MCCB is a kind of electrical protection device, which can be regarded as the "Big Brother" of MCB, which is often used in small equipment of family or office. They are usually used when the load current exceeds the capacity of the MCB, or in applications where the trip current needs to be adjustable.

Although there are also versions with tripping current of only tens of amperes, MCCBs are generally much larger in size than MCBs and can handle up to thousands of amperes of current. Like all types of thermal magnetic circuit breakers, MCCB has two main protection modes:

Overload protection is realized by using bimetal strips. Under normal working conditions, the current passes through the bimetal strip continuously. However, if the current rises too long, the bimetal strip will bend due to heating effect and the contact will be disconnected, thus cutting off the load power supply.

Fault protection is an instantaneous response electromagnetic function, because the fault current needs to be cut off immediately. Once a fault occurs, the electromagnetic coil in the plastic case circuit breaker will be energized and the contacts tripped, thus cutting off the power supply of the circuit. Many plastic case circuit breakers have arc suppression function, which is used to cut off large current.

The MCCB also includes a circuit breaker that can manually trip the circuit breaker. This switch is used to disconnect the device from the power supply during maintenance or system upgrade.

Recent research and development of MCCB focuses on making "connection" more powerful, enabling remote control and monitoring. Many MCCB manufacturers now provide smart modules that meet factory 4.0 standards and can monitor and measure parameters such as phase current and voltage remotely. It also helps to calculate power and energy use, enabling plant operators to better understand their operating costs.