The vacuum interrupter is the core component of a vacuum circuit breaker and is known as its "heart." Its primary function is to rapidly extinguish the arc when the current crosses zero using a high vacuum medium, establishing reliable insulation strength and thus disconnecting the circuit.
Let's break down the main functions of each component of the vacuum interrupter in detail:
Core Components and Their Functions
1. Insulating Housing
Composition: Typically cylindrical and made of glass, ceramic, or glass-ceramic. Modern products often use ceramic.
Main Functions:
Sealing and Support: Forms a completely sealed container, maintaining a high vacuum (above 10^-4 Pa) inside, providing a stable operating environment for the contact system and serving as the mechanical support framework for the entire arc extinguishing chamber.
Insulation: In the open state, it withstands the high voltage between the moving and stationary contacts, preventing current from flowing through the housing and causing breakdown.
2. Moving and Stationary Contact System
This is the core component of the arc extinguishing chamber, responsible for conducting and interrupting current.
Stationary Contact: Fixed end, connected to one end of the circuit breaker.
Moving Contact: Moveable end, connected to the external operating mechanism via a bellows.
Main Functions:
Conducting Current: In the closed position, the moving and stationary contacts are in close contact, providing a low-resistance path for current.
Arc Generation: At the moment of opening, the contacts separate, generating a high-temperature, high-pressure metal vapor arc (vacuum arc).
Arc Extinguishment: The contacts utilize a special cup-shaped longitudinal magnetic field or transverse magnetic field structure (such as spiral groove contacts). These structures generate a magnetic field that drives the arc to rotate at high speed across the contact surface, preventing local overheating. When the current passes through zero, the metal vapor rapidly diffuses and condenses, thereby extinguishing the arc.
3. Bellows
Composition: An axially expandable, elastic, thin-walled metal tube.
Main Functions:
Dynamic sealing: This is the most critical function of the bellows. It connects the moving contact and the moving end cover, allowing for free expansion and contraction during opening and closing operations while maintaining a high vacuum seal within the arc extinguishing chamber to prevent air from entering.
Transmitting Mechanical Motion: Transmits the linear motion of the external operating mechanism to the internal moving contact.
4. Shielding Covers
The arc extinguishing chamber typically has multiple shielding covers, which are key components for ensuring its performance and lifespan.
Main Shield (Armed Shield):
Purpose: Surrounds the contacts.
Condensation Prevention: Absorbs and condenses metal vapor generated by the contact arc, preventing it from condensing on the inner wall of the insulating casing, thereby maintaining the insulation strength of the casing.
Protective Casing: Protects the insulating casing from direct arc erosion and heat radiation.
Equalizing Shield:
Purpose: Located between the contacts and the end caps.
Improving Electric Field Distribution: Optimizes the electric field distribution within the arc extinguishing chamber, preventing localized excessive electric field strength and improving the overall insulation withstand voltage.
5. End Caps (Moving and Static End Caps)
Composition: Typically metal (such as oxygen-free copper) discs.
Main Function:
Sealing: Sealed to the insulating casing by brazing or other methods, forming the two ends of the vacuum-sealed chamber.
Conductivity and connection: The static end cover is connected to the static contact, and the moving end cover is connected to the bellows and the moving contact, serving as the inlet and outlet of current and connected to the external circuit.
Summary and Brief Operational Process
For a more intuitive understanding, we can relate the operation of the vacuum interrupter to the functions of its components:
Closed State:
The moving and stationary contacts are closed, forming a path for current through the end cap, contact, and end cap.
The insulating housing and shield ensure insulation from ground.
Opening Process:
The operating mechanism pulls the moving contact, compressing the bellows.
At the moment the contacts separate, a vacuum arc is generated.
The magnetic field design of the contacts causes the arc to rotate and spread.
The main shield quickly absorbs and condenses the metal vapor.
When the AC current passes through zero, the arc extinguishes due to a lack of a sustaining dielectric.
Opened State:
A certain distance is maintained between the moving and stationary contacts.
The insulating housing and shield work together to withstand the high recovery voltage and prevent breakdown.
The bellows maintain a seal, ensuring a continuous high vacuum inside.
In summary, the various components of the vacuum interrupter work together precisely to achieve the ability to quickly and reliably interrupt large currents in an extremely small space. Its core advantages lie in the strong insulation and arc-extinguishing capabilities of the high vacuum medium and the dynamic sealing achieved by the bellows.
Contact Us
Shaanxi Huadian is well aware of the importance of the "heart" components and always regards product quality as the lifeline of the enterprise. The vacuum interrupter produced by it is known as a model of "excellent quality".If necessary, please contact:pannie@hdswitchgear.com.
