Transformer Foil Coil Edge Shielding for Partial Discharge Control
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Solution Overview
Problem
Transformer coils with foil winding arrangements face challenges in reducing electric field stress at edges, leading to suboptimal performance in partial discharge tests and dielectric ageing, especially when solid insulation is used between low and high voltage windings.
Innovation Solution
A conductor element, typically a bent metal foil with a curled edge region, is used to electrically shield the foil winding arrangement, reducing electric field stress at the edges and improving performance by covering at least one of the four edge regions, which can be completely surrounded by an insulation element like epoxy resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a foil winding arrangement is used in a transformer coil, then the coil structure is simplified and manufacturing is easier, but electric field stress concentrates at the edges leading to poor performance in partial discharge tests and dielectric ageing
Solution Approach 1:
A conductor element is introduced as an intermediary component between the foil winding arrangement and the surrounding insulation. This conductor element serves as a mediator that redistributes the electric field, preventing concentration at the edges of the foil winding while maintaining the simplicity of the foil winding structure itself.
Solution Approach 2:
The conductor element is specifically positioned at the edge regions of the foil winding arrangement where electric field stress concentrates. By applying this additional conductive component only at the critical edge locations rather than throughout the entire winding, the electric field distribution is locally improved without compromising the overall manufacturing simplicity.
2Volume of stationary object
If solid insulation is used between low voltage and high voltage windings, then the insulation structure is compact and space is reduced, but dielectric stress increases leading to accelerated ageing
Solution Approach 1:
The conductor element acts as an intermediary that redistributes electric field stress within the compact solid insulation structure. By introducing this conductive element, the electric field is more evenly distributed throughout the insulation volume, reducing peak stress concentrations that would otherwise accelerate dielectric ageing while maintaining the compact design.
3Reliability
If conductor elements are added to shield edge regions, then electric field stress is reduced and reliability improves, but device complexity increases
Solution Approach 1:
The conductor element is implemented as a thin, flexible component that can be easily conformed to the edge regions of the foil winding arrangement. This thin-film approach provides effective electric field shielding while adding minimal structural complexity and maintaining ease of integration into the existing coil structure.
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 conductor element effectively reduces electric field stress, enhancing performance in partial discharge tests and allowing for reduced clearance distances, thereby improving dielectric ageing and overall transformer assembly efficiency.
Implementation Method 1
The conductor element allows for a reduction in an electric field that arises during an operation of the transformer assembly at the edges of the foil winding arrangement
Data Source
AI summary
A coil for a transformer assembly is provided. The coil extends circumferentially around a longitudinal axis. The coil comprises a foil winding arrangement and a conductor element. The foil winding arrangement extends circumferentially around the longitudinal axis and has four edge regions. The conductor element covers at least partially at least one of the edge regions of the foil winding arrangement. The conductor element allows for a reduction in an electric field that arises during an operation of the transformer assembly at the edges of the foil winding arrangement. In this manner, a performance improvement in partial discharge tests and lightning impulse tests can be achieved.