What is a circuit breaker?

In the modern world, we are surrounded by so many different technical devices that some of them we just do not notice. This statement may seem incredible, but everyone can be sure of this at any moment. It is enough, for example, to try to remember which trees are growing around a high-rise building. Or to say exactly how many steps are in the stairwell. Most will not succeed. And, in fact, we encounter these things thousands of times. This is explained very simply: the mind unloads itself, interacting with some things without accentuating attention. Needless to say, the circuit breaker - this necessary element of almost all electric circuits - turns out to be a "dark horse".

The unobtrusive helper

Once I happened to witness an amazing situation: a person with a higher education, whose work experience with electrical installations was calculated for years, bought a modern washing machine and decided to make the work with it more convenient, without further ado, connected to the network through a switch. The idea is really good. But only the circuit was broken not by an automatic switch, but by a toggle switch on a chain, similar to that installed in wall lamps - sconces. Not surprisingly, after a short time, everything in this switch burned out. So, today we will talk about how to choose a circuit breaker, what they are and why they are needed. After all, if a person whose specialty is electrical engineering has thought of this, what can you expect from the others?

Indispensable circuit breaker

Let's see why it is called that way. The word "switch" is known to everyone - it is a device that provides the possibility of switching the electrical circuit. Clicking the toggle switch - and the light in the room lights up, a second click - and everything goes out. When the light is on, the switch passes a current through itself. In part, it can be compared to a ball valve in a water supply system.

But the word "automatic" means that the device can in some cases automatically turn on or off. Usually the circuit breaks. Inside the case there are two mechanisms that constantly monitor the magnitude of the current and, if it is excessively increased, the circuit breaker is switched off. The first is a thermal release. It is represented by a bimetallic plate, which bends when heated and releases the return mechanism from the lock. The second one is magnetic. It is made in the form of an inductor, which by its magnetic field (if the current is too high) breaks the circuit in the device.

Kinds of "automatic machines"

Depending on the number of switched lines, one-and multi-pole devices are distinguished. That is, with the movement of one toggle switch, several chains can be used at once. For example, a bipolar circuit-breaker installed in an electrical panel protects the connected branches from overload and heating (thermal release), as well as from a short circuit (magnetic set point).

Selection

Thus, the selection of the "automatic machine" is performed on the rated current. This value is always indicated on the housing. It should not be less than a line that will be switched and protected by this device. By the way, that's why you can not install simple toggle switches on powerful equipment, since the amount of current flowing is too high.

The number of poles is selected individually. Here it is necessary to take as much as necessary. Some models allow you to combine the chassis into a single unit, increasing the number of switched lines.

Type (B, C, D) indicates the short-circuit breaking ratio . "B" will break the chain with current growth of only 3-5 times, but the popular "C" class will work already at a tenfold excess of the nominal value.