Transformer Cooling Method

                                               Transformer Cooling Method

(1) Air Natural Type transformer Cooling :

•  This method is used for small dry type transformer. The air in the surrounding vicinity of the transformer is used for cooling. This method is suitable for transformer up to a rating of 25 KVA 

(2) Air Forced Type Transformer Cooling : 

• This cooling method also is suitable for the dry type transformer of slightly higher ratings. The air is forced upon the tank surface to increase the rate of heat dissipation.
• Fans are turned on automatically to facilitate forced air cooling whenever the winding temperature rises beyond the permissible limit.

(3) Oil Natural Air Natural Type Cooling :

• This type of cooling is used for oil filled transformer up to a rating of about 30MVA. As the oil in the tank gets heated due to heated up core and winding it ( oil ) flows upwards and the cold oil comes down as per the principle of convection.
• The heat is transferred from various parts of the transformer to the oil and the heated oil is cooled by the natural air.
• It is possible to increase the cooling are by providing the cooling tubes.

(4) Oil Natural Air Forced Cooling :

• In this method. the transformer of heat from various parts of a transformer takes place naturally as explained for the O.N.A.N. type cooling.
• However the hot oil is now cooled by means of fans mounted near the transformer 
• The forced air from the fans is directed to the cooling tubes to increase the rate of cooling.
• A thermostat is used to automatically sense the temperature of oil and winding and turns the fans on when it increase above the permissible limit.
  

(5) Oil Forced Air Forced Cooling :

• This type of cooling is  preferred for the transformer of ratings above 60 MVA.
• A separate cooler is mounted away from the transformer tank . This cooler is connected to the transformer with pipes at the bottom and top.
• The Oil is circulated from the transformer to the cooler with the help of an oil pump. This oil is then subjected to forced air cooling with the help of fans installed the cooler.
• The O.F.A.F. type of cooling is used for the big transformer used at the substations and Power stations.
  

(6) Oil Forced, Water Forced Cooling :

• O.F.W.F. type cooling for large transformer. This type of cooling needs a heat exchanger.
• Inside the heat exchanger the heat from thr oil is transformer to the cooling water.
• The cooling water is taken away and cooled in separate coolers. The oil is forced to circulate through the heat exchanger by using a pump.
• This type of cooling is useful for transformer having ratings of few MVA ( generating transformer. )