1. Open type: A common type where the transformer body is in direct contact with the atmosphere. Suitable for relatively dry and clean indoor environments (relative humidity should not exceed 85% at an ambient temperature of 20 degrees Celsius). Generally, it uses either air self-cooling or wind cooling.
2. Enclosed type: The transformer body is located within a closed outer shell and is not in direct contact with the atmosphere (due to poor sealing and heat dissipation, it is mainly used in mining and is classified as explosion-proof).
3. Cast resin type: Epoxy resin or other resins are used as the main insulation. It has a simple structure and small size, suitable for smaller capacity transformers.
