The commonly used transformer cores are generally made of silicon steel sheets. Silicon steel itself is a highly magnetic material, which can produce a significant magnetic induction intensity when used in energized coils, thereby reducing the size of the transformer.
Definition of Transformer
As a crucial device in the power system for regulating voltage and transmitting electricity, a transformer primarily consists of components such as the core and windings. The core can be considered the “heart” of the power transformer.
Definition of Silicon Steel
Silicon steel refers to silicon alloy steel that contains 1.0% to 4.5% silicon and less than 0.08% carbon. It is characterized by high magnetic permeability, low coercivity, and high electrical resistivity, which contribute to lower hysteresis and eddy current losses. It is mainly used in motors and transformers.
Operating Principle of Transformers
The operating principle of a transformer is primarily based on Faraday’s Law of Electromagnetic Induction. It converts alternating current (voltage) of a certain value into another or several voltages (currents) of the same frequency but different values. Thus, the entire working process of a power transformer is accomplished through the core and windings.
Various materials exhibit magnetic conductivity, such as silicon steel, titanium alloys, copper alloys, and strontium titanate iron. However, silicon steel stands out due to its numerous advantages.
Why Silicon Steel Sheets Are Used in Transformers
| Low Eddy Current Loss: During transformer operation, the alternating current produces an alternating magnetic flux that generates eddy currents in the core. These currents cause heating and energy loss. Silicon steel sheets reduce eddy current losses by fabricating the steel into insulated thin sheets, thereby allowing eddy currents to flow through smaller cross-sections in elongated loops and increasing resistance in the eddy current path. Additionally, the inclusion of silicon increases the material’s resistivity, further reducing eddy currents.
| High Magnetic Permeability: The addition of silicon to silicon steel optimizes the lattice structure of iron, significantly enhancing the material’s magnetic permeability. In transformers, high-permeability silicon steel sheets allow the core to establish a sufficiently strong magnetic field with lower exciting current, enhancing the electromagnetic induction capability and achieving efficient voltage transformation, as well as reducing the transformer’s size for easier installation.
| Good Mechanical Properties and Machinability: Silicon steel sheets have certain mechanical strength, capable of withstanding pressure and vibration from transformer components like windings, ensuring structural stability. The smooth and even surface of silicon steel sheets, along with their uniform thickness, facilitates processes such as punching and stacking, allowing them to be shaped into various designs and sizes to meet different structural requirements of transformers.
| Low Hysteresis Loss: Hysteresis loss is the energy loss associated with magnetization due to hysteresis phenomena, proportional to the area surrounded by the material’s hysteresis loop. Silicon steel has a narrower hysteresis loop, resulting in lower hysteresis loss. Using it for transformer cores significantly reduces heating and improves efficiency while lowering energy consumption during operation.
Why Silicon Steel in Transformers is Made into Sheets
During transformer operation, the alternating current in the coils generates alternating magnetic flux. This changing flux induces eddy currents in the core; these currents circulate in planes perpendicular to the magnetic flux, hence termed eddy currents. Eddy current loss causes heating of the core.
Shaping silicon steel into sheets can reduce iron losses, particularly “eddy current losses.” The transformer core is constructed from stacked silicon steel sheets that are insulated from one another, resulting in a smaller cross-sectional area that forces eddy currents to flow through narrower paths, increasing resistance and thus reducing eddy current losses.
Moreover, the sheet manufacturing method is more flexible and easier to process. During production, high-quality silicon steel sheet materials can be selected for precise cutting and machining according to design requirements while maintaining consistent thickness and flatness. This manufacturing approach conserves materials, lowers production costs, and enhances the performance of transformers.
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