What is the importance of cooling in a transformer?

Transformers operate at high temperatures, which causes energy losses in the transformer. The energy losses in a transformer are due to Copper losses(I²R). if transformer temperature is increased up to threshold value their efficiency is disturbed. Cooling plays an important role in optimizing transformer performance. Effective cooling ensures that the transformer operates at its Maximum efficiency. When temperatures of the transformer are controlled, it increases the lifespan of transformers.

10 Types of Electrical Transformers with Usage 2024

we used a different method to cool down the transformer when their temperature are increased. The method of cooling depends on the type of transformer and its working condition. Some other factors play an important role when selecting of cooling method. The different types of cooling methods of transformers including

Factors to consider when selecting a cooling method for transformers

Regulatory Standards
Transformer Type and Capacity
Maintenance Requirements
Environmental Conditions
Load Variations
Energy Efficiency
Safety and Reliability

10 Method of cooling Transformer (Dry + Forced)

Dry Type Transformer

Self-air cooled Transformer
Air blast-cooled Transformer(AB)

Oil Immersed Type Transformer

Oil-immersed, self-cooled Transformer(ONAN)
Oil-immersed, self-cooled & air-blast Transformer(ONAB)
Oil-immersed, water-cooled Transformer
Oil-immersed, forced oil-cooled Transformer
Oil-immersed, self-cooled & water-cooled Transformer
Oil-forced, air-forced cooled Transformer (ONAF)
Forced oil, water-cooled Transformer
Forced oil, self-cooled Transformer

10 Method of cooling Transformer (Dry + Forced)

15 Main parts of the Electrical Transformer

Self-air cooled Transformer(1.5MVA- 3MVA)

The capacity of a Self-air-cooled transformer is 1.5MVA to 3MVA. This type of transformer is cooled down by atmospheric air. These transformers are used in schools, hospitals, shops, shopping centres etc. Self-air cooled transformer protects against humidity or resistance. The transformer core or coil is not enclosed in a container. The low-voltage instrument transformer is based on the self-air-cooled transformer.

Air blast-cooled Transformer(15 MVA - 35 MVA)

To Cool down the transformer, Air is circulated with the help of a blower from bottom to top is called an Air blast-cooled transformer. This type of transformer is enclosed in a metal box with a capacity between 15 MVA to 35 MVA.

Oil-immersed, self-cooled Transformer( UPto 30 MVA)

This type of transformer is also called ONAN(Oil Natural Air Natural). It's widely used because of its simple working operation. The manufacturing capacity of this type of transformer is up to 30MVA. This type of transformer is enclosed in a metal tank in which the transformer core and windings are immersed in insulating oil. In this type of transformer oil is circulated in the transformer naturally. The small oil-immersed self-cooled transformer surface is plane but the large transformer surface is corrugated with external tubes. we also used radiators on large-capacity transformers. The main principle of this type of transformer is the convection method.

Oil-immersed(self-cooled & air-blast)Transformer(up to 60 MVA)

Large transformers use combinations of self-cooled and air blast methods. The construction of this type of transformer is like an oil-immersed self-cooled transformer. The main difference is just we used blowers with the main tank. This circulating air provides very fast cooling for the transformer. The motor of the blowers is controlled with a thermostat automatic method. The thermostat on the motor circuit and operate the blowers. when the temperature reaches its normal state, the thermostat senses this temperature and turns off the motor.

Oil-immersed, water-cooled Transformer( Upto 500MVA)

Large self-cooled transformers are expensive, due to this we used an oil-immersed water-cooled method. The core and windings are totally immersed in insulating oil, but we circulate the water in the external tubes. This type of transformer is used in the high voltage transmission lines. we prefer this method where water is available in excess quantity, and we achieve the head of water easily. The main disadvantage of this system is we need a water tube system in the transformer. Due to the leakage of water tubes, the insulation of oil deteriorates.
Method of Three-Phase Transformer Connection

Oil-immersed forced oil-cooled Transformer

In this type of method, both the core and winding of the transformer are immersed in oil. A pump is also used to circulate the oil in external tubes, For this purpose, we use a pressure system that circulates the oil in tubes to provide efficient cooling. In this method, we also used heat exchangers like automotive radiator type which consists of oil-to-heat exchanger tubes. The pump rotates the oil quickly up to down which cools down the transformer temperature quickly.