What is the principle of using a vacuum arc extinguishing chamber for outdoor vacuum circuit breakers?

The core principle of the vacuum arc extinguishing chamber used in outdoor vacuum circuit breakers is to quickly extinguish the arc in a high vacuum environment, relying on the diffusion cooling of the arc plasma in the vacuum and the rapid recovery of the medium strength.

High vacuum insulation: The internal pressure is extremely low (about 10 ⁻³~10 ⁻⁵ Pa), gas molecules are rare, ionization is difficult, and the insulation strength is very high.

Arc formation and diffusion: When the contact is disconnected, high-temperature metal vapor ionizes to form an arc, but charged particles and metal vapor will diffuse rapidly in vacuum.

Zero crossing extinction of current: At the moment of AC zero crossing, the supply of metal vapor is interrupted, residual particles are diffused and adsorbed, and the insulation strength recovery speed of the vacuum gap far exceeds the voltage recovery speed, making it impossible for the arc to reignite.

Key design assistance: The spiral groove or special shape of the contact generates a magnetic field, causing the arc to rotate and avoiding local overheating; The shielding cover collects metal vapor to prevent contamination of the insulation shell.