Types Of MCBs And Their Functionss

What is a Miniature Circuit Breaker? 

An MCB is a sort of electrical switch that runs on its own. Miniature circuit breakers are intended to safeguard an electrical circuit from damage caused by high currents. They are intended to trip in the event of an overload or short circuit to protect against electrical failures and equipment failure.

MCBs are frequently utilised in residential, commercial, and industrial environments as isolating components. They are part of a larger family of more potent circuit-breaking components.

What Is the Function of a Miniature Circuit Breaker?

Overcurrent – electrical current that exceeds a defined safe current – triggers tiny circuit breakers, which use a moderately robust mechanical mechanism designed to minimise failures and false alarms.

Excess current heats, bends and trips the bimetallic strip within the MCB. This activates a switch that separates the electrical contact points, causing the arc to be contained (electrical discharge). The arc chute is an insulated metal strip that divides and cools the arc. Once the fault has been repaired, and the MCBs have been reset, the connections shut again.

Explanation of Various MCB Types

There are several MCB types available: A, B, C, D, K, and Z. The three important variations, however, are type B, type C, and type D. Each is intended to respond to the probable strength of electrical surges in various contexts. These fluctuations are commonly referred to as their ‘trip curve,’ but they can also be their tripping characteristics or overcurrent characteristics.

Let’s look at the distinctions between each primary type:

  • Type B Circuit Breakers 

These are designed to trip when the current flowing through them reaches three to five times the acceptable maximum rated load.’

This is the most sensitive form of MCB, suited for household and low voltage commercial applications where any current surges are mostly minor.

  • Type C Circuit Breakers 

These are utilised for more powerful electrical devices in locations where surges are more likely – mainly commercial and industrial settings.

They are designed to trip at currents ranging from 5 to 10 times their rated load. Smaller electric motors and fluorescent lighting are two good examples.

  • D-type Circuit Breakers 

These MCBs are the least sensitive, triggering only when current exceeds ten to twenty times the acceptable maximum.

D-rated MCBs are designed for heavy-duty commercial and industrial applications where very high current surges occur occasionally. Welding equipment, X-ray machines, and other such items are examples.

Other MCB Varieties

There are a few more specialised MCB models available. These are some examples:

  • Type K MCBs 

These will trip when the current reaches eight to twelve times the limit recommended, and they are an excellent alternative for motors.

  • Z-type MCBs 

These are very sensitive MCBs. They trip when the current exceeds the rated load two to three times. They are employed with more fragile equipment, such as semiconductors, prone to short circuits. They are designed to trip at currents ranging from 5 to 10 times the rated load. 

Head over to Legrand to know more about MCBs!


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