What is a Molded Case Circuit Breaker (MCCB) ?

What is a Molded Case Circuit Breaker (MCCB) ?

What is a Molded Case Circuit Breaker?

Molded case circuit breakers (MCCBs) are a type of electrical protection device that is designed to protect electrical circuits from overload or short circuits and also used for switching ON/OFF the circuits. MCCB is commonly used when load currents exceed the capabilities of Miniature Circuit Breaker (MCB).

MCCBs are commonly used in heavy-duty industrial applications.

How does the Molded Case Circuit Breakers work?

MCCB works by interrupting the flow of electricity when the current flowing through it exceeds its rated capacity. When a fault occurs, the trip unit of the MCCB detects the fault and sends signals to the operating mechanism, which opens the contacts of the MCCB and stops the flow of current.

MCCB Operating Mechanism;

Thermal Magnetic Mechanism

In a thermal magnetic trip unit, there are two elements: thermal and magnetic element. The thermal element is made up of a bimetallic strip that bend due to the heat generated by an overload current. The bimetallic strip bends and activates the trip unit, which then sends a signal to the operating mechanism to open the contacts of the MCCB when the current exceeds a pre-set level.

The magnetic element consists of a coil that generates a magnetic field when a short circuit occurs. Magnetic fields pull a plunger when the trip unit detects a fault condition, the magnetic fields pull a plunger, activating trip unit and opening the contact of the MCCB.

Electronic Mechanism

In an electronic trip unit, microprocessors and sensors are used to monitor the current flowing through the MCCB. The trip unit compares the measured current with the pre-set current values and sends a signal to the operating mechanism to open the contacts if a fault condition is detected.

MCCB can also act as a manual switch to switch ON/OFF the power supply to the circuit. It is used whenever the power supply must be disconnected in case of emergency or maintenance.


MCCB is a crucial component in modern electrical systems. They help to protect circuits from overloads and short circuits, helping to prevent electrical fires and other hazards. If you are installing a new electrical system or upgrading an existing one, make sure to take into account the benefits of using MCCBs to protect your circuits and keep your premise safe.

At See Kwong we have varieties of MCCB for you to choose.

#Terasaki #LS #Shihlin Electric

Come visit our Ipoh store or browse www.seekwong.com for more info.