The performance and service life of a dry-type transformer largely depend on the selection and combination of key materials. Appropriate material application not only ensures a harmonious balance between electrical insulation, mechanical strength, and heat dissipation, but also enhances the equipment's fire resistance, moisture resistance, and environmental adaptability, meeting the stringent requirements of various application scenarios.
The core material is the foundation of the magnetic circuit and energy efficiency of a dry-type transformer. Currently, high-permeability cold-rolled grain-oriented silicon steel sheets are commonly used. Their low iron loss and high permeability effectively reduce no-load losses and temperature rise. The thickness of the silicon steel sheets and the quality of the surface insulation coating directly affect the eddy current loss level. A high-quality coating can reduce inter-sheet eddy currents and improve overall energy efficiency. In some special applications, to achieve even lower losses and noise, ultra-thin specifications or amorphous alloy materials can be selected. Although the cost is higher, they offer significant advantages in energy saving and emission reduction.
The selection of winding conductor materials is related to conductivity and thermal stability. The mainstream solutions are oxygen-free copper or aluminum alloy. Copper conductors have high conductivity and strong oxidation resistance, reducing resistance and heat generation for the same cross-sectional area. Aluminum conductors are lightweight and relatively inexpensive, suitable for projects with weight sensitivity or budget constraints. Regardless of the material used, the conductor surface must be insulated or coated to prevent inter-turn and inter-phase breakdown.
The insulation system is the core safety barrier of dry-type transformers. Epoxy resin cast products use solvent-free epoxy resin as the matrix, adding curing agents, fillers, and flame retardants to form a high-strength composite insulation material. After vacuum casting and curing, the windings are completely encapsulated, providing excellent electrical insulation, mechanical protection, and moisture resistance. For non-cast structures, high-temperature resistant and flame-retardant materials such as glass fiber reinforced resin, Nomex paper, and polyimide film are commonly used, maintaining insulation reliability over long periods at higher temperatures. Material selection must consider both the heat resistance rating (e.g., B, F, H) and the temperature margin of the operating environment to avoid premature insulation aging.
Heat dissipation and structural component materials are also crucial. The outer casing and support frame are mostly made of high-quality cold-rolled steel sheet or galvanized steel sheet. The former has good formability and high strength, while the latter has strong corrosion resistance. The choice can be made according to the climate characteristics of the installation site. The cooling fan blades of air-cooled models are commonly made of aluminum alloy or engineering plastic. The former has high strength and long service life, while the latter is lightweight and low-noise.
In terms of protection and sealing, the sealing strips are mostly made of EPDM rubber or silicone rubber, which have good weather resistance, temperature resistance, and aging resistance. They can effectively prevent moisture and dust intrusion and maintain a stable internal insulation environment.
Overall, the material selection for dry-type transformers needs to achieve a balance between electrical performance, mechanical strength, heat resistance and flame retardancy, environmental adaptability, and economy. Appropriate configuration of silicon steel sheets, conductors, insulation, and structural materials for different voltage levels, capacities, and operating environments can not only significantly improve the safety and reliability of equipment operation but also provide a solid guarantee for its promotion and application in green buildings, intelligent power distribution, and other fields.