Application of oriented silicon steel in power transformers

GNEE Electrical Steel Sheet

Silicon steel sheet is the main material of transformer core. The basic material requirements for 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 intensity.
Classification of transformers
According to the capacity, they are divided into large 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, it is divided into 6kV, 10kV, 35kV, 60kV, 110kV, 220kV, 330kV, 500kV, 800kV and 1000kV, etc.; thirdly, according to the purpose, it is divided into transformers, step-up transformers, step-down transformers, distribution transformers, power plant transformers, etc. According to the transformer windings, there are double windings, three windings, multi-winding transformers and autotransformers.

According to the transformer cooling conditions, there are oil-immersed self-cooling, dry air-cooled, oil-immersed air-cooled, oil-immersed water-cooled, dry cast insulation, forced oil circulation air cooling, forced oil circulation water cooling, etc. transformer.

In addition, there are special transformers, rectifier transformers, electric furnace transformers, test transformers, mining transformers, marine transformers, traction transformers, medium frequency transformers, large current transformers, etc.

Transformer demand for electrical steel

For transformers, silicon steel sheets are the main material of the transformer core. The silicon steel sheets must be annealed and pickled before leaving the factory. Unit iron loss hours is the most important indicator of silicon steel sheets. Generally speaking, 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 sheets. 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 also include electromagnetic wires, insulation materials, transformer oil, etc. However, the cost of silicon steel sheets accounts for 30-40% of the transformer production cost.

Typical transformer requirements for silicon steel

1. The main grades of silicon steel sheets for transformers of 50kV and above include: 30ZH120, 30ZH110, 27ZH100, etc. A transformer with a capacity of 250MVA requires an average of 80 tons of high magnetic induction oriented silicon steel sheets per year, and a transformer with a capacity of 720MVA-840MVA requires an average of about 240 tons per year. tons of high magnetic induction oriented silicon steel sheets.

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

3. The main grades of silicon steel sheets used in 110kV-220kV transformers are: 30Q130, 30ZH120, and 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 for 35kV transformers are 30Q130 and 30Q120 silicon steel sheets, and the required grades for 10kV distribution transformers are 30Q130, 30Q120, 30ZH120 and 27ZH100 silicon steel sheets. Usage is determined by capacity.

Requirements for use of transformers on grain-oriented silicon steel

Small unit iron loss is the most important indicator of silicon steel sheets. Countries around the world divide the grade of silicon steel sheets by the iron loss value. The lower the iron loss, the higher the grade and the better the quality. A smaller excitation current per unit magnetizing capacity can obtain a larger magnetic induction intensity. Under the same magnetic field intensity, a silicon steel sheet with a higher magnetic induction intensity can be obtained, and the volume and weight required to manufacture the product are smaller. Relatively speaking, It can save silicon steel sheets, copper wires and insulating materials; the silicon steel sheets with good flatness have a smooth, flat surface and uniform thickness. The paint film has good adhesion and weldability, and the growth rate of coercive force or iron loss that changes with use time during magnetic aging is small. The silicon steel sheet must be delivered after annealing and pickling.