Electrical Transformer | Main Parts | Construction Of Electrical Transformer

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In this tutorial, I am describing one of the most important topics- what is an Electrical Transformer? with transformer construction and its main parts.

Also, I will add the functions of each part of the Transformer. So, it will make you understand easily.

Let’s study of the transformer in detail.

What is Electrical Transformer?

The basic definition of a transformer-

An electromagnetic device which is used for step up or step down the voltage level with respect to increasing or decreasing current level at constant frequency. This device called as Electrical Transformer.

Sometimes, an electrical transformer is called an Electrostatic device.  Because, it doesn’t consist of removing apart.

Here are listing some important points about the transformer.

  • The electrical connection does not occur in the transformer, only the magnetic connection occurred.
  • It works on a principle of Faraday’s Laws of Electromagnetic induction.
  • It requires and works only the AC voltage source. And AC source helps to generate the magnetic flux in the electromagnetic field.
  • It is a protective device by regulating (raising or lowering) voltage in an electrical power system.
  • The main function transformer is to transform the power from one circuit to another circuit at a constant frequency.
  • The transformer is more power-efficient and has very low transformer losses as compared to other electrical machines.
  • The generating power in the transformer is always measured in KVA rating, not kW.

What is the Construction of the Transformer?

The transformer is made of laminated iron core and steel strips. Core laminations consist of thin metal strips of insulated metal.

These laminations are insulated by a coat of varnishes or papers and wrap around the limb.

You can easily understand the following figure.Electrical Transformer (Basic Diagram)

It consists of two types of windings such as primary winding and secondary winding. These windings are separate and made by an electrical copper coil (number of turns).

AC voltage source is provided to the primary winding and load is connected to the secondary winding.

We were already discussing, the transformer winding is not electrically connected to each other, but it is magnetically connected.

The main function of the core to support the winding and to provide a low reluctance path for flowing magnetic flux whose maybe a flowing useful flux.

What are the Main Parts of a Transformer?

Several parts of the transformer are given different function with the works as follow.

  1. Laminated Iron Core
  2. Transformer Winding
  3. Insulating Material
  4. Tap Changer
  5. Transformer Tank
  6. Oil Conservator Tank
  7. Breather
  8. Buchholz Relay
  9. Bushing
  10. Cooling Tube and Radiator
  11. Explosion Vent

Let’s study of each part one by one.

1. Laminated Iron Core

The transformer’s core is made up of iron or silicon steel or ferromagnetic materials.

The iron core made of thin metal strips and lamination insulated by a coat of varnishes or papers. Each metal strip has a thickness near about the o.5mm.

In the below figure, you can see the number of metal strips connected to each other with the lamination layer and form a single core.

 Laminated Iron Core

Basically, ‘L’ and ‘E’ shaped laminations are used in different types of transformer. In the core type transformer, ‘L’ or ‘U’ shaped lamination is used.

Lamination of core type transformer

And shell types transformer ‘E’ or ‘I’ shaped lamination is used.Lamination of shell type transformer

This core lamination helps to reduce the eddy current loss and hysteresis loss. And It provides a low reluctance path and high permeability for the flux in the magnetic circuit.

2. The winding of the Transformer

The transformer winding is consists of several turns of the copper coil. It is wrapped around the limb or core with the lamination.

These windings laminated by the insulation coating because it prevents the short circuit condition.

On the basis of supply two types as

  • High voltage winding
  • Low voltage winding

Simply two types of winding are used as

  • Concentric types winding
  • Sandwich types winding

I. Concentric types of Winding:

Concentric types of windings are generally used in core types of transformer. It contains the only single path for mutual flux (Φ).  And theses flowing flux are equally distributed on the side limbs of the core.

The single flux path is shown in the following figure.

Concentric types of winding consist of various kinds of winding like,

  • Helical types winding
  • Disc types winding
  • Core types winding

In these core types of the transformer, windings are surrounded by the core. So, it requires a huge amount of copper coil and laminated materials.

II. Sandwich types of the Winding:

Sandwich types of winding are used in shell-type transformers. In a shell-type transformer, the primary and secondary winding is placed on the central limb.

This central limb carries two flux paths (mutual flux and leakage flux) in the magnetic circuit.Shell type transformer (Types)

You can see the above diagram, in shell types of the transformer, the core surround by the winding.

Read more details: Core Type Transformer vs Shell Types Transformer

3. Insulating Material

In the transformer, insulating materials rely on their voltage rating. Different types of insulating materials are used in the transformer.

These insulating materials maybe a transformer oil,  insulating paper, wood, the insulating glass material, tap changer insulating coil from grounding, etc.

