Ecologically friendly resin impregnation of rotating machines with the use of the joule effect

Windings of rotating machines or electrical generators (e. g. wind and water power generators) are impregnated with resin. A new technology using the heating effect of current is investigated. The high efficiency of heating with the joule effect results in quick heating of stator leading to fast gelling of the resin, which implies low emission.

Short Description



Actual Situation

The state of the art technology of impregnating rotating machines and electrical generators is the VPI process (vacuum pressure impregnation).

The objects to be impregnated (for example stators for wind power) are evacuated and then flooded with an impregnating resin. Then, the stator is transported to a convection oven, where the resin gels at 80°C to 100°C and then hardens through within a few hours.

When impregnating big stators it may take hours for the resin to reach hardening temperature, so up to approximately 50% of the resin may leak out of the winding. Finally, the resin hardens at 150°C to a cross-linked and therefore hard material, which primarily improves the insulation and increases the hardness of the winding but also protects it from environmental stress.

Contents and Targets

A new procedure of impregnating wind power stators using the joule effect (in German "Strom - UV - Verfahren") has to be investigated. Technical problems have to be tackled in order to design for a suitable impregnation facility.

An advantage of heating stators by current supply is the high efficiency of 97% as opposed to approximately 40% efficiency of a typical forced-air oven. Energy consumption is reduced by 70%. A reduction of emission of at least 70% is feasible.

This is due to the fact, that that gelling temperature can be reached very quickly. Therefore, the resin is gelling very fast and almost no fluid resin may drop out of the slots.

The advantages of this technology have to be verified and proven by investigations. The applicability of this technology for impregnating large wind power stators in round wire or form wound coil design will be verified by theoretical and practical tests.


Detailed theoretical and practical examinations have proven the applicability of this new technology for wind power stators, especially for wind power stators up to several megawatts completed in form wound coil design.

The advantages of this technology using the joule effect, which have been proved by extensive testing, are among others: a raise of energy efficiency, emission reduction to 1/10 of the emission caused by the VPI process and the better impregnation quality. The compatibility for future use is also certain.

Furthermore, fundamental research to adept this technology to high voltage coils has been done, the results encourage continuing the investigations.

The main goal of the project at hand - the installation of a new impregnation facility - has been reached. Such a facility has been designed and will be installed in Weiz in the ELIN EBG Motoren GmbH in the course of the demonstration project "Factory of Tomorrow - 4th call".

Project Partners

Project manager

DI Walter Schmidt
Tel.: +43 (3172) 606 2991


DI Dominik Brunner (GF)
Tel.: +43 (0)3172 606 2225


ELIN EBG Motoren GmbH
Elingasse 3, A-8160 Weiz
Internet: Elin Motoren

Project partners:

Bäuerle Elke
Gottlob Thumm GmbH
Daimlerstr. 6, D-78549 Spaichingen
Tel.: +49 (0)7424 2314

Hansjörg Köfler
TU-Graz, Institut für elektrische Maschinen und Antriebstechnik
Steyrergasse 21(B), A-8010 Graz
Tel.: +43 (0)316 873 8600