What is a transformer radiator?
A transformer radiator is an external cooling device installed on an oil-immersed transformer to dissipate heat generated during operation. It is assembled from multiple heat dissipation fins, featuring thin steel walls, a large heat dissipation area, and a lightweight design. The radiator is typically installed on the sides or back of the transformer tank, utilizing natural air convection or forced air cooling to accelerate heat dissipation from the transformer's interior.
Its working principle involves allowing high-temperature insulating oil to flow through finned metal plates, transferring heat to the surrounding air. This process can occur naturally (through convection) or with the aid of fans to increase airflow and cooling efficiency. Transformer radiators are crucial for maintaining safe internal temperatures and supporting higher load conditions.
Why do transformers need radiators?
In power systems, transformers play a crucial role in voltage transformation. During operation, transformers generate a significant amount of heat due to losses. If this heat cannot be dissipated in time, it can cause internal insulation aging, shorten service life, and in severe cases, even lead to safety accidents. Therefore, plate-type radiators are needed to assist in transformer cooling and reduce operating temperature.
Every operating transformer experiences two primary forms of power loss:
|
Loss Type |
WHY |
Location |
|
ore Losses |
Hysteresis & eddy currents in magnetic core |
Iron core (central area) |
|
Copper Losses |
I²R (resistive) losses in windings |
Primary and secondary coils |
How do radiators work?
The working process of a finned radiator consists of four key steps:
Hot oil rises: During transformer operation, the heat generated by the windings and core causes the temperature of the insulating oil to rise. The hot oil, with its lower density, naturally rises.
Flow into the radiator: The hot oil flows through the oil collector pipes and into the oil delivery pipes within the radiator.
Heat transfer: The heat from the insulating oil is transferred to the air through the extremely thin steel walls, lowering the oil temperature.
Cool oil returns: The cooled transformer oil, with its increased density, flows back to the bottom of the tank along the other side of the radiator, and the cycle continues.
This process repeats itself, continuously cooling the transformer without the need for additional power.
How to choose a transformer radiator
Depending on the cooling type, they are generally divided into two categories:
|
Code |
Cooling Type |
Use cases |
|
ONAN |
Oil Natural, Air Natural |
Distribution transformers |
|
ONAF |
Oil Natural, Air Forced (fans) |
Power transformers |
In addition, based on the structure, transformer radiators can be further divided into fixed type and detachable type. The detachable type is easy to transport and assemble on site, and is often used in ultra-high voltage or large-capacity projects.
When selecting and matching a plate-type radiator for a transformer, the following parameters need to be carefully considered:
Heat dissipation capacity matching: The total heat dissipation power of the radiator should be greater than the total losses (iron loss + copper loss) of the transformer under full load.
Number of fins and center distance: The center distance (the distance between the upper and lower oil collector pipes) determines the effective height of the radiator and should match the height of the transformer tank.
Oil flow rate and temperature rise: Ensure smooth oil circulation under the rated temperature rise (typically the top oil temperature rise should not exceed 55K).
Environmental conditions: In areas with high altitude, heavy sandstorms, or high humidity, radiators with enhanced anti-corrosion coating should be selected, and additional cooling margin should be reserved.
Noise requirements: For transformers installed near residential areas, natural cooling (self-cooled) radiators are preferred, or low-noise fans should be configured if forced air cooling is used.
Conclusion
Radiators play a key role in oil-immersed transformers. They help control temperature by enabling heat exchange between the transformer oil and the surrounding air. The design and performance of radiators directly affect transformer reliability, efficiency, and service life. Correct selection, proper installation, and regular maintenance are all needed. These ensure safe operation under different electrical loads and environmental conditions. Without radiators, thermal stress becomes a problem. It can cause frequent failures and lead to high maintenance costs.
