Parts of a Power Transformer

Updated on May 29, 2018
goodnews11 profile image

Electrical and Automation Engineer . Specialized in LV Switchgear Design and process automation

What Is a Transformer?

A transformer is an electrical device that transfers electrical energy from one circuit to another by electromagnetic induction (also called transformer action). It is used to step up or step down AC voltage.

Components of a Transformer

Basic Parts of a Transformer

These are the basic components of a transformer.

  1. Laminated core
  2. Windings
  3. Insulating materials
  4. Transformer oil
  5. Tap changer
  6. Oil Conservator
  7. Breather
  8. Cooling tubes
  9. Buchholz Relay
  10. Explosion vent

Of the above, laminated soft iron core, windings and insulating material are the primary parts and are present in all transformers, whereas the rest can be seen only in transformers having a capacity of more than 100KVA.

Don't have the patience to read? Watch the video.

Core

Core

The core acts as support to the winding in the transformer. It also provides a low reluctance path to the flow of magnetic flux. It is made of laminated soft iron core in order to reduce eddy current loss and Hysteresis loss. The composition of a transformer core depends on such as factors voltage, current, and frequency. The diameter of the transformer core is directly proportional to copper loss and is inversely proportional to iron loss. If the diameter of the core is decreased, the weight of the steel in the core is reduced, which leads to less core loss of the transformer and the copper loss increase. When the diameter of the core is increased, the vise versa occurs.

Why Are Windings Made of Copper?

  • Copper has high conductivity. This minimizes losses as well as the amount of copper needed for the winding (volume & weight of winding).
  • Copper has high ductility. This means it is easy to bend conductors into tight windings around the transformer's core, thus minimizing the amount of copper needed as well as the overall volume of the winding.

Winding

Two sets of winding are made over the transformer core and are insulated from each other. Winding consists of several turns of copper conductors bundled together, and connected connected in series.

Winding can be classified in two different ways:

  1. Based on the input and output supply
  2. Based on the voltage range

Within the input/output supply classification, winding are further categorized:

  1. Primary winding - These are the winding to which the input voltage is applied.
  2. Secondary winding - These are the winding to which the output voltage is applied.

Within the voltage range classification, winding are further categorized:

  1. High voltage winding - It is made of copper conductor. The number of turns made shall be the multiple of the number of turns in the low voltage winding. The conductor used will be thinner than that of the low voltage winding.
  2. Low voltage winding - It consists of fewer number of turns than the high voltage winding. It is made of thick copper conductors. This is because the current in the low voltage winding is higher than that of high voltage winding.

Input supply to the transformers can be applied from either low voltage (LV) or high voltage (HV) winding based on the requirement.

Insulating Materials

Insulating paper and cardboard are used in transformers to isolate primary and secondary winding from each other and from the transformer core.

Transformer oil is another insulating material. Transformer oil performs two important functions: in addition to insulating function, it can also cool the core and coil assembly. The transformer's core and winding must be completely immersed in the oil. Normally, hydrocarbon mineral oils are used as transformer oil. Oil contamination is a serious problem because contamination robs the oil of its dielectric properties and renders it useless as an insulating medium.

Parts of the Transformer

Conservator

The conservator conserves the transformer oil. It is an airtight, metallic, cylindrical drum that is fitted above the transformer. The conservator tank is vented to the atmosphere at the top, and the normal oil level is approximately in the middle of the conservator to allow the oil to expand and contract as the temperature varies. The conservator is connected to the main tank inside the transformer, which is completely filled with transformer oil through a pipeline.

Breather

Breather

The breather controls the moisture level in the transformer. Moisture can arise when temperature variations cause expansion and contraction of the insulating oil, which then causes the pressure to change inside the conservator. Pressure changes are balanced by a flow of atmospheric air in and out of the conservator, which is how moisture can enter the system.

If the insulating oil encounters moisture, it can affect the paper insulation or may even lead to internal faults. Therefore, it is necessary that the air entering the tank is moisture-free.

The transformer's breather is a cylindrical container that is filled with silica gel. When the atmospheric air passes through the silica gel of the breather, the air's moisture is absorbed by the silica crystals. The breather acts like an air filter for the transformer and controls the moisture level inside a transformer. It is connected to the end of breather pipe.

Tap Changer

Tap Changer

The output voltage of transformers vary according to its input voltage and the load. During loaded conditions, the voltage on the output terminal decreases, whereas during off-load conditions the output voltage increases. In order to balance the voltage variations, tap changers are used. Tap changers can be either on-load tap changers or off-load tap changers. In an on-load tap changer, the tapping can be changed without isolating the transformer from the supply. In an off-load tap changer, it is done after disconnecting the transformer. Automatic tap changers are also available.

