Close this search box.

Miniature Circuit Breaker (MCB)

A Miniature Circuit Breaker (MCB) is a crucial component in electrical systems designed to protect circuits from overloads and short circuits. As a safety device, the MCB automatically disconnects the electrical circuit when it detects excessive current, preventing potential damage to equipment and reducing the risk of electrical fires.

How Does a MCB Work?

A Miniature Circuit Breaker (MCB) works on the principle of thermal-magnetic protection, combining two mechanisms to provide effective circuit protection against overloads and short circuits. Let’s break down how each mechanism operates:

  • Thermal Protection:
      • The thermal component of the MCB is responsible for detecting prolonged overcurrents, such as those caused by an overload or a sustained high-power demand.
      • Inside the MCB, there is a bimetallic strip made of two different metals with different thermal expansion rates. When the current exceeds the rated value for an extended period, the bimetallic strip heats up.
      • As the strip heats, the metals expand at different rates, causing it to bend or warp. This bending action triggers the tripping mechanism.
  • Magnetic Protection:
    • The magnetic component of the MCB responds to short-circuit currents, which are sudden and high-intensity surges of electrical current.
    • Within the MCB, there is an electromagnetic coil that surrounds the current-carrying conductors. When a short circuit occurs, the intense magnetic field generated by the high current causes the coil to produce a force.
    • This force pulls down a metal lever, known as the tripping mechanism, which is connected to the MCB’s contacts. The downward movement of the lever leads to the rapid opening of the contacts, interrupting the current flow and disconnecting the faulty circuit.

Types of Miniature Circuit Breaker

MCBs come in various sizes and current ratings to accommodate different applications and load requirements. Commonly used in residential, commercial, and industrial settings, MCBs offer a reliable and standardized method of safeguarding electrical circuits.

Type B MCBs:

  • Suitable for general domestic applications.
  • Designed to trip when the current exceeds 3 to 5 times the rated current, making them versatile for a range of household appliances and circuits.

Type C MCBs:

  • Ideal for applications with inductive loads, such as motors and transformers.
  • Trip characteristics are set to respond to higher levels of inrush current, providing better protection for devices with moderate inductive components.

Type D MCBs:

  • Suited for circuits with high inrush currents, often found in industrial settings.
  • Designed to trip at currents higher than those encountered by Type B and C breakers, making them suitable for heavy-duty applications with substantial inductive loads.

Type K MCBs:

  • Specifically designed for air-conditioning and heat pump circuits.
  • They have unique trip characteristics that consider the inrush currents associated with these types of equipment.

Type Z MCBs:

  • Intended for circuits with high levels of impedance, such as those with long cable runs.
  • Their trip characteristics are adjusted to accommodate the increased impedance and prevent nuisance tripping.

MCB price in Bangladesh

Miniature Circuit Breaker (MCB) price in Bangladesh is influenced by various factors, each contributing to the overall cost. Brand reputation, current rating, number of poles, and additional features all play a significant role in determining the price of an MCB. The price range can vary based on the brand, with well-known names typically commanding a slightly higher cost. The current rating of an MCB, measured in amperes, is a critical factor affecting its price. Higher-rated MCBs, capable of handling larger electrical loads, often come with a higher price tag. 


In conclusion, the price of a Miniature Circuit Breaker is influenced by a combination of factors, and understanding these factors is crucial for making an informed purchase. Whether considering brand reputation, current rating, or additional features, consumers in Bangladesh have a variety of options to explore when looking for reliable MCBs.