Vacuum Interrupter Contact Undulations for Resistance Reduction
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Solution Overview
Problem
Vacuum interrupters face challenges in achieving high continuous current carrying capability due to significant electrical resistance caused by limited contact areas between planar mating surfaces of movable and fixed contacts, especially in axial magnetic field types, where current is forced into a long circular path.
Innovation Solution
The introduction of purposely designed undulations on the mating surfaces of vacuum interrupter contacts, which are three-dimensional in nature, allowing for increased contact area and reduced resistance without compromising current interruption capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If planar mating surfaces are used for contacts, then the structure is simple and easy to manufacture, but the contact area is limited resulting in significant electrical resistance
Solution Approach 1:
The patent applies curvature by introducing undulations (convex and concave portions) on the contact surfaces of the movable and fixed contacts. These undulated surfaces increase the effective contact area when the contacts are closed, thereby reducing electrical resistance while maintaining a relatively simple manufacturing process through standard machining or forming operations.
2Reliability
If the current path is made longer to generate stronger axial magnetic field, then the current interruption capability is improved, but the total resistance of the vacuum interrupter increases
Solution Approach 1:
The undulated contact surfaces with convex and concave portions increase the effective contact area, which compensates for the increased resistance caused by the longer current path. This allows the vacuum interrupter to maintain strong axial magnetic field for current interruption while reducing the total resistance through improved contact surfaces.
3Device complexity
If multiple discrete contact locations are used on planar surfaces, then the contact structure is simple, but the electrical resistance becomes significant
Solution Approach 1:
The patent introduces undulations on the contact surfaces that create multiple convex and concave portions which interengage when the contacts are closed. This increases the effective contact area from a few discrete points to a more distributed contact pattern, reducing electrical resistance while maintaining relatively simple contact structures.
4Reliability
If surface roughening is applied to increase contact area, then the electrical resistance may be reduced, but the surface imperfections worsen the discrete contact locations problem
Solution Approach 1:
Instead of relying on surface roughening which creates unpredictable imperfections, the patent introduces controlled undulations with specific convex and concave portions. These geometric features provide predictable and repeatable contact patterns that increase the effective contact area while maintaining manufacturing precision through controlled forming or machining processes.
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~5C
AI summary
A contact (20) is for a vacuum interrupter (110). The contact )20) includes a contact member (24) having a generally planar mating surface (28) with a planar contact plane (32) and a plurality of purposely introduced undulations (36) therein. The undulations (36) are structured 5 to contact a plurality of purposely introduced undulations (38) of another contact member (26). The undulations (38) are in a dimension perpendicular to the planar contact plane. The planar contact plane has a diameter (40). The undulations (38) have a depth substantially smaller than the diameter of the planar contact plane.