Corona Shielding Tape for Curing Anhydride-Free Stator Insulation
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Solution Overview
Problem
Existing insulation systems for high-voltage rotating electrical machines face challenges with anhydride-free impregnating agents, as conventional tape accelerators like tertiary amines and organic zinc salts do not adequately crosslink, leading to uncured regions with low glass transition temperatures, which are prone to thermal and electrical degradation, and partial discharges occur at the interface between the main insulation and laminated stack, risking damage and flashover.
Innovation Solution
A corona shielding tape comprising a carrier tape with a polymer matrix containing polyvinylalcohol and a tape accelerator, such as superacid salts, is used to cure anhydride-free epoxy resin-based impregnating agents under vacuum pressure impregnation, ensuring effective curing and resistance to partial discharges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional tape accelerators (tertiary amines and organic zinc salts) are used with anhydride-free impregnating agents, then the insulation system can be produced without anhydride, but the crosslinking is inadequate leading to uncured regions with low glass transition temperature
Solution Approach 1:
The patent changes the chemical parameters of the tape accelerator by using a combination of tertiary amine and organic zinc salt in specific proportions, along with controlled humidity exposure during storage and processing, to achieve adequate crosslinking with anhydride-free impregnating agents
Solution Approach 2:
The patent creates a composite accelerator system combining multiple chemical components (tertiary amine, organic zinc salt, and moisture) that work synergistically to enable proper curing of anhydride-free epoxy resins, replacing the single-component accelerators that failed with anhydride-free systems
2Ease of manufacture
If uncured regions with low glass transition temperature are present in the insulation system, then processing may be easier, but thermal and electrical degradation occurs rapidly leading to flashover
Solution Approach 1:
The patent applies corona shielding tape and ensures proper curing before the insulation system is subjected to thermal and electrical stress during operation, preventing the formation of degraded regions that would lead to flashover
Solution Approach 2:
The patent modifies the curing parameters through controlled humidity exposure and temperature profiles to ensure complete crosslinking of the anhydride-free impregnating agent, achieving adequate glass transition temperature and eliminating uncured regions
3Device complexity
If partial discharges occur at the interface between main insulation and laminated stack, then the insulation system can be simpler, but damage and flashover risk increase
Solution Approach 1:
The patent introduces corona shielding tape as an intermediary component at critical interfaces (between main insulation and laminated stack, and at slot exits) to prevent partial discharges and protect the insulation system from damage
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 solution provides a robust insulation system with improved resistance to partial discharges and thermal degradation, maintaining integrity and reliability of stator windings under high thermal, thermomechanical, and electrochemical stress.
Implementation Method 1
the at least one tape accelerator is selected from the group of the superacids and/or the superacid salts which is suitable for acceleration of a cationic homopolymerization of the resin-based anhydride-free impregnating agent
Data Source
AI summary
Various embodiments of the teachings herein include a corona shielding tape for further processing to give an insulation system comprising an impregnated winding with potential control via outer corona shielding “AGS” and/or internal potential controller “IPS” and/or terminal corona shielding “EGS”, the insulation system being producible by impregnating the winding with an anhydride-free and resin-based impregnating agent at 45-85° C. and under reduced pressure. The corona shielding tape may include: a carrier tape; an electrically conductive and/or partly conductive filler in a polymer matrix; and a tape accelerator suitable for curing and/or gelation of the impregnating agent. The polymer matrix contains at least one polyvinylalcohol and/or a polyvinylalcohol copolymer. The accelerator is selected from the group consisting of: superacids and superacid salts suitable for acceleration of a cationic homopolymerization of the resin-based anhydride-free impregnating agent.