Laminating steel sheets are commonly used for transformer cores. Laminating containing silicon has a silicon content of 0.8%~4.8%. Due to the fact that laminate steel is a magnetic material with strong magnetic permeability, silicon steel is used as the iron core of the transformer. The actual transformer does always work in the AC state, and in this state, the power loss is not only due to the resistance of the coil but also to the magnetization of the iron core as a result of the alternating current. Power loss in the iron core is usually referred to as “iron loss”, which is caused by two factors: hysteresis loss and eddy current loss.
The hysteresis loss occurs during the magnetization process of the iron core and is proportional to the size of the area enclosed by the hysteresis loop. As laminate steel has a narrow hysteresis loop, and iron core transformers have a small hysteresis loss, the heat generated by the transformer can be greatly reduced.
Why not use the whole piece of silicon steel as the iron core, but also process it into sheets?
Due to its ability to reduce eddy current losses, the chip core can reduce another type of iron loss. Transformers work with alternating current in the coil, and the magnetic flux they produce is alternating as well. In the iron core, this changing magnetic flux induces a current. An eddy current is an induced current generated in the iron core that circulates perpendicular to the magnetic flux direction.
The core is also heated by eddy current losses. To reduce eddy current loss, the iron core of the transformer is made up of silicon steel sheets that are insulated from each other, so the eddy current passes through a smaller cross-section and a narrow loop to increase resistance; Additionally, silicon in silicon steel increases its resistivity and reduces eddy currents. The iron core of the transformer is usually made from cold-rolled silicon steel sheets with a thickness of 0.35mm. These sheets are cut into long pieces, then overlapped into a “日” shape or a “口” shape. In theory, the thinner the silicon steel sheet and the narrower the spliced sheet, the better the effect on reducing eddy currents. In addition to reducing eddy current loss and temperature rise, laminate steel sheets are also more environmentally friendly.
