What is the DC circuit breaker?

Promulgator : TAIXIDate : 2018-09-14Views : 15

DC circuit breakers are mainly used for overload and short-circuit protection of DC electrical circuits and equipment, and also belong to the controller of DC electrical circuits. Just like the tap used in our daily life, the tap controls the flow of water, while the DC mini circuit breaker controls the current.

DC circuit breaker is different from ordinary AC circuit breaker. DC mcb mainly adopts special arc extinguishing and current limiting system, which can quickly break the fault current of DC distribution system and greatly improve the stage difference coordination. Especially in the DC system of power engineering, the series has excellent performance and can avoid the above-mentioned faults. The differential characteristics of this series of products are the best of similar products at home and abroad.

The main contact of the DC mini circuit breaker is operated by manual or electric switching. After the main contact is closed, the free tripping mechanism locks the main contact on the closing position. The coil of the overcurrent release and the thermal element of the thermal release are in series with the main circuit, and the coil and the power supply of the undervoltage release are in parallel. When the circuit is short-circuited or seriously overloaded, the armature of the over-current release closes and the free release mechanism acts, and the main contact disconnects the main circuit. When the circuit is overloaded, the heat element of the thermal release causes the bimetal sheet to bend and pushes the free release mechanism to move. When the circuit is under voltage, the armature of the undervoltage release is released. It also enables the free tripping mechanism to act. Split-excitation tripper is used for long-distance control. In normal operation, its coil is power-off. When distance control is needed, press the start button to make the coil energized and the armature drives the free tripping mechanism to disconnect the main contact.

DC mini circuit breaker consists of an arc extinguishing chamber with a metal grid, a dynamic and static contact, an operating mechanism and other control components. For a DC mcb, the arc voltage of the break must rise to a high enough level during the breaking process, resisting the DC system power supply voltage to force the current to drop to zero, and then quickly realize the dielectric recovery process to complete the breaking. The arc voltage can be set up by stretching arc, decreasing arc column temperature and increasing near-pole voltage drop, and these arc extinguishing methods are often used in practical circuit breakers.

In the breaking process of a DC mini circuit breaker, the static and dynamic contacts are separated by the operating mechanism, and the arc between the static and dynamic contacts will be elongated by mechanical motion. At the same time, the arc will be further elongated and will move upward along the arc track under the magnetic blowing force produced by the current path and the arc itself. When the arc enters the interrupter, the arc column is cut into several short arcs in series under the action of the metal grid. On the one hand, the arc is elongated, on the other hand, a series of near-polar pressure drops are formed on the metal surface. On the other hand, the arc is also affected by the cooling effect of the grid and the erosion of steam on the wall. The arc voltage will rise sharply, forcing the loop current to drop rapidly to zero. It is noteworthy that the arc motion and the arc voltage rise are the fundamental reasons for determining the interruption performance, so the key to this interruption technology is to control the arc to enter the interrupter smoothly and quickly, and be cut into a short arc section quickly. Therefore, the study of arc phenomenon and the development of control technology are the core and key of the DC mcb.