As a core component of power systems, the performance and reliability of oil-immersed transformers depend largely on the primary materials used. These materials must not only meet electrical performance requirements but also possess excellent heat resistance, mechanical strength, and chemical stability.
1. Core Material
The core of an oil-immersed transformer is typically made of laminated high-permeability silicon steel sheets, such as cold-rolled grain-oriented silicon steel (e.g., 30Q130, 30Q140, etc.). Silicon steel sheets contain approximately 3% silicon, which effectively reduces eddy current and hysteresis losses, thereby improving transformer efficiency. The surface of the silicon steel sheets is typically coated with an insulating coating (such as magnesium oxide or an inorganic coating) to reduce inter-sheet short-circuit losses.
2. Winding Material
The winding is the conductive core of the transformer and is divided into high-voltage and low-voltage windings. High-voltage windings typically use electrolytic copper or aluminum conductors (such as T2 copper or 1060 aluminum) for their excellent conductivity and mechanical strength. To enhance insulation performance, conductors are coated with high-temperature-resistant insulating materials such as polyimide film or Nomex paper. In recent years, some high-performance transformers have begun using transposed conductors (such as self-adhesive transposed conductors) to optimize current distribution and reduce the risk of localized overheating.
3. Insulation and Cooling Medium
The core insulating medium of oil-immersed transformers is mineral oil (such as 25# transformer oil). Its main components are cycloalkyl or paraffin-based mineral oils, which offer excellent insulation (breakdown voltage ≥ 60kV) and heat dissipation. In addition, some new transformers use vegetable insulating oils (such as natural esters) or synthetic esters to improve environmental friendliness and fire resistance.
4. Fuel Tank and Structural Components
The fuel tank is typically welded from high-quality carbon steel (such as Q235B) or low-alloy high-strength steel (such as Q345) and treated with rust-proof treatments (such as painting or galvanizing). Seals are often made of nitrile rubber or fluororubber to ensure airtightness during long-term operation.
In summary, the material selection of oil-immersed transformers directly affects their efficiency, lifespan and safety. Modern technology is continuously optimizing towards high thermal conductivity, low loss and environmental protection.