Eco-Friendly Impregnation of Electrical Machines

Initial situation

At present, the VPI process (vacuum-pressure-impregnation) is the standard process for resin impregnation in the electrical industry. In this process the components are "soaked" in a vacuum chamber. Then, the resin is cured in a forced-air oven. Especially with large components it takes more than two hours for the resin to reach the gel point temperature. During this time, part of the resin may drain off the windings and is thus lost.

Challenge

Contrary to the conventional method, the present project developed and tested a method of resin impregnation using the Joule effect (heat from electric current) and ultraviolet light for curing. Heating of the stator in this approach is realized by feeding electric current to the windings. The windings thus reach adequate temperatures more quickly so that the gel point occurs earlier and virtually no uncured resin runs off. Resin impregnation using the Joule effect and ultraviolet light for curing reaches gel point temperatures more quickly and can reduce emissions by up to 70 %. Additionally this method requires considerably less time and energy input. Also, the electric current-UV technology permits to use a wider range of isolating resins.

Results

In addition to analyzing the strengths and weaknesses of the electric current- UV impregnation method the research project also investigated what isolation systems can be impregnated using this technology and how existing isolation systems have to be adapted in order to be suitable for the electric current- UV curing technology. In addition to conducting comprehensive investigations, researchers also tested the impregnation of a form wound type wind power generator in a testing facility designed by Gottlob Thumm GmbH for this purpose.

Photos: Elin EBG Motoren GmbH