Transformer cores are commonly made of silicon steel sheets. Silicon steel, a type of carbon with silicon content ranging from 0.8 to 4.8%, strong magnetic properties. silicon steel sheets for transformer cores allows for higher magnetic induction, leading to reduced size.
In practical, transformers work under current conditions, resulting in losses in both the resistance and the core. These losses consist of two components: hysteresis loss and eddy current loss.
hysteresis loss and eddy current loss
Hysteresis loss occurs due to the magnetic hysteresis phenomenon in the core material during the magnetization process. Silicon steel has a narrow hysteresis loop, which minimizes hysteresis loss and reduces heat generation in the core.
Why do we process silicon steel into laminated sheets instead of using a solid block? The answer lies in minimizing another type of iron loss called "eddy current loss." When alternating current flows through the winding, it generates a varying magnetic flux in the core. This changing flux induces eddy currents within the core material, resulting in heat generation. To minimize eddy current loss, transformer cores are made by stacking insulated laminations of silicon steel, creating a compact and efficient pathway for eddy currents with reduced cross-sectional area. Additionally, the silicon content in the steel increases its resistivity, further mitigating eddy current effects.
Typically, transformer cores are constructed using cold-rolled silicon steel sheets with a thickness of 0.2 to 0.5mm. These sheets are cut into elongated shapes and then stacked in a "E-shaped" or "C-shaped" configuration, depending on the specific needs. Thinner laminations and narrower interleaved sections result in better eddy current suppression, decreased temperature rise, and material cost savings.