Miniature circuit breaker (MCB)

A miniature circuit breaker (MCB) is an Electrical Switch that automatically switches off the electrical circuit during an abnormal condition of the network means an overload condition as well as a faulty condition.

Nowadays we use an MCB in a low-voltage electrical network instead of a fuse. The fuse may not sense it but the miniature circuit breaker does it in a more reliable way. MCB is much more sensitive to overcurrent than a fuse.

Miniature Circuit Breaker architecture

Working Principle of MCB

Working principle of MCB

Different types of MCBs used in Electrical Protection Systems

In the context of Miniature Circuit Breakers (MCBs), the terms Type A, Type B, Type C, Type D, Type E, and Type F refer to different levels of protection provided by the device.

  1. Type A: Type A MCBs are designed to provide protection against over-current. They are suitable for use in circuits where the maximum expected current is known and relatively constant, such as lighting circuits.
  2. Type B: Type B MCBs are designed to provide protection against over-current and short circuits. They are suitable for use in circuits where the load is variable, such as in motor circuits.
  3. Type C: Type C MCBs are designed to provide protection against both over-current and earth fault currents. They are suitable for use in circuits where there is a high risk of earth fault currents, such as in circuits powered by direct current (DC) or in circuits that include sensitive electronic equipment.
  4. Type D: Type D MCBs are designed to provide protection against over-current and earth fault currents, with a higher tripping threshold than Type C MCBs. They are suitable for use in circuits where there is a high risk of earth fault currents, but where the fault current is expected to be higher than what can be protected by Type C MCBs.
  5. Type G: Type G MCBs are designed to provide protection against over-current and earth fault currents in residual current devices (RCDs) used in electrical systems.
  6. Type H: Type H MCBs are designed to provide protection against over-current and earth fault currents in electrical systems that are powered by direct current (DC).
  7. Type K: Type K MCBs are designed to provide protection against over-current and short circuits in electrical systems with high fault levels.