GO Insulation Types
PowerCore™ Grain Oriented Steel is usually delivered with a thin inorganic coating C5G applied on both surfaces, on top of the so called glass film layer formed during annealing. The coating thickness of 2-5 microns provides good electrical resistance simultaneously ensuring a high stacking factor. The stress relief annealing of wound cores or punched laminations, usually performed at temperature around 840°C. It is unaffected by, and in turn does not affect, the various types of oils used in transformers.
Insulation Type
Product CRGO
Parameter C5(G)
AISI Class C5
Coating Type Phosphate Over Glass Film
Range of Application Power & Distribution Transformer
Colour Grey
Average Coating Thickness µm 3.5+/-1.5
Space Factor (%) / Stacking Factor >96.0
Typical Average Insulation Resistivity in Amps. 0.38
Typical Average Insulation Resistivity in Ω.cm²/La 10
Stress relief Annealing in Nature / Reducing Atmosphere Temperature at 800 Deg C Can Withstand
Corrosion Resistance Good
Resistance to organic solvent oil, lubricant oil & transformer oil Resist
  • 1 Colour Deviation is possible without effect of on coating properties
  • 2 Coating Thickness is checked by FISHER DELTASCOPE Coating Thickness Tester
  • 3 Space factor is checked in accordance, with IS 649:1997
  • 4 Insulation Resistivity is checked in accordance with IS 649:1997