How does a MCB work ? Leave a comment

An MCB is an automatically operated electrical switch. Miniature circuit breakers are intended to prevent damage to an electrical circuit as a result of excess current. They are designed to trip during an overload or short circuit to protect against electrical faults and equipment failure.

MCB is an automatic switch that opens when excessive current flows through the circuit. It can be reclosed without any manual replacement. In the case of a fuse, once it has been operated, it must be replaced or rewired, depending on the type of the MCB. Hence, fuse is known as one of the sacrificial devices.

MCB protects wires from overloads and short-circuits. When we look on the inside of an MCB we can see how that actually works.

Short-circuit protection is located in the electromagnetic coil (green area). In the event of a short-circuit, the current rises very sharply and the coil creates a magnetic field that both trips the switching mechanism and opens the contacts via a quick release mechanism. The additional quick release for opening the contacts in the event of a short-circuit helps to keep the energy of the short-circuit to a minimum, which in turn keeps the ‘stress’ the wires are subjected to, as low as possible.

MCBs or Miniature Circuit Breakers are electromechanical devices which protect an electrical circuit from an overcurrent. The overcurrent, in an electrical circuit, may result from short circuit, overload or faulty design. An MCB is a better alternative to a Fuse since it does not require replacement once an overload is detected. Unlike fuse, an MCB can be easily reset and thus offers improved operational safety and greater convenience without incurring large operating cost.

MCB stands for Miniature Circuit Breaker. It is an electromechanical device used in electrical installations to protect circuits and electrical equipment from overcurrents and short circuits. The MCB is designed to automatically interrupt the flow of electric current in a circuit if it exceeds a predetermined value, thus preventing damage to the circuit or connected devices.

Here’s a simplified explanation of how an MCB works:

Bimetallic Strip: Inside the MCB, there is a bimetallic strip made up of two different metals with different thermal expansion coefficients. These metals are bonded together to form a strip that bends when heated.

Current Sensing: The MCB has a current-carrying path, and when current flows through it, it passes through a current-sensing mechanism. This mechanism usually consists of an electromagnetic coil or a current transformer that creates a magnetic field proportional to the current.

Magnetic Trip (Short Circuit Protection): In the event of a short circuit, where a very high current passes through the MCB, the magnetic field generated by the current-sensing mechanism becomes strong enough to attract the bimetallic strip. This causes the strip to bend rapidly, which triggers the tripping mechanism.