Tap Changer Vacuum Interrupter Actuating Assembly
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Solution Overview
Problem
Current on-load tap changers face challenges in efficiently and reliably switching transformer taps while maintaining high voltage integrity, particularly in the operation of vacuum interrupter assemblies which require precise choreography of mechanical components to avoid arcing and ensure safe contact changes.
Innovation Solution
The design incorporates a vacuum interrupter assembly with a rotatable cam, shuttle, and impact mass connected by springs, where the holding device stores compression and tension forces to facilitate smooth contact opening and closing, and a unidirectional damper and contact erosion damper to manage movement and prevent damage during switching operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vacuum interrupter assembly is used to switch transformer taps under load, then continuous current flow can be maintained during tap changes, but arcing between contacts may occur during contact opening and closing operations
Solution Approach 1:
The bypass switch assembly is activated before the vacuum interrupter contacts open, establishing an alternative current path. This preliminary action ensures that when the vacuum interrupter contacts separate, the current seamlessly transitions to the bypass path, preventing arcing. Similarly, the bypass switch opens before the vacuum interrupter contacts close, ensuring the contacts are ready to carry current immediately upon closure without arcing.
Solution Approach 2:
The bypass switch assembly acts as an intermediary element that temporarily carries the current during the transition period when the vacuum interrupter contacts are open. This intermediary current path allows the vacuum interrupter to switch taps without directly interrupting the load current, thereby eliminating arcing at the vacuum interrupter contacts.
2Reliability
If mechanical components are precisely choreographed to avoid arcing, then contact switching reliability improves, but device complexity increases due to multiple interdependent assemblies
Solution Approach 1:
The vacuum interrupter assembly, bypass switch assembly, and selector switch assembly are merged into a single integrated tap changer unit with a common drive mechanism. This integration allows the multiple assemblies to operate in coordination through a single rotational input, reducing the overall system complexity while maintaining the precise choreography needed for reliable arcing-free switching.
Solution Approach 2:
The rotatable cam mechanism serves multiple functions simultaneously: it actuates the bypass switch assembly, controls the vacuum interrupter assembly, and operates the selector switch assembly. This multi-functionality reduces the number of separate actuating mechanisms needed, thereby simplifying the overall device complexity while maintaining reliable contact switching.
3Force
If impact mass is held and then released to move the shaft for contact switching, then contact opening and closing force is sufficient, but spring tension and compression forces must be precisely managed
Solution Approach 1:
The spring assembly is pre-configured to store both tension and compression forces that will be released when the impact mass is freed from the holding device. This beforehand cushioning ensures that the impact mass receives sufficient force to reliably open and close the contacts without requiring excessive precision in the release mechanism, as the spring forces are already prepared to provide the necessary impulse.
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 continuous current flow during tap changes without arcing, ensures reliable contact switching, and extends the life of the vacuum interrupter by managing forces effectively, thereby improving the overall efficiency and reliability of the tap changer.
Implementation Method 1
An impact mass is connected to the shuttle by springs such that the impact mass tends to follow the shuttle when the shuttle moves
Implementation Method 2
The holding of the impact mass when the shuttle starts to move causes the springs to store both a compression force and a tension force, which are released when the impact mass is released
Implementation Method 3
a vacuum interrupter (54) with contacts; a rotatable cam (102), the vacuum interrupter assembly (52) being disposed within a tank (18) containing a dielectric fluid
Data Source
AI summary
An on-load tap changer is provided having a vacuum interrupter actuatable by a shaft. A movable shuttle is connected to an impact mass by springs such that the impact mass tends to follow the shuttle when the shuttle moves. A pawl assembly is operable to hold and then release the impact mass when the shuttle starts moving. The holding of the impact mass when the shuttle starts to move causes the springs to store both a compression force and a tension force, which are released when the impact mass is released.