It is well-known that because a DC circuit breaker, unlike an AC circuit breaker, does not have a null-point arc extinguishing function and it is difficult to open the short circuit direct current (even small multiples of fault current) and extinguish an electric arc, it is much more difficult for the DC circuit breaker to perform open arc extinguishment than the AC circuit breaker. The current solution is generally to increase the distance between a moving contact and a stationary contact. Two electrodes in a three-electrode or four-electrode AC circuit breaker are often connected in series to form a two-electrode DC circuit breaker, wherein one or two electrodes are two open ports. The distance between the moving contact and the stationary contact is increased in such a manner of serial connection of the open ports so that each open port carries a part of electric arc energy, thereby achieving the purpose of arc extinguishment (extinction). The current common connection modes are shown in FIG. 1, FIG. 2 and FIG. 3.
FIG. 1 belongs to a three-electrode circuit breaker which adopts a cable or a cope busbar 400 for external wire connection to form a DC circuit breaker, and the wire connection mode is that switches are connected in series from top to bottom (between an input end and an output end). Although the current directions are consistent, the wire connection is complicated and the external wire connection of input incoming wires and the cable generates mutual intersection. It is not safe and not convenient for installation.
FIG. 2 belongs to a four-electrode circuit breaker which adopts a cable or a copper busbar 400 for external wire connection to form a DC circuit breaker. The exposed copper busbar 400 is not safe, and insulating and protecting measures are required to be increased. The wire connection mode is that the lower switches (between output ends) are connected in series and the upper switches (between input ends) are connected in series. Meanwhile, the current directions are not consistent.
FIG. 3 is a four-electrode circuit breaker which adopts a cable or a copper busbar 400 for external wire connection to form a DC circuit breaker. The wire connection mode is that switches are connected in series from top to bottom. Although the current directions are consistent, the wire connection is complicated and the external wire connection of input incoming wires and the cable generates mutual intersection. It is not safe and not convenient for installation.
Each of the above circuit breakers becomes a DC circuit breaker in the mode, of externally connecting the cable or the copper busbar or the conducting wire in series, having the following defects:
1 The wire connection is complicated and insulating and protecting measures are required to be increased.
2. The copper busbar or the conducting wire comes into contact with the outside, and the safety is poor.
3. The DC circuit breaker is not beautiful and more installation space is needed.
4. The switch state of the circuit breaker cannot be clearly indicated.