In order to increase the magnetic induction intensity, the iron core is used in the transformer, but when the alternating current is passed through the coil of the transformer, a large eddy current will be generated in the iron core, which not only consumes a large amount of energy, but may even burn these devices. . Large conductors move in a magnetic field or in a changing magnetic field, generating an induced electromotive force that creates eddy currents, causing large eddy current losses.
In order to reduce the eddy current and its loss, the EI lamination for 3 Phase transformer is usually used instead of the whole core, and the plane of the silicon steel sheet is parallel to the magnetic induction line. On the one hand, because the EI lamination of the three-phase transformer itself has a large resistivity, on the other hand, each piece is coated with an insulating varnish or a natural insulating oxide layer to limit the eddy current in each sheet, so that the eddy current is greatly reduced. Small, thus reducing the loss of electrical energy.
The sheets are separated into a trapezoidal shape with a thin layer of insulating varnish or insulating oxide. When passing through a narrow section of the sheet, the eddy current is confined to flow through some narrow loops in the sheets. The electromotive force is small, the length of the loop is large, and since the resistivity of the sheet material is large, the eddy current loss can be significantly reduced. Therefore, EI lamination of three-phase transformers is widely used in AC motors and electric appliances.