[Exact] Function of MCB Explained with examples

MCB Function advantages

Hey, we are going to discuss the detailed explanation of the MCB Function. MCB means Miniature Circuit Breaker. In this article, your all doubts will clear about the function of MCB. MCB is a very commonly known and widely used electrical protective equipment used from low voltage to high voltage circuits.

MCB can be called an Interrupting Device because it interrupts the current flow in a circuit when fault or error occurs. It also can be called an electromechanical device because is its construction and working depends on the mechanical arrangements operated by electricity.

Exact Function of MCB

MCB can provide only two functions to protect an electric circuit. Don't confuse about that, because most of the people have so many doubts and wrong arguments about MCB Function. Don't worry we will discuss in later. So, the two important Functions of MCB are,

1. Overcurrent Protection
2. Short Circuit Protection

Overcurrent Protection by MCB

Now, we will discuss how an MCB provides  Overcurrent Protection. MCB has an arrangement of Bimetallic strip which is connected with the Latch Mechanism of the MCB. The latch mechanism is associated with spring pressure, and it is used to turn on or off the MCB.

So when in normal condition current always flowing through the bimetallic strip and the magnetic coil but it does not affect the latch mechanism, because, in normal condition rated current flowing through the bimetallic strip, it does not become hot and no physical changes also occur.

But when overcurrent flowing through the bimetallic strip, it starts to become hot, and after some time the bimetallic strip will deflect by bending and it will hit the latch mechanism of MCB to turned off or trip the MCB.

So, when overcurrent fault occurs, MCB takes some time until the bimetallic strip becomes enough heated for bending and to hit the latch mechanism to turned off the MCB. This time depends upon the overcurrent flowing through the circuit, current ratings of the MCB.

So, remember that during an overcurrent fault, MCB cannot give instant protection, it takes some time.

Shortcircuit Protection by MCB

Now, we will discuss, how an MCB provides protection against short-circuit fault. For short circuit protection, MCB has a solenoid coil or tripping coil. As I told before, in normal condition always current flowing through the bimetallic strip and the magnetic coil or solenoid coil but no effect occurs to trip the MCB. During overcurrent fault, only the bimetallic strip affected and it trips the MCB after taking some time but the solenoid coil does not do anything.

In overcurrent fault, no effect occurs in the solenoid coil, because it is designed for extremely high current because we know that during short circuit fault, extremely high current flow and that time we need to trip the circuit instantly.

So, when a short circuit fault occurs, a very high current flow through the solenoid coil and it produces a magnetomotive force(MMF) which causes the plunger to hit the latch mechanism of the MCB to trip the MCB instantly.

So, remember that during short-circuit fault, MCB provides instant protection.

MCB can provide overvoltage or surge voltage protection?

Now we will discuss, can an MCB provide protection against overvoltage or surge voltage or voltage fluctuations. In simple words, NO. Don't be confused with Overvoltage and Overcurrent protection, both are different.

MCB is a current-controlled device, that means when overcurrent or high current flowing through it due to a short circuit or any other fault, it will trip and interrupt the circuit. But if there is high voltage or voltage fluctuation occur it does not do anything. Of course, if the high current flow due to that overvoltage, it will trip the circuit.

MCB can provide protection against Neutral Fault, Earth Fault, or Ground Fault?

MCB cannot give protection against Neutral Fault, Earth Fault, or Ground Fault because it cannot sense if there is any neutral fault or earth fault occurs in an electrical circuit. MCB only provides protection against the Overcurrent fault and Shortcircuit fault.

MCB can give protection against Electrical Shock?

The sudden convulsion of muscles with pain in the human body due to the flow of current through the body is called electrical shock. Only a few milliamperes current flow through the human body creates electrical shock. So when anyone got electrical shock only a few milliamperes extra current will flow in the circuit which does not any effect the operation of the MCB. So MCB cannot give protection against electrical shock.

Advantages of MCB(Miniature Circuit Breaker)

1. MCB provides protection against major important faults in any electrical circuit that is overcurrent fault and short-circuit fault.

2. During short circuit fault MCB provides instant protection which is a very good advantage of MCB.

3. MCB has ARC preventive arrangement in its construction, so during manually turn on or off no spark will occur.

4. MCB more sensitive than a fuse and its operation also so fast.

5. Instant power supply resume is possible with an MCB just manually turn on the MCB. 

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[Exact] Function of MCB Explained with examples [Exact] Function of MCB Explained with examples Reviewed by Author on October 06, 2020 Rating: 5
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