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Views: 0 Author: Site Editor Publish Time: 2025-12-18 Origin: Site
ONAN (Oil Natural Air Natural) cooling works only with natural movement of oil and air to remove heat. This simple method needs almost no care and fits best in places with steady, medium-size loads. ONAF (Oil Natural Air Forced), however, adds electric fans to push more air over the radiators. The extra airflow handles bigger loads or hot weather, but the system becomes more complex and costs more to run. Choose ONAN when low price and easy upkeep matter most. Choose ONAF when the transformer faces heavy or changing loads. SHENGTE’s S11 series shows how good ONAN design can be, with energy-saving cores and pure natural cooling that give many years of quiet service.
ONAN cooling is a completely natural way to keep oil-immersed transformers from getting too hot. No pumps or fans take part. Heat from the core and coils warms the insulating oil. Warm oil becomes lighter and rises on its own. Cooler oil then moves down to take its place. This steady loop carries heat to the tank walls or radiators. There, normal air flow around the metal surfaces carries the heat away.
The oil itself has low thickness, strong heat-moving ability, and excellent insulation strength. These features protect the iron core and windings, slow down insulation aging, and help the transformer last longer.
ONAN units contain no moving parts. Without fans or pumps, almost nothing can break from normal wear. Maintenance stays very low. Reliability rises because fewer things can go wrong. Such transformers work especially well in cool rooms, indoor stations, or places where the load changes little.
Noise stays quiet since only natural air moves. The whole system also costs less over many years. Most users pick this type for small to medium power needs where natural cooling is enough.
The SHENGTE’s S11 500kVA 10kV 400V Core 3-Phase ONAN Cooling Distribution Oil Transformer follows true ONAN rules. It uses top-quality silicon steel sheets in the core to keep energy loss small. The unit meets all national energy-saving rules. The transformer's key performance parameters are as follows: the no-load loss is 680 W, while the load loss measures 5410 W (or 5150 W under specified conditions). The no-load current stands at 0.8%, and the short-circuit impedance is rated at 4%. This model serves perfectly in city or village networks that need steady temperature control without extra machines.
ONAF starts with the same natural oil flow as ONAN. The big difference appears outside. Electric fans blow air directly over the radiators. Sensors watch the oil temperature. When the heat rises above a set point, the fans turn on by themselves. Extra air movement pulls heat away much faster. This setup keeps the transformer safe even during heavy work or very warm days.
This mixed method gives higher power rating in the same size tank compared to pure ONAN units.
ONAF transformers fit best where summer heat stays high or where daily power use jumps up and down. Factories, solar farms, and busy city substations often need this extra cooling power. The fans give quick help exactly when the load peaks, so the equipment stays inside safe temperature limits.
ONAN depends only on nature’s own forces. Oil moves because warm liquid rises and cool liquid falls. Air flows because warm metal makes the nearby air rise. Nothing mechanical helps. This pure passive way brings great dependability in calm settings. But ONAF keeps the natural oil loop but adds forced air on the outside. Fans start only when needed. The active airflow removes heat much faster, yet the system now has motors, switches, and wires that need checking.
ONAN models cost less to buy and almost nothing to run. No extra controls or power supply is required. Budget projects and places with steady load love this choice. However, ONAF models include fans, temperature sensors, and control boxes that increase both initial investment and long-term operational costs. However, this is justified by their improved capacity to manage dynamic load profiles.
ONAN units have fewer components that can fail. The corrugated oil tank is manufactured from high-quality cold-rolled steel plates on a dedicated production line, enhancing durability and reducing maintenance costs further. However, ONAF systems are more complex. The failure of fans or temperature controls can compromise cooling effectiveness, potentially leading to overheating if not addressed promptly.
ONAN transformers operate best in indoor settings or moderate climates where ambient temperatures remain within manageable limits for passive heat dissipation. However, ONAF units are engineered for outdoor installations or extreme climates. Their fan-driven heat rejection makes them suitable where ambient conditions or load fluctuations push thermal boundaries.
ONAN systems are cost-effective and dependable under predictable load conditions. However, their thermal capacity is inherently limited by passive convection, making them less suitable for high-demand or thermally volatile applications.
ONAF offers greater performance under load stress due to active airflow but introduces complexity via mechanical components that require periodic inspection and potential replacement. This added complexity must be weighed against performance requirements.
Choose ONAN-cooled systems when the installation environment is thermally stable, loads are consistent, and minimizing maintenance is a priority. Small town networks, schools, and office buildings often fit this picture.
Choose ONAF when summer heat is strong or when daily power use rises and falls a lot. Solar plants, steel factories, and busy city stations usually need the extra fan help.
S11 500kVA 10kV 400V Silicon Iron Core Distribution Transformer exemplifies ONAN efficiency through its silicon iron core structure designed for minimal energy loss. Fully compliant with national energy efficiency standards, it supports stable output across various distribution settings with high reliability and minimal noise.
The S11-M-1000/10 ONAN Copper Aluminum type Three Phase Fully Sealed Distribution power transformer combines robust structural sealing with passive ONAN cooling. It is suitable for urban distribution networks requiring low noise and high reliability. It features a sealed tank that minimizes oil leakage and extends equipment life while ensuring silent operation.
Q1: Can an ONAN transformer be upgraded to use ONAF cooling later?
A: Many models allow fans to be added later, but the radiator size and original heat design must have enough extra capacity.
Q2: What are the typical maintenance requirements for an ONAN transformer?
A: Regular oil tests, simple visual checks, clean radiators, and insulation measurements keep it healthy. No moving parts mean almost no mechanical trouble.
Q3: How does SHENGTE ensure efficiency in its ONAN transformers?
A: SHENGTE uses high-grade silicon steel, vacuum drying, smart winding layout, and improved oil paths to reach top energy-saving levels while keeping cooling fully natural.
