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.

Classification of transformers

According to the size of the capacity, it is divided into large-scale transformers (capacity greater than or equal to 8000kVA) and small and medium-sized transformers (capacity less than or equal to 6300kVA).

According to the voltage level, there are 6kV, 10kV, 35kV, 60kV, 110kV, 220kV, 330kV, 500kV, 800kV and 1000kV, etc.; the third is according to the purpose of the transformer, step-up transformer, step-down transformer, distribution transformer, power plant transformer wait.Divided by transformer windings, there are double-winding, three-winding, multi-winding transformers, and autotransformers.

According to transformer cooling conditions, there are oil-immersed self-cooling, dry air self-cooling, oil-immersed air-cooled, oil-immersed water-cooled, dry pouring insulation, forced oil circulation air cooling, forced oil circulation water cooling and other transformers.

In addition, there are special transformers, rectifier transformers, electric furnace transformers, test transformers, mining transformers, marine transformers, traction transformers, intermediate frequency transformers, high-current transformers, etc.

Transformer demand for electrical steel

For transformers, silicon steel sheets are the main material for transformer cores, and silicon steel sheets must be annealed and pickled before delivery. The unit iron loss hour is the most important indicator of silicon steel sheets. Generally, the smaller the iron loss, the higher the grade and the better the quality. In addition, flatness is also an important indicator of silicon steel sheet, good flatness, high lamination coefficient, good coating adhesion, and good weldability. In addition, in addition to silicon steel sheets, the core materials for manufacturing transformers include electromagnetic wires, insulating materials, transformer oil, etc. However, the cost of silicon steel sheets accounts for 30-40% of the production cost of transformers.

Typical transformer demand for silicon steel

1. The grades of silicon steel sheets used for transformers of 50kV and above mainly include: 30ZH120, 30ZH110, 27ZH100, etc. Transformers with a capacity of 250MVA require an average of 80 tons of high magnetic induction oriented silicon steel sheets per year, and transformers with a capacity of 720MVA-840MVA each require about 240 tons on average. Tons of high magnetic induction oriented silicon steel sheet.

2. The grades of silicon steel sheets used in ±500kV and above converter transformers mainly include: 27ZDKH90, 23ZDKH90, 23ZDKH70, etc. Each converter transformer needs about 80 tons of laser irradiated silicon steel sheets.

3. The grades of silicon steel sheets used in 110kV-220kV transformers mainly include: 30Q130, 30ZH120, 30ZH110. A 220kV transformer with a capacity of 120MVA-180MVA requires an average of 50-70 tons of silicon steel sheets, and a 110kV transformer with a capacity of 16MVA-63MVA requires an average of 10-30 tons of silicon steel sheets.

4. The required grades of 35kV transformers are 30Q130 and 30Q120 silicon steel sheets, and the required grades of 10kV distribution transformers are 30Q130, 30Q120, 30ZH120, and 27ZH100 silicon steel sheets. The use is determined by capacity.

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

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.