Transformer test equipment is a kind of stationary electrical equipment, which uses the principle of electromagnetic induction to transform the alternating current energy of one voltage level into the alternating current energy of another voltage level.

The primary role of transformers in power systems is to change voltage levels to facilitate power transmission. Increasing voltage can reduce line losses, improve the economic efficiency of power transmission, and achieve the goal of long-distance power transmission. Reducing voltage, transforming high voltage into the various usage voltages required by users, meets user needs.

Common Classifications of Transformers

1.By Phase:

Single-phase transformer: Used for single-phase loads.

Three-phase transformer: Used for stepping up or stepping down voltages in three-phase systems.

Single-phase transformer

A single-phase transformer has both primary and secondary windings as single-phase windings. A unipolar switching power supply, which means the output is unipolar, i.e., only positive and negative outputs, compared to a bipolar switching power supply that has three outputs, divided into positive, negative, and ground lines.

Three-phase transformer

The connection methods of three-phase transformers are divided into Y/Y, or Y/Yn, Y/△ or Yn/△, △/Y or △/Yn, and △/△.

Y, Yn represent star connections, △ represents delta connections as shown below.

Due to different wiring methods, there is a certain phase difference between the line voltages of the primary and secondary windings of a three-phase transformer. Taking the primary line voltage as the long hand and fixing it at 12 o'clock, the corresponding secondary line voltage vector as the short hand, if they are 150 degrees apart, then the secondary line voltage vector must fall at 150°/30=5 o'clock, as shown above.

2.By Cooling Method:

Dry-type transformer: Cooled by air convection.

Oil-immersed transformer: Cooled using oil as the cooling medium, such as oil-immersed self-cooling, oil-immersed air cooling, oil-immersed water cooling, forced oil circulation air cooling, etc.

3. By Usage:

Power transformer: Used for stepping up or stepping down voltages in transmission and distribution systems.

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

Test transformer: Capable of generating the required voltage for testing electrical equipment.

Special transformer: Such as furnace transformers, rectifier transformers, etc.

4.By Winding Configuration:

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

Three-winding transformer: Generally used in regional substations of power systems, connecting three voltage levels.

Autotransformer: Used to connect power systems of different voltages. It can also be used as a regular step-up or step-down transformer.

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