First of all, let's distinguish in the following five ways:
1/Dry-type transformers and wet-type transformers are divided into phases:
1) Single-phase transformer: used for single-phase load and three-phase transformer set.
2) Three-phase transformer: used for the rise and fall voltage of the three-phase system.
2/Dry-type transformers and wet-type transformers are divided according to the cooling method:
1) Dry-type transformer: relies on air convection for cooling, generally used for local lighting, electronic circuits and other small-capacity transformers.
2) Oil-immersed transformer: relying on oil as the cooling medium, such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling, forced oil circulation, etc.
3/ Dry-type transformers and wet-type transformers are divided according to their uses:
1) Power transformer: used for the rise and fall voltage of the transmission and distribution system.
2) Instrument transformers: such as voltage transformers, current transformers, measuring instruments and relay protection devices.
3) Test transformer: It can generate high voltage and carry out high voltage test transformer on electrical equipment.
4) Special transformers: such as electric furnace transformers, rectifier transformers, adjustment transformers, etc.
4/Dry-type transformer and wet transformer are divided into winding forms:
1) Double-winding transformer: used to connect two voltage levels in the power system.
2) Three-winding transformer: generally used in the regional substation of the power system, connecting three voltage levels.
3) Autotransformer: used to connect power systems with different voltages. It can also be used as an ordinary step-up or step-down transformer.