Shielded Power Transformer Winding for Recovery Voltage Control
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Solution Overview
Problem
The use of tie-in resistors in power transformers for on-load tap changers increases dimensions, costs, and no-load losses, and affects the transformer's performance, particularly the Peak Efficiency Index (PEI), while requiring additional space and increasing the tank and oil volume.
Innovation Solution
A conductive or semiconductive shield is positioned externally around the outermost winding of the transformer, reducing recovery voltage without the need for tie-in resistors, thereby minimizing space requirements and no-load losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tie-in resistors are used to control recovery voltage, then recovery voltage is reduced below maximum level, but transformer dimensions and tank volume increase
Solution Approach 1:
The invention extracts the recovery voltage control function from the external tie-in resistors and relocates it to an internal shield structure. The shield is positioned within the transformer tank, eliminating the need for external resistors and reducing overall transformer dimensions while maintaining recovery voltage control below maximum levels.
Solution Approach 2:
The shield structure is nested within the existing transformer tank and winding arrangement. By placing the shield internally rather than using external tie-in resistors, the solution utilizes the existing space efficiently, avoiding increases in tank volume while achieving the same recovery voltage control function.
2Reliability
If tie-in resistors are used to control recovery voltage, then recovery voltage is reduced below maximum level, but no-load losses increase
Solution Approach 1:
The invention removes the energy-dissipating tie-in resistors from the system and replaces them with a passive shield structure that controls recovery voltage through capacitive coupling rather than resistive dissipation. This eliminates the continuous energy losses associated with resistors while maintaining effective recovery voltage control.
3Reliability
If tie-in resistors are used to control recovery voltage, then recovery voltage is reduced below maximum level, but transformer costs increase
Solution Approach 1:
The shield structure is integrated into the existing transformer assembly, combining the recovery voltage control function with the internal winding structure. This eliminates the need for separate external tie-in resistors and associated switching devices, reducing component count, assembly complexity, and overall manufacturing cost.
4Reliability
If tie-in resistors are used to control recovery voltage, then recovery voltage is reduced below maximum level, but device complexity increases
Solution Approach 1:
The invention extracts the recovery voltage control function from complex external tie-in resistor assemblies with switching mechanisms and simplifies it to an internal passive shield structure. This dramatically reduces device complexity by eliminating external components, connection terminals, and switching mechanisms while maintaining effective control.
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 shield effectively reduces recovery voltage levels below the maximum allowable limit, avoiding the need for tie-in resistors and maintaining transformer efficiency, while being cost-effective and space-saving.
Implementation Method 1
a shield comprising a conductive or semiconductive material, wherein the shield is located at an outer side of an outermost one of the windings
Data Source
AI summary
A power transformer for an on-load tap changer application is disclosed. The power transformer comprises a winding arrangement with a core, several windings wound around the core, and a shield located at an outer side of an outermost one of the windings, wherein the shield comprises or consists of a conductive or semiconductive material.