The role of transformer core

The actual transformer core operates under AC conditions, and power loss occurs not only in the resistance of the coil, but also in the core magnetized by alternating current. The power loss in the iron core is usually called "iron loss". 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 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, and the hysteresis loss of the core of a transformer made of silicon steel is small, which can greatly reduce the heat generation.

Since silicon steel has the above advantages, why not use a whole piece of silicon steel as the iron core but process it into sheets? This is because the sheet core can reduce another type of iron loss - "eddy current loss".

When the transformer is working, there is alternating current in the coil, and the magnetic flux it generates is of course alternating. This 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 direction of the magnetic flux, so it is called eddy current. Eddy current losses also heat the core.

In order to reduce eddy current losses, the core of the transformer is stacked with silicon steel sheets that are insulated from each other, so that the eddy currents pass through a smaller cross-section in a long and narrow circuit to increase the resistance on the eddy current paths; at the same time, the silicon in the silicon steel makes The increased resistivity of the material also plays a role in reducing eddy currents.