Vacuum Interrupter Insulating Tube Structure for Flashover Control
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Solution Overview
Problem
Vacuum interrupters face a risk of reduced withstand voltage performance due to high electric fields at the joint portions between the insulating tube and end plates, particularly at the metallized layer, which can lead to creeping flashover, and existing solutions complicate manufacturing and potentially weaken the insulating tube.
Innovation Solution
A vacuum interrupter design featuring a cylindrical insulating tube with projection portions and end plate joining portions that project inwardly, a metallized layer extending radially and axially, and an electric field relaxation shield to mitigate high electric fields, thereby improving voltage withstand without altering the tube's diameter or shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a groove is formed on the end surface of the insulating tube to relax the electric field, then the withstand voltage performance is improved, but the manufacturing process becomes complicated and the insulating tube strength is reduced
Solution Approach 1:
The insulating tube end surface is segmented into multiple functional regions: a projection portion that extends axially to cover the metallized layer end, and a base end portion with an end plate joining portion. This segmentation allows the electric field relaxation function to be achieved through the projection geometry rather than requiring groove formation, thereby simplifying manufacturing while maintaining reliability.
Solution Approach 2:
The projection portion acts as an intermediary structure between the metallized layer and the external environment. By providing this intermediate geometric feature, the electric field is naturally relaxed without requiring additional processing steps like groove formation, thus improving withstand voltage performance without complicating the manufacturing process.
2Reliability
If a groove is formed on the end surface of the insulating tube to relax the electric field, then the withstand voltage performance is improved, but the insulating tube strength is reduced
Solution Approach 1:
The insulating tube end surface is segmented into multiple functional regions: a projection portion that extends axially to cover the metallized layer end, and a base end portion with an end plate joining portion. This segmentation allows the electric field relaxation function to be achieved through the projection geometry rather than requiring groove formation, thereby simplifying manufacturing while maintaining reliability.
Solution Approach 2:
The projection portion acts as an intermediary structure between the metallized layer and the external environment. By providing this intermediate geometric feature, the electric field is naturally relaxed without requiring additional processing steps like groove formation, thus improving withstand voltage performance without complicating the manufacturing process.
3Quantity of substance
If the metallized layer is made extremely thin to reduce material usage, then the manufacturing cost is reduced, but the electric field intensity increases causing creeping flashover risk
Solution Approach 1:
The projection portion acts as an intermediary structure between the metallized layer and the external environment. By providing this intermediate geometric feature, the electric field is naturally relaxed without requiring additional processing steps like groove formation, thus improving withstand voltage performance without complicating the manufacturing process.
Solution Approach 2:
The geometric parameters of the insulating tube end surface are changed by adding a projection portion. This parameter change modifies the electric field distribution in the vicinity of the metallized layer, allowing the use of thinner metallized layers without increasing electric field intensity to dangerous levels, thereby preventing creeping flashover.
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 effectively reduces electric field values at the metallized layer's outer peripheral end, enhancing the vacuum interrupter's withstand voltage performance and structural strength while maintaining the original dimensions and shape of the vacuum container.
Implementation Method 1
The insulating tube is formed on its end surface with a metallized layer. To this metallized layer, the fixed-side end plate or the movable-side end plate is joined by brazing.
Implementation Method 2
By providing such projection portion, an end portion of the metallized layer on an outer peripheral side of the insulating tube is not exposed to the surroundings of the vacuum interrupter, and electric field of an end portion of the metallized layer on the outer peripheral side of the insulating tube is relaxed.
Data Source
AI summary
A vacuum interrupter is equipped with a vacuum container and fixed and movable electrodes provided in the vacuum container. The vacuum container is constructed by hermetically respectively joining fixed-side and movable-side end plates to one and the other end portions of an insulating tube. The insulating tube is equipped at its end portion with a projection portion that projects in an axial direction of the insulating tube along an outer periphery of the insulating tube. The insulating tube is equipped at its end portion with an end plate joining portion that projects from a base end portion of the projection portion inwardly in a radial direction of the insulating tube. The end plate joining portion is equipped on its surface with a metallized layer to which the fixed-side or movable-side end plate is joined by brazing.