Definition:
Insulating varnish, also known as insulating coatings, is a coating with excellent electrical insulation. It has good electrochemical, thermal, mechanical and chemical properties, mostly varnish, but also colored paint. Insulating varnish is a special type of varnish. Insulating varnish is an important insulating material based on high molecular polymers that can be cured into an insulating film or an insulating whole under certain conditions. Insulating varnish is composed of base material, flame retardant, curing agent, pigment, filler, and solvent.


Insulating varnish can be divided into seven categories according to insulation grade: Y, A, E, B, F, H, and C [2].
The specific introduction is as follows:
Heat resistance grade: Maximum allowable working temperature (℃)
Y grade: 90℃ Insulation structure composed of unimpregnated cotton yarn, silk and paper or their combination
A grade: 105℃ Insulation structure composed of impregnated or immersed in liquid dielectric (such as cotton yarn, silk and paper in transformer oil or their combination)
E grade: 120℃ Insulation structure composed of synthetic organic film, synthetic organic enamel and other materials or their combination
B grade: 130℃
F grade: 155℃
H grade: 180℃ Insulation structure composed of mica, glass fiber, asbestos and other materials or their combination bonded or impregnated with suitable resin (such as silicone resin)
C grade: above 180℃ Insulation structure composed of mica, glass fiber bonded or impregnated with suitable resin, and mica, ceramic, quartz and other materials or their combination that have not been impregnated.

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