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Etude du vieillissement de matériaux hautes températures pour machines tournantes et définition de méthodes d'essais accélérées

Abstract : Conductor bars of large rotating electrical machines are insulated with a composite material. This material contains an epoxy matrix, reinforced with glass fabric and mica paper. Insulation systems are classified in thermal classes according to the highest temperature they can tolerate without major deterioration in long time usage (at least 20 000 h). In this study, an experimental device was developed in order to realize very accelerated ageing under increased oxygen pressure, at class temperature (155°C and 180°C). The results of these ageing experiments were compared with results obtained by ageing in air at atmospheric pressure. Two new materials have been studied and compared with a reference. The progress of ageing was studied by changes of electrical properties (dielectric spectroscopy and partial discharges measurements), thermo-mechanical properties (Dynamic Mechanical Analysis - DMA) and the mass loss. Samples with different dimensions were studied, allowing to observe the effects of material anisotropy. Different kinetics could be distinguished for degradation within the mica plan and perpendicular to it. The evolution of mass loss can be well described by kinetics of order zero and 1. Using these models and referring to actual standards, lifetimes were evaluated for the three materials, when used in an industrial context, under oxygen pressure and under air at atmospheric pressure.
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Submitted on : Wednesday, April 13, 2011 - 9:57:55 AM
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Vincent Boucher. Etude du vieillissement de matériaux hautes températures pour machines tournantes et définition de méthodes d'essais accélérées. Sciences de l'ingénieur [physics]. Université de Grenoble, 2010. Français. ⟨tel-00585496⟩

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