As a representative of oil-free power distribution equipment, the design principles of dry-type transformers revolve around three core objectives: safety and reliability, efficient heat dissipation, and environmental adaptability. Through a rational electromagnetic structure, advanced insulation system, and optimized heat dissipation scheme, stable power transmission and long-term operation are achieved.
At the electromagnetic design level, dry-type transformers follow the law of electromagnetic induction, achieving voltage transformation through the turns ratio of the primary and secondary windings. The core uses high-permeability cold-rolled grain-oriented silicon steel sheets, and multi-stage stacking reduces eddy current losses and hysteresis losses, improving no-load efficiency. The windings use copper or aluminum conductors, with cross-sections designed according to capacity and current density requirements, and a reasonable turns distribution to keep magnetic flux density and current density within the economic operating range, reducing heat generation and energy consumption. The electromagnetic design also needs to consider short-circuit impedance matching to ensure effective limitation of short-circuit current during system faults, protecting equipment and the power grid.
Insulation design is the key difference between dry-type transformers and oil-immersed transformers. Its insulation system is primarily composed of solid materials, commonly using epoxy resin vacuum casting, glass fiber reinforced resin encapsulation, or high-temperature resistant film wrapping. Epoxy resin type transformers encapsulate the windings as a whole during manufacturing, forming a high-mechanical-strength, moisture-proof, and pollution-proof integral insulation structure that can withstand harsh environments such as humidity and pollution. During design, heat-resistant insulation materials must be selected according to the operating temperature class (e.g., B, F, H) to ensure that the insulation does not age or deteriorate under long-term operation and to maintain sufficient insulation margin to cope with transient overvoltages.
The heat dissipation design directly affects the transformer's load capacity and lifespan. Dry-type transformers rely on air as the cooling medium and are divided into natural air cooling (AN) and forced air cooling (AF). In natural cooling structures, heat is dissipated naturally through convection by optimizing the arrangement of the core and windings, increasing the heat dissipation area, and setting up reasonable air ducts. In forced cooling structures, axial flow fans or centrifugal fans are added to increase airflow velocity, which can improve short-term or continuous load capacity at the same temperature rise. The design process requires calculating the thermal resistance network, matching the insulation heat resistance rating with the ambient temperature, and ensuring that the hottest spot temperature does not exceed the limit.
Structural protection design is equally important. The outer shell uses cold-rolled steel or galvanized steel, providing mechanical protection and a certain degree of electromagnetic shielding. Protection ratings range from IP00 to IP54, depending on the installation environment, preventing the intrusion of foreign objects, moisture, or corrosive gases. Internal supports and fasteners must have good seismic resistance to reduce the impact of transportation and operational vibrations on insulation and conductive components.
Furthermore, dry-type transformer design incorporates safety and environmental protection concepts, eliminating insulating oil to eliminate leakage and explosion risks and reduce pollution hazards during maintenance. Simultaneously, low-loss materials and efficient heat dissipation structures improve energy efficiency, meeting energy conservation and emission reduction requirements.
Overall, the design principle of dry-type transformers seeks the optimal balance between electromagnetic performance, insulation reliability, heat dissipation efficiency, and structural protection. Through multidisciplinary collaborative optimization, the equipment achieves comprehensive advantages in fire safety, environmental adaptability, and operational economy, providing a green and robust power distribution solution for modern power systems.