They are produced in the power range of 10-100,000 kVA, up to 66 kV high voltage level, three or single phase, oil-lubricated, ONAN, ONAF cooled, with no-load tap changer or automatic under load tap changer, both external and internal.
The dimensions of the expansion tanks of the transformers are designed as a result of calculations to store the expansion of the oil increasing with temperature. Since transformers with expansion tanks are open to the atmosphere, the changing oil pressure due to thermal effects and the silica gel (air dryer) in the tank of the transformer remove the humidity of the air and provide air exchange.
They are produced in the power range of 10-3.150 kVA, up to 36 kV high voltage level, three- or single-phase, oiled, ONAN, ONAF cooled, with no-load tap changer or automatic under load tap changer, for both external and internal use.
In Hermetic Transformers, there is no oxygen in the environment because oil does not come into contact with air. Therefore, there is no aging due to oxidation.
Since there is no contact with air in Hermetic Transformers, transformer oil will not absorb moisture. In this way, Hermetic Transformers have a longer life than transformers with expansion tanks.
Since there is no expansion tank in Hermetic Transformers, the height is low. Allows mounting in smaller spaces. It is particularly advantageous in compact transformer substations.
