03/07/2014
DO YOU KNOW ? WHY VARNISH IS USED ?
Fibrous material, such as paper, was traditionally used as the primary insulation on inductor coils. To improve the insulation properties of the coils without having to use wire with thicker insulation, a secondary insulation (i.e. impregnation resin) was used to "impregnate" the assembled coils of wire.
Primary insulation is considered impregnated when all the spaces and gaps between fibers are completely filled by the impregnation resin, which is why secondary insulation and impregnation resin are interchangeable terms. By this definition, a winding can be impregnated even if there are still spaces between coils--as long as the spaces between the fibers of the primary insulation are filled in.
Insulating varnish refers to the electrical insulation used for impregnating coils of wire, such as the inductor coils found in transformers. It is also known as impregnating or transformer resin.
Keep in mind that insulating varnish may refer to the primary insulation (wire enamel) used to initially coat a bare conductor, or it may refer to the secondary insulation that is applied to assembled windings of enameled wire.
