Miniature circuit breaker or MCB is an electrical protection device which cuts off electric circuit from power source during short circuit. During short circuit the circuit draws abnormally high current which can cause fire or other damage. To avoid such damage it is a must to isolate the shorted circuit from the rest of the power system or the power source. A miniature circuit breaker acts like an automatic fuse. In older days fuse was used in electrical system to protect the circuit. Whereas in today's modern installations circuit breakers are used in place of fuse. Fuse has the same function but it could not be switched on back after tripping once it broke. It requires to replace the whole burned fuse or to rewire it in case of re-wire-able fuse. Whereas in case of miniature circuit breaker, it could be reset after short circuit repair like a switch. The reset time is way too less for a miniature circuit breaker compared to a fuse repair or replacement. MCB or miniature circuit breaker is frequently used in latest installations and wiring. Some people think that miniature circuit breaker or MCB is more sensitive than a fuse. But this is not the reality. In reality the fuse is way too sensitive then miniature circuit breaker or mcb and a fuse works in almost all conditions. But in some special cases like in elcb or earth leakage circuit breaker. In case of earth leakage circuit breaker it provides a special feature of protection which a fuse can't provide. The research says that it needs half a cycle time of ac wave form to blow a fuse whereas a miniature circuit breaker needs one complete cycle or even more to trip it and to isolate the circuit. Anyway miniature circuit breaker is still the best choice of protection.
How MCB or miniature circuit breaker works
There are two types of trip arrangements in MCB or miniature circuit breaker. First is bimetallic temperature trip and second is electromagnetic trip. If high current or over current flows through bimetallic strip, it bends due to over temperature. A mechanical latching mechanism is attached to the bimetallic strip. The bend of bimetallic strip releases the latch. The mechanical latch is further attached to the tripping mechanism of the circuit breaker. The release of the latch cases to trip the circuit breaker and opens the contact and isolate the circuit attach to it. The other way is opening the contacts by electromagnetic force. When high current flows through the mcb, the electromagnet inside the mcb becomes stronger and attracting the plunger inside. The plunger is attached to the latch. the attraction of the plunger releases the latch and in this way the tripping mechanism of the circuit breaker is activated to the circuit breaker tirps and isolates the defective circuit from the power source.
MCB is designed to use and is not repaired if it is going defective. Normally they are thrown and replaced when they become defective. The replacement of the mcb is easy and it takes less time to replace. There are two types of protections inside an mcb. It provides protection against short circuit as well as against overloading. The electromagnet part provides protection against short circuit and the bimetallic part provides protection against overloading.
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