Classification by Cooling Medium

High-frequency transformers can also be categorized by their cooling methods, such as dry-type, oil-immersed, or gas-filled transformers. Among these, dry and oil-immersed types are the most common.

Dry-type transformers, like high frequency flyback transformers, have exposed cores and coils and are often used indoors, especially in areas requiring fire and explosion protection, such as commercial or high-rise buildings. In contrast, oil-immersed transformers are sealed within a casing and are typically installed outdoors or in areas with oil containment pits due to the risk of oil leakage or combustion.

While oil-immersed units generally offer higher capacity, dry-type high-frequency transformers are more expensive at equivalent power levels but offer enhanced safety and lower maintenance.