Vacuum Bulb Electrode Integration for Dielectric Stress Reduction
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Solution Overview
Problem
The reduction in size of vacuum cartridges for medium or high voltage electrical switchgear apparatus leads to increased dielectric stress, necessitating a design that minimizes this stress while maintaining simplicity and economy.
Innovation Solution
A vacuum interrupter with a cylindrical body, where the second cover acts as both a fixed electrode and a busbar connection, featuring rounded contact areas and a metal fastening flange to distribute electric field effectively, and a metal screen to mitigate edge stress, reducing the number of components and enhancing dielectric behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the vacuum cartridge size is reduced, then the vacuum interrupter becomes smaller and more economical, but the dielectric stress on the vacuum cartridge increases
Solution Approach 1:
The patent applies spheroidality by providing rounded contact areas on the electrodes instead of sharp edges or flat surfaces. Specifically, the movable electrode has a rounded contact area and the fixed electrode has a rounded contact area, both with defined radii of curvature. This curvature distributes the electric field more uniformly, reducing dielectric stress concentration at sharp edges while maintaining the reduced vacuum cartridge size for economical design.
2Volume of moving object
If the vacuum interrupter is placed in bypass rather than main circuit, then the vacuum cartridge size is reduced, but the dielectric stress during opening operation increases
Solution Approach 1:
The rounded contact areas on both movable and fixed electrodes create a more uniform electric field distribution during opening operations. This curvature prevents electric field concentration at sharp edges, thereby enhancing the dielectric withstand capability of the reduced-size vacuum cartridge when it operates in bypass mode carrying the full current during opening.
Solution Approach 2:
The patent changes the geometric parameters of the contact areas by specifying rounded shapes with defined radii of curvature (movable electrode contact area radius: 3-10mm, fixed electrode contact area radius: 5-15mm). This parameter change optimizes the electric field distribution to reduce dielectric stress while maintaining the compact bypass configuration.
3Device complexity
If the second cover serves as both fixed electrode and busbar connection, then the number of components is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent merges the second cover with the fixed electrode and busbar connection functions into a single integrated component. This reduces the total number of parts and simplifies assembly while the rounded contact area geometry with specified radii of curvature helps distribute manufacturing tolerances, making the precision requirements more manageable despite the multi-functional integration.
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 dielectric stress, allows for a smaller and more economical vacuum cartridge, and improves electric field distribution, ensuring reliable operation under transient recovery voltages.
Implementation Method 1
The fixed contact region has a radius of curvature greater than that of the movable contact area... effectively reduces dielectric stress... improves electric field distribution
Implementation Method 2
It just needs to be able to withstand a transient recovery voltage (Transient Voltage Recovery - TRV) after the power failure in the main circuit
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a vacuum bulb (10) intended for an electrical switching device. It comprises a cylindrical body (11) made of insulating material closed at each end by respectively a first cover (14) and a second metallic cover (20), and a movable electrode (12) which passes through the first cover (14) and which cooperates with a fixed electrode between a closed position in which the two electrodes are in contact with each other and an open position in which the two electrodes are separated, the bulb being characterized in that the second cover (20) corresponds to the fixed electrode of the vacuum bulb (10).