How to cool power transformers?

Power transformers are designed to operate under high load and voltage levels for extended periods. In this context, heat is a major factor affecting their performance, efficiency, and lifespan. Therefore, cooling systems play a crucial role: they dissipate internally generated heat, ensuring safe, stable, and reliable operation.

Choosing the right cooling method not only improves transformer efficiency, but also reduces component wear, minimizes the risk of failure, and optimizes long-term operating costs.

Why is cooling important in power transformers?

During operation, a transformer generates heat due to two main factors:

Magnetic core losses

Losses in windings due to Joule effect

If this heat is not dissipated properly, it can cause:

Degradation of the insulation system

Reduction in the useful life of the equipment

Decreased energy efficiency

Higher risk of failures or interruptions

An efficient cooling system allows the temperature to be kept within safe limits, ensuring the reliability of the transformer even under demanding conditions.

Method 1: Natural air cooling (NA)

This method is primarily used in dry-type transformers. The generated heat is dissipated directly into the environment through natural air circulation, without the need for fans or additional systems.

Main features:

Simple and low-maintenance system

It does not use insulating oil.

Ideal for indoor installations

Lower heat dissipation capacity than other methods

It is a reliable solution for industrial, commercial and building applications where the power required is moderate.

Method 2: Natural Oil and Natural Air Cooling (ONAN)

It is one of the most common methods in power transformers . It uses insulating oil to absorb the heat generated in the core and coils, and transfers it to radiators where it is cooled by natural air circulation.

Main advantages:

High thermal efficiency

Robust and reliable system

It does not require forced ventilation

Low energy consumption

This system is widely used in electrical substations and industrial applications.

Method 3: Natural Oil and Forced Air Cooling (ONAF)

This system is an evolution of the ONAN method that incorporates fans that increase the thermal dissipation capacity.

Benefits:

Greater load capacity

Better temperature control

Ideal for high-demand applications

It allows the transformer to operate under more demanding conditions.

It is widely used in heavy industries, mining, and high-power electrical networks.

Method 4: Forced Oil and Forced Air (OFAF) Cooling

This system uses pumps to force oil circulation and fans to cool the radiators, significantly improving heat dissipation.

Key features:

Maximum cooling efficiency

Ideal for very high power transformers

It allows continuous operation under high loads

Improved thermal control and operational stability

It is common in power plants, mining, and large industrial facilities.

Method 5: Oil and Water Cooling (OFWF)

This system uses heat exchangers where water cools the transformer oil. It is one of the most efficient methods available.

Main advantages:

Excellent cooling capacity

Ideal for installations with high continuous loads

Greater thermal stability

It allows for a reduction in the size of the transformer.

It is used in critical industrial environments where the temperature must be kept under constant control.

How to choose the right cooling method?

The selection of the cooling system depends on several technical factors:

Transformer power

Environmental conditions

Installation type (indoor or outdoor)

Operational load level

Reliability requirements

A properly selected system guarantees a longer lifespan, better energy efficiency, and a lower risk of failure.

In industrial, energy, or mining applications, having transformers designed with the appropriate cooling system is key to ensuring operational continuity. That's why it's essential to work with specialists who can advise on, design, and maintain transformers tailored to the specific requirements of each project.

At DeYan, we have the best transformers in China, designed to offer you high-quality, high-performance solutions. If you need a specific transformer or customized solutions for your electrical project, explore our product range and find what you're looking for. We also offer specialized services to ensure your equipment operates flawlessly. If you have any questions or need advice, please don't hesitate to contact us . We're here to help you optimize your electrical system and take it to the next level.