Charakterisierung und Evaluierung von Schlüsselparametern für die Herstellung defektfreier Isolationsverbundmaterialien

Translated title of the contribution: Characterization and evaluation of key parameters for the manufacture of defect-free insulating composite materials

Helena Weingrill

Research output: ThesisMaster's Thesis

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The life-time of rods and coils of high voltage rotating machines is mainly governed by the performance of the high voltage insulation which is a multilayer composite comprising mica and glass layers. After undergoing the VPI-process (vacuum pressure impregnation) the insulating composite is usually impregnated with low viscous thermosetting resin and cured at elevated temperature. A complete, defect-free impregnation is crucial here as even small holes and defects can lead to partial discharges under high electrical fields. Partial discharges cause accelerated ageing of the insulation material and can lead to a breakdown to the generator. In the present master thesis key parameters were evaluated in order to produce defect-free insulating composite materials after the VPI-process and to investigate their effect on resin pathways and insulation quality. In the first step, the influence of selected process parameters on the resin flow into the multi-layer composite was investigated. A vacuum oven together with a model build-up was used in compliance with large-scale vacuum impregnation processes to optically monitor the pathways of the epoxy-based resin. During this work, several phenomena and their effects on the undesired formation of defects in the insulting composite were observed. Furthermore, these effects were provoked and intensified by the employment of special experimental setups. A correlation between selected process parameters and impregnation quality of the insulating composite was found. Based on these results the optimization of the vacuum pressure impregnation process can be pursued in order to avoid early ageing of the insulation and even a breakdown of the rotating machine. The second part of the present work dealt with the characterization of the cure kinetics of the epoxy-based thermosetting resin. Due to their excellent dielectric properties, epoxy resins play an important role in electrical engineering. The accelerator which is needed for the curing reaction is immobilized on different tape materials. To determine the curing yields and the corresponding viscosity of small areas within the multilayer composite, a correlation between FT-IR and viscosity measurements was established. The calculated calibration curves enabled an space-resolved determination of the viscosity and the corresponding degree of crosslinking in small resin layers between the accelerator containing tape materials. This method further made the evaluation of the reactivity of different accelerator containing insulation tapes feasible.
Translated title of the contributionCharacterization and evaluation of key parameters for the manufacture of defect-free insulating composite materials
Original languageGerman
  • Kern, Wolfgang, Supervisor (internal)
Award date19 Dec 2014
Publication statusPublished - 2014

Bibliographical note

embargoed until 01-11-2019


  • high voltage insulation
  • high voltage generator
  • epoxy resin
  • anhydride curing agent
  • VPI
  • hydro generator
  • curing kinetics
  • mica tape
  • insulation composite
  • vacuum oven
  • resin viscosity

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