Vacuum interrupter is the core component of high-voltage switchgear, and its performance directly affects the breaking capacity and service life of the circuit breaker. Understanding the function and maintenance method of each component will help ensure the long-term stable operation of the equipment.
1. Role of vacuum interrupter components
| Component | Function | Key features |
| Shell (insulating tube) | Provides mechanical support and maintains a high vacuum environment to prevent external gas from penetrating. | Usually made of ceramic or glass materials, with high temperature resistance and high insulation strength. |
| Moving contact & stationary contact | Conduct current and generate arc when breaking, relying on vacuum environment to quickly extinguish arc. | The material is mostly copper-chromium alloy (CuCr), which is arc erosion resistant and has low cutoff value. |
| Bellows | To achieve sealed movement of the moving contact and prevent external air from entering the vacuum chamber. | Made of stainless steel, it must have high elasticity and fatigue resistance, and its service life is usually tens of thousands of times. |
| Main shield | Absorbs metal vapor generated by the arc to prevent it from condensing on the inner wall of the shell and affecting the insulation performance. | Usually made of oxygen-free copper or stainless steel, high temperature resistance. |
| Auxiliary shield | Further protect the inner wall of the shell and reduce metal vapor pollution. | Simple structure, mainly used for large current arc extinguishing chamber. |
| End cap (metal flange) | Connects to external circuits, provides mechanical fixation and electrical conduction. | Good electrical conductivity, welded to the housing to ensure airtightness. |
2. Maintenance methods of vacuum interrupter
The vacuum interrupter itself is basically maintenance-free, but its related components need to be checked regularly to ensure long-term reliable operation.
(1) Daily inspection
Appearance inspection:
Check whether the outer shell (ceramic/glass) has cracks, damage or discharge marks.
Observe whether the bellows is deformed, rusted or leaking (if it leaks, the inside of the interrupter may turn black).
Electrical performance test:
Power frequency withstand voltage test: Check whether the vacuum degree decreases (if the withstand voltage is unqualified, there may be vacuum leakage).
Contact resistance test: Measure the contact resistance of the contact. If it increases abnormally, the contact may be severely burned.
(2) Operation and maintenance
Mechanical operation inspection:
Check the flexibility of the circuit breaker operating mechanism to avoid damage to the bellows due to mechanical jamming.
Regularly lubricate transmission parts (such as connecting rods and bearings) to reduce mechanical wear.
Vacuum degree detection (if necessary):
Use the magnetron discharge method or vacuum tester to detect the internal vacuum degree (normally it should be ≤10⁻⁴ Pa).
If the vacuum degree drops significantly, the arc extinguishing chamber needs to be replaced (cannot be repaired).
(3) Replacement standard
Contact wear exceeds the standard (usually 3~6mm wear is allowed, refer to the manufacturer's standard for details).
The vacuum degree is unqualified (breakdown or leakage in the power frequency withstand voltage test).
The bellows is damaged (causing leakage in the arc extinguishing chamber, which needs to be replaced immediately).
3. Common faults and solutions
| Fault phenomenon | Possible cause | Solution |
| The circuit breaker is opening and closing abnormally | The machine is stuck, and the bellows is damaged. | Check the operating mechanism and replace the arc extinguishing chamber. |
| The withstand voltage test failed | The vacuum degree decreased, and the internal pollution occurred. | Replace the arc extinguishing chamber. |
| The contact resistance is too large | The contact is burned or oxidized. | Clean the contact or replace the arc extinguishing chamber. |
| Shell crack or discharge | Mechanical shock, insulation deterioration. | Stop operation immediately and replace |
4. Maintenance precautions
Avoid mechanical shock: Avoid collision during installation or transportation to avoid damage to the ceramic shell or bellows.
Prevent pollution: The contact surface must not be touched directly by hand to avoid grease or dust affecting conductivity.
Regular testing: It is recommended to perform vacuum testing every 3 to 5 years (especially in important occasions).
Matching parameters when replacing: The rated current, voltage, and short-circuit breaking capacity of the new arc extinguishing chamber must be consistent with the original model.
5.Conclusion
The core advantage of the vacuum arc extinguishing chamber is maintenance-free, but its mechanical and electrical conditions must be checked regularly to ensure reliable operation. Key maintenance objects include:
✅ Bellows (leakage prevention)
✅ Contacts (check ablation)
✅ Vacuum (power frequency withstand voltage test)
✅ Operating mechanism (avoid mechanical jamming)
If abnormalities are found (such as unqualified withstand voltage, leakage), they should be replaced in time and cannot be repaired. Proper maintenance can significantly extend its service life (usually more than 20 years).
Any interest, welcome to contact for more details:pannie@hdswitchgear.com.
