The silicon steel sheet is coated with insulating paint, and its purpose is to limit the eddy current loop, so that the eddy current can only flow in one piece, so that the impedance of the eddy current loop is large, which limits the value of the eddy current. If there is no insulation between the sheets, the eddy current will pass through the adjacent silicon steel sheets, so that the impedance of the eddy current loop is smaller than that of a single sheet, the eddy current will increase, and the loss caused by the eddy current will increase rapidly. Generally speaking, the eddy current loss is proportional to the thickness of the silicon steel sheet. If the silicon steel sheet is not insulated, the iron core is equivalent to a whole piece of iron, or equivalent to a thick steel plate, so the eddy current loss will be greatly increased. Therefore, the surface of the silicon steel sheet should be painted.

The insulating layer requirements for silicon steel sheets are:

1) Brush evenly, the paint film should not be too thick (too thick paint film will reduce the coefficient of lamination), the adhesion is strong, and it can resist impact and bending.

2) The paint film is required to have good insulation, heat resistance, moisture resistance, and fast drying.

In the production process of the cold silicon steel sheet, a thin insulating layer has been formed on the surface, and generally does not need to be painted again, but for large high-voltage transformers, in order to ensure the insulation between the sheets, a layer of insulation is often coated on the outer layer of the insulation. paint. But for the hot silicon steel sheet, it must be guaranteed to be painted to ensure the insulation between the sheets.

The silicon steel sheet of the transformer is usually about 0.35-0.5mm, the purpose is to limit the eddy current loss of the silicon steel sheet and the weakening of the main magnetic flux caused by it. If the silicon steel sheet is too thick, the effective contact area of the iron core is large, and the lamination is more convenient. However, the eddy current loss will increase, and the heat generation will also increase accordingly. The silicon steel sheet is too thin, it is difficult to stack and uneconomical.