On-Load Tap Changer Equipotential Bridging Switch
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Solution Overview
Problem
Existing on-load tap changers for transformers face challenges in achieving high surge voltage resistance with minimal mechanical switching contacts and vacuum interrupters, while maintaining cost-effectiveness and safety.
Innovation Solution
The design incorporates a changeover switch with three contacts that can assume different positions, including a bridging position, along with a current-limiting element and a switching element, allowing both moving contacts to simultaneously contact fixed contacts at a defined potential, eliminating the need for voltage-limiting elements like varistors and reducing the number of mechanical switching contacts and vacuum interrupters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional on-load tap changers use multiple mechanical switching contacts and vacuum interrupters to ensure safe operation, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies the equipotentiality principle by designing a changeover switch with a bridging position that connects both changeover contacts to a common potential through the third changeover contact. This ensures that both moving contacts are at the same potential during switching operations, eliminating surge voltage risks without requiring additional protective components like varistors, thereby reducing device complexity while maintaining reliability
Solution Approach 2:
The patent extracts and eliminates unnecessary components from traditional on-load tap changer designs. By implementing the equipotential bridging mechanism, the design removes the need for voltage-limiting elements such as varistors and reduces the number of mechanical switching contacts and vacuum interrupters, simplifying the overall device structure while preserving surge voltage resistance
2Reliability
If voltage-limiting elements such as varistors are added to protect against surge voltages, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes voltage-limiting elements such as varistors from the circuit by implementing an equipotential bridging mechanism. The third changeover contact creates a common potential connection that inherently protects against surge voltages, making additional protective components unnecessary and thereby reducing device complexity
Solution Approach 2:
By establishing an equipotential connection through the bridging position of the changeover switch, the patent eliminates potential differences that could cause surge voltages. This inherent protective mechanism replaces the need for external voltage-limiting elements, reducing both component count and device complexity while maintaining reliability
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 enhances surge voltage resistance, reduces costs, and ensures safety by maintaining the on-load tap changer at a defined potential with fewer mechanical contacts and vacuum interrupters, while allowing for flexible design options.
Implementation Method 1
an auxiliary branch connecting the second moving contact to the second changeover contact via a current-limiting element
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
A load stepping switch (1) for uninterrupted changeover between winding taps (n, n+1) on a control winding (20) comprises – a changeover switch (2) that comprises a first, second and third changeover contact (2.1, 2.2, 2.3) and can adopt a first position, in which the first and third changeover contacts are connected, a second position, in which the second and third changeover contacts are connected, and a bridge position, in which the changeover contacts are connected; – a first fixed contact (4) that can be connected to a first winding tap; – a second fixed contact (5) that can be connected to a second winding tap; - a first moving contact (6) that can optionally make contact with each of the fixed contacts; – a second moving contact (7) that can optionally make contact with each of the fixed contacts; - a main path (8) that connects the first moving contact to the first changeover contact; – an auxiliary path (9) that connects the second moving contact to the second changeover contact via a current-limiting element (10); - a switching element (11) that is connected between the main path and the second changeover contact.