Insulation class

 

Insulation class Identifies the temperature rating of an insulating material used, where a letter code indicates the maximal working temperature of the transformer. Exceeding this temperature during continuous operation would shorten the service life of transformer and the period of its failure-free operation.

Insulation class symbol Maximal temperature allowed continuously Maximal increase of windings temperature for maximal ambient temperature of 40oC
as per IEC 61558
Maximal increase of windings temperature for maximal ambient temperature of 40oC
as per EN 60726
[°C] [°C] [°C]
A 105 60 60
E 120 75 75
B 130 80 80
F 155 100 100
H 180 125 125
C 220 --- 150

 

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