The classification of common transformer skeletons 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: It relies on air convection to cool, and is generally used for small-capacity transformers such as 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 skeleton: 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, adjusting transformers, etc.

4, according to the form of winding:

1) Two-winding transformer: used to connect two voltage levels in the power system.

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 skeleton: power transformer for high voltage.

2) 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.