Multilayer Transformer Insulation Without Polymer Binders
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Solution Overview
Problem
Kraft paper used for electrical insulation in transformers faces issues with thermal stability and mechanical strength due to hydrolysis from high temperatures, and the addition of polymer binders causes non-uniformity and sticking problems during processing and use.
Innovation Solution
A multilayer structure comprising a first layer with aramid and cellulose, and a second layer without aramid, where the first layer contains meta-aramid and cellulosic pulp fibers in specific weight percentages, and additional layers can be added without aramid, formed using conventional paper-making techniques to enhance insulation properties and prevent thermal degradation and sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polymer binder is added to blend synthetic fibers with cellulose pulp, then thermal stability and mechanical strength are improved, but non-uniformity and sticking problems occur during processing and usage
Solution Approach 1:
The invention removes the polymer binder component from the paper composition entirely. Instead of using a polymer binder to bond synthetic fibers and cellulose pulp, the patent relies on the natural bonding properties of the fiber mixture during papermaking processing, thereby eliminating the sticking problems and non-uniformity caused by polymer binders while maintaining thermal stability and mechanical strength through the fiber blend itself
Solution Approach 2:
The invention uses a composite material approach by blending high-temperature synthetic fibers with cellulose pulp in specific proportions without requiring a polymer binder. The composite structure of different fiber types provides both thermal stability (from synthetic fibers) and bonding capability (from natural fiber interactions during processing), resolving the contradiction between strength improvement and processing uniformity
2Temperature
If polymer binder is added to blend synthetic fibers with cellulose pulp, then thermal stability is improved, but sticking problems occur during processing and usage
Solution Approach 1:
The invention extracts and removes the polymer binder from the system, eliminating the source of sticking problems during processing and usage. The thermal stability is maintained through the synthetic fiber content itself rather than through a polymer binder, which would cause adhesion issues during high-temperature operations in contact with transformer coils
Solution Approach 2:
The invention applies local quality by using different fiber types in specific proportions tailored for different functional requirements: synthetic fibers provide thermal stability in high-temperature zones, while the cellulose pulp provides natural bonding properties during processing. This localized functional distribution achieves both thermal stability and sticking resistance without requiring a polymer binder
3Temperature
If high temperature synthetic fibers are blended with cellulose pulp, then thermal stability is improved, but non-uniformity occurs in the paper
Solution Approach 1:
The invention applies parameter changes by optimizing the proportion of synthetic fibers to cellulose pulp and controlling the fiber size distribution. By adjusting these parameters and relying on natural fiber bonding during papermaking, the patent achieves uniform paper structure with improved thermal stability without the non-uniformity caused by polymer binders
Data Source
AI summary
A multilayer structure particularly useful in a transformer which contains(a) a first layer of aramid and cellulose wherein(i) the aramid is present as an meta-aramid in an amount of 0 to 50 weight percent floc and 50 to 100 weight percent fibrid,(ii) the cellulose is present in the form of cellulosic pulp fiber and(iii) the aramid is present in an amount of 16 to 75 weight percent andthe cellulose is present in an amount of 25 to 84 weight percent,said percentages on the basis of the aramid and cellulose and(b) a second layer containing cellulosic pulp fiber with the proviso that the second layer does not contain aramid.