Variable Diameter Piston for Medium Voltage Switching Pole
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Solution Overview
Problem
Medium voltage switching poles with spiral contacts or multicontacts face challenges due to high friction, which complicates the drive mechanism and increases costs, as the contact force required for safe current transfer is difficult to manage, especially during the transition from open to closed configurations.
Innovation Solution
The design incorporates a piston with a variable diameter profile that reduces contact pressure in the open position and increases it in the closed position, ensuring low electrical resistance and reduced static friction, allowing for more uniform closing times and speeds, even with drives that cannot generate high opening forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact force is increased to ensure safe current transfer, then electrical connection reliability is improved, but friction increases making the drive more complex and larger
Solution Approach 1:
The piston diameter varies dynamically along its length, creating different contact pressures at different positions. The larger diameter section provides higher contact force when needed for current transfer, while the smaller diameter section reduces friction during movement, eliminating the need for an overly complex drive mechanism designed to overcome maximum friction at all times.
Solution Approach 2:
Different sections of the piston have different diameters to provide locally optimized contact pressure. The larger diameter section is positioned where high contact force is needed for reliable electrical connection, while the smaller diameter section is positioned where reduced friction is beneficial for easier movement, allowing each local region to have the quality it needs.
2Loss of energy
If contact force is increased to reduce electrical resistance, then current transfer efficiency is improved, but the drive must generate higher forces increasing its size and cost
Solution Approach 1:
The variable piston diameter creates dynamic contact pressure that is high when needed for low electrical resistance during current transfer, but low during the closing operation. This means the drive mechanism only needs to generate enough power to overcome the reduced friction during movement, not the full power that would be needed to maintain high contact force throughout the entire cycle.
3Stability of the object's composition
If uniform contact pressure is maintained throughout operation, then electrical connection is stable, but friction during closing operation is too high
Solution Approach 1:
Instead of uniform contact pressure, the piston has varying diameter that creates different contact pressures at different positions and times. During closing operation, the smaller diameter section reduces friction for easier operation. When closed and carrying current, the larger diameter section provides stable, high contact pressure for reliable electrical connection.
Solution Approach 2:
Different sections of the contact interface have different pressure characteristics. The larger diameter section provides high stable pressure for electrical connection stability, while the smaller diameter section provides low pressure for ease of operation during closing, allowing each local region to optimize for its specific function.
Data Source
AI summary
A medium voltage switching pole includes: a fixed contact of a vacuum interrupter; a movable contact of the vacuum interrupter; a piston; at least one electrical contact; a first terminal; and a second terminal. The fixed contact is fixedly connected to the first terminal. The movable contact is fixedly connected to the piston. The piston moves within the second terminal along an axis. The at least one electrical contact makes an electrical connection between the piston and the second terminal. An outer surface of the piston and an inner surface of the second terminal are arranged such that: when in an open configuration the fixed contact and movable contact are separated, at least one first radial line perpendicular to the axis extends through locations of the at least one electrical contact, and a first distance along the at least one first radial line extends from the outer surface.