# Thermomagnetic circuit breaker, how does it work and what is it for?

Do you know how a thermomagnetic circuit breaker works? The circuit breaker is a very important protection device! In case you don’t know, there are several types of circuit breakers and each one has its specific characteristics. In this article, the World of Electrical will talk about thermomagnetic circuit breakers, come on guys!

The main function of the circuit breaker is to always protect the electrical conductors that are supplying the loads, regardless of the type of circuit breaker! It is important to always observe if the circuit breaker dimensioning is correct, in addition to other factors such as the circuit breaker curve .

Thermomagnetic Circuit Breaker
As the name suggests, this type of circuit breaker offers thermal protection and magnetic protection. It is one of the most used circuit breakers on the market, precisely because it has these two protection functions.

When we look at the price, we notice that the thermomagnetic circuit breaker is cheaper than the magnetic breaker. When comparing the price with the thermal breaker we can see that the price is very similar, but the thermal breaker has only one protective function, that is, it is much more worth investing in the thermomagnetic

! Thermal Protection: How does it work?

Let’s start by explaining the thermal protection, which is done through a bimetallic plate that is highlighted in the image below. This is the component responsible for the thermal protection of this circuit breaker.

What is the thermomagnetic circuit breaker for
Internal components of the thermomagnetic circuit breaker with detail on the bimetallic plate

The electric current that passes through the bimetallic plate causes heating, releasing energy in the form of heat, this phenomenon is known as the Joule effect. Now let’s explain how the protection happens, but to illustrate this, imagine a 10A circuit breaker.

In ideal operating conditions of the circuit breaker, the bimetallic plate will withstand any current less than or equal to 10A, that is, in these cases it will not suffer any kind of change in its mechanical characteristic, remaining the same way.

If the current exceeds 10A, remaining for a long time, it will cause the bimetallic plate to change shape, and this will cause the plate to come into contact with the internal mechanism that performs the circuit breaker shutdown.

It is important to highlight that even with the electric current below its nominal value, there are other factors that can generate heating and consequently the circuit breaker shutdown.

Magnetic Protection: How does it work?
Now we will explain the magnetic protection that is done through a coil in conjunction with a metallic piston as shown in the following image. The coil works as an inductor and the metallic piston is positioned inside the coil, but understand that there is no physical contact between them.

How does the circuit breaker work?
Internal components of the thermomagnetic circuit breaker with the highlight on the coil and metallic piston!

In case you don’t know, a magnetic field is created around the electrical conductor when current flows through it. This is important to understand because even under normal operating conditions there will be a magnetic field present.

Another important detail that you need to know is that the magnetic field is proportional to the current peak, that is, when a short circuit occurs, the current rises rapidly, so the magnetic field also increases inducing the metallic piston as if it were a magnet, and that’s where it all happens!

This movement of the piston causes it to activate the mechanism that will trip the circuit breaker. It is essential to understand that this whole process happens very quickly!

However well explained the article is, this activation of the circuit breaker protection mechanism cannot be completely imaged. So we recommend that you watch this video below the Mundo da Elétrica channel, because it is possible to see in detail how the protections are activated, and this will certainly make a difference in your knowledge about electrical.

I could see that the thermomagnetic circuit breaker is a simple device, but extremely efficient! Now imagine the risks that incorrectly sized electrical installations offer.

To avoid serious accidents it is important to always study electrical, so we invite you to continue accessing the articles on the site because they have a lot of free quality information just waiting for your access!