How are large transformers cooled?

Large transformers are cooled primarily by immersion in oil. This method is effective because oil has excellent thermal conductivity, allowing it to efficiently transfer heat away from the transformer's components. The immersion of the transformer in oil not only provides cooling but also acts as an electrical insulator, thus enhancing the safety and operational reliability of the transformer. The oil circulates through the unit, absorbing heat generated during operation and transferring it to a cooling mechanism, typically a radiator or heat exchanger, where it can dissipate into the surrounding environment.

Other cooling methods, such as air circulation by fans, while used in some contexts, may not be sufficient alone for larger transformers due to their increased heat generation. Free flowing water can also be used for cooling in certain applications but is less common in transformer cooling due to potential contamination and operational challenges. Stationary air conditioners could theoretically provide cooling, but they are not a standard practice for large transformers, which are typically designed with oil cooling systems in mind to manage their specific thermal characteristics effectively.