1. According to purpose:
1. Power transformer: used to increase and decrease the voltage of the power 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 conduct high voltage test on electrical equipment.
4. Special transformers: such as electric furnace transformers, rectifier transformers, adjustment transformers, etc.
2. According to the winding form:
1. Double winding transformer: used to connect two voltage levels in the power system.
2. Three-winding transformer: generally used in the power system area substation, connected to 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.
Three, according to the number of phases:
1. Single-phase transformer: used for single-phase loads and three-phase transformer groups.
2. Three-phase transformer: used to increase and decrease the voltage of a three-phase system.
Fourth, according to the cooling method:
1. Dry-type transformer: Relying on air convection for cooling, generally used for small-capacity transformers such as local lighting and electronic circuits.
2. Oil-immersed transformer: Relying on oil as the cooling medium, such as oil-immersed natural cooling, oil-immersed air cooling, oil-immersed water cooling, forced oil circulation, etc.