Difference between MCB and MCCB : Introduction & Working principle

Nowadays we use more commonly Miniature Circuit Breaker or MCB in low voltage electrical network instead of fuse.

Compared to fuse,The MCB has following advantages.

  1. Automatically switches off the electrical circuit during abnormal condition such as over load and short-circuit condition
  2.  MCB is much more sensitive to over current than fuse.
  3. by using MCB the faulty zone of the electrical circuit can easily be identified. But in case of the fuse, for  faulty zone,fuse wire should be checked by opening fuse grip or cutout from fuse base.
  4. Quick restoration of supply can not be possible in case of the fuse as because fuses is rewirable for restoring the supply. But in the case of MCB, quick restoration is possible by just switching on operation.
  5. MCB provides more electrically safety than fuse.

Because of so many advantages of MCB over fuse units, in modern low voltage electrical supply, MCB is mostly used instead of fuse unit.Disadvantage of MCB over fuse is that MCB is more costlier than fuse unit system.

Miniature Circuit Breaker Working Principle

There are two modes of operation of miniature circuit breaker. One is due to electromagnetic effect of over current  and other due to thermal effect of over current. During short circuit condition, sudden rising of electric current, causes electromechanical displacement of plunger associated with tripping coil or solenoid of MCB. The plunger strikes the trip lever causing immediately open the circuit breaker contacts.The thermal operation of miniature circuit breaker is achieved with a bimetallic strip.when continuous over current flows through MCB, the bimetallic strip is deflected due to heating and by bending. This deflection of bimetallic strip releases mechanical latch.This causes to open the miniature circuit breaker contacts. This was a simple working principle of miniature circuit breaker working principle.

Difference between MCB and MCCB :- Mostly people are confused between MCB and MCCB. Although both are circuit breakers, there are actually some key differences between the two.

Let’s understand  the abbreviation stands for. “MCB” stands for “Miniature Circuit Breakers” while “MCCB” is “Molded Case Circuit Breaker.”

  • An MCB has less than 100 amps while an MCCB goes as high as 2,500 amps:-  The main difference between them  is their capacity with the MCB rated under 100 amps with an interrupting rating of under 18,000 amps. On the other hand, an MCCB can be used at high amps as 2,500 or as low as 10 depending on what is necessary. Their interrupting rating can be around 10,000 amps to 200,000 amps.
  •  MCB is mainly used for low-energy application such as home wiring or small electronic circuits. The MCCB is more used in application for high-power equipment.
  • Although an MCCB has a higher capacity than an MCB, both are classified under low voltage circuit breakers and  some MCCB units  can be tripped using only a remote control in electrical motor operation.

it is important to consider the amount of power when choosing between using an MCB and an MCCB. MCBs are mostly installed for home use while an MCCB is generally utilized for commercial or industrial purposes. As mentioned above, MCCB is more suited for higher energy application because of better capacity. In home use, the MCB is usually the choice. For heavier power requirements beyond the 2,500 amps, medium or high-voltage circuit breakers would be the next best possible choices.


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