- Radiator in Transformer Definition: A radiator in a transformer is defined as a component that helps cool the transformer by dissipating heat from the transformer oil.
- Heat Generation: When a transformer operates, current through its windings produces heat, increasing the temperature of the transformer oil.
- Importance of Cooling: Controlling the temperature of the oil is crucial to extend the transformer’s capacity and prevent overheating.
- Working Principle: The radiator increases the surface area to dissipate heat, aiding in efficient cooling of the transformer oil.
- Operation and Enhancement: Radiators cycle warm oil from the transformer through their fins to cool it down, and this process can be boosted with fans or oil pumps.
Function of Radiator
When a transformer is energised, its core losses produce heat. Under load, current also produces winding and stray losses. The insulating liquid carries this heat from the active parts to the tank and cooling surfaces, so the temperature of the transformer oil rises. The allowable top-oil and winding hot-spot temperatures are part of the transformer’s thermal design. Keeping the transformer insulating oil within those limits protects insulation life. The radiator of transformer increases the oil-to-air heat-transfer area and helps the unit meet its stated cooling-class rating. It does not by itself authorise loading above the nameplate rating. This is the basic function of radiator on a liquid-filled power transformer.
Many larger liquid-filled transformers use detachable pressed-steel radiators with isolating valves. Smaller distribution units may instead use radiators or corrugated cooling surfaces that are welded into the transformer tank. The working principle of radiator is heat transfer through added surface area. Detachable units may be shipped separately where transport dimensions require it. Their flanges and the tank radiator valves are sealed with gaskets and blanking plates for transport. The exact arrangement depends on the manufacturer and transformer design.
Assembling and Mounting of Transformer Radiator
Only trained personnel should mount transformer radiators, using the manufacturer’s instructions for that unit. Thin pressed-steel panels can be damaged during lifting, and damaged panels or gasket faces can leak. Keep every open flange clean and dry to prevent moisture or dirt entering the transformer. If internal flushing is required, use compatible transformer insulating oil and the oil-processing method specified by the manufacturer.
Before assembly, de-energise and isolate the transformer, release tank pressure as specified and confirm that the radiator valves are closed. Mount one clean, dry radiator at a time. Remove each blanking plate only when the matching flange is ready. Inspect the gasket face, fit the specified gasket and tighten the flange fasteners to the manufacturer’s sequence and torque. Do not reuse a damaged gasket.
After all radiator units are mounted, fill and vent them only under the transformer’s approved oil-handling procedure. A common arrangement admits oil through the bottom valve while air is released at the top plug, but the required sequence, pressure and vacuum treatment vary by design. Oil should enter the transformer radiator without aeration. Close the air-release plug after bubble-free transformer insulating oil appears, then place both valves in the specified service position. Complete the required leak checks, oil processing, oil-level checks and electrical tests before energising.
Operation of Transformer Radiator
In a natural-oil cooling circuit, warmer, less dense oil rises to the top of the main tank and enters the radiator through the upper connection. Heat passes through the radiator walls to the surrounding air. The cooler, denser oil returns through the lower connection, sustaining natural circulation while the transformer produces losses. Fans provide forced-air cooling in a designed ONAF stage. Oil pumps provide forced or directed oil circulation in transformer designs rated for those cooling classes. Fans or pumps must not be added or used to claim extra loading unless the transformer manufacturer has assigned the corresponding rating.