Cooling Tubes

Cooling tubes are used to cool the transformer oil. The transformer oil is circulated through the cooling tubes. The circulation of the oil may either be natural or forced. In natural circulation, when the temperature of the oil rises the hot oil naturally rises to the top and the cold oil sinks downward. Thus the oil naturally circulates through the tubes. In forced circulation, an external pump is used to circulate the oil.

Buchholz Relay

The Buchholz Relay is a protective device container housed over the connecting pipe from the main tank to the conservator tank. It is used to sense the faults occurring inside the transformer. It is a simple relay that is operated by the gases emitted during the decomposition of transformer oil during internal faults. It helps in sensing and protecting the transformer from internal faults.

Explosion Vent

The explosion vent is used to expel boiling oil in the transformer during heavy internal faults in order to avoid the explosion of the transformer. During heavy faults, the oil rushes out of the vent. The level of the explosion vent is normally maintained above the level of the conservatory tank.

More About Transformers

I have written a series of articles to help the reader understand power transformers. I've listed two here, and if you are interested in finding more, you can find them by clicking on my author profile at the top of this article.

How Does a Transformer Work - Basic working principles of the transformer.

Questions & Answers

    Comments

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      • profile image

        Dinesh Kumar 

        3 weeks ago

        Dg and transformer rating from low to high explain and DG rating depends upon what factor in company and industries,home , residential complex etc ..

      • profile image

        JSV 

        4 weeks ago

        Thanks for your article, Sir.

      • profile image

        MAAN Shahzada 

        5 weeks ago

        Thanks sir for me help

      • profile image

        ishrat gull 

        6 weeks ago

        thanks, sir

      • profile image

        Nahabwe Bruno 

        6 weeks ago

        Thanks for that helpful information

      • profile image

        Shweta Pandit 

        7 weeks ago

        Nice explanation...

        My question is what are the various insulating materials used in trasformer and for what purpose?

      • profile image

        Prakash.b 

        2 months ago

        Super notes

      • profile image

        Mahendra Patil 

        2 months ago

        Send to HT to LT voltage and current formula.

      • profile image

        salman 

        2 months ago

        nice explanation

        thnxxxxxx

      • profile image

        Ashish mundele 

        4 months ago

        Very nice explen sr.

      • profile image

        Dibya 

        4 months ago

        Please send electrical book

      • profile image

        Sundaraperumal 

        4 months ago

        Transformer

      • profile image

        Sai 

        4 months ago

        Give more information about the how the instrument in transformers are made up and some other things which are not in books

      • profile image

        Emmanuel Mba Santumah 

        4 months ago

        Thanks a lot, you are really ready to help. Great work.

      • profile image

        eldhose k shaju 

        4 months ago

        very much helpful information..thank you for your help...

      • profile image

        Parag 

        5 months ago

        Very Nice, simply understood about transformer operation

      • profile image

        Solomon 

        5 months ago

        Now i understand better,well done.

      • profile image

        pury 

        5 months ago

        well done

      • profile image

        Shaik Ali shabbeer 

        5 months ago

        Superb and nice

      • profile image

        Visi 

        5 months ago

        Nice

      • profile image

        prashanth kuamr 

        6 months ago

        Short answer and very nice

      • profile image

        Rakesh Kumar 

        6 months ago

        Very useful article and perfectly explained details of transformer. Which is easy to understand.

      • profile image

        RUTH AMANKWAH 

        6 months ago

        Well done,

        The arrangement and the simplification of the concept is understandable and meaningful for a certain standard.

      • profile image

        Nisha 

        6 months ago

        Easy to understand..

        U have any u tube channel..

      • profile image

        abidoye smuel 

        7 months ago

        this is a very good lecture

      • profile image

        Bharamana gouda 

        7 months ago

        Nice

      • profile image

        Kiran kumar 

        7 months ago

        Very a simple answer in transformer parts

      • profile image

        Dinesh 

        7 months ago

        Very use full to get the knowledge about transformer.thanks a lot.

      • profile image

        Anthony Opara 

        7 months ago

        Good lecture, I have learnt lot today

      • profile image

        Umesh Singh 

        8 months ago

        If we measure voltage between neutral and a phase, we'll get 220V.

        But if we measure the voltage between two phases say phase R and phase Y, we'll get nearly 400

        (√3 x 220), due to three phase.

