A lot of people are unable to differentiate between MCB and MCCB. The two are both circuit breakers but there are actually specific differences between them. Both MCB and MCCB are made for specific functions. Let us start with the fundamentals.

What is an MCB?

First, MCB is initial for Minor Circuit Breaker. A Miniature Current Breaker is an electrical button that is operated automatically. The purpose of a Miniature Circuit Breaker is to prevent excess current from damaging an electric circuit. The MCB is made in a way that the trip in case of electric overload or short circuit. This way, MCB protects electrical appliances from electrical failure and electrical damage.

The Miniature Circuit Breakers are majorly used in domestic, business, and industrial settings as isolating components. Among the many circuit-breaking appliances, MCBs form part of this circuit-breaking group.

How does Miniature Circuit Breaker work?

The major trigger for Miniature Circuit Breaker is the current overload. An excess current is a current that exceeds the designated safe current. The MCBs have a relatively advanced mechanical system that is formulated to reduce electric failure and unnecessary alarms.

Current overload overheats the bimetallic part within the Miniature Breaking Circuit which bend and trip. The tripping of the bimetallic strip causes the release and separation of the switch that moves the point of electrical contact apart hence causing electrical discharge by confining the arc. The arc chute is an insulated metal strip that cools and divides the arc. Once the MCBs are reset and the fault has been fixed, the contact is made again to allow current flow.

A Miniature Circuit Breaker is structured to protect the circuits from both excess flow of electric current and short-circuits. There are different processes the MCB detects current overload and short-circuiting. Protection from excess current is prevented using thermal operation provided by the metallic strip of the MCB while the tripping of the coil provides protection against short-circuiting through electro-magnetic action.

In case the electric discharge is high, the bimetallic strip of the MCB will trip and activate at a fast speed of close to a second. If there is a current overload closer to the recommended limits, MCB will respond slowly.

What is an MCCB

What is an MCCB?

MCCB stands for, Moulded Case Circuit Breaker. Like the MCB, MCCB is also used in the electrical protection of electrical devices. MCCB can be used for a variety of voltages with a trip setting that is adjustable.MCCB is mostly used for voltages above 250 amp. Essentially molded case circuit breakers protect the whole electrical system from excess current and cases if short-circuiting.

How does MCCB WORK?

Just like the MCB, MCCB uses thermal elements (temperature-sensitive device) and the electro-magnetic sensitive device to cause the tripping action of the bimetallic strip for separation and protection function. MCCB provides protection from; current overload, short-circuit current, and electrical switch disconnection.


The thermal components or temperature-sensitive elements f MCCB protects the circuits from current overload. The bimetallic strip allows the current to flow at a normal temperature but when there is current overload, it causes the bimetallic strip to overheat and bent away hence separating the contact which interrupts the current flow hence protecting the entire electrical circuit system.

2. Electrical short circuit protection

The quick response of the MCCB protects the circuit using the electromagnetic principle. The magnetic fields pull the trip upwards which opens the contact. In addition, MCCB can be fixed as the main switch which can be used to manually disconnect the flow of current during an emergency.

What are the differences between MCB and MCCB?

Although both the MCB and MCCB have similarities in functioning and operational principles, they have a lot of differences.

1. Initials and definitions

MCCB stands are initials for molded case circuit breakers while MCB is initials for miniature circuit breakers. The operational principle for MCCB and MCB are similar but MCCB has an air-break system found within the housing molded with non-conducting materials.

2. Difference in size

The miniature circuit breaker is smaller than MCCB. The size of a single-pole of MCB is 17.5mm while MCCB has a much bigger size than that.

3. Difference in the current rating

The current rating for MCB is about 125A while that of MCCB is 3200A indicating that MCCB has the ability to carry more current which allows the MCCB to be applicable in a wide variety of functions.

4. Current adjustment and time delay

The tripping action of MCCB is adjustable by use of dipswitches and trip units while the tripping action of MCB is a little bit slower. Electronic MCCB that has long delay tripping features can o be used to attain its protective characteristics.

5. Difference in-circuit location

MCCB is mainly used to break upstream circuits while MCB is used in breaking branch circuits. MCB is preferably used in installations in the small business and domestic settings while MCCB is used in installations of bigger industries and businesses.

6. Maintenance difference

The simple design of MCB makes its maintenance routine simple. However, MCCB has a lot of sophisticated parts which are modern and call for sufficient maintenance and inspection routine. It is not advisable to use MCB for appliances intended for regular short-circuiting.

Fundamentals features of Circuit breaker

There are basic characteristics of current breaker which include;

Current operational rate

The voltage level at which the circuit breaker performs the best in conducive conditions is called the voltage rate.

The current rate (ln)

The circuit breaker is designed to operate at a specific temperature called rated current. The current-carrying parts of the circuit breaker are not supposed to exceed the current rate.

Framing size rating

Some circuiting breakers can be made with dropping features with ranges of varying current measures to match the highest tripping unit.

More characteristics of circuit breaker

(Ui) Insulated rated voltage

Creepage distance and the dielectric voltage test are measured using the rated insulated voltage. The value of Ui ahold always remains higher than that of the value of voltage.

(lcm) Rated making capacity

The excess current instantaneous values that the circuit breaker is able to attain at a specified voltage are called the lcm.

Other features of CB are; rated servicing -circuit breaking capacity, fault voltage limitations, and rated impulse withstand voltage.

CHINT CB products center

CHINT CB products center has CBs ranging from low voltage devices, power transform devices, meters, and instruments. It also deals in building equipment and all the products are of good quality and at affordable prices.


It is crucial to select the correct MCB and MCCB for the required application. It will help in protecting facilities with high current power appliances. Maintenance of circuit breakers is also important when the trip action has occurred.

Nelson James
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