What is MCB? Full Form, Working, Use, Applications

what is mcb

MCB is an electrical protective device that automatically disconnects or isolates a circuit when an electrical fault(overload or short circuit) occurs. The full form of MCB is Miniature Circuit Breaker. MCB also can be called an automatic electrical switch that is used to protect low voltage electrical circuits. MCB is the lowest power or voltage-rated circuit breaker. It is available up to 125A. Above 125A circuits, other types of circuit breakers are used. MCB replaced the fuses used in older days for electrical protection. Nowadays, MCB is the most usable protective device for low voltage circuits in domestic as well as industrial applications. They used as Protective Device as well as Switching Device.

How does an MCB Works?

The working principle of MCB is very simple. It is an electromechanical device. It provides two functions - 1. Overcurrent Fault Protection and 2. Short Circuit Fault Protection

For the overcurrent fault protection, the MCB has bi-metallic strips. The current always flows through these bi-metallic strips. When overcurrent fault occurs, the bi-metallic strips got heated and their shapes change. The bimetallic strips are arranged in such a way that in the normal condition they keep the contacts closed when the strips overheated due to the overcurrent fault they break the contact so the current flow stops or the load disconnect from the main power supply. During the Overcurrent fault, it does not trip instantly, it takes some time to trip that depends on the magnitude of the fault current.

For the short circuit fault protection, the MCB has an electromagnetic coil. When the short circuit fault occurs a very high current flows through this coil. So this coil breaks the contacts by tripping the plunger. In normal conditions, this electromagnetic coil remains energized but it does not any action. As we know during the overcurrent fault, the MCB takes some time to trip or break the circuit. This time depends upon the heating of the bimetallic strip or magnitude of the fault current. But during the short circuit fault, the MCB instantly trips or breaks the circuit as the coil energized quickly.

Without rectifying the fault, if we try to turn On the MCB, it will got tripped again and again until we remove the fault.

MCB Features

1. MCB can automatically trip or break the circuit when an overcurrent fault or short circuit fault occurs.

2. It is very easy to use and safe to operate.

3. After removing the fault the MCB can easily turn on there is nothing to replace like a fuse.

4. MCB is very sensitive than a Fuse, compact, and easy to instal and easy to connect.

5. MCB can be used as a Switching Device also as well as a protective device.

MCB is classified into many types based on poles, construction, response time, etc. But you can find the MCBs in the market classified according to poles such as Single Pole MCB, Double Pole MCB, Triple Pole MCB. 

Single pole MCB allows only one input and one output. Generally, the single-pole MCB is used with phase or live wire when it is used in a single-phase system. On the other hand, the double pole MCB allows two inputs and two outputs. Same, the Tripple pole MCBs are used in three-phase systems that allow three inputs and three outputs.

MCB Use and Applications

1. MCB is used in the house wiring circuits as the main breaker or as a switch of electrical appliances such as Air Conditioner, refrigerator, washing machines.

2. MCB is not only used in domestic applications even it is used in industrial applications as a protective device.

3. MCB is used as protective device in electrical appliances instead of fuse.

4. MCB used in machinery Control, motor control, power control devices, circuits, or systems.

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What is MCB? Full Form, Working, Use, Applications What is MCB? Full Form, Working, Use, Applications Reviewed by Author on December 08, 2021 Rating: 5
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