Silicon steel sheets are used in transformers to form the core because of their ability to reduce energy losses due to eddy currents and hysteresis losses. Cutting silicon steel into thin sheets (called laminations) is essential to achieve optimal efficiency. Here's why:
1. Reduction of Eddy Currents:
Eddy currents are circular currents induced within the core material when subjected to a changing magnetic field.
These currents cause power losses in the form of heat.
By laminating the core, the thickness of each sheet limits the path of eddy currents, minimizing these losses.
2. How it helps:
Thin laminations with an insulating coating between them prevent the eddy currents from flowing freely through the entire core.
As a result, smaller eddy currents flow only within each individual sheet, reducing energy loss.
3. Hysteresis Loss Reduction:
Hysteresis loss occurs due to the continuous magnetization and demagnetization of the core material as the alternating current flows.
Silicon steel improves magnetic properties, reducing these losses. The silicon increases electrical resistivity and decreases the energy required to align magnetic domains.
4. Improved Magnetic Permeability:
Silicon steel allows for efficient magnetic flux flow within the core with minimal energy loss, improving transformer performance.
5. Mechanical Flexibility and Core Assembly:
Cutting the core into sheets allows manufacturers to shape and stack the laminations for different transformer types (like E-I cores or toroidal cores).
This also makes it easier to repair or reassemble transformers if necessary.
6. Why Not Use a Solid Core?
A solid iron or steel core would result in large, continuous eddy currents, causing excessive heat and energy loss.
Laminating the core reduces these losses and makes the transformer much more efficient.
7. Typical Thickness of Silicon Steel Sheets:
0.23 to 0.35 mm for high-performance transformers.
Thinner sheets lead to lower eddy current losses but increase manufacturing costs.
In summary, silicon steel sheets are cut into thin laminations to reduce eddy current losses, improve magnetic properties, and ensure the efficient operation of the transformer.
