This is because the sheet core can reduce another type of iron loss - "eddy current loss". When the transformer is working, there is an alternating current in the coil, and the magnetic flux it generates is of course alternating. This varying magnetic flux produces an induced current in the core. The induced current generated in the iron core circulates in a plane perpendicular to the direction of the magnetic flux, so it is called eddy current. Eddy current losses also cause the core to heat up. In order to reduce the eddy current loss, the core of the transformer is laminated with silicon steel sheets insulated from each other, so that the eddy current flows through the narrow cross section to increase the electric resistance on the eddy current path; at the same time, the silicon in the silicon steel makes The resistivity of the material increases and also acts to reduce eddy currents.
As the core of the transformer, a 0.35mm thick cold-rolled silicon steel sheet is generally used. According to the size of the required core, it is cut into long pieces and then overlapped into a "day" shape or a "mouth" shape. In theory, if the eddy current is reduced, the thinner the thickness of the silicon steel sheet, the narrower the spliced strip, and the better the effect. This not only reduces the eddy current loss, reduces the temperature rise, but also saves the silicon steel sheet. But actually when making silicon steel sheet iron core. It is not only based on the above-mentioned favorable factors, because the iron core is produced in that way, the working time is greatly increased, and the effective cross section of the iron core is also reduced. Therefore, when using a silicon steel sheet to make a transformer core, it is necessary to weigh the pros and cons from the specific situation and choose the best size.