Single-phase circuit breaker: description, device and connection

The most common protective electrical device is a single - phase circuit breaker that breaks one line.

Appointment

The circuit is disconnected when the current exceeds the rated value. The bigger it is, the higher the response speed. In addition, the machine shuts down when there is a short circuit, when a very high current appears in the protected circuit. Here, the cutoff occurs instantaneously.

As an example, you can consider a block of plugged-in sockets, to which several powerful consumers are connected at the same time. The current thus exceeds the nominal value, and the power wires begin to heat up. So that they do not melt, the machine automatically switches off the chain in time.

The response of the device is selected so that the wires do not overheat. The circuit breaker also protects the connected loads. But man does not save from direct exposure to electric current. For this , the residual current device is used .

Operating principle

Despite the external simple appearance, the single-phase circuit breaker is a complex device. It can be electronic, but the most common is the classical electromechanical design.

The input terminal is always on top of the instrument. It is connected to a stationary contact. The lower output terminal is connected to the top via a movable contact and a thermal release in the form of a bimetallic plate. An electromagnetic tripping device is also connected to them.

The movable contact is fixed by a spring in two stable positions - in the switched on and off states. The automatic machine is set to the operating state only manually through the lever. Disconnection is automatic. The device can also be used as a switch.

In normal mode, electric current flows through the closed contact group of the machine. When the nominal value is exceeded, the circuit is overloaded. If this happens a long time, the bimetallic plate gradually heats up and flexes, pushing the release lever lever. The machine is triggered, the contacts open and the circuit is broken.

If a short circuit occurs, the electromagnetic tripping mechanism is activated, instantly turning the power off. 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, contacts begin to burn. The machine is designed primarily to protect the wiring and often use it as a switch is not recommended. Knobs are used for switching.

How to choose the machine?

A single-phase circuit breaker is selected for the wire section and load characteristics indicated on the label on the front side of the device.

With these parameters, you can select the desired machine.

1. E.NEXT - the trade mark (from above) indicates the manufacturer. It is recommended to choose well-known brands. In doing so, it should be guided by the fact that the level of the device is not much different from other electrical equipment.
2. 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.
3. 4500 - the value of the limiting current in A, at which the breaker will operate at least once (the current limit class is 3).
4. C16 - time-current characteristic (C) means that the trip mechanism will trip when the rated current is increased fivefold. It is best suited for household appliances and lighting. The number 16 shows the nominal. A single-phase 16A circuit-breaker will not operate for a long time at a current of 16 amps. If you increase it by 13%, the circuit will turn off after an hour. The larger the value, the faster the trigger will be.

In residential wiring, Class B devices are often used, where the cut-off current is 3 times the nominal value. If you sequentially connect machines with categories B and C, the first will work faster. Thus, the selectivity of the protection devices is ensured, when all other characteristics are the same.

Automatic switch single-phase: price

Apparatus with one pole is the cheapest in the size range of the line of automatic machines.

If we compare prices with the same characteristics, then it turns out that it has the lowest one for single-phase ones. Manufacturers of circuit breakers are now many and you can always choose a suitable price and quality brand.

On a single-phase circuit breaker, Moscow offers a wide range of products at affordable prices. You can choose reliable devices popular brand ABB from 147 rubles. And above, from one to four poles.

Connecting the machine

A single-phase circuit-breaker is mounted in the shield, except for devices built into household electrical appliances. The device is fixed to the DIN-rail and fixed by a latch.

The machine is installed as follows.

1. Before connecting a single-phase circuit-breaker, the electrical panel is de-energized taking measures to prevent accidental supply of voltage.
2. The machine is installed in a certain place. If there are a number of empty spaces, metal stops are installed.
3. The power supply is connected to the upper terminal, and the protected circuit to the lower terminal. The wires are laid without sharp bends and tensions. Multi-stranded ends are supplied with tips, which should be crimped with a crimper.
4. If there are a number of other machines with the distribution of one phase, comb-type tires or jumpers with two-wire tips are used. The tightening is done tight, but not too strong.
5. The board is energized and the voltage at the input and output terminals of the machine is checked.
6. The circuit breaker is marked with the indication of the protected circuit.

Selection errors

1. You should not focus on the total power of consumers. First of all, you need to calculate the wiring for overload protection.
2. On all lines the same automata are not installed. For sockets, they are taken for a current of 25 A, and for lighting - by 16 A.
3. First of all, the devices are chosen according to their characteristics and reliability, and then - at a price.

Conclusion

A single-phase circuit breaker is designed to protect wiring and electrical appliances. Its characteristics must correspond to the cross section of the conductors and the loads. Competent use of automata of categories B and C ensures correctness of operations. For correct selection, it is necessary to understand the markings printed on the front side of the device.