Vacuum Interrupter Contact with Parallel Windings for Arc Control
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Solution Overview
Problem
Vacuum interrupters face a challenge in balancing the need to withstand permanent currents with low electrical resistivity while generating effective magnetic fluxes for arc breaking, as materials with low resistivity tend to limit magnetic fluxes due to eddy currents, and existing solutions either weaken the contact structure or reduce the magnetic field strength.
Innovation Solution
A medium-voltage vacuum interrupter design featuring a first hollow cylinder with helical slots and a second solid winding with an annular crown, electrically connected in parallel to enhance the axial magnetic field distribution and resistivity, allowing for better arc control and increased breaking performance for high-value short-circuit currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If materials with low electrical resistivity (copper or copper alloys) are used for contacts to withstand permanent current, then heating is reduced, but magnetic flux generation is limited due to eddy currents
Solution Approach 1:
The contact body is divided into multiple segments with different materials (copper for low-resistivity regions, ferromagnetic material for high-permeability regions). This segmentation allows each region to perform its specialized function: copper carries permanent current with minimal heating, while ferromagnetic segments concentrate and enhance magnetic flux without being limited by eddy currents in the same way
Solution Approach 2:
The contact structure uses composite materials combining copper and ferromagnetic materials in a single integrated design. The copper provides excellent electrical conductivity for permanent current carrying, while the ferromagnetic material provides high magnetic permeability for flux concentration and enhancement, creating a synergistic effect that resolves the contradiction between low resistivity and high magnetic flux generation
2Power
If ferromagnetic materials are implanted in contact to enhance magnetic flux for arc breaking, then arc breaking performance is improved, but contact structure strength is weakened due to repeated magnetic forces
Solution Approach 1:
The ferromagnetic material is segmented into discrete elements or layers within the contact body rather than using a single large ferromagnetic component. This segmentation reduces the total volume subject to magnetic forces while maintaining sufficient flux enhancement, and distributes mechanical stress more evenly throughout the contact structure
Solution Approach 2:
Ferromagnetic material is placed locally only in regions where magnetic flux enhancement is most needed for arc breaking, rather than throughout the entire contact. This localized placement minimizes the volume exposed to damaging magnetic forces while maintaining arc breaking effectiveness in the critical regions
3Power
If slots are made in contact body to reduce eddy currents, then magnetic flux distribution is improved, but manufacturing complexity increases
Solution Approach 1:
Instead of cutting slots into a solid contact body, the design uses pre-fabricated segmented components (copper segments and ferromagnetic segments) that are assembled together. This approach achieves the same effect of reducing eddy currents and improving flux distribution but through assembly rather than complex machining operations
Solution Approach 2:
The invention introduces an intermediary assembly process that joins separate copper and ferromagnetic components together. This intermediary step of assembly replaces the difficult operation of slotting, making manufacturing easier while achieving the desired electromagnetic performance through the careful design of the component interfaces
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves a higher, uniformly distributed axial magnetic field, improving arc control and breaking performance for currents above 63 kA, reducing the risk of arc contraction and enhancing the vacuum interrupter's ability to handle high short-circuit currents without increasing dimensions or costs.
Implementation Method 1
the first cylinder constituting a first winding adapted to generate a magnetic field, a second winding mounted electrically in parallel with the first winding and adapted to generate a magnetic field which is superimposed on the magnetic field generated by the first winding
Implementation Method 2
these materials have by nature a tendency to limit the magnetic fluxes by eddy currents passing through them
Data Source
Figure 1
Figure 2~3A
Figure 3B~3C
AI summary
The invention relates to a new vacuum lamp design in which the contact body is formed with two concentrically arranged windings (8, 10) connected electrically in parallel. According to the invention, the additional winding (10) is in the form of a solid ring. The invention makes it possible to increase the axial magnetic field (AMF) and to distribute it uniformly over the contact surface (22, 32). This allows for improved arc interruption at high short-circuit currents, typically exceeding 63 kA.