Miniature Circuit Breaker (MCB) is a safety circuit that is equipped with a thermal component (bimetal) for overload protection and is also equipped with an electromagnetic relay for short circuit protection.
Or in easy terms it can be defined that MCB is an alternating current breaker that works at a frequency of 50/60 Hz, voltage of 230/400 V, nominal current of no more than 125 A, and nominal short-circuit capacity of no more than 25 kA.
MCB symbol
MCB is a combination of a switch in the form of a mechanical system (to open and close the circuit) and a trip unit breaker (in the form of a bimetallic trip and a magnetic trip).
MCB parts:
How Do MCBs Work?
We can see in the picture above, when it is turned on (ON), the moving contact touches the fixed contact so that the MCB is ON (working). Then current flows in the bimetal (bimetap strip), this current can make the bimetal hot, causing the bimetal to bend.
The current that flows when it exceeds the ampere rating limit, the bimetal will be more curved until it is able to touch the trigger and pull the trip component so that it does not contact the upper terminal and at the same time the toggle/operating lever becomes OFF.
Advantages of using MCB
MCB is widely used for single-phase and three-phase circuit protection. The advantages of using MCB, namely:
- Can break a three-phase circuit even if there is a short circuit in one of the phases.
- Can be reused after the circuit is repaired due to short circuit or overload.
- Has a good response in the event of a short circuit or overload.
Security on MCB
There are two types of safety on the MCB, namely thermal and electromagnetic. What's the difference, here's a further explanation. Thermal protection serves to secure the overload current. And the electromagnetic safety has the function of securing in the event of a short circuit.
Thermal protection on the MCB has the same principle as thermal overload, namely using two metals that are combined (bimetal), thermal security has a delay, this depends on the amount of current that must be secured, while electromagnetic protection uses a coil that can pull an armature from iron. soft.
For more details, please look back at the picture of the MCB section.
Pole on MCB
Often termed MCB 1 Pole/1pole, MCB 2 Pole, 2 Pole, MCB 3 Pole. 3 poles to MCB 4 Pole/4 poles. Unlike the MCCB, the pole or poles on the MCB lever union with the desired number of poles are not permanent, meaning that we can remove them as needed. However, by merging this lever, it is intended that if there is a disturbance at one pole, the other poles will also be cut off.
