The commonly used transformer cores are generally made of silicon steel sheets. Silicon steel is a kind of steel containing silicon (silicon is also called silicon), its silicon content in 0.8 ~ 4.8%. The core of the transformer is made of silicon steel, because the silicon steel itself is a kind of magnetic material with strong magnetic conductivity. In the energized coil, it can produce larger magnetic induction intensity, so that the volume of the transformer can be reduced. The induced current generated in the core circulates in a plane perpendicular to the direction of the flux, so it is called eddy current.