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Requirements for the use of transformers on grain-oriented silicon steel

27 Nov 2023
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GNEE Silicon Steel Sheet
Silicon steel sheet is the main material for the transformer core. The basic requirements for the material of the transformer core are low core loss at a certain frequency and magnetic flux density and high magnetic flux density at a certain magnetic field strength.
1) Requirements for transformers on silicon steel sheets
Small unit iron loss is the most important indicator of silicon steel sheet. All countries in the world divide the grade of silicon steel sheet by iron loss value. The lower the iron loss, the higher the grade and the better the quality. The excitation current with a smaller unit magnetization capacity can get a larger Magnetic induction intensity, higher saturation magnetic induction intensity Under the same magnetic field intensity, silicon steel sheets with higher magnetic induction intensity can be obtained, and the volume and weight required for manufacturing products are small, relatively speaking, silicon steel sheets, copper wires and insulating materials can be saved; The surface of the silicon steel sheet with good flatness is smooth, flat, and uniform in thickness. The adhesion and weldability of the paint film are good, the growth rate of the coercive force or iron loss that changes with the use of time in magnetic aging is small, and the silicon steel sheet must be delivered after annealing and pickling.

2) The main relationship between the transformer performance index and the silicon steel sheet
Silicon steel sheet and iron loss: Transformer iron loss is the no-load loss of the transformer. The no-load performance of the transformer mainly refers to the no-load loss and no-load current of the transformer during operation. When the transformer is put into power grid operation, no matter how much load it carries, there will be no-load loss. In order to reduce the energy consumption of grid operation, the main task is to reduce the no-load loss of the transformer. The no-load loss of the transformer is mainly determined by the material of the silicon steel sheet, and it is also related to the design and manufacturing process of the iron core.
Hysteresis loss: The energy loss consumed by the friction of the magnetic domain boundary when the magnetic domain is reversed and rotated in the process of repeated magnetization of ferromagnetic materials is called hysteresis loss. The hysteresis loss is related to the crystal orientation, crystal purity, and internal grain distortion of the silicon steel sheet. It is the loss caused by hysteresis in the process of repeated alternating magnetization of ferromagnetic materials. The hysteresis loss is proportional to the frequency, and the size of the hysteresis loss is proportional to the area of the hysteresis loop. The smaller the area of the hysteresis loop, the smaller the hysteresis loss. The area of the hysteresis loop is proportional to the square of the maximum magnetic density Bm, and the hysteresis loss is proportional to the square of the maximum magnetic density Bm. The hysteresis loop depends on the characteristics of the material and is a function of the peak value of the magnetic flux density, accounting for iron 80% of the core loss. The method of reducing the loss of silicon steel sheet: from the manufacturing method of silicon steel sheet material alone, it is required to reduce the loss of silicon steel sheet itself, so as to reduce the no-load loss of transformer core;
Silicon steel sheet and iron core temperature rise: When the transformer is running, the limit value of the iron core temperature rise depends on the inner temperature of the silicon steel sheet material. At the same time, it is limited by the high temperature resistance of the insulating coating on the surface of the iron core silicon steel sheet. The requirements for the insulating coating on the surface of silicon steel sheet are: the surface of oriented electrical steel products is coated with a layer of inorganic insulating coating, which has excellent coating characteristics: high interlayer resistance, ensuring good interlayer insulation; Excellent sheet performance, the coating and the bottom layer are closely combined, with good adhesion, which can prevent the coating from falling off during processing; high lamination coefficient - the surface coating is uniform and thin, with excellent lamination performance; good heat resistance - coating The layer can withstand annealing at 800°C without being damaged; good corrosion resistance - the coating is incompatible with cooling oil, insulating oil, mechanical oil, freon, antifreeze oil, etc., and is free from corrosion;

Silicon steel sheets and noise: Reducing the hysteresis of silicon steel sheets can effectively reduce the noise of no-load transformers.
Silicon steel sheet and stacking coefficient: The lamination coefficient is an important index reflecting the manufacturing level of the transformer. It is closely related to the material quality of the silicon steel sheet. Layer thickness and insulation layer thickness tolerance and punching, shearing process burr, waviness, flatness, etc.
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