than the nominal value. If you connect machines with categories B and C in series, the first one will work faster. This ensures the selectivity of the protection devices when all other characteristics are the same.
Single-phase circuit breaker: price
Single-pole devices are the cheapest in the range of automatic machines.
If we compare prices with the same characteristics, it turns out that for single-phase it is the lowest. There are many manufacturers of circuit breakers and you can always choose a brand that is suitable in cost and quality.
On a single-phase circuit breaker, Moscow offers a wide range of products at affordable prices. You can choose reliable devices from the popular ABB brand from 147 rubles. and above, from one to four poles.
Machine connection
A single-phase circuit breaker is mounted in the panel, with the exception of devices built into household appliances. The device is mounted on a DIN rail and secured with a latch.
The machine is installed as follows.
- Before connecting a single-phase circuit breaker, the electrical panel is de-energized with measures taken to prevent accidental supply of voltage.
- The machine is installed in a specific place. If there are empty spaces nearby, metal travel stops are installed.
- Power is connected to the top terminal, and the protected circuit is connected to the bottom. Wires are laid without sharp bends and strains. Stranded ends are provided with tips that should be crimped with a crimper.
- In the presence of a number of other machines with the distribution of one phase, comb busbars or jumpers with tips on two wires are used. The puff is tight, but not too strong.
- Power is supplied to the shield and the presence of voltage at the input and output terminals of the machine is checked.
- The circuit breaker is marked with an indication of the circuit to be protected.
Selection errors
- You should not focus on the total capacity of consumers. First of all, you need to calculate the wiring for protection against overload.
- The same machines are not installed on all lines. For sockets, they are taken at a current of 25 A, and for lighting - at 16 A.
- First of all, the devices are selected by characteristics and reliability, and then - by price.
Conclusion
The single-phase circuit breaker is designed to protect wiring and electrical appliances. Its characteristics should correspond to the cross section of the conductors and the loads. The competent use of automatic machines of categories B and C ensures the correct operation. For the right choice, you must understand the markings on the front of the device.