25 -2500 kVA power range, up to 36 kV high voltage level, or single-phase, oiled, naturally cooled (ONAN), with no-load tap changer or with automatic tap changer under load, they can be used both externally and indoors.

Expansion tank transformers are the same as hermetic transformers with their core and coil structure. 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 air exchange are provided by removing the humidity of the air thanks to the slicagel (air dryer) in the transformer product tank.

The transformer with expansion tank put into operation loses its slicagel property over time as a result of air exchange caused by temperature differences depending on the load, and causes the oil to become moist and its structure to deteriorate. It has maintenance such as measuring the breakdown voltage.