The article will talk about the circuit breaker. Its characteristic and principle of operation will also be described. This simple device is used today in everyday life and industry, it has replaced fuse-links (fuses). True, the latter are still used, but for the most part as protection against short circuits on high voltage lines. But they have a design different from that which you are used to observing in household appliances. These are ceramic containers filled with sand, inside of which there is a conductor - the working fusible part.
Circuit breaker operation
But it’s worth talking about such a design as circuit breakers, their technical characteristics and their applications can be considered in more detail. In fact, this is a device for switching. With its help, current is carried out in the circuit, but the most important thing is protection against short circuit and overloads. It is also worth noting that protection also occurs with a decrease or increase in supply voltage, a change in the direction of current flow. True, often such devices are used as a switch for electrical equipment (lighting, sockets, other consumers).
But it is worth paying attention to the fact that the device has a certain resource, therefore it is not recommended to use it for frequent switching on and off. The use of simple switches will be much more effective. Most circuit breakers carry out manual circuit switching. You independently turn the lever to the "On" position or off. But there are models that work with an electric drive. Thanks to the introduction of such nodes, it is possible to control the operation of the circuit breaker at any distance.
What is the principle of operation based on?
As mentioned earlier, circuit breakers, the technical characteristics of which are discussed in the article, can be switched off manually. True, there is a small nuance - during a power surge or an excess of current, automatic operation occurs. But these are emergency modes of operation - it is from them that the electrical equipment included in the circuit is protected. It is possible to divide all circuit breakers into three categories:
- The maximum current value.
- Reduced supply voltage.
- Increases reverse power.
It is these functions that circuit breakers perform. The former opens the circuit when an increase in current occurs. This occurs with a short circuit or an increase in load in excess of permissible limits.
But the circuit breaker, the characteristic of which is given, has an advantage over the fuse - it is restored, therefore, to close the circuit, you only need to move the lever. It should be noted that the installation of devices should be made in special shields. When choosing, it is necessary to be guided by data on what conditions are present in the room. Based on them, the choice is made of the protection class of the shield.
Classification of circuit breakers
And now about what classification VA circuit breakers have, whose technical characteristics are almost the same and differ only in values. So, the categories of standard devices:
- Installation class circuit breakers are made in a plastic case that is fully protected. Therefore, they can be mounted in public places. In particular, for switching lighting circuits.
- Without a case, universal types are available. Their purpose is installation exclusively inside switchgears.
- Circuit breakers with a response time of less than 5 milliseconds belong to the class of high-speed. Therefore, with a response time in the range of 10 milliseconds - belong to the category of non-operating. Another type of automatic machines in which the response time is the main characteristic is selective. The user can change the time value independently. For this purpose, a small plastic disc with graduation is provided.
- Reverse current circuit breakers are necessary to protect circuits only in one case: if there is a possibility of a change in the direction of current flow along the circuit.
- Unpolarized and polarized. The former disconnect the circuit when current flows in different directions. The second - only when the current changes in the forward direction.
The main elements of circuit breakers
It is based on a plate of bimetal, but it alone cannot ensure the full operation of the device. The circuit breaker, the characteristic of which is considered in the article, consists of several elements that directly affect all parameters. So, the main parts of any machine:
- Contact system.
- Arcing grid.
- Trip units.
- Control mechanism.
- The mechanism for free trip.
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, therefore, when running out of resources or the smallest breakdown, it is necessary to replace the machine with a new one. You shouldn’t even try to repair it, nothing will come out anyway.
Contact Group and Arcing Grid
Please note that the current characteristics of the circuit breakers are different, therefore, the designs of the elements also differ. The higher the current, the stronger and more reliable the design of all components. A group of contacts is fixed metal elements located on the machine body and lever. With their help, an electrical circuit is closed.
When turning off or on between the contacts a small spark gap is formed. An arc extinguishing system is a chamber inside which there is a steel grate. With the help of this simple mechanism, the characteristics are improved, the life of the device is increased, since the contacts are not damaged and no deposits remain on them.
Trip units
A device for free disengagement is a mechanism consisting of hinges. With its help, the contact group is closed and opened in all modes. There are electromagnetic trip devices. They are based on an electromagnet whose anchor controls a group of contacts. Sometimes in the design you can find a hydraulic deceleration system.
Many machines use thermal releases. 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 semiconductor based release. In its design there is a current transformer, due to which the parameters are constantly measured. Here is such a difficult circuit breaker. The response characteristic of it depends on the type of release.