Why Oil-Cooled Transformer Radiators Use Fan Groups
In ONAN and ONAF cooling, oil can circulate naturally between the transformer tank and external radiators. Adding fans changes the air-side heat transfer while the oil loop remains buoyancy driven.
Follow the air through the process
Losses warm the oil
The core and windings transfer their loss heat to the surrounding oil. Warmer, less dense oil rises toward the upper radiator connection.
The radiator cools the oil
Heat crosses the radiator metal into the surroundings. Cooling makes the oil denser, helping it descend.
The lower connection closes the loop
The cooler oil returns through the lower connection to the tank. This selected oil-natural arrangement has no oil pump.
Fan control adds air-side capacity
Fans drive air along the radiator surfaces when the configured cooling control requires it. Some transformers provide successive fan stages; the sequence and rating are design specific.
Airflow function
- Along the external radiator bank, where fan groups move air over the metal surfaces while buoyancy circulates the oil inside.
- An axial assembly can provide direct air movement across the radiator. Fan spacing and control must maintain useful coverage as the cooling stages change.
What can change the result
- Poor airflow distribution leaves some radiator regions less effectively cooled.
- Obstructions or installation losses change the available fan airflow.
- Environmental or control mismatch can prevent the selected assembly from serving its intended cooling duty.
Start with the complete air path
Share your layout and the information you already have. Unknown values can be identified before a configuration is selected.
Match the fan to this air path
LONGWELL EC axial motor-and-impeller families can be assessed for the radiator air side. Review the fan assembly, mounting ring, outdoor exposure and control interface together with the transformer cooling design.
Where it sits
Along the external radiator bank, where fan groups move air over the metal surfaces while buoyancy circulates the oil inside.
Why consider this configuration
An axial assembly can provide direct air movement across the radiator. Fan spacing and control must maintain useful coverage as the cooling stages change.
Check the result in your equipment
Discuss your transformer radiator
Send radiator geometry and fan locations, required operating airflow and resistance, cooling-stage or speed-control logic, ambient temperature and weather exposure, acoustic requirement at the installation, required electrical and environmental qualification. Ask LONGWELL to review a suitable configuration, fan curve, drawing and control details. A layout or existing fan model can start the review.
A layout, installation photos or your existing model is enough to start the discussion.