Insulation class of generator
Insulation class of generator means resist heat class of insulation material, classified by A,E,B,F,H grade. permitted temperature increase means generator increased temperature compared to environment temperature.
Temperature class of insulation A E B F H
Max. permitted temperature(℃) 105 120 130 155 180
winding tem. increase limit（K） 60 75 80 100 125
Performance reference temperature（℃）80 95 100 120 145
Insulation material is inferior to other equipments in generator. because it is easy to age or be affected by high temperature, the performance of heatproof is different for different insulation materials. so electrical equipments have different heatproof performance if different insulation material used. thus general electrical equipment has confirmed max. working temperature.
7 permitted Max. temperatures have been stipulated as per insulation differences, classifying Y、A、E、B、F、H and C in order of temperature from highest to lowest. and permitted working temperature are 90、105、120、130、155、180 and above 180℃.
as to the limit working temperature of insulation material, it means the hottest point of winding insulation when running. the lifetime can reach 10 years if A class material with 105℃ and B class material 130℃ according to experiences. but environment temperature and temp. increase reach to setting value in practice, so the general lifetime is around 15～20 years, if working temperature always exceed limit working tempeature, aging of insulation will be accelerated, and lifetime will be shortened. temperature is main factor of lifetime.