Class of Insulating Matrials

In this theory, classification of insulation, its types and maximum allowable temperature limits is given. The temperature rise of the electric machine depends upon temperature rise of the insulating materials. The different types of insulating material are classified according to maximum temperature limits.

Class of Insulations

Class Y

• Cotton yarns and Fabrics, paper and fibrous material of cellulose, silk neither impregnated nor immersed in liquid dielectric
• Maximum Temperature Limits: 90 ⁰C

Class A

• Cotton yarns and Fabrics, paper and fibrous material of cellulose, silk impregnated or immersed in liquid dielectric
• Maximum Temperature Limits: 105 ⁰C

Class E

• Synthetic organic films and material having same thermal stability Maximum Temperature Limits: 120 ⁰C 

Class B

• Mica, asbestos or glass fiber base material combined with an organic binding agent
•  Maximum Temperature Limits: 130 ⁰C

Class F

• Mica, asbestos or glass fiber base material combined with suitable synthetic binding and impregnated agent
• Maximum Temperature Limits: 155 ⁰C

Class H

• Mica, asbestos or glass fiber base material combined with suitable silicon binding and impregnated agent
• Maximum Temperature Limits: 180 ⁰C

Class C

• Mica, ceramic, glass, quartz used with or without inorganic binding agents
• Maximum Temperature Limits: Above 180 ⁰C 

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