The classification of commonly used transformers can be summarized as follows:1. According to the number of phases:1) Single-phase transformer: for single-phase load and three-phase transformer group.2) Three-phase transformer: used for the rise and fall voltage of three-phase systems.2, according to the cooling method:1) Dry-type transformer: relying on air convection for natural cooling or increasing fan cooling, it is mostly used for small-capacity transformers such as high-rise buildings, high-speed toll stations, local lighting, and electronic circuits.2) Oil-immersed transformer: rely on oil as cooling medium, such as oil-immersed self-cooling, oil-infiltrated air-cooled, oil-immersed water-cooled, forced oil circulation, etc.3. According to the purpose:1) Power transformer: used for the rise and fall voltage of transmission and distribution systems.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 on electrical equipment.4) Special transformers: such as electric furnace transformers, rectifier transformers, regulating transformers, capacitive transformers, phase shifting transformers, etc.4, according to the form of winding:1) Two-winding transformer: used to connect two voltage levels in a power system box transformer.2) Three-winding transformer: Generally used in power system regional substation, connecting three voltage levels.3) Autotransformer: A power system used to connect different voltages. It can also be used as a normal boost or post-down transformer.5, according to the iron core form:1) Core transformer: Power transformer for high voltage.2) Amorphous alloy transformer: Amorphous alloy core transformer is a new type of magnetic conductive material, the no-load current is reduced by about 80%, which is an ideal distribution transformer for energy saving, especially suitable for rural power grids and developing regions. Lower place.3) Shell-type transformer: special transformer for high current, such as electric furnace transformer, electric welding transformer; or power transformer for electronic equipment and television, radio, etc.