Commonly used insulation materials are classified into six grades: A, E, B, F, H and C according to their heat resistance
Class A insulation
Class A insulation includes impregnated cotton yarn, silk, paper and other organic fiber materials, as well as enamel on ordinary enameled wires. Currently only used in transformers. The maximum allowable operating temperature of Class A insulation is 105°C.
Class E insulation
Class E insulation includes films made of polyester resin, epoxy resin, and triacetate. Enamel on polyvinyl acetal high-strength enameled wire. Used in medium and small AC and DC motors. The maximum allowable operating temperature of Class E insulation is 120°C.
Class B insulation
Class B insulation includes inorganic materials such as mica, asbestos, glass filament, etc., made of organic paint or resin (with heat resistance treatment) as a binder and their composition, and enamel on polyester high-strength enameled wire. Generally used in large and medium synchronous machines and medium and small AC and DC motors. The maximum allowable working temperature of Class B composite insulating paper is 130℃
Class F insulation
Class F insulation includes synthetic resin paint modified with silicon organic compounds for inorganic substances such as mica, asbestos, and glass wool. Or materials or combinations thereof made of alkyd and epoxy resins that meet the requirements of this level of heat resistance. The maximum allowable working temperature of Class F composite insulating paper is 155℃.
Class H insulation
Class H insulation includes silicon organics and inorganic materials such as mica, asbestos, glass filaments, etc., made of silicon organic paint as a binder. It is mainly used in occasions that require the smallest possible size and weight reduction, such as aviation motors, crane motors and traction motors. The maximum allowable working temperature of H-grade heat-resistant insulating paper is 180℃.
Class C insulation
Class C insulation includes mica, quartz and glass wire without dry mixture. Organic resin, polyimide impregnating varnish and other treated asbestos, glass fiber fabric or other products with particularly good thermal stability, as well as polyimide-based enameled wire enamel, polyimide film, etc. Class C insulation is a more demanding insulation material and is currently being promoted. Its maximum allowable working temperature is above 180℃.
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