      • profile image

        tej 

        8 months ago

        three phases are R,Y and B

        voltage between R and Y is 220

        voltage between Y and B is 220

        voltage between R and B is sum of ry and by is 440.

        it is ideally practically 220 to 240 volts in single phase

      • profile image

        Shaikh F.A 

        8 months ago

        Sir, I want to work in the field of transformer designing

        How can I?

      • profile image

        sareem deshmukh 

        8 months ago

        In the transformer each phase have 230V a transformer have three phase 230+230+230=690

        how does become 440V

        Why not come to 690?

      • profile image

        NAGARAJ 

        9 months ago

        Thanks u for sharing this post.

      • profile image

        nitin 

        10 months ago

        nice...

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        10 months ago from CHENNAI

        The primary function of the transformer is insulation. Apart from that it also acts as a coolant and arc suppressor also. When the temperature of the oil rises the hot oil naturally rises to the top and the cold oil at the top moves downward. (Natural Cooling) Evaporating point of transformer oil is above 200 deg. celsius. So it is a rare phenomenon.

        More: https://owlcation.com/stem/Cooling-of-transformers

      • profile image

        GAURAV KUMAR JHA 

        10 months ago

        OIL IS JUST US AS A COOLANT ,HEAT PRODUCED IN TRANSFORMER IS ABSORBED BY THE OIL THEN OIL GET EVAPORATE AND COMES OUT FROM CONSERVATOR.

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        10 months ago from CHENNAI

      • profile image

        Sunny 

        10 months ago

        Plz tell me something about oil function

      • profile image

        mahee 

        11 months ago

        Thank you very much for sharing your knowledge like this. it is very helpful to me to enhance my knowledge.

      • profile image

        Tirupati Transformers 

        11 months ago

        Thanks for sharing this post and make us the part of this epic post.

      • profile image

        Saddam hossain 

        12 months ago

        Can we say explosion vent another name PRD=Pressure Relief Device.

      • profile image

        Kishor chandegara 

        13 months ago

        Dear sir

        I don't no English language so please all information in Hindi language

      • profile image

        arun kumar verma 

        13 months ago

        sir , how can i make my career in transformer field

      • profile image

        kuldeep kumar 

        13 months ago

        who many temperature of winding and oil in transformer

      • profile image

        PURUSHOTTAM KUMAR 

        14 months ago

        Its topic my favourite topic so I'm very very thankyou

      • profile image

        Joginder pal 

        14 months ago

        Please taken to knowledge for transformer

      • profile image

        Srinu 

        14 months ago

        Thangs

      • profile image

        sadiq suhail abubakar 

        14 months ago

        Thank you very much sir,my que. Hare is that, what brought the change of windings of tranformer.

      • profile image

        vairachelvam 

        14 months ago

        Difference between kVA AND KW

        KVA

        transfprmer losses depents on voltage ang current (not in pf).so that we are mention in KVA

        KW

        motor losses depnts on load(pf) so that we are mention Kw

      • profile image

        SK 

        15 months ago

        It's awesome....

      • profile image

        Rj H.S.Meena 

        15 months ago

        Is there were 22 parts in the transformer?????????

      • profile image

        Nikunj 

        15 months ago

        Plz u tell me about motor concept

      • profile image

        manoranjan 

        15 months ago

        Deiffrsnce between kva and kw

      • profile image

        Frank mkony 

        15 months ago

        In like it

      • profile image

        SUMAN DEKA 

        15 months ago

        It is nice

      • profile image

        Nnamdi Onwuania 

        15 months ago

        A very useful information on transformer. Now is with me on it components and function. Assembly of it is very important. In de sense of avoiding likely problem that can erupt in de transformer when not properly installed.

      • profile image

        Firoz khan 

        16 months ago

        it is so helpfull web. thnx sir

      • profile image

        tamil 

        16 months ago

        Very usefull sir

      • profile image

        fs 

        16 months ago

        Sir,what's the process during transfer power one circuit to another circuit.....????

      • profile image

        saisaran 

        16 months ago

        what is the current value

      • profile image

        sonam (BHUTAN) 

        16 months ago

        Can u give more information about tabchanging

      • profile image

        Gorakh 

        16 months ago

        Thanks

      • profile image

        dileep 

        17 months ago

        thanks ur informaction

      • profile image

        Ashutosh Dubey 

        17 months ago

        Thank you.....Sir.

      • profile image

        Hassan Iqbal 

        17 months ago

        Information about tap changers is not enough, Can U explain it more precisely? please

      • profile image

        Hassan Iqbