Miniature circuit breaker

What is a Miniature Circuit Breaker (MCB)?

A miniature circuit breaker (MCB) is the most basic safety device in consumer units and machine control panels. It is used to prevent electrical faults such as short circuits or overcurrent issues that can damage an operating electrical system. In addition to industrial use, MCBs are also commonly found in residential homes and small buildings.

Components of a Miniature Circuit Breaker (MCB)

Thermal Unit / Bimetal Miniature Circuit Breaker (MCB)

• Component: Bi-metallic strip (two types of metal bonded together with different coefficients of thermal expansion)
• Function: Overload protection
• Operation: When the current exceeds the rated value (e.g., a 16A breaker with a 20A current flow), the bi-metallic strip heats up and gradually "bends" to trigger the mechanism that cuts off the circuit (with a delay according to standards, not immediate).

Magnetic Unit / Trip Coil Miniature Circuit Breaker (MCB)

• Component: Solenoid coil and iron core
• Function: Short circuit protection
• Operation: In the event of a short circuit, the current rapidly increases (hundreds or thousands of amps), creating a strong magnetic field that pulls the iron core to trigger the mechanism cutting off the circuit immediately (within 0.04 seconds or less).

Arc Chute / Arc Chamber Miniature Circuit Breaker (MCB)

• Function: To extinguish arc when contacts separate
• Operation: When the contacts separate while current is flowing, an arc is generated. This arc is pushed into multi-layer metal plates in the Arc Chute to divide it into smaller arcs and reduce its temperature until it extinguishes, preventing the breaker from exploding or burning.