A transformer is a device that uses the principle of electromagnetic induction to change AC voltage. Its basic structure consists of a primary coil, a secondary coil, and an iron core. It has a wide range of applications in industry, transportation, and other fields. The following is a brief introduction to the common types and main classifications of transformers.

(I) Common Types of Transformers

Distribution transformers, power transformers, fully sealed transformers, combined transformers, dry-type transformers, oil-immersed transformers, single-phase transformers, electric furnace transformers, rectifier transformers, reactors, anti-interference transformers, lightning protection transformers, box-type transformer test transformers, angle transformers, high-current transformers, excitation transformers, etc.

(II) Main Classifications of Transformers

1. By iron core form:

(1) Core-type transformers: Used for high-voltage power transformers.

(2) Amorphous alloy transformer: Amorphous alloy core transformers use new magnetic materials, reducing no-load current by about 80%, making them energy-efficient distribution transformers, especially suitable for rural power grids and developing areas with low load rates.

(3) Shell-type transformer: Special transformers used for high current applications, such as electric furnace transformers and welding transformers; or power transformers for electronic instruments, televisions, radios, etc.

2. By application:

(1) Power transformer: Used for stepping up and down voltage in power transmission and distribution systems.

(2) Instrument transformer: Such as voltage transformers and current transformers, used for measuring instruments and relay protection devices.

3. By winding type:

(1) Two-winding transformer: Used to connect two voltage levels in a power system.

(2) Three-winding transformer: Generally used in regional substations of power systems to connect three voltage levels.

(3) Autotransformer: Used to connect power systems with different voltages. Can also be used as a general step-up or step-down transformer. 4. Classification by Cooling Method:

(1) Dry-type transformers: Rely on air convection for natural cooling or additional fan cooling. They are mostly used in high-rise buildings, highway toll stations, and small-capacity transformers for local lighting and electronic circuits.

(2) Oil-immersed transformers: Rely on oil as the cooling medium, such as oil-immersed self-cooling, oil-immersed air-cooling, oil-immersed water-cooling, and forced oil circulation.

5. Classification by Number of Phases:

(1) Single-phase transformers: Used for single-phase loads and three-phase transformer banks.

(2) Three-phase transformers: Used for stepping up and down voltage in three-phase systems.