Oil-free pillow transformer
The power transformer without oil pillow structure is a encapsulated dry type transformer.
There is a pipe (oil column) above the transformer tank so that the oil level of the transformer is not lower than the transformer bushing. The fuel tank is covered with a heat sink, and the heat sink is a hollow thin plate that directly communicates with the fuel tank. When the oil temperature increases, the heat sink will protrude to both sides, and the plurality of heat sinks can accommodate the expanded oil.
Due to the poor heat dissipation effect of the heat sink, it is generally used for a transformer with a small capacity.
Dry power transformer
At present, transformers used in urban and large buildings have gradually adopted dry power transformers. The transformer has no fuel tank, and the iron core and the winding are installed in a common box. Dry-type transformer windings are sealed with epoxy resin to ensure sealing and insulation. There are also heat dissipation channels in the larger capacity windings. The large capacity transformer is equipped with a fan for forced ventilation. Due to material and process limitations, the current dry power transformer voltage does not exceed 35kV, and the capacity is not more than 20000kV. Large high-voltage power transformers still use oil cooling.