MINIATURE CIRCUIT BREAKERS (MCB) - How MCB work

MCB are electromechanical devices which protect an electrical circuit from an overcurrent. The overcurrent, in an electrical circuit, may result from short circuit, overload or faulty design. An MCB is a better alternative to a Fuse since it does not require replacement once an overload is detected. Unlike fuse, an MCB can be easily reset and thus offers improved operational safety and greater convenience without incurring large operating cost.

The principal of operation is simple. An MCB functions by interrupting the continuity of electrical flow through the circuit once a fault is detected. In simple terms MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowable limit. Generally MCB are designed to protect against over current and over temperature faults (over heating).

 

There are two contacts one is fixed and the other movable. When the current exceeds the predefined limit a solenoid forces the movable contact to open and disconnect from the fixed contact. So the MCB turns off thereby stopping the current to flow in the circuit. In order to restart the flow of current the MCB is manually turned on. This mechanism is used to protect from the faults arising due to over current or over load.

 

To protect against fault arising due to over heating or increase in temperature a bi-metallic strip is used. MCBs are generally designed to trip within 2.5 millisecond when an over current fault arises. In case of temperature rise or over heating it may take 2 seconds to 2 minutes for the MCB to trip.

 

This article covers the insight of a single pole MCB commonly used in the house hold. The following image shows the different internal parts of an MCB with top casing removed.

 

THE IMPORTANCE OF CIRCUIT BREAKERS

A circuit breaker is a very important part of electrical wiring in a home because it is a very essential safety feature. Without circuit breakers, household electricity would not even be practical because of the potential danger of a fire and other hazards. It is an automatically, operated electrical switch that is especially designed to protect electrical circuits from any kind of damage, if there is a short circuit or overload. The main function of the circuit breaker is to detect any fault condition and stop continuity in order to discontinue the flow of electricity. Majority of the households, short circuits are responsible for the outbreaks of fire.

Short Circuit and the Importance of a Breaker

A short circuit is generally an abnormal low-resistance current, in between two nodes of an electrical circuit that are usually meant to have different voltages. This ends up having an excess flow of electric current and causes circuit damage that can lead to a fire, overheating and even explosion. Short circuit mainly occurs due to overloading or mostly due to fire breakout. To avoid this, a good circuit breaker is important to protect your home. It is also necessary to get the electrical appliances checked by licensed and professional electrician.

The breakers are generally more expensive than fuses. But most homeowners prefer breakers than fuses because of the safety factor associated with them. Plus, most electricians and electrical wiring experts prefer these breakers instead of old fashioned fuses.