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What are Miniature Circuit Breakers (MCBs)?

Earlier, the technology in use was – fuse. The efficiency of fuse was less and protection was almost impossible. Therefore, fuses had to be replaced with MCB for safety and better control for the electric system. MCBs or Miniature Circuit Breakers work as automatic electrical switches that are designed to protect an electrical circuit from damage. These are time delay tripping devices controlled by the magnitude of overcurrent. Generally, these are programmed to operate at less than 2.5 milliseconds during a short circuit and 2 seconds to 2 minutes in case of overloads (depending on the magnitude of current).

The device opens when excessive current flows through the circuit. Once the magnitude of current in the circuit returns to normal, it can go to its normal state without any manual replacement. To fulfill what it is required to do, the MCB is characterised by low current ratings and fixed trip settings. To comply with the domestic and commercial needs, a wide variety of MCBs have been in use nowadays with a breaking capacity of 10KA to 16 KA. However, the MCBs do not respond to transient loads such as switches surges and motor starting currents. On the basis of the current range at which they trip instantly, the MCBs are divided into three broad categories, i.e. Type B, Type C and Type D. Type B generally trip at 3 to 5 times rated current which is suitable for resistive or slightly inductive loads. The Type C one’s trip at 5 to 10 times rated current, therefore, it suitable for moderate inductive loads. The Type D MCB trip at 10 to 20 times rated current hence are suitable for loads with a high inductive component.

Whenever continuous current of higher magnitude flows through MCB, the bimetallic strip in the device is heated and deflects and bends. This deflection releases a mechanical latch that is linked to the operating mechanism. The current open the miniature circuit breaker contacts and breaks the flow of current in the circuit. To bring back power to the device, the MCB must be manually turned on. This mechanism protects electrical damage due to overcurrent or overload.

Schneider Electric India has designed Miniature Circuit Breakers which deploy electronic and thermal-magnetic technology. The protection of light switches, switchboards etc. is ensured because of the trust and the name the company carries. Thus, installations of MCBs and surge arresters are installed to protect from overload and short circuit. These are the best solution for residential and commercial applications.


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