(1) The rated current of the circuit breaker is determined by the calculated current of the circuit; (About 99% of the designers have done this).

(2) The short-circuit setting current of the circuit breaker should avoid the normal starting current of the circuit. (About 30% of designers noticed this one.)

(3) Check the breaking capacity of low-voltage circuit breakers according to the maximum short-circuit current of the line; (About 10% of the designers have noticed this).

(4) Check the sensitivity of the circuit breaker according to the minimum short-circuit current of the line, that is, the minimum short-circuit current of the line should be no less than 1.3 times of the short-circuit setting current of the circuit breaker; (About 5% of the designers have noticed this)

(5) According to the short circuit impulse current (i.e. the maximum instantaneous value of the full short circuit current) on the line, the rated short circuit switching capacity of the circuit breaker (the expected peak value of the maximum current) should be checked, that is, the latter should be greater than the former.

Firstly, according to one selected circuit breaker, the applicability of type A, B, C and D can be distinguished.

Article 3, 4 and 5 are all factories'business. Now the micro-breaking capacity has reached 15KA, mainly Article 4. Schneider and other products also give the distribution length table.