Three Phase Oil Immersed Transformer: Construction and Working Principle
A three phase oil immersed transformer plays a critical role in power distribution systems, helping deliver stable electricity to factories, buildings, industrial facilities, public infrastructure, and utility networks
Thanks to its oil insulation and cooling system, this transformer can operate reliably in power distribution networks, outdoor substations, and industrial electrical systems.
What is a Three Phase Oil Immersed Transformer?
A three phase oil immersed transformer is a type of transformer used in three phase power systems to increase or decrease voltage levels. It is commonly used in power distribution networks, outdoor substations, factories, industrial facilities, and infrastructure projects.
This transformer is designed for stable operation in systems that require reliable power supply and continuous voltage conversion. Thanks to its practical design and wide capacity range, the three phase oil immersed transformer is one of the most common transformer types used in electrical distribution and industrial power systems.
Construction of a Three Phase Oil Immersed Transformer
The construction of a three phase oil immersed transformer is mainly based on three essential parts: the magnetic core, the windings, and the transformer tank. These parts form the basic structure of the transformer and support the voltage transformation process in a three phase power system.
Magnetic Core
The magnetic core is the main path for magnetic flux inside the transformer. In a three phase transformer, the core usually has three limbs, corresponding to the three phases. It is commonly made from laminated electrical steel sheets to reduce losses and improve operating efficiency.
Magnetic Core
Windings
The windings are the electrical circuits of the transformer. A three phase oil immersed transformer includes high voltage windings and low voltage windings. These windings are arranged around the magnetic core and are designed according to the required voltage ratio and rated capacity.
Windings
Transformer Tank
The transformer tank is the outer housing that contains the magnetic core, windings, and transformer oil. It protects the internal parts from external conditions and provides space for oil insulation and cooling. The tank also supports the installation of bushings, radiators, valves, indicators, and other accompanying parts.
Tank of Transformer
Optional Accessories for Three Phase Oil Immersed Transformers
In addition to the main components, a three-phase oil-immersed transformer can be equipped with several accessories to support operation, protection, monitoring, and maintenance:
- Voltage tap changer
- Oil level indicator
- Oil temperature indicator
- Gas relay…
Working Principle of a Three Phase Oil Immersed Transformer
The working principle of a three phase oil immersed transformer is based on electromagnetic induction. When three phase AC voltage is supplied to the primary windings, alternating current flows through the windings and creates a changing magnetic flux in the magnetic core.
This magnetic flux links with the secondary windings and induces voltage on the secondary side. The output voltage depends on the turns ratio between the primary and secondary windings. If the secondary winding has fewer turns, the transformer works as a step-down transformer. If it has more turns, the transformer works as a step-up transformer.
During this process, electrical energy is transferred from the primary side to the secondary side through the magnetic field, without changing the frequency of the power system. In an oil immersed design, transformer oil supports this operation by providing insulation and helping dissipate heat generated from the core and windings.
Common Product Options for Three-Phase Oil-Immersed Transformers
Three phase transformers are used in many power distribution systems, from industrial facilities and outdoor substations to renewable energy projects. Depending on the operating conditions and application requirements, three phase oil immersed transformers can be designed in different product types.
Below are some common three phase oil immersed transformer products and their main applications.
Sealed Type Transformer
A sealed type transformer has a closed oil system that limits direct contact between transformer oil and outside air. It is commonly used in distribution networks and outdoor substations where stable operation and lower maintenance are required.
Sealed Type Three Phase Transformer
Open Type Transformer
An open type transformer is an oil-immersed transformer with a conservator tank and breather system. It allows transformer oil to expand and contract during temperature changes while supporting easier oil level monitoring and maintenance.
Open Type Three Phase Transformer
Amorphous Transformer
An amorphous transformer uses an amorphous metal core to reduce no-load loss. It is suitable for distribution systems that operate continuously and require better long-term energy efficiency.
Three Phase Amorphous Transformer
Solar Transformer
A solar transformer is designed for solar power systems. It is used to step up the output voltage from inverters and connect the solar power system to the medium-voltage grid.
Solar Transformer
Distribution Transformer
A distribution transformer is used to step down medium voltage to low voltage for factories, buildings, residential areas, and industrial facilities. It is one of the most common applications of three phase oil immersed transformers.
Distribution Transformer
Comparison table oil immersed transformers and dry type transformers
| Criteria | Oil Immersed Transformer | Dry Type Transformer |
|---|---|---|
| Insulation & Cooling | Uses transformer oil for insulation and cooling | Uses air and solid insulation, commonly epoxy resin |
| Installation Area | Commonly used outdoors or in separate transformer rooms | Commonly used indoors or near load centers |
| Fire Safety | Requires oil leakage and fire protection control | Oil-free design with higher fire safety |
| Maintenance | Requires oil monitoring and periodic inspection | Lower maintenance, no oil monitoring required |
| Typical Applications | Outdoor substations, factories, industrial facilities, utility networks | Buildings, hospitals, shopping malls, data centers, urban infrastructure |
| Main Advantage | Effective cooling, wide capacity range, stable outdoor operation | Compact installation, higher safety, oil free operation |
Three Phase Oil Immersed Transformers from MBT
A three phase oil immersed transformer is a reliable solution for power distribution systems that require stable voltage conversion, effective cooling, and long-term operation. With transformer oil used for both insulation and heat dissipation, this transformer type is widely applied in outdoor substations, factories, industrial facilities, infrastructure projects, and renewable energy systems.
At MBT, three phase oil immersed transformers are developed to meet different project requirements, from capacity and voltage level to installation conditions and operating environments. Depending on the application, customers can choose suitable designs such as sealed type, open type, amorphous, solar, or general distribution transformers.
By understanding the structure, working principle, common product types, and application characteristics of three phase oil immersed transformers, customers can make a more suitable choice for their power distribution systems. For projects with different installation or safety requirements, customers may also refer to dry type transformers as an alternative option.
FAQ About Three-Phase Oil-Immersed Transformers
When should a three-phase oil-immersed transformer be used?
A three-phase oil-immersed transformer is suitable for projects that require stable voltage conversion, effective heat dissipation, and reliable long-term operation. It is commonly selected for outdoor substations, factories, industrial facilities, infrastructure systems, and renewable energy projects.
What is the difference between sealed type and open type oil-immersed transformers?
A sealed type transformer has a closed oil system that limits contact between transformer oil and outside air. An open type transformer usually has a conservator tank and breather system, allowing oil expansion and easier oil level monitoring during operation.
How does transformer oil support the operation of a three-phase oil-immersed transformer?
Transformer oil helps insulate the internal components and dissipate heat generated by the core and windings. This supports stable operation, reduces overheating risk, and helps maintain transformer performance during long-term use.
What are the common types of three-phase oil-immersed transformers?
Common types include sealed type transformers, open type transformers, amorphous transformers, solar transformers, and distribution transformers. Each type is designed for different operating conditions, energy efficiency requirements, and power distribution applications.
