Currently, there are two main materials for manufacturing transformer cores in the world: silicon steel and amorphous alloy.
Silicon steel sheet
This is the main material for transformer cores, usually stacked with hot-rolled or cold-rolled silicon steel sheets with a high silicon content. Silicon steel sheet is a silicon-containing steel with a silicon content between 0.8% and 4.8%. Silicon steel is used as the core of the transformer because silicon steel itself is a magnetic material with strong magnetic conductivity. It can generate a large magnetic induction intensity in the energized coil, thereby reducing the size of the transformer. The quality of silicon steel sheet is usually expressed by the magnetic flux density B. Different types of silicon steel sheets have different magnetic flux densities. For example, the B value of black iron sheet is 6000-8000, low silicon sheet is 9000-11000, and high silicon sheet is 12000-16000. In order to reduce eddy current loss, insulating paint will be applied between each silicon steel sheet to form an independent conductor.
Since the transformer will generate eddy current loss during operation, in order to reduce the eddy current loss, the transformer core is stacked with insulated silicon steel sheets, so that the eddy current passes through a smaller cross-section in a narrow loop 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, which also plays a role in reducing the eddy current.
Silicon steel sheet is a special electrical steel material with a series of advantages such as high magnetic permeability, low resistivity, and low hysteresis loss.
Characteristics of silicon steel sheets
1.The surface of the silicon steel sheet has a very thin oxide layer, which has certain anti-corrosion properties.
2.The hysteresis loss of the silicon steel sheet material is relatively small, it is not easy to generate heat, and will not affect the normal operation of electromagnetic equipment.
3.Silicon steel sheet material is easy to process and can be made into iron cores of different shapes and sizes by shearing, pressing, etc. Its main characteristics are: Silicon steel has high magnetic permeability, low coercive force, large resistivity, small hysteresis loss, and can greatly reduce the degree of heat generation.
Amorphous alloys
Amorphous alloys have become the focus of research and development in the material science community at home and abroad since the 1980s. Because it has a metastable structural characteristic of short-range order and long-range disorder. In the solid state, the three-dimensional space of its atoms is topologically disordered and remains relatively stable within a certain temperature range.
In terms of mechanical properties, it has extremely high strength and hardness, but a low elastic modulus. The elongation of metallic glass is small when stretched (1.5%-2.5%), but it shows high plasticity when compressed and bent, indicating that it has good toughness while having high strength.
In terms of physical properties, amorphous alloys generally have higher resistivity and smaller temperature coefficient of resistance. Amorphous alloy is a new type of material with outstanding magnetic permeability. It has a completely different crystal structure from silicon steel and is more conducive to magnetization and demagnetization. The iron loss (i.e. no-load loss) of amorphous alloy transformers is 70-80% lower than traditional transformers that generally use silicon steel as the iron core. As losses are reduced, power generation demand also falls, and emissions of greenhouse gases such as carbon dioxide are reduced accordingly.
Characteristics of amorphous alloy materials
1.The thickness of the amorphous alloy iron chip is extremely thin.
2.The amorphous alloy iron core has low saturation magnetic density.
3.The hardness of amorphous alloy is 5 times that of silicon steel sheet.
4.The amorphous alloy iron core material is very sensitive to mechanical stress, and both tensile force and bending stress will affect its magnetic properties.
5.The magnetic domain stretch of amorphous alloy is about 10% higher than that of silicon steel sheet, and it should not be over-clamped. Amorphous alloys have the characteristics of high saturation magnetic induction intensity, low loss (equivalent to 1/3~1/5 of silicon steel sheets), low coercive force, low excitation current, and good temperature stability.
In terms of the price of transformers made of the two materials, the price of amorphous alloy transformers is much higher than that of silicon steel sheet transformers. Because for customers, they need higher performance transformers, and they need to make a comparison in the selection of materials.
