As a static device that transforms electrical energy into voltage based on the principle of electromagnetic induction, the stable operation of a power transformer highly depends on precise structural design and the coordinated operation of its various components.The overall structure can be divided into core parts such as the core, windings, insulation system, tank and cooling system, tap changer, and accessories. Each part reflects rigorous engineering logic in its material selection, geometric layout, and functional implementation.
The core is the main body of the transformer's magnetic circuit, responsible for guiding and concentrating magnetic flux. To reduce hysteresis and eddy current losses, the core is typically made of grain-oriented silicon steel sheets stacked along the magnetic flux direction, with insulating varnish applied between the sheets to block eddy current paths. Modern large transformers often use stepped or fully oblique joint stacking processes for their cores to reduce air gaps and magnetic reluctance, improving permeability and operating efficiency. The structural design of the core columns and yoke must ensure uniform magnetic flux distribution to avoid additional heating and noise caused by local saturation.
The windings are the core of the transformer's circuitry, formed by winding highly conductive copper or aluminum materials onto insulating cylinders or supports in a concentric or overlapping arrangement. The primary winding is connected to the power supply side, while the secondary winding outputs the transformed voltage; both are coupled through a shared magnetic flux. The cross-sectional area and number of turns of the winding conductors are determined by the rated capacity and voltage ratio, and the design considers current density, temperature rise limits, and mechanical strength to withstand short-circuit current surges and long-term thermal aging. Interlayer and inter-turn insulation uses paper-insulated, film-insulated, or composite insulating materials to ensure reliable electrical isolation.
The insulation system is a critical barrier ensuring the safe operation of the transformer, encompassing various forms such as solid insulation, liquid insulation, and gas insulation. Oil-immersed transformers commonly use mineral insulating oil, which serves both insulation and cooling functions; oil gaps are distributed between windings, between windings and the core, and within the tank. Dry-type transformers, on the other hand, use epoxy resin casting or insulating films for fully enclosed insulation, suitable for locations with high fire safety requirements. The insulation structure design must consider dielectric strength, thermal stability, and aging life, while allowing sufficient margins to cope with overvoltage and moisture corrosion.
The oil tank and cooling system constitute the mechanical casing and thermal management system of the transformer. The oil tank not only houses the core, windings, and insulating oil but also withstands internal oil pressure and external environmental loads. Cooling methods are categorized based on capacity and heat dissipation requirements, including self-cooling, air cooling, forced oil circulation, and guided oil circulation. Components such as radiators, oil pumps, and fans work together to promptly dissipate heat generated during operation, maintaining winding and oil temperatures within design limits.
Tap switches are used to adjust the transformer turns ratio to compensate for grid voltage fluctuations or optimize load distribution. On-load tap switches can switch taps without power interruption, have a complex structure, and require extremely high arc extinguishing and insulation standards. Off-load tap switches must operate under power-off conditions and are mostly used in applications with small voltage adjustment ranges or low continuity requirements.
The accessory system includes an oil conservator, dehumidifier, explosion-proof pipe, pressure relief valve, thermometer, oil level gauge, and gas relay, which respectively realize functions such as oil level regulation, moisture protection, overvoltage protection, and temperature and gas status monitoring, providing important information support for transformer operation monitoring and maintenance.
In summary, the structure of a power transformer is an organic unity of magnetic circuit, electrical circuit, insulation, cooling, and monitoring functions. The high standards required for material performance, geometric precision, and process control of each component ensure the safe, stable, and economical operation of the equipment under high voltage, large capacity, and complex operating conditions, and also provide a solid hardware foundation for reliable power supply to the power system.