Distribution circuit breaker refers to the circuit breaker specially used for distributing electric energy in low-voltage network, including power supply main switch and load branch switch. In the selection of such circuit breakers, in addition to following the general selection principles, should also be limited system fault range and prevent the expansion of circuit fault as the focus of consideration. Therefore, the following selection principles need to be added

① The setting value of the long delay operating current of the circuit breaker is less than or equal to the allowable carrying current of the wire. For the use of wire and cable distribution, desirable wire and cable allowable carrying capacity of 80%

② The return time of the three-times long delay action current setting value is greater than the starting time of the motor with large starting current in the circuit.

③ Calculate the load current of the small and medium circuit with the setting value of short delay operation current ≥11(x+ 1.35ki); K motor’s starting current multiple h motor’s rated current

④ Instantaneous current setting value ≥11(Kx + 1.35K1KLM in the K1 motor starting current impact coefficient, generally take K1 =1.7~2; The rated current of a large motor

⑤ short delay time ladder, according to the distribution system. The general time ladder is 2~3 steps. The short delay time difference between each stage is 01~0.2s, which depends on the action precision of the circuit breaker delay mechanism. The return time should ensure the selective action of each stage. After the short delay ladder is selected, it is better to check the thermal stability of the protected object

The temperature of the surrounding medium of the photovoltaic circuit breaker shall not be higher than +70℃ and not lower than -35℃ (capacity reduction shall be considered for use in high and low degrees)

Photovoltaic circuit breaker can be affected by humid air; Photovoltaic circuit breakers can be affected by salt fog and oil fog; DC circuit breaker can be affected by mold; Photovoltaic circuit breaker can work reliably when subjected to normal vibration of the ship.