Core Arc-Extinguishing Mechanism
The arc-extinguishing chamber maintains a high vacuum level (better than 10⁻⁴ Pa); with extremely few gas molecules present, collisional ionization is virtually impossible, providing inherently strong insulation capabilities.
Upon opening, the moving and fixed contacts separate; high temperatures cause metal vapor to volatilize from the contact surfaces, forming a vacuum arc sustained by the ionization of this vapor.
Specially designed contact structures generate longitudinal or transverse magnetic fields that drive the arc to move rapidly across the contact surfaces, preventing localized overheating and contact ablation.
When the alternating current naturally passes through zero, the energy supply to the arc is interrupted; metal vapor rapidly diffuses and condenses onto the shielding cover. The dielectric strength of the contact gap recovers within microseconds, completely preventing arc reignition; the entire arc-extinguishing process takes only 10–15 milliseconds.
Complete Operational Workflow
Closing Operation: A spring or permanent-magnet operating mechanism releases stored energy, driving the moving contact toward the fixed contact. They make firm contact with a pressure of 2000–3000 N to minimize contact resistance, thereby completing the circuit connection.
Opening Operation: A fault current triggers the release mechanism, causing the operating mechanism to rapidly separate the moving contact. The resulting vacuum arc is extinguished instantly as the current passes through zero-with an arcing time of no more than 20 ms-reliably interrupting the faulty circuit.
Insulation Recovery: After the arc is extinguished, residual ions and metal vapor in the contact gap rapidly recombine and condense. The dielectric strength of the contact gap quickly recovers to over 80% of its initial level, fully withstanding the system's recovery voltage.