AC molded case circuit breaker can not be used in DC circuit. Because AC system and DC system have different grounding modes, the breaking capacity of molded case circuit breaker will be greatly affected. Can the DC mccb be used only in the DC system?

The main difference between DC mccb and AC moulded case circuit breaker is the ability to eliminate arcing.

Because the AC moulded case circuit breaker has zero crossings per cycle, it is easy to extinguish the arc at zero crossing, while the DC molded case circuit breaker has no zero crossing point, and the arc extinguishing ability is very poor, so additional arc extinguishing devices need to be added. In general, the DC arc is difficult to extinguish, while the AC is zero and arcing is easy.

Because the direct current AC zero crossing unlike characteristics, the short-circuit current (DC fault current or even multiple small) open; have difficulty in arc quenching, so the connection should use diode triode series or to increase the fracture, the fracture bear part of the arc energy.

Of course, the DC mccb is not only used in the DC system. In the ship power system and the electric propulsion system, the DC circuit breaker is one of the most important components. It protects the faults of the power distribution system and the electrical equipment, and takes many kinds of protection to ensure the safety of the power supply system and the electrical equipment. DC special molded case circuit breaker for fast breaking is also an important component in rail transit.