Transformers can be classified from four dimensions: purpose, cooling method, winding form, and core structure. Different types correspond to specific application scenarios and technical characteristics. The following is a detailed description:
1. Classification by purpose
Power transformers
Used for voltage conversion and power transmission in power systems, they are the most common type of transformers in power systems. For example, the step-up transformer in a substation increases the voltage to support long-distance power transmission, while the step-down transformer reduces the high voltage to a voltage level suitable for household electricity or industrial equipment.
Special transformers
Including rectifier transformers, electric furnace transformers, welding transformers, voltage regulating transformers, test transformers, mining transformers, audio transformers, medium frequency transformers, high frequency transformers, pulse transformers, etc., used in special applications. For example, test transformers are mainly used for testing and research of power systems, such as voltage measurement, insulation performance testing, etc.; electric furnace transformers are used in arc furnaces and arc welding machines to provide high-voltage power to generate arcs.
Instrument transformers
Such as voltage transformers and current transformers, they provide stable and isolated voltages for instruments to protect them from grid voltage fluctuations. They are generally used in control, measurement, and monitoring systems.
Other functional transformers
Include excitation transformers (powering the generator excitation system), isolation transformers (isolating power supply and load to improve safety), voltage regulating transformers (adjusting grid voltage stability), etc.
2. Classification by cooling method
Oil-immersed transformers
Immerse the transformer windings in transformer oil, and cool the transformer through oil circulation. It has good heat dissipation and insulation performance and is suitable for outdoor or high heat dissipation requirements, but it is necessary to prevent oil leakage and fire risks.
Dry-type transformers
Rely on natural air cooling or forced air cooling, no oil, completely rely on air or forced air cooling, suitable for indoor places or places with high environmental requirements, such as high-rise buildings, high-speed toll stations, electricity and local lighting, etc., with the advantages of fire prevention and explosion prevention.
Air-cooled transformers
Use fans for forced cooling to enhance the heat dissipation effect.
Water-cooled transformers
Use water as a cooling medium to remove heat through water circulation, suitable for special scenarios with extremely high heat dissipation requirements.
3. Classification by winding form
Dual-winding transformer
It has two windings, one for the primary winding and the other for the secondary winding. The primary and secondary voltages are different. It is used to achieve voltage rise and fall conversion. It is the most common type of transformer.
Three-winding transformer
It has three windings, which can realize the conversion between three different voltage levels. It is generally used in regional substations of power systems to connect three voltage levels to improve power supply flexibility and efficiency.
Autotransformer
There is a part between the primary and secondary windings that is common. It has a higher voltage conversion ratio and a smaller volume. The cost is low, but the safety is relatively low. It is suitable for occasions where the voltage conversion ratio is not large and the safety requirements are not strict.
Multi-winding transformer
It has multiple windings, which can meet the needs of various voltage levels, and is suitable for voltage conversion and distribution of complex power systems.
4. Classification by core structure
Core transformer
The core is composed of multiple silicon steel sheets stacked together to form multiple magnetic circuits. It has a higher magnetic flux density and a smaller excitation current. It is suitable for large-capacity and high-efficiency occasions. It is widely used in power transformers, and the core production accounts for a large proportion.
Shell transformer
The core is frame-shaped, and the winding is surrounded by the core frame. It has a compact structure and good heat dissipation. It is suitable for large-capacity transformers, such as electric furnace transformers, welding transformers, etc. It is also used for power transformers of electronic instruments, televisions, radios, etc.
Amorphous alloy transformer
The amorphous alloy core is used, and the no-load current drops by about 80%, with an ideal energy-saving effect. It is especially suitable for places with low load rates, such as rural power grids and developing areas, but the short-circuit resistance is poor and the noise is relatively large.
Toroidal transformer
The core is ring-shaped, and the winding is evenly distributed on the ring-shaped core. It has the advantages of small leakage, high efficiency, low vibration and noise, etc. It is often used in places with high requirements for electromagnetic interference and noise, such as audio equipment, precision instruments, etc.