DC circuit breaker, also known as DC air switch or DC mcb, is the most common component of low-voltage circuit breaker. Mainly used for circuits of rated voltage 250V ~ 1000V, rated working current to 1 ~ 60A DC, as the DC line overload, short circuit protection and line frequent conversion. The circuit breaker can also be equipped with auxiliary contacts, alarm contacts and excitation tripper and other accessories to achieve long-distance breaking and provide control signals.

Miniature DC circuit breakers are used for DC voltage to DC1000V, rated current to 63A line for overload and short circuit protection. They can also be used in solar photovoltaic power generation system. The maximum operating voltage of DC mini circuit breaker can reach DC500V. They can quickly break the fault current of DC distribution system and protect important devices in solar system. The photovoltaic module is protected from the harm of DC side reverse current and AC side feedback current caused by inverter fault, so as to ensure the reliable operation of solar photovoltaic power generation system.

After selecting the structure of the circuit breaker, the electrical parameters of the circuit breaker should be selected. The so-called determination of electrical parameters mainly refers to the rated voltage, rated current and breaking capacity of the circuit breaker, an important issue is how to choose the setting current and protection characteristics of the over-current tripper of the circuit breaker, as well as coordination, so as to achieve a more ideal coordinated action.

DC mcb are mostly non-selective, and the capacity is small, generally below 600A, the new type of DC air switch can also be made into selective, and the capacity continues to increase, some capacity has reached more than 3000A. Small capacity circuit breakers (below 50A) generally use non-energy storage closed, manual operation; large capacity circuit breakers operating mechanisms are mostly energy storage closed, but also can carry out remote control. It should be noted that in addition to general selection principles, the use of circuit breakers should also be considered. Circuit breakers for distribution and motor protection as well as conductor protection circuit breakers for lighting and daily use should be selected according to their use characteristics.

DC mini circuit breaker can be equipped with various accessories to meet the needs of various control and protection, with high short-circuit breaking ability, dynamic stability and relatively complete selective protection function. Compared with the universal circuit breaker, it has the characteristics of compact structure, small volume, simple operation, safety and reliability. The disadvantages are lower on-off capacity, less protection and operation mode, and some can be repaired, some can not be repaired. The circuit breaker is widely used in distribution lines as protection and distribution switches for main circuits and small-capacity generators. It can also be used as main switches for low-voltage side outgoing lines of small distribution transformers, as well as control and protection of lighting circuits in various large buildings (such as hotels, buildings, airports, stations, etc.) and residential buildings. It can also be used as various production equipment. Power switch.

Operation time of DC mini circuit breaker

It refers to all the time needed from the instant when the network is short-circuited to the time when the contact is separated, the arc is extinguished, and the circuit is completely disconnected. It includes the following three parts:
(1) The time required for DC mcb to increase from normal working current to release current.
(2) The general time when the circuit breaker starts to operate from the signal obtained by the overcurrent release to the action time of the contact system by the free release mechanism and the moving contact begins to separate and the arc appears. This time is customarily called the intrinsic time.
(3) The arcing time is customarily called the arcing time when the arc is produced between the driven contacts and the arc is completely extinguished and the current is cut off.