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Performance data of cold-rolled silicon steel sheets commonly used in transformers

08 Jan 2024
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GNEE Steel Transformer Grain Oriented Electrical Silicon Steel

Transformer is an essential electrical equipment used in power systems to transmit and distribute energy at different voltage levels. The transformer core is made up of laminations of cold-rolled grain-oriented silicon steel sheets. The reason for using silicon steel is that it exhibits high magnetic permeability and low core loss, which are desirable properties for transformers. In this blog, we will discuss the performance data of the cold-rolled silicon steel sheets commonly used in transformers.

Magnetic Properties

The magnetic properties of the silicon steel sheets are crucial factors in the design of transformers. The two essential magnetic properties are permeability and core loss.

Permeability – It is a measure of the ability of the material to conduct magnetic flux. For transformer cores, a high permeability is desirable as it reduces the magnetizing current required.

Core Loss - Core loss is the energy dissipated in the transformer core resulting from the constantly changing magnetic field. It is essential to keep the core loss low as it results in a higher efficiency transformer.

The performance of cold-rolled silicon steel sheets is determined by the manufacturing process and composition of the material. The magnetic properties of cold-rolled Silicon steel sheets depend on the thickness of the sheet, orientation of the grains, and percentage of silicon in the steel.

Transformer Non Grain Oriented Electrical Silicon Steel
Transformer Non-Oriented Electrical Silicon Steel Coils

The performance criteria of cold-rolled silicon steel sheets are specified by the international standards organization. The standard specifies the maximum values of core loss and the minimum value of permeability for different thicknesses of steel sheets.

The electrical steel sheet specification standard by the International Electrotechnical Commission (IEC) for transformer applications is IEC 60404-8-4. The standard provides three categories of electrical steel sheets - M0, M2, and M3. The M0 steel sheet has the highest magnetic properties and is suitable for high-end transformers.

Thermal Properties

Thermal properties of cold-rolled silicon steel sheets are critical for ensuring the longevity of the transformer. The two essential thermal properties are Curie temperature and peculiar thermal expansion rate.

Curie Temperature - Curie temperature is the temperature at which the magnetic properties of the steel change. The transformer cores will lose their magnetic properties above the Curie temperature.

Peculiar thermal expansion rate - The transformer core and winding will experience changes in temperature during operation. The thermal expansion rate should be the same for the core and winding laminate to avoid mechanical stress.

Conclusion

The selection of excellent quality cold-rolled Silicon steel sheets with high magnetic properties and low core loss is essential for the efficient working of a transformer. The steel specification standard by the International Electrotechnical Commission (IEC) plays a crucial role in defining the performance criteria of cold-rolled Silicon steel sheets for transformer applications, ensuring the longevity of the transformer.

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