4. Tap Changer

Tap changer to regulate supply voltage or load and maintain both conditions by changing the variable turn.

The tap changer is easily removed from the first turn and connects to the next turn ratio. Tap changers can occur on the primary side or secondary side.

Generally, a tap changer use in the high voltage winding side because it reduces load current.

Classification of Tap Changer –

It is classified into two following category,

  • No-load tap changer
  • On-load tap changer

5. Transformer Tank

The transformer tank is a cylindrically shaped tank. It is made of steel metal with a high thickness. Core and transformer winding is placed in the transformer tank.

The transformer tank is needed to store the oil especially mineral oil. This oil provides insulation and cooling to the transformer winding.

6. Oil Conservator Tank

The oil conservator tank looks like a rectangular tank. It stores the extra oil and directly connected with the transformer tank.

The oil conservator tank is played an important role in the transformer.

The purpose of the conservator tank is to protect the expansion of oil in the main tank of the transformer. The oil is used in the transformer for two purposes-

  • Insulation
  • Cooling

When the oil level reduces due to losses or leakage, the conservator will be delivering oil to the transformer. Thus, It acts as reservoir oil.

7. Breather

The breather is connected with the conservator tank. It is a cylindrical vessel which filled with blue color silica gel.

They have two purposes – to remove the moisture from the air and to have the capacity to absorb the moisture in a transformer.

It plays a role to act as the air filter and provide free moisturizing air to the conservator tank.

8. Buchholz Relay

Buchholz relay is a protective device that is oil and gas-operated the relay. It is connected to the main transformer tank and conservator tank.

When the internal fault occurs in the transformer due to leakage flux, insulation core, core connection, breakdown core, etc. by producing excess heat.

This excess heat decomposes oil in the transformer and gas bubbles formed. Gas bubbles flow in the upward direction to the conservator and collected in the relay.

Buchholz relay is a fault detected by the amount of nature of gas and oil level in a transformer.

During several fault conditions, an alarm is alert then this command send to the circuit breaker and isolates the transformer.

9. Bushing

The bushing is an insulating device that is made up of porcelain materials. The terminal of the bushing is provided a path of the conductor to the transformer tank.

With the help of the terminal, the transformer gives and provides the supply to another system.

In the transformer, two types of bushing are mostly used- high voltage (HV) bushing and low voltage (LV) bushing. It relies on voltage ratings may be high voltage or low voltage.

10. Cooling Tube and Radiator

The cooling tube is necessary for maintaining the temperature and circulating cooling coil in the transformer.

And the radiator is connected with the transformer tank. It is also made of a number of metal strips or pipes.

Both the cooling tube and the radiator provide the same function in a different way. When losses occur in the transformer, heat is produced.  This heat absorbs by the cooling tube and radiator in the form of cooling systems.

It is divided into two types of cooling systems.

  • Natural cooling system
  • Forced cooling system

In the natural cooling system, a cooling tube and radiator are used. And In the forced cooling system, we can connect the extra air fan to the transformer.

11. Explosion Vent

The explosion vent is located at the topmost position on the transformer.  The conservator tank is directly connected to the explosion tank with the help of a pipe.

The main purpose to prevent damage transformer oil tank by expelling boiling oil during an internal fault. And it is necessary to remove heated oil (in the form of gas) in the transformer.

This explosion tank use only for emergency purposes. It mostly works when a breather and Buchholz relay will not doing work properly.

These eleven main important parts of transformers are covered with the help of the tutorial.

If you are interested more about to learn practically and building projects, here is the listing of the topmost challenging ideas for the Electrical Engineering Project based on Transformer.

Related read the following article:

Ready for online test:

If you are ready to give the online quiz, you can directly join the Electrical Transformer Quiz.


Let me know if you have any queries, you can share in the comment section.

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41 thoughts on “Electrical Transformer | Main Parts | Construction Of Electrical Transformer”

  1. how to decrease voltage drop of transformer.
    which type of lamination use for core assembly.(best material)
    which type of coating used on lamination

  2. – By using the winding
    Provide the high resistivity and low permeability materials
    By using the tap changer

    – Silicon steel, Amorphous metal, Ferrite ceramic.
    Mostly the Silicon steel provides the high electrical resistivity.

    – The lamination which depends on the construction types of the transformer.
    Lamination Maybe ‘E-I’,’E-E’,’L-L’,’U-I’ Types.
    E-I core laminated transformer construction is mostly used in transformers.

  3. Hey Dipali, I have seen your tutorial. I want to suggest to you one thing your theoretical concept is remarkable.

    But if you provide video tutorials as well then it’s very easy to understand (especially in the case of PLC languages and MATLAB).Great work.


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