Transformers come in many different types, but their working principle is always based on electromagnetic induction. The commonly used classification methods for transformers are summarized as follows:
Table of Contents
1. Classification by Application
① Power Transformers
Used for voltage step-up or step-down in power transmission and distribution systems; this is the most common type of transformer.
② Test Transformers
Used to generate high voltage for high-voltage testing of electrical equipment.
③ Instrument Transformers
Such as voltage transformers (VTs) and current transformers (CTs), used for measuring instruments and relay protection devices.
④ Special-Purpose Transformers
Including furnace transformers for smelting, rectifier transformers for electrolysis, welding transformers for arc welding, and variable transformers for test and laboratory use.
2. Classification by Number of Phases
① Single-Phase Transformers.
Used for single-phase loads.
② Three-Phase Transformers.
Used in three-phase systems for stepping up or stepping down voltages.
3. Classification by Winding Structure
① Autotransformers：
Used for ultra-high-voltage, large-capacity power systems where the voltage ratio change is relatively small.
② Two-Winding Transformers.
Used for connecting two voltage levels in a power system.
③ Three-Winding Transformers.
Used for connecting three voltage levels, typically applied in regional substations of power systems.
4. Classification by Core Structure
① Core-Type Transformers
Commonly used for high-voltage power transformers.
② Shell-Type Transformers
Used for special transformers requiring high-current handling, such as furnace transformers and welding transformers, as well as power transformers for electronic instruments, televisions, and radios.
5. Classification by Cooling Method
①Oil-Immersed Transformers
Include oil-immersed natural air cooling (ONAN), oil-immersed forced air cooling (ONAF), oil-immersed water cooling, forced oil circulation, and water-cooled systems.
② Dry-Type Transformers
Cooled by natural air convection, typically used for local lighting, electronic circuits, or small-capacity applications.