- Posted by Tomáš Zedníček
- On January 27, 2021
Because paper is porous it has to be impregnated in order to prevent corona effects and flash-overs. It is done by use of melted wax or different kinds of oils, among other things mineral and silicone oils. The oils increase the tensional stability but decrease to a certain extent the εr. A fibrous paper has a εr ≈ 6.6 and the mineral oil ≈ 2.3 which gives the impregnated winding a εr varying between 3.1 and 4.5. The differences depend above all on the winding pressure produced by the tensile force during winding.