What is Molded Case Circuit Breaker? Where is it used for?

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MCCB stands for Molded Case Circuit Breaker and helps protect electrical equipment from fault currents such as overcurrents, short circuits and other electrical faults. Molded case circuit breakers are suitable for switchboards, plug-ins, switchboards and motors. It also works like a fuse and doesn't need to be replaced when a short circuit is detected.

MCCB circuit breakers are available in frame sizes ranging from 15 amps to 3200 amps. The trip unit is divided into thermal magnetic trip and electronic trip. Commonly used current ratings are 16, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 400 and 630A. It is widely used in military, industrial, commercial and mining fields.


Working principle:

Current limiting breaking capacity

When a short circuit occurs in the circuit breaker, the rapid opening of the contacts will produce an arc. The less time the circuit breaker is disconnected, the closer Ics is to lcu, the better the current limiting effect, which can also greatly reduce the electromagnetic, electric and thermal effects caused by short-circuit current on the circuit breaker and electrical equipment, and prolong the service life of the circuit breaker.


Short-circuit protection

Short-circuit protection is a short-circuit instantaneous tripping. Attention should be paid to the timely adjustment of the protection after the load change, to prevent the calibration value is too small frequent tripping affect the quality of power supply, or the calibration value is too ambassador lines and equipment can not be effectively protected.


Overload delay protection

Overload delay protection refers to the load current exceeds the limited range of equipment in danger of burning equipment, the protection device can cut off power within a certain period of time. Overload has a process of heat accumulation, the protection action does not need to be too fast. For short time overcurrent, the protection should not act.


Isolation function

Isolation function is to require the circuit breaker to break the leakage current does not cause harm to people and equipment. After multiple short-circuit tripping switch performance decreases, the leakage current will increase. For the human body below 30mA is a safe leakage current, and in a harsh environment, more than 300mA leakage current for more than 2 hours, it is possible to damage the insulation phase to phase short circuit and thus cause a fire.


In addition, molded case circuit breakers can also be installed with different functional modules to achieve leakage protection, under voltage protection and other functions.



* Provide secondary side protection for transformer.

* Short circuit protection for the motor.

* Maintain 2-6 times the continuous current of the generator.

* Personnel safety.

How to choose a suitable molded case circuit breaker?

More information on molded case circuit breaker and accessories.

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