Circuit breaker: characteristic. Current characteristics of circuit breakers

The article will tell you about the circuit breaker. Its characteristics and working principle will also be described. This simple device is now used in everyday life and industry, it replaced fusible inserts (fuses). True, the latter are still used, but for the most part as a protection against short circuits on high-voltage lines. But they have a design different from the one you used to observe in household appliances. These are ceramic containers filled with sand, inside which is a conductor - a working fusible part.

Operation of the circuit breaker

But it's worth talking about such a design as circuit breakers, technical characteristics and application areas to consider in more detail. In fact, this is a device for switching. With its help, current is carried in the circuit, but most importantly - protection against short circuits and overloads. It is also worth noting that protection also occurs with a decrease or increase in the supply voltage, a change in the direction of current flow. However, often such devices are used as a switch of electrical equipment (lighting, sockets, other consumers).

But it is worth paying attention to the fact that the device has a certain resource, so it is not recommended to use it for frequent switching on and off. It is much more effective to use simple switches. Most of the circuit breakers carry circuit switching manually. You independently move the lever to the "On" or "Off" position. But there are models that work with an electric drive. Thanks to the introduction of such units, it is possible to control the operation of the circuit breaker at any distance.

What is the principle of action based on?

As it was said before, automatic switches, technical characteristics of which are considered in the article, can be switched off manually. True, there is a small nuance - during the jump in voltage or excess current, an automatic trigger occurs. But these are emergency operation modes - it is from them that the protection of the electrical equipment included in the circuit is made. It is possible to divide all circuit breakers into three categories:

1. The maximum current value.
2. Decrease in supply voltage.
3. Increase in reverse power.

It is these functions that are performed by circuit breakers. The first open the circuit when an increase in current occurs. This is due to a short circuit or an increase in the load beyond the permissible limits.

But the circuit-breaker, the characteristic of which is given, takes precedence over the fuse - it is restored, therefore, to close the circuit it will only be necessary to move the lever. It should be noted that the installation of devices must be done in special shields. When choosing, it is necessary to be guided by data on what conditions are present in the room. Proceeding from them, a choice is made for the protection class of the shield.

Classification of circuit breakers

And now about what classification automatic circuit breakers VA have, technical characteristics of which are practically identical and differ only in their values. So, the categories of standard instruments:

1. Automatic switches of the installation class are manufactured in a plastic housing, which is completely protected. Therefore, they can be mounted in places with shared access. In particular, for switching lighting circuits.
2. Without the case, universal types are produced. Their purpose is to install exclusively inside the switchgear.
3. Circuit breakers with a response time of less than 5 milliseconds belong to the class of high-speed ones. Consequently, with a response time in the range of 10 milliseconds - are classified as non-fast. Another type of machine, in which the response time is the main characteristic - it is selective. The user can change the time value independently. For this purpose, a small plastic disc with a graduation is provided.
4. Reverse current circuit breakers are necessary for circuit protection in only one case: if there is a possibility of changing the direction of current flow through the circuit.
5. Non-polarized and polarized. The first disconnect the circuit when the current flows in different directions. The second - only when the current changes in the forward direction.

Basic Elements of Circuit Breakers

At the heart of the plate is a bimetal, but it alone can not ensure the full operation of the device. There is a circuit breaker, the characteristic of which is considered in the article, from several elements that directly affect all parameters. So, the main parts of any machine:

1. Contact system.
2. Arc interrupter.
3. Release.
4. The control mechanism.
5. The mechanism for free tripping.

Of course, if there is a case, then it must also be indicated in this list. Please note that the design does not provide for the repair of the device, so when developing a resource or the smallest breakdown, it is necessary to replace the machine with a new one. Do not even try to repair it, it still will not work.

Contact group and arrester

Note that the current characteristics of circuit breakers are different, therefore, the design of the elements also varies. The higher the current, the stronger and more reliable the design of all components. A group of contacts are fixed metal elements located on the body of the machine and the lever. With their help, the electrical circuit closes.

When disconnected or switched on, a small spark gap is formed between the contacts. The system for damping the arc is a chamber inside which there is a steel grating. With this simple mechanism, there is an improvement in performance, an increase in the life of the device, since the contacts are not damaged and there is no deposit left on them.

Release

The device for free uncoupling is a mechanism consisting of hinges. With its help, the contact group is closed and opened in all modes. There are electromagnetic release devices. They are based on an electromagnet whose anchor controls a group of contacts. Sometimes in the construction you can find a hydraulic deceleration system.

In many machines, thermal releases are used. Due to the heating of the bimetallic plate, when a large current flows, deformation occurs and the contacts disengage. But one of the most modern is a release based on semiconductors. In its design there is a current transformer, thanks to which the parameters are continuously measured. This is such a complicated circuit breaker. The characteristic of its operation depends on the type of release.