What is Miniature Circuit Breaker (MCB) and Work

Have you ever wondered why some of your appliances' switches are different from others, or why we have this box with cables running in and out? So, in this episode, we're going to address these concerns. Miniature circuit breakers, or MCBs, are the name given to these devices. They're used to guard against overload and short circuits, and they have separate mechanisms for each of the actions we'll look at. C 16 is printed on this MCB. As a result, this is a class C device with a 16-amp overload current. Let's open it up by removing the rivets. This is the input side of the equation.

This is where the phase wire is linked. After that, there's a bimetallic strip. This strip is composed of two metals. When metals are heated, they expand, and the rate of expansion varies depending on the metal. When two different metals are heated together, one metal expands more than the other, causing them to bend. Passing a current through a conductor, as in an MCB, may create heat. Then there's the contact that can be moved. The mechanism is used to switch on or off the MCB. The contact's other half is fixed. The solenoid coil receives electricity from the fixed contact.

This solenoid coil generates a magnetic field that pushes a plunger with a pin when it's needed. The output, which is sent to the appliances, comes next. An ark, or spark divider, is also included, which extinguishes the spark created while separating the contacts. Let's look at both scenarios because these MCBs are intended to guard against overload and short-circuit. We'll start with the overload problem. When the MCB is activated, current travels through the bimetallic strip, causing it to bend. Because the bending of the strip is determined by how it is made, various strips bend by varying amounts for the same current. The strip's bending is also influenced by the heat created by the current flowing through it.

The current through the MCB is plotted against the moment that the MCB trips. The bimetallic strip bends as the current increases. After that, the strip pushes on the little plastic portion, which rotates the mechanism. The springs then assist in breaking the circuit, reducing the time to break and causing the MCB to trip. The current flowing through the bimetallic strip stops when the circuit breaks and the strip regains its form. A spark can be created between the contacts at the same moment. Because this spark may cause harm to the components, it must be put out as quickly as possible. As a result, we now have a spark divider. The spark divider is just a collection of electrically separated metal plates that are spaced using insulators. With the aid of these guides, this spark travels from the contacts to the spark divider.

The guide is shaped in such a way that the spark will move towards the spark divider. Due to the increased distance between the guides, this spark may shatter, but if it does not, the spark is fractured into small numerous fragments by the spark divider, and they will not be able to sustain the spark for a long time, and it will be extinguished. You may also be aware that a spark is plasma and generates a great deal of heat. Because this heat might destroy the plastic case, we put a ceramic plate beneath and above it to protect it. The spark divider also aids in the dissipation of the spark's heat. Let's have a look at the short-circuit scenario now. A huge quantity of current goes through the MCB in a short circuit. A strong magnetic field is created as electricity runs through the solenoid.

The pin in the solenoid is pushed by the magnetic field. The pin pushes the mechanism, which separates the contacts, causing the MCB to trip and the current flow to halt. The spark divider also generates a spark, which dissipates. But why do we require two processes to complete the circuit breaker? Let's look at the first scenario, where the circuit breaker trips at 16 amps due to an overload, and the solenoid is used as the trigger. The solenoid will push the pin and the MCB will trip if the current exceeds 16 amps for a short period of time. You may also be aware that some appliances might draw more current than their rated amount during power surges. As a result, we'll need a mechanism that takes a long time to activate and won't trip the MCB during brief increases. As a result, we have a bimetallic strip.

When a little overload lasts for a long period or a huge overload lasts for a short time, this will be triggered. So, since the bimetallic strip may protect us from a short circuit, why do we need this solenoid trigger? Because the bimetallic strip takes time to heat up and expand, time is crucial in a short circuit. Because a short circuit must be terminated as quickly as possible, the solenoid is used to trigger the MCB. You now understand how an MCB works, but you may need to utilize it.