Why Do Transformers Use Silicon Steel Sheets As Cores?

The core of a power transformer is usually made of silicon steel sheets and is stacked in steps. Do you know why transformers use silicon steel sheets as cores? TSTY transformer supplier with 30 years of experience will answer this question for you.

About silicon steel sheets

Silicon steel sheets are a type of silicon steel, which is an alloy steel with a silicon content between 0.8% and 4.8%, and has good magnetic conductivity. It can generate strong magnetic induction when current passes through the coil, thereby reducing the volume of the transformer and reducing losses (iron loss).

The core of the transformer generally uses 0.35mm cold-rolled silicon steel sheets, which are cut into long sheets according to the required core size and then stacked in a "日" or "口" shape. In principle, in order to reduce eddy currents, the thinner the silicon steel sheet thickness and the narrower the stacked sheet spacing, the better the effect.

Why do transformer cores use stepped stacking?

Do you have any questions, why the core does not use a whole piece of steel but a stack of silicon steel sheets as the core? The transformer works under AC state, and the power loss is not only in the resistance of the coil, but also in the iron core under the magnetization of the alternating current. The power loss in the iron core is usually called "iron loss". The iron loss is caused by two reasons, one is "hysteresis loss" and the other is "eddy current loss".

"Hysteresis loss" is the iron loss caused by the hysteresis phenomenon during the magnetization 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, and the hysteresis loss of the iron core made of it is small, which can greatly reduce its heating degree, thereby reducing power loss.

"Eddy current loss" is different from "hysteresis 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 changing magnetic flux generates an induced current in the iron 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 loss also causes the iron core to heat up and cause power loss. In order to reduce eddy current losses, the iron core is stacked with insulated silicon steel sheets, so that the eddy current passes through a smaller cross-section in a narrow loop, thereby increasing the resistance in the eddy current path; at the same time, the silicon in the silicon steel increases the resistivity of the material, which also plays a role in reducing eddy currents.