Commonly used transformer cores are generally made of silicon steel sheets. Silicon steel is a kind of steel containing silicon, and its silicon content is in. 0.8%~4.8%. The iron core of the transformer is made of silicon steel because silicon steel itself is a magnetic material with strong magnetic permeability. It can produce a large magnetic induction intensity in the energized coil. This can reduce the size of the transformer. The transformer operates under AC conditions. [Power loss occurs not only in the resistance of the coil, but also in the iron core magnetized by alternating current. The power loss in the iron core is usually called "iron loss". Iron loss is caused by two reasons: "hysteresis loss" and "eddy current loss".
Hysteresis loss is the iron loss caused by the existence of hysteresis during the magnetization process of the iron core. The size of this loss is proportional to the area surrounded by the hysteresis loop of the material. The hysteresis loop of silicon steel is narrow. Using it as the core of a transformer has less hysteresis loss, which can greatly reduce the heat generation.
When the transformer is working, the magnetic flux generated by the alternating current in the coil is of course alternating. The changing magnetic flux produces an induced current in the iron core. The induced current generated in the iron core circulates in a plane perpendicular to the dielectric direction, so it is called eddy current. Eddy current loss also causes the iron core to heat up. In order to reduce the eddy current loss, the core of the transformer is stacked with silicon steel sheets that are insulated from each other. The current is allowed to flow in a long and narrow circuit through a smaller cross-section to increase the electric limit on the eddy current path; at the same time. Silicon increases the resistivity of the material and also plays a role in reducing eddy currents.
As the core of the transformer, 0.35 mm thick cold-rolled silicon steel sheet is generally used. Cut it into a long piece according to the required size of the iron core, and then overlap it into a '·日' shape or a '口' shape. Logically speaking, in order to reduce eddy currents, the thinner the silicon steel sheets and the narrower the spliced strips, the better the effect. This reduces the eddy current loss, lowers the temperature rise, and also saves the material used for silicon steel sheets. However, when actually making a silicon steel sheet core, it is not just based on the above-mentioned favorable factors. Because making the iron core in this way requires a lot of investment. It also reduces the effective cross-section of the iron core. Therefore, when using silicon steel sheets to make transformer cores, you must weigh the pros and cons based on the specific situation and choose the best size.
