The most common electrical protective device is a single-phase circuit breaker that breaks one line.
Destination
The circuit is disconnected when the current exceeds the rated value. The larger it is, the higher the response speed. In addition, the machine turns off in the event of a short circuit, when a very large current occurs in the protected circuit. Here the cutoff is instantaneous.
As an example, we can consider a block of sockets connected by a loop, to which several powerful consumers are simultaneously connected. The current in this case exceeds the nominal value, and the power wires begin to heat up. So that they do not melt, the machine turns off the circuit in time.
The reaction of the device is selected so that the wires do not overheat. The circuit breaker also protects the connected loads. But a person from direct exposureit does not save electricity. Residual current devices are used for this.
Operation principle
Despite its simple appearance, the single-phase circuit breaker is a complex device. It may be electronic, but the most common is the 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 one through a movable contact and a thermal release in the form of a bimetallic plate. They also have an electromagnetic disconnect device connected to them.
The movable contact is fixed by a spring in two stable positions - in the on and off states. The automatic machine is set to working condition only manually through the lever. Shutdown is automatic. The machine can also be used as a switch.
In normal mode, electric current flows through the closed contact group of the machine. If the rating is exceeded, the circuit is overloaded. If this happens for a long time, the bimetal plate gradually heats up and bends, pushing the lever of the release mechanism. At the same time, the machine works, the contacts open and the circuit breaks.
If a short circuit occurs, the electromagnetic trip mechanism is activated, cutting off the power instantly. In this case, a spark discharge occurs between the contacts, forming an electric arc, which is extinguished between the plates in a special chamber.
Over timecontacts start to burn. The machine is designed primarily to protect wiring and is often not recommended as a switch. Knife switches are used for switching.
How to choose the right machine?
The 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 side 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, you should be guided by the fact that the level of the device does not differ much 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 - the value of the limiting current in A, at which the circuit breaker will operate at least once (current limiting class - 3).
- C16 - time-current characteristic (C) means that the trip mechanism will operate at a fivefold increase in the rated current. It is best suited for household appliances and lighting. The number 16 shows the denomination. A single-phase 16A circuit breaker will not work for a long time at a current of 16 amperes. If it is increased by 13%, the circuit will turn off in an hour. The larger the value, the faster the response will be.
Class B devices are often used in apartment wiring, where the cut-off current is 3 times higher thanface value If you connect machines with categories B and C in series, the first one will work faster. This ensures the selectivity of protection devices when all other characteristics are the same.
Single-phase automatic switch: price
Single pole machines are the cheapest in the machine range.
If you compare prices with the same characteristics, it turns out that single-phase it is the lowest. There are many manufacturers of circuit breakers now and you can always choose a brand that is suitable for cost and quality.
On single-phase circuit breaker Moscow offers a wide range of products at reasonable prices. You can choose reliable devices of the popular ABB brand from 147 rubles. and above, from one to four poles.
Connecting the vending machine
The single-phase circuit breaker is mounted in a panel, with the exception of devices built into household electrical appliances. The device is mounted on a DIN rail and fixed with a latch.
The machine is installed as follows.
- Before connecting a single-phase circuit breaker, the electrical panel is de-energized with the adoption of measures to prevent accidental voltage supply.
- The machine is installed in a certain place. If there are empty seats nearby, metal movement stops are installed.
- Power is connected to the upper terminal, and protected to the lower terminalchain. Wires are laid without sharp bends and tensions. Stranded ends are supplied with ferrules, which should be crimped with a crimper.
- In the presence of a number of other machines with the distribution of one phase, bus-combs or jumpers with lugs for two wires are used. The puff is made 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 the protected circuit.
Choice errors
- You should not focus on the total power of consumers. First of all, you need to calculate the wiring for overload protection.
- 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, devices are selected according to their characteristics and reliability, and then - by price.
Conclusion
Single-phase circuit breaker is designed to protect wiring and electrical appliances. Its characteristics must correspond to the cross-section of conductors and loads. Proper use of automatic machines of categories B and C ensures the correct operation. For the right choice, you need to understand the markings on the front side of the device.
