Transformer Coil Interlayer Insulation

Air cooled transformer coils operate at 350 Deg. C temperatures and lower quality Mica film is used as an interlayer insulation for this requirement.In this application the Power Factor of the Mica is not of great importance and heavily stained and black spotted Mica Film can be used as interlayer insulation for this requirement. In this application, Mica Film 0.001" (0.025mm) thick X 3" to 4" (7.5 cm to 10 cm) wide X 10" to 12" (25 cm to 30 cm) long is used.The Mica is spread on a backing that has been impregnated with a mixture of silicon varnish and fine Mica powder backing that is still tacky.This material serves as an excellent surface for coil windings and for interlayer insulation in transformers, particularly Class 'H' transformers.