Q) Why Silicon ( 3 to 5 % ) is added to steel for making Transformer core lamination?
Ans) Higher content of silicon raises the resistivity of material and thus reduces the eddy current losses.
Q) Why Cold Rolled Steel is used?
Ans) Because it permits high flux densities 1.8 Wb/sq.m
This reduces the amount of material. For HR its just 1.3 Wb/sq.m
Insulations for HR:- Kaolin, Varnish
Insulation for CR:- Phosphate base.