Epoxy-Cast Primary Coil Insulation for Void-Free Transformer Windings
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Solution Overview
Problem
State-of-the-art medium voltage transformers with epoxy cast insulation face issues with partial discharges due to incomplete penetration of silica-filled epoxy resin between winding layers, leading to high scrap rates and reduced service life.
Innovation Solution
The use of PET nonwoven interlayer insulation impregnated with low viscosity epoxy and an embedded grounded screen within the epoxy-cast structure of the transformer winding, eliminating electrical fields and enabling complete impregnation without voids, thereby reducing partial discharges and enhancing safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If silica filled epoxy resin is used for impregnation, then thermal conductivity is improved, but penetration capability deteriorates due to high viscosity
Solution Approach 1:
The patent changes the viscosity parameter of the epoxy resin by removing silica fillers, transforming it from a high viscosity state (with silica) to a low viscosity state (without silica), enabling complete penetration while maintaining thermal conductivity through alternative means
Solution Approach 2:
The patent extracts the silica fillers from the epoxy resin composition, separating the penetration function (achieved by low viscosity resin) from the thermal conductivity function (achieved by the resin matrix itself and interlayer contact), thereby resolving the contradiction between viscosity and thermal performance
2Strength
If interlayer insulation sheets are used, then mechanical support is improved, but resin penetration deteriorates due to high viscosity epoxy
Solution Approach 1:
The patent changes the viscosity parameter of the epoxy resin to a low viscosity state, enabling it to fully penetrate the interlayer insulation sheets and completely displace air pockets, thereby eliminating partial discharge pathways while maintaining the mechanical support function of the insulation sheets
Solution Approach 2:
The low viscosity epoxy resin acts as an intermediary that completely fills the spaces between interlayer insulation sheets, creating a continuous dielectric medium that bridges adjacent windings and eliminates air pockets that would otherwise serve as partial discharge initiation sites
3Reliability
If complete impregnation is achieved, then partial discharges are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent changes the viscosity parameter of the epoxy resin to low viscosity, which enables complete impregnation through simple gravity-driven or vacuum-assisted processes, achieving reliable partial discharge reduction without requiring complex multi-step manufacturing procedures
Solution Approach 2:
The patent applies preliminary action by using low viscosity resin that naturally flows and penetrates all spaces during the initial impregnation stage, ensuring complete displacement of air pockets before curing, thereby simplifying the overall manufacturing process while achieving reliable impregnation
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 solution significantly reduces scrap rates and costs, extends the service life of medium voltage transformers by eliminating partial discharges and providing a touch-proof feature, while allowing for modular design and easier manufacturing.
Implementation Method 1
The interlayer insulation and the primary winding are impregnated with a low viscosity epoxy
Implementation Method 2
an embedded grounded screen within the epoxy-cast structure of the transformer winding, eliminating electrical fields
Implementation Method 3
The primary coil, in the form of an epoxy cast, suitable to use in a transformer
Data Source
AI summary
A primary coil suitable for use in a transformer includes a primary winding bobbin onto which a layer of a primary winding and at least one layer, which includes a fixed number of 1 to 3 layers, of an interlayer insulation material are wound alternately, wherein the interlayer insulation material and the primary winding are impregnated with an epoxy, and wherein the interlayer insulation material is a nonwoven material or a crepe paper.