Hermetic Transformers

Hermetic oil transformers are manufactured with an output of 25 to 5000 kVA and a mains voltage of up to 36 kV. Three-phase, oil-cooled standard transformers (ONAN) are available with internal (plug-in type) or externally mounted insulators (porcelain insulators). At the customer's request, special load-free tap changers and other cooling systems such as ONAF, OOAF, etc. can also be installed.

Hermetic transformers have no expansion tank and are completely filled with oil. The hermetic seal protects against atmospheric influences and is adjusted at the factory. The elastic tank with its corrugated walls controls the thermal expansion of the oil. These louvre walls are used for cooling on the one hand and also provide additional volume for the expansion of the oil.

The oil in hermetic transformers does not come into contact with air, so there is no risk of air or moisture ingress. They are particularly suitable for small spaces or compact transformer stations and are basically maintenance-free, requiring only occasional cleaning and inspection of protective devices.

In line with eco-design principles, these transformers are engineered for long service life, minimal energy losses, and the use of recyclable materials — reducing both operational and environmental impact.