Molded Case Circuit Breaker Protection

Update date:2018-05-21 Source:MAXGE

Molded Case Circuit Breaker Protection

Short circuit protection

Short-circuit protection is short-circuit instantaneous tripping. Pay attention to adjust the protection setting value timely after the load change, prevent the setting value from being too small and affect the power supply quality due to frequent tripping, or the setting value will not be effectively protected by the ambassador's circuit and equipment.

Circuit breaker

Overload delay protection

Overload delay protection means that the load current exceeds the limit of the equipment and there is a danger of burning the equipment. The protection device of the molded case circuit breaker can cut off the power within a certain period of time. Overloading has a process of heat accumulation and the protection action does not need to be too rapid. For short-time over-current, the protection should not act.

Isolation function

The isolation function is to require that the leakage current after the circuit breaker is disconnected does not cause harm to people and equipment. After multiple short-circuit trips, the switching performance drops and the leakage current increases. For a human body, a leakage current of 30 mA or less is a safe leakage current. In a severe environment, if a leakage current exceeding 300 mA lasts for more than 2 hours, a short-circuit may occur between the insulation damage and cause a fire.

Molded Case Circuit Breaker

Leakage Protection

Molded case circuit breakers have two kinds of thermal magnetic and electronic types of leakage devices. Compared with electronic leakage devices, they have the advantages of small size, high accuracy, and high sensitivity, but their anti-interference ability is poor. At present, the electronic leakage protector occupies the mainstream. When the leakage current reaches the setting value, the execution circuit receives the induced voltage signal of the secondary side of the zero-sequence current transformer and drives the conversion contact to output the leakage protection signal, so that the tripping operation cuts off the power supply.


The current setting of the general terminal switch is 30mA and the setting value of the upper branch switch is 300mA. Arcing short circuit with high risk of fire is difficult to be effectively cut off by the short circuit protection, and the leakage device can reliably break the ground fault to prevent the occurrence of personal electric shock and short circuit fault.

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