A transformer is a device that changes voltage, current and impedance using electromagnetic mutual inductance. The main functions of the transformer are: voltage transformation; Current transformation, impedance transformation; Isolation; Voltage regulator (magnetic saturation transformer), etc.

The classification of commonly used transformers can be summarized as follows:

(I) By cooling method:

(1) Dry-type transformer: it is used for natural cooling or fan cooling by air convection. It is mainly used for high-rises, high-speed toll stations, electricity, local lighting, electronic lines and other small-capacity transformers.

(2) Oil-immersed transformer: oil is used as cooling medium, such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling, forced oil circulation, etc.

(ii) According to the winding form:

(1) Double-winding transformer: used to connect two voltage classes in a power system.

(2) Three-winding transformer: generally used in regional substation of power system to connect three voltage levels.

(3) Autotransformer: used to connect power systems with different voltages. It can also be used as a common boost or drop transformer.

(3) According to the core form:

(1) Core transformer: Power transformer used for high voltage.

(2) Amorphous alloy transformer: Amorphous alloy iron core transformer is a new magnetic conductivity material, with no load current reduced by about 80%. It is a distribution transformer with ideal energy saving effect at present, especially suitable for rural power grid and developing areas where the load rate is low.

(3) Shell transformer: special transformer used for large current, such as furnace transformer, welding transformer; Or power transformers for electronic instruments, televisions, radios, etc