MCB

What is Miniature Circuit Breaker (MCB)?

Miniature Circuit Board (MCB) is a safety device with significant commercial and residential applications. It is an electro-mechanically driven automatic circuit protection device. It’s an automatic safety mechanism that prevents damage to electrical circuits due to excess current flow. It uses for low-voltage electrical networks like lighting and small electrical appliances.
It operates automatically, meaning if a short circuit or overcurrent occurs, the MCB will automatically trip, disrupting the power supply and preventing any damage. However, these are sensitive to minimal current variations and detect minute levels that exceed safety limits. MCB uses to interrupt a circuit during overload & short circuits. It can be used as a substitute for fuses for domestic applications. The benefit of MCB over-fuses is that they are reusable even after interruption of the circuit after an overload or short circuit.

An MCB or miniature circuit breaker uses an electromagnetic device with a full enclosure encapsulated in molded insulation. Its primary function is to switch the circuit, i.e., to open the circuit (connected to it) automatically when the current passing through it (MCB) exceeds its setting. It can be manually switched ON and OFF, similar to a normal switch.

An MCB operates according to the magnitude of the overcurrent, which controls how long it operates. This means these get operated whenever overloads exist long enough to create a danger to the circuit being protected.

Therefore, MCBs don’t respond to transient loads such as switch surges and motor starting currents. Generally, these are designed to operate at less than 2.5 milliseconds during short circuit faults and 2 seconds to 2 minutes in case of overloads (depending on the current level). Read more