On-Load Tap Changer Circuit With High-Ohmic Voltage Stabilization
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Solution Overview
Problem
On-load tap changers experience issues with change-over selectors being exposed to voltages above their withstand limits during the operation of galvanic disconnection of tapped windings, necessitating costly winding layouts to ensure safe operation.
Innovation Solution
Incorporating high-ohmic resistances in the electric connection between diverter switches and tapped windings to maintain a defined potential during change-over selector operations, preventing excessive voltage exposure and allowing for cost-efficient winding arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If tapped windings are galvanically disconnected during change-over selector operation to enable tap changing, then tap selector functionality is improved, but change-over selectors are exposed to voltages above their withstand limits
Solution Approach 1:
High-ohmic resistances are introduced as intermediary elements between the tapped windings and the change-over selectors. These resistances provide a galvanic connection path that prevents the change-over selectors from being exposed to excessive voltages during operation, while still allowing the tap changing function to work properly.
Solution Approach 2:
The electrical connection parameters are changed by introducing high-ohmic resistances with specific resistance values (e.g., 50 kOhm to 500 kOhm). This parameter change ensures that the change-over selectors operate within their voltage withstand limits while maintaining the necessary electrical connectivity for tap selection.
2Reliability
If high-ohmic resistances are added to maintain defined potential during change-over operation, then voltage exposure of change-over selectors is reduced, but device complexity increases
Solution Approach 1:
The high-ohmic resistances serve multiple functions: they protect change-over selectors from excessive voltages, maintain defined potential during galvanic disconnection, and enable cost-efficient winding layouts. By making these components multi-functional, the overall device complexity is justified by the multiple benefits provided.
Solution Approach 2:
The high-ohmic resistances are simple, inexpensive passive components that can be easily integrated into the existing circuit. Their low cost and simplicity offset the increase in device complexity, making them an economical solution for protecting the change-over selectors.
3Adaptability or versatility
If tapped windings are connected in series to achieve larger regulating range, then voltage regulation capability is improved, but change-over selectors are exposed to higher voltages during disconnection
Solution Approach 1:
High-ohmic resistances are placed in the electrical connections between the series-connected tapped windings and the change-over selectors. These intermediary resistances ensure that even when the tapped windings are connected in series to expand the regulation range, the change-over selectors remain protected from excessive voltages during galvanic disconnection.
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 use of high-ohmic resistances ensures that change-over selectors are not exposed to excessive voltages, enabling the use of more cost-effective winding layouts and reducing operational losses by maintaining a defined potential during tap changes.
Implementation Method 1
The on-load tap changer comprises one or more high-ohmic resistances in an electric connection between at least one of the diverter switches and at least one of the tapped windings
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An on-load tap changer (1) comprises a first tap selector (6), a second tap selector (7), a first diverter switch (8) and a second diverter switch (9), a first change-over selector (14) and a second change-over selector (15) and one or more high-ohmic resistances (10, 11), wherein the diverter switches (8, 9) are connected to each other such that the tapped windings (2, 3) are connected in series and the one or more high-ohmic resistances (10, 11) are in an electric connection between at least one of the diverter switches (8, 9) and at least one of the tapped windings (2, 3).