Construction And Working Of MCB Or Miniature Circuit Breaker

Hello Guys, welcome back to my blog. In this article, I will discuss the construction and working of MCB or miniature circuit breaker, quiz questions.

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Also read – Electrical Estimation And Costing Questions And Answers.

Miniature Circuit Breaker

The miniature circuit breaker is a protective device that protects the circuit from a fault condition. But the earth leakage circuit breaker has any advantages compared to the miniature circuit breaker. Before the circuit breaker, the fuse was used for protection but the fuse has disadvantages like once the fault occurs the lead inside the fuse will melt then again someone has to go to replace the lead, but the circuit breaker does not consist any lead, it is safe and it can be operated easily, low maintenance and we can operate circuit breaker manually or automatically.

The circuit breakers are again classified into various types: for domestic and industrial purposes, we use MCB and ELCB. A circuit breaker consists of fixed and moving contacts, both the contacts are touching each other while the circuit breaker is under normal conditions when the fault occurs the moving contact is pulled back by some mechanism.

Construction And Working Of MCB Or Miniature Circuit Breaker

The parts of the miniature circuit breaker are:

• 01. Outgoing Terminals
• 02. Bimetal Carrier
• 03. Bimetal Strip
• 04. Trip Lever
• 05. Solenoid Coil
• 06. Plunger
• 07. Operational Knob
• 08. Arc Chutes
• 09. Incoming Terminals

The miniature circuit breaker is a protective device that breaks or interrupts the circuit when an overload or short circuit occurs. The outer and inner layer of the circuit breaker is shown in the above figure. The circuit breaker mainly operates during short circuits and overloads. 

The overhead protection is achieved by a bimetallic strip when the overload occurs the bimetallic strip becomes heat and starts to deflect or bend. In doing so, it releases the latch mechanism and causes the contact to open. 

Whereas, the short circuit protection is given by the solenoid coil. On the occurrence of a short circuit, the short circuit current energizes the solenoid coil, thus the coil operates the plunger to move and to strike the trip lever which causes an immediate release of the latch mechanism. 

The operating time of a miniature circuit breaker is less than 5 milliseconds. The miniature circuit breakers are available with different ratings such as 5, 6, 10, 16, 20, 25, etc.

The arc cutes are used to vanish the arc produced in the circuit breaker while interrupting the circuit.

The outgoing and incoming terminals are used to connect the phase wires to the circuit breaker.

Quiz On MCB Or Miniature Circuit Breaker

01. The overload protection in the miniature circuit breaker is provided by?

• a. Plunger
• b. Solenoid Coil
• c. Bimetallic Strip
• d. All the above

Ans is a bimetallic strip, which gives protection against overload.

02. The short circuit protection in the miniature circuit breaker is provided by?

• a. Solenoid Coil
• b. Plunger
• c. Bimetallic Strip
• d. All the above

Ans is a solenoid coil, which gives protection against short circuit current.

03. The arc chutes are used to?

• a. To avoid overload
• b. To avoid short circuit
• c. To vanish arc
• d. To produce arc

Ans is to vanish arc.

04. Which is the most reliable?

• a. Earth Leakage Circuit Breaker
• b. Miniature Circuit Breaker
• c. Fuse.
• d. None of the above

The answer, you guys comment below.

05. Circuit Breaker can operate?

• a. Manually
• b. Automatically
• c. Both
• d. None of the above

The answer, you guys comment below.

I hope this article may help you all a lot.

Thank You For Reading……Bye…

Tags: Construction And Working Of MCB Or Miniature Circuit Breaker, What is MCB.

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