Insulation materials used in transformers and motors are classified based on the temperature withstand capability.
Some of the insulation classes used in transformers and induction motors are: Class Y, Class A, Class E, Class B, Class F, Class H and Class C.
- Maximum hot spot temperature for this type of insulator is 90oC
- Some of the materials used are cotton, silk, paper, wood without impregnated
- Maximum hot spot temperature for this type of insulator is 105oC
- Cotton, Silk, and Paper when suitably impregnated are the type of materials used
- Hot spot temperature is 120oC
- Materials possessing degree of thermal stability allowing them to be operated at a temperature 15oC above higher than Class A. Ex: wire, enamel etc
- Maximum hotspot temperature is 130oC
- Mica, Glass fibre, asbestos, etc with suitable impregnation or coating substance
- Hot spot temperature is 155oC
- Mica, glass, asbestos etc with suitable binding impregnation or coating substances capable of withstanding 25oC higher than Class B
- Maximum hotspot temperature of 180oC
- Combination of materials such as mica, glass fibre, asbestos suitably bonded
- Hotspot temperature above 180oC
- Mica, porcelain, glass, quartz and asbestos with and without inorganic binder