Working principle of vacuum circuit breaker
Compared with other circuit breakers, the working principle of vacuum circuit breaker is different arc extinguishing medium. There is no conductive medium in vacuum, so that the arc is quickly extinguished. Therefore, the distance between the dynamic and static contacts of the circuit breaker is very small. The circuit breaker is generally used in plant power configuration with relatively low voltage level.
The vacuum circuit breaker mainly consists of three parts: vacuum arc extinguishing chamber, electromagnetic or spring operating mechanism, support and other components.
Vacuum arc extinguishing chamber
According to different switching types, there are ceramic vacuum quench chamber with external shield cover, medium sealed cup-shaped longitudinal magnetic field miniaturized vacuum quench chamber and inner sealed glass bubble quench chamber. The basic structure is as follows:
- Airtight insulation system (housing)
The air-tight insulation system composed of ceramic, glass or glass-ceramics, air-tight insulation cylinder, movable end cover plate, fixed-end cover plate and stainless steel bellows is a vacuum sealed container. In order to ensure air tightness, in addition to the sealing type to have a strict operation process, but also requires the material itself air permeability and internal exhaust gas small.
- Conductive system
It is composed of a fixed conductor rod, a fixed running arc surface, a fixed contact, a moving contact, a moving running arc surface and a moving conductor rod. There are roughly three kinds of contact structure: cylindrical contact, transverse magnetic field contact with spiral groove running arc surface, and longitudinal magnetic field contact. At present, the technology of longitudinal magnetic field is adopted. This kind of arc extinguisher has strong and stable ability of arc breaking.
- Shielding system
Shielding cover is an indispensable component in vacuum arc extinguishing chamber, and there are many kinds of shielding cover around the contact, bellows shielding cover and shielding cover for pressure equalization. The function of the main shielding cover is: a to prevent arc products from splashing into the inner wall of the insulation shell in the process of arc burning, thus reducing the insulation strength of the shell. b Improves the uniformity of electric field distribution in the arc extinguishing chamber, which is conducive to reducing the local field intensity and promoting the miniaturization of the vacuum arc extinguishing chamber. c Condenses arc products, absorbs part of arc energy, and helps to recover the strength of back-arc gap medium.
According to the different type of circuit breaker, the operating mechanism is different. Commonly used operating mechanisms include spring operating mechanism, CD10 electromagnetic operating mechanism, CD17 electromagnetic operating mechanism, CT19 spring energy storage operating mechanism, CT8 spring energy storage operating mechanism.
Base, insulating support, insulator, etc.
The working principle of vacuum circuit breaker is: When the moving and static contacts are opened under the action of the operating mechanism, an arc is generated between the contacts. The surface of the contacts volatilizes steam at high temperature. Due to the special shape of the contacts, a magnetic field is generated when the current passes through. The arc is extinguished at the natural zero crossing and the strength of the medium between the contacts quickly recovers.