Transformer Cooling Methods
Heat is one of the most common destroyers of transformers. Operation at only 8 ºC above the transformer rating will cut transformer life by 50%. Heat is caused by internal losses, due to loading, high ambient temperature, and solar radiation. It is important to understand how your particular transformers are cooled and how to detect problems in the cooling systems. ANSI and IEEE require the cooling class of each transformer to appear on its nameplate. Cooling classifications, with short explanations, appear in sections 3.3 and 3.4. The letters of the class designate inside atmosphere and type or types of cooling. In some transformers, more than one class of cooling and load rating is indicated. At each step of additional cooling, the rating increases to correspond with increased cooling. Note that the letter “A” indicates air, “FA” indicates forced air (fans), “O” indicates oil, “FO” indicates forced oil (pumps), “G” indicates some type of gas, and “W” indicates there is a water/oil heat exchanger.
Transformer Cooling Methods Dry-type transformer maintenance summary