Ordinary EI transformers are made of silicon steel sheets into E-type and I-type sheets with a thickness of 0.35–0.5 mm, and then inserted into the windings after heat treatment. Most of these iron cores are hot-rolled silicon steel sheets (the high-quality silicon steel sheets with high silicon content are D4 1, D42, D43, D30 1). The iron cores of ring-type and C-type transformers are wound with cold-rolled silicon steel sheets, and C-type transformers are cut after heat treatment and dipping in paint.
The commonly used models of several high-quality silicon steel sheets are as follows: d 41–d42, and the maximum magnetic flux density (unit–GS gauss) is10000–12000 GS; D43, the maximum magnetic flux density is11000–12000gs; D30 1, maximum magnetic flux density12000–14000gs.