Transformer Cooling and Methods of Cooling | Bowers Electrical Ltd (2024)

Every month we share an industry word or acronym to translate some of the jargon from the electrical engineering world!

This month’s topic is: Transformer CoolingTransformer Cooling and Methods of Cooling | Bowers Electrical Ltd (1)

Transformer Cooling and Methods of Cooling | Bowers Electrical Ltd (2)

Transformer Cooling and Methods of Cooling:

Cooling of transformers is the process by which heat generated in the transformer is removed so that the transformer can be performing to the best efficiency.

Heat is generated in the transformer while running and is produced by the excitation of the windings and core. If the temperature of the transformer continues to increase rapidly, it results in the degradation of the various parts, specifically the insulation materials, and could lead to the failure of the equipment.

Cooling methods were created to compensate for the heat and control the transformer’s temperature rise. The various coolants used for the cooling purpose of the transformer are air, synthetic oils, mineral oils, gas, and water.

Depending on the cooling methods used, transformers can be divided into two types: dry and oil type.

Dry vs Oil Type Transformers:

Oil and air are the primary cooling materials used in a transformer.

Dry-type transformers, are normally cooled by air. The following two transformer cooling methods are adopted in dry-type transformers.

  • Air Natural (AN) cooling – Cooled by surrounding air. Heat transfer by natural air convection.
  • Air Force (AF) cooling – Forced air circulation using fans and blowers.

Oil-type transformers are cooled using oil-air cooling or oil-water cooling method. There is a wider range of cooling methods for oil-type transformers.

  • (Mineral) Oil Natural Air Natural (ONAN)– The core and coils are cooled by surrounding in oil. Heat transfer of oil by natural air convection.
  • (Non-Mineral) Oil Natural Air Natural (KNAN)– The core and coils are cooled by surrounding in synthetic oil. Heat transfer of oil by natural air convection.
  • Oil Natural Air Forced (ONAF)– Cooled by surrounding in oil. Forced air circulation using pumps, fans and blowers.
  • Oil Forced Air Forced (OFAF)– Forced oil and air circulation using fans and blowers.
  • Oil Natural Water Forced (ONWF)– Cooled by surrounding in oil. Forced water circulation using heat exchanges.
  • Oil Forced Water Forced (OFWF)– Forced oil and water circulation using oil-to-water heat exchanges.

Transformer cooling class letter descriptions:

Transformer Cooling and Methods of Cooling | Bowers Electrical Ltd (3)

Bowers Electricals standard distribution transformers use ONAN or KNAN cooling method. You can view our standard transformers here.

Transformer Cooling and Methods of Cooling | Bowers Electrical Ltd (2024)
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