According to its structure, the low-voltage circuit breaker can be divided into ACB, MCCB and MCB. The overload protection of MCB is realized by the inverse time limit characteristic composed of two pieces of metal with different thermal expansion coefficient. The larger the overload current is, the shorter the action time is. The short circuit protection is realized by electromagnetic release.

Circuit breakers play a very important role in protecting the safety of lines and electrical equipment. So how to choose the right low-voltage circuit breaker, which factors should be considered when choosing the low-voltage circuit breaker? The circuit breaker shall be selected according to the use environment; for dusty environment, the dust-proof circuit breaker shall be selected; for chemical corrosion environment, the anti-corrosion circuit breaker shall be selected; for the installation site with an altitude of more than 2000m, the air cooling and the decrease of dielectric strength shall be considered, and the circuit breaker used at a high altitude shall be selected.

For places with explosion and fire hazards, the requirements of corresponding environment and specifications for circuit breakers shall be met; for places with high temperature (ambient temperature is higher than 40 ℃), humidity (relative humidity is higher than 90%), the anti humid heat type products shall be selected. Select according to the normal working conditions; the rated frequency and rated voltage of the circuit breaker shall be suitable for the nominal value of the circuit. In some cases, the maximum voltage or the minimum voltage that may occur in the circuit under normal conditions is also considered.

The setting current of the circuit breaker is less than or equal to the allowable continuous current carrying capacity of the conductor, which is to realize the protection line. If the setting value of the circuit breaker is greater than the allowable continuous current carrying capacity of the conductor, the conductor heating may be greater than the allowable maximum temperature of the conductor in normal operation when the circuit breaker is under overload operation, which will accelerate the aging of the conductor insulation for a long time, degrade the insulation performance, and may occur when overvoltage occurs Insulation breakdown, causing electrical fire accidents.