Miniature Circuit Breakers- What Are They?

INTRODUCTION:

Miniature Circuit Breakers are electromechanical devices used to protect the electrical circuits from over current. Miniature

Circuit Breakers are also called as MCB in short form. Over current in the electrical circuits are majorly caused by the following three things, short circuit, overload and faulty design. Miniature Circuit Breakers are better alternate to Fuse, because once an overload is detected, MCB does not require replacement. MCB offers most improved safety operation and it can be easily reset. It has also a greater convenience without incurring larger operating cost.

OPERATION:

The function of MCB is too simple. Once a fault in circuit is detected, MCB interrupts the flow of continuity current through the circuit. In simple terms, MCB operates like a switch, when the current flowing through it reaches a maximum fixed limit, it automatically turns off.  MCB are designed generally to protect against over current and over temperature faults which means in the sense of overheating.

There are two contacts available in the circuit, one is fixed and the other moveable. When the current reaches or exceeds the predefined limit a solenoid will give force to the moveable contact to open (At that time the fixed contact will be disconnected) and the MCB turns off by stopping the current to flow in the circuit. Therefore to restart the flow of current the MCB will be manually turned on. This is the mechanism used to protect the circuits from the faults arising due to over current or over load. A bi-metallic strip is used to protect against the fault arising due to over heating or increase in temperature. Generally MCBs are designed to trip within 2.5 millisecond when an over current fault arises. In case of overheating and temperature rise it will take for the MCB to trip 2 seconds to even 2 minutes.

 ADVANTAGES OF MCB COMPARED TO FUSE:

1. MCBs automatically switch off the electrical circuit when it meets faulty condition. MCB is more sensitive to over current than fuse.

2. When the switch operating knob comes to off position during tripping, the faulty portion of the electrical circuit can be easily identified. But in case of fuse, it is not possible.

3. In MCB fast restoration of supply is possible by switching operation and it is not possible in Fuse.

4. Electrically it is more safety in MCB than Fuse.

The only one disadvantage is MCB is bitwise costlier than Fuse.

APPLICATIONS:

MCBs are majorly used in Home electrical panels to protect from overload. Also used in lighting systems such as lamp lights, fluorescent lights etc, MCBs are more beneficial when we use heaters. It also used in many industrial appliances.