MCB (Miniature Circuit Breaker)

Miniature circuit breakers are the circuit breakers used in residential and small commercial installations. They control and protect the electrical supply within respective electrical circuits. The MCBs have been in use for a long time. The design has been modified continuously to make a reliable and effective circuit breaker which can be manufactured economically on a large scale. They include an electrical contact placed on a moving contact carrier that moves away from a fixed contact to disturb the current path.

Circuit breakers are used to protect and control the electricity supply in the electrical circuits. They are electrical switching appliances which protect the electrical circuitry from being damaged. The damage or disruption occurred in the circuits can be due to several reasons. It can be due to excess of current, or due to overload conditions.

The structure of electrical systems is almost similar in all purpose applications whether in industrial, commercial or residential. All of them include a panel board for receiving power from the source. It is then transmitted from the panel board to designated branch circuits. Then different types of circuit interrupters are connected to these branch circuits. These interrupters are added to minimize the risk of injuries, harms from fire or any other damages.

The circuit interrupters include circuit breakers, MCB, motor starters, motor controllers etc. They all have a trip mechanism which breaks the electrical contact inside the circuit breaker in case an over current condition occurs. It stops the flow of current through the circuit.

Miniature circuit breakers (MCB) are being used now-a-days in recent devices in place of fuses. They are replacing fuses rapidly because their biggest advantage is that there is no need to replace any wire or components like as in fuses. They can be reset manually. They are equipped either with a button that can be put on or a lever that can be flicked to reset it. The tripping of MCB indicates that either there is some problem in the path of circuit. Either it has been overloaded or a short circuit has occurred. It is important to identify the fault before resetting the MCB.

Usually all MCBs have a movable handle extended outside the frame. They have three main positions: on, off, and tripped. The positions exhibit the operator about the condition of contacts within the frame. The on condition tells that the contact inside the frame is closed and the current is flowing. The off condition tells that the contact is open and no current is flowing in that circuit. While the third option is automatically releasable to effect tripping operations. The trip mechanism may include either a thermal trip capability or a magnetic trip capability. The former one responds to continuous low level over current and the later one responds to higher overload current.

MCB may also be used in combination with arc fault or ground fault trip systems. Some of them are provided with a ground fault detection system connected with the active mechanism. They open the contacts in case there is any occurrence of the event of a neutral-to-ground fault or a line-to-ground fault. They are known as ground fault circuit breakers. It is made of a toroidal coil and a circuit board.

• Industrial uses: There are a lot of applications of miniature circuit breakers in different types of industries. Usually they are high voltage circuit breakers. They are used in automobile industry, iron industry, production industries etc.
  
  
• Domestic uses: They are equally useful for domestic applications. For domestic uses high voltage circuit breakers are rarely used.
  
  
• Commercial uses: In different commercial organizations the sophisticated electrical equipment require an additional care. MCBs are very helpful in these conditions.