The ”Core” of Transformer：Silicon Steel Sheet

The iron core of the transformer, which is the magnetic circuit part of the transformer, usually composed of silicon steel sheets.It plays the role of supporting the winding and transferring the magnetic flux, which is crucial for improving the efficiency of the transformer and reducing the loss.

 

The core components of the transformer include the iron core and the winding, wherein the winding is the circuit part of the transformer, which is divided into high voltage winding and low voltage winding. They are responsible for the input and output voltage respectively, and realize the transformation of voltage through the principle of electromagnetic induction.

The other core is the iron core of the transformer, which is the magnetic circuit part of the transformer, usually composed of silicon steel sheets.It plays the role of supporting the winding and transferring the magnetic flux, which is crucial for improving the efficiency of the transformer and reducing the loss.

 

 

Then,let's take a look at the core of the transformer: silicon steel sheet.

 

What is Silicon Steel Sheet Used For?

 

The main component of silicon steel sheet is alloy steel containing silicon. The material has the characteristics of high permeability, low coercivity, low core loss, etc., and is widely used in the manufacture of electrical equipment such as motors, transformers and generators.

The silicon content of silicon steel sheet is generally between 0.5% and 4.5%, according to the different silicon content, silicon steel sheet can be divided into low silicon and high silicon two types, respectively suitable for different application scenarios. The silicon content of low silicon steel sheet is less than 2.8%, mainly used in motor manufacturing; The silicon content of high-silicon steel sheet is between 2.8% and 4.5%, which has good magnetic properties and is mainly used in transformer manufacturing.

 

 

Working Principle of Silicon Steel Sheet

 

We know that the actual transformer always works in the AC state, and the power loss is not only in the resistance of the coil, but also in the core under the alternating current magnetization. Usually the power loss in the core is called "iron loss", and the 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 existence of hysteresis phenomenon in the magnetization process of the iron core, and the size of this loss is proportional to the size of the area surrounded by the hysteresis loop of the material. The hysteresis loop of silicon steel is small, and the hysteresis loss of transformer core with it is small, which can greatly reduce its heating degree.

 

 

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

When the transformer works, there is alternating current in the coil, and the magnetic flux generated by it is of course alternating. This changing flux creates an induced current in the core. The induced current generated in the 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 the eddy current loss, the iron core of the transformer is stacked with silicon steel sheets insulated from each other, so that the eddy current passes through a small section in the narrow and long circuit to increase the resistance on the eddy current path. At the same time, the silicon in the silicon steel increases the resistivity of the material and also plays a role in reducing the eddy current.

 

 

Used as a transformer core, the general selection of 0.35mm thick cold rolled silicon steel sheet, according to the size of the required core, cut it into a long shape, and then folded into a "日" shape or "口" shape. In principle, in order to reduce the eddy current, the thinner the thickness of the silicon steel sheet and the narrower the splicing strips, the better the effect. This not only reduces the eddy current loss, reduces the temperature rise, but also saves the material used in the silicon steel sheet. But actually when you make a silicon steel core. Not only from the above side of the favorable factors, because that the production of iron core, to greatly increase the working hours, but also reduce the effective cross-section of the iron core. Therefore, when making transformer core with silicon steel sheet, we should start from the specific situation, weigh the advantages and disadvantages, and choose the best size.

 

Silicon Steel Sheet Performance Indicators

 

1.Low iron loss: the most important indicator to measure the quality of silicon steel sheet.

2.High magnetic induction. The silicon steel sheet with higher magnetic induction can be used to manufacture transformer core with smaller volume and weight, which can save silicon steel sheet, copper wire and insulating materials.

3.High stacking coefficient. The surface of the silicon steel sheet is smooth, flat and uniform in thickness, and the stacking coefficient of the iron core is high.

4.Good film performance. This is more important for the manufacture of small and micro motor cores.

5.The adhesion and weldability of the insulating film on the surface are good.

6.Magnetic aging. 

7.Silicon steel sheet must be annealed and pickling before delivery.

 

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