Common circuit breakers are commonly used for the AC circuit and off, whether for a direct current, DC current key is the ability to cut.
For alternating current, while the breaking of the contacts, an arc will be generated, i.e., a so-called "arcing." However, the characteristics of the alternating current belongs to the "zero crossing" state, when the current zero crossing, with the interrupter's cooling effect, quickly extinguish the arc, thereby cutting off the circuit. Here, the current is cut off contacts is important, but what really matters is how to cut off the arc. Because the arc caused by high temperature and ablation, is a key determinant of contact life.
The so-called direct current does not easily cut, it is not easy to cut off the DC arc means. The reason is that no current arc state "zero crossing", so that despite the cooling of the arc chute, not easy to cut off the arc. The presence of arc time, is a key determinant of contact life. As for why the circuit breaker by one-tenth of a direct current exchange only, it should be the manufacturer's test data. In fact, Ye Hao understand, smaller DC current through the circuit breaker, when breaking, despite the long arc of time, but it is quite easy interrupter. Natural life and to ensure that the contact system through the exchange of the same. We chose breaker, when the contactors and relays can also refer to the principle of election. If you ask the manufacturers, AC contactor can be used direct current, he would say so.
By the way, the DC current circuit breakers can be used, not only the contact system can cut off a direct current, but also to ensure the operation life of the contact system. If the contact system can only be disconnected hung up several times, so the breaker can not be used.
DC circuit breaker has its internal contacts and interrupter system, and substantially the same exchange. Calibrated by manufacturers to only the magnitude of the DC current. So you see, it looks big volume circuit breakers, adopted the "DC current rating" is not big, the reason why. He concluded that the proposed election breaker or DC circuit breaker, breaker, after all, in addition to know whether to cut off direct current, but also the need for the setting value. If the DC breaker is selected, it is carried by a direct current setting, instead of direct use of the exchange, there is no setting value, and is only able to ensure that only the direct current cut off manually. Of course, if the selected contacts and relays is another matter.