Vacuum Variable Capacitor Pre-Vacuum Enclosure for Bellows Stress Reduction
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Solution Overview
Problem
State-of-the-art vacuum variable capacitors are limited in speed due to high motor power requirements and pressure-velocity limitations, leading to wear and reduced lifetimes of the screw/nut system and bellows, with increasing size and cost being necessary to achieve higher torque and speed.
Innovation Solution
Incorporating a pre-vacuum enclosure at a pressure below atmospheric pressure to reduce the pressure differential across the bellows, allowing for faster adjustment speeds and increased lifetimes without increasing motor size or reducing resolution, by reducing the torque required to move the bellows and minimizing membrane and bending stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a vacuum enclosure is used to maintain high voltage capabilities, then voltage capability is improved, but adjustment speed deteriorates due to high motor power requirements
Solution Approach 1:
The vacuum enclosure is segmented into two separate vacuum chambers: a first vacuum chamber containing the capacitor electrodes and a second vacuum chamber containing the drive means. This segmentation allows the drive means to operate in a higher pressure environment while the electrodes remain in high vacuum, resolving the contradiction between voltage capability and adjustment speed.
2Device complexity
If a single vacuum enclosure is used, then device complexity is reduced, but reliability deteriorates due to wear of screw/nut system and bellows
Solution Approach 1:
The single vacuum enclosure is divided into two separate vacuum chambers, each optimized for its specific function. This separation prevents wear and contamination from affecting both systems simultaneously, thereby improving reliability without significantly increasing overall device complexity.
Solution Approach 2:
A bellows component acts as an intermediary between the two vacuum chambers, allowing mechanical movement transmission while maintaining vacuum separation. This intermediary protects the drive means from direct exposure to high vacuum conditions, reducing wear and extending component lifetime.
3Speed
If motor power is increased to achieve faster adjustment, then adjustment speed is improved, but device size and cost increase
Solution Approach 1:
By segmenting the vacuum enclosure into two chambers, the drive means can operate in a higher pressure environment where less motor power is required to achieve the same adjustment speed. This eliminates the need for oversized motors while maintaining fast adjustment capabilities.
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
This configuration enables faster capacitance adjustments with reduced motor torque, extended lifetimes of the bellows and screw/nut system, and maintains high voltage and power capabilities while minimizing heat-related issues, allowing for more efficient and reliable operation.
Implementation Method 1
reduce the pressure differential across the bellows
Implementation Method 2
the vacuum dielectric medium gives the name to such capacitors
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A vacuum variable vapacitor (1) comprising a pre-vacuum enclosure (21) for reducing a pressure differential across the bellows (11). The vacuum force load on the drive system (9, 14) can thereby be reduced, allowing faster movement of the movable electrode (7), faster capacitance adjustment of the vacuum variable capacitor (1) and longer lifetimes of the device.