Forced Oil Air Coolers (OFAF - Oil Forced Air Forced)

Forced Oil Air Coolers (OFAF - Oil Forced Air Forced)

OFAF (Oil Forced Air Forced) is an advanced cooling method used in large power transformers where both oil circulation and airflow are mechanically forced (using pumps and fans) to enhance heat dissipation. This system is highly efficient and is typically employed in high-capacity transformers (usually above 60 MVA) where natural cooling methods are insufficient.

How OFAF Cooling Works

Forced Oil Circulation: Oil pumps actively circulate hot transformer oil through cooling radiators or heat exchangers.

Forced Air Cooling: Fans blow air over the radiators to maximize heat transfer.

Staged Cooling: Many OFAF systems have multiple cooling stages (e.g., 2 or 3 stages) where additional fans activate as temperature rises.

Cooling Process Flow:

Heat Generation – Transformer windings and core produce heat during operation.

Oil Absorption – Hot oil flows through the windings, absorbing heat.

Pump Circulation – Oil pumps push the heated oil to external radiators.

Forced Air Cooling – Fans blow air across the radiator fins, cooling the oil.

Return to Transformer – Cooled oil re-enters the transformer, completing the cycle.

Advantages of OFAF Cooling

✔ Higher Cooling Efficiency – Better than ONAN (natural convection) and ONAF (forced air only).

✔ Increased Load Capacity – Allows transformers to handle higher loads without overheating.

✔ Compact Design – Requires smaller radiators compared to natural cooling methods.

✔ Flexible Operation – Cooling stages can adjust based on temperature (e.g., 50% fans at low load, 100% at full load).

✔ Better Thermal Management – Reduces hotspots, extending transformer life.

Maintenance Best Practices

Oil Pump Checks – Ensure proper oil flow and no leaks.

Fan Inspections – Clean blades, check bearings, and verify operation.

Radiator Cleaning – Remove dust/debris blocking airflow.

Temperature Monitoring – Verify cooling stages activate correctly.

Backup Power for Pumps—Ensures cooling continues during power interruptions.

Applications of OFAF Cooling

Grid power transformers (100 MVA and above).

Industrial transformers (steel plants, data centers).

HVDC converter transformers.

Locations with high ambient temperatures.