Types, Parts, and Application of Distribution Transformers

Types, Parts, and Application of Distribution Transformers

Distribution Transformers

There are several sorts of transformers used in commercial and residential areas. A distribution transformer is one of the widely used transformers for power distribution. This post will check out the various types, applications, and parts of distribution transformers.

Types of distribution transformers

● Single-phase transformer

● Pad-mounted transformer

● Three-phase transformer

● Pole-mounted transformer

● Underground transformer

These are the different types of distribution transformers. They differ from each other by their sizes. 

Parts of a distribution transformer

The distribution transformer has two sides – one side is a primary side containing high tension bushing, and the other side is a secondary side containing low tension bushing. 

Let’s check out the components of distribution transformers in detail:


The hidden and vital part of the transformer is the core inserted in the main transformer tank. 

The primary function of the transformer is to hold high-tension and low-tension winding. It links magnetic flux between the windings. It also provides a low reluctance path.

This transformer core is made from stepped core Laminated Silicon Steel Sheet or Cold Rolled Grain Oriented Steel.


There are two types of bushing used – High tension bushing and Low tension bushing. These are three-phase high tension bushing that lies on the primary side of the transformer. These are made from porcelain.

High tension Bushing is a hollow electrical insulator that can withstand 11 kV pressure. A bushing is used to pass the electrical conductor through the conducting barrier of the transformer tank without making electrical contact with it.

Low tension bushing lies on the secondary side of the transformer. It has four terminals that are marked as 2W, 2U, 2V, and 2N. Here U, V, and W represent three different phases, and 2 represents secondary.

Cooling Fins

The appearance of these cooling fins is like blades. It is also known as the radiator of the transformer.

It is mainly a hollow plate through which oil can easily flow when the load increases, then the heat produced inside the core is also increased. 

Then the oil inside the transformer helps to radiate the heat by flowing through these fins. The surrounding air cooldowns the oil by flowing through the gaps of the fins.

It increases the effective area of the tank. For the larger size of the transformer, the heat production is more so the number of fins will be more. A separate fan is used for cooling by the air force.

Explosion Vent

This explosion vent is made from an Aluminium diaphragm, and this vent is a bent pipe. An explosion vent prevents damage to the transformer tank.

It prevents damage by releasing excessive pressure generated inside the transformer by heating.

Oil temperature gauge

It can also be known as a thermometer. The minimum temperature it can measure is -5 degrees Celsius, and the maximum temperature it can measure is -95 degrees Celsius. The standard or average temperature it can measure is -80 degrees Celsius. 

This gauge is used to measure the transformer oil. It is placed on the conservator tank.

Conservator tank

The conservator tank is used to provide adequate space for oil expansion inside the transformer. The tank also acts as a reservoir for the transformer oil.


Two vertical pipes are directly fitted with the main transformer tank, and the right-angled bent pipe is fitted with a breather, and the topmost pipe is for the oil inlet purpose.

Lifting eye

The drilled plate is fitted with the main transformer tank. These are called the lifting eye. It is used to lift and transform the transformer.

Oil Inlet valve

It is provided on the top level of the main transformer tank. It is used to fill the transformer oil into the tank.

Oil Outlet valve

Since it is an outlet valve, the oil is left out from this valve.


There are two types of core construction – Core type construction and Shell type construction. Here Core type Construction is mainly used. The high tension and low-tension terminals are internally connected with the high-tension and low-tension windings of the transformer. 

The phase windings are placed at the limb of the core. The high tension and low-tension windings are placed on the same limb to consume less space and better flux linkage in the windings. 

The high-tension windings require more insulation, as the low-tension windings require less insulation. The low-tension windings are placed nearest to the core, and high-tension windings are placed on the low-tension windings for better insulation. 

The high-tension winding is connected to delta having only three-phase terminals, and the low-tension winding is connected to a star having three-phase phases with neutral terminals. This connection is called Dy11.

The transformer acts as a container for the core and windings and is filled with container oil. The transformer oil plays a vital role in the distribution transformer. 

The transformer oil is the paraffinic-based mineral oil used for cooling and providing extra insulation for the windings depending on the time and continuous use of the transformer oil. The oil quality gets spoiled, and after a certain period, the oil should replace it.

Application of distribution transformers

● The distribution transformer is mainly used for step-down purposes.

● It is used to lessen the voltage and current level according to our needs.

● A distribution transformer is otherwise known as a safety level transformer. Distribution transformer manufacturers India means the supply is given to consumer, domestic, and industrial from the distribution transformer.

● It is used in the distribution network for lower voltages.

● It is used in distribution stations, also for industrial and domestic purposes.

● The rating availability is 11Kv, 6.6Kv, 3.3Kv, 440V, 230V.

● Distribution transformers are used for rating but 200 MVA.

● The distribution transformer is smaller in size.

● They are designed for 50-70 % efficiency.

● Distribution transformer manufacturers in India consider distribution transformers as all-day efficiency transformers.

● The output ratio in kilowatt-hour (kWh) KR watt-hour (Wh) to the input in kWh or What of a transformer over 24 hours.

● Iron losses happen for twenty-four hours, and copper losses are supported by the load cycle.

● Load fluctuations are very high.

● Operated at load but full load as load cycle fluctuates.

● It is time-dependent.

● The flux is lower in the distribution transformer.

● They are used as end-user connectivity.


From the above article, we have gained complete knowledge about the types, parts, construction, and uses of the distribution transformer. Distribution transformer manufacturers in India take the primary use of distribution transformers for step-down purposes.

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