What are the advantages of switch plum blossom contacts?
2025-10-13 10:54:26
The core advantage of the plum blossom contact is that it provides excellent electrical performance, higher mechanical stability and longer service life through multi-point and surface contact.
1. Excellent Electrical Performance
Low and Stable Contact Resistance: Multiple contact fingers simultaneously contact the moving contact (usually a cylindrical conductive rod), forming multiple parallel current paths. This significantly reduces overall contact resistance, thereby reducing heat generation and energy loss during energization.
High Current Carrying Capacity: Due to their large contact area and excellent heat dissipation, the plum blossom contact can carry a higher rated current and short-term withstand current (thermal stability current).
High Arc Erosion Resistance: During closing and opening, arcs typically erode the contact surface. The multi-finger design of the plum blossom contact distributes the arc energy across multiple contact points, avoiding severe erosion at a single contact point and thus extending the electrical life of the contact.
2. Excellent Mechanical Performance and Reliability
Self-cleaning: During each closing and opening operation, the contact surfaces between the moving contact and the contact fingers generate a slight friction and relative sliding motion. This action removes impurity films formed on the contact surface due to oxidation or arcing, preserving the metallic luster and maintaining low contact resistance. This is one of its most critical advantages.
High and Uniform Contact Pressure: Each contact finger acts like an independent spring, applying pressure to the moving contact. The total pressure generated by the numerous contact fingers is extremely high and evenly distributed, ensuring tight and stable contact. It effectively resists electrodynamic forces (especially the huge electrodynamic forces generated during a short circuit) and prevents contact bounce or separation.
Strong Resistance to Welding: In the event of a severe short circuit, the huge current can cause the contact surfaces to melt and weld together (known as "welding"). The multiple contact points and excellent heat dissipation of the contact fingers reduce the risk of single-point overheating and melting. Even if even a small amount of welding occurs on a single contact finger, the strong spring pressure and opening operation can easily break it apart.
3. Long Life and High Stability
Long electrical and mechanical life: Thanks to their resistance to ablation, welding, and self-cleaning, the rosette contact maintains its performance even under frequent operation, significantly extending the service life and maintenance intervals of the switchgear.
Good Adaptability: Insensitive to slight misalignment, machining errors, or installation deviations of the moving contact. Because the contact fingers are elastic, they automatically compensate for these minor deviations, maintaining good surface contact.
4. Compact Structure
While providing equivalent or even superior performance, the rosette contact structure can be designed to be relatively compact, helping to reduce the overall size of the switchgear.
Typical application comparison
| Parameters | Plum blossom contacts | Traditional single-piece contacts |
|---|---|---|
| Contact resistance | 40-60 μΩ (12kV vacuum circuit breaker) | 80-120 μΩ |
| Rated current | 4000A (contact finger shunt design) | 2500A (limited by heat dissipation) |
| Short circuit withstand | 63kA/4s (no welding) | 40kA/3s (prone to localized welding) |
| Mechanical life | 10,000 cycles | 5,000 cycles |
| Maintenance cost | Single contact finger replacement | Complete replacement |
Summary and Application Scenarios
The core advantages of the plum blossom contact can be summarized as: low resistance, high current carrying capacity, strong arc resistance, self-cleaning, high pressure resistance, and long life.
Precisely because of these advantages, the plum blossom contact is widely used in medium- and high-voltage switchgear with extremely high reliability and performance requirements. Examples include:
The static contacts of vacuum circuit breakers (very common).
The contact system of SF6 circuit breakers.
The contact portion of disconnectors.
The primary connectors in high-voltage switchgear (such as the upper and lower contacts of trolley-type circuit breakers).
In short, the plum blossom contact design is a classic and successful one in the electrical switchgear industry. Through its ingenious flexible multi-point contact structure, it perfectly meets the stringent requirements of high-current switchgear for electrical connection reliability, stability, and durability.
If you are interested or want to know more, please contact us：pannie@hdswitchgear.com.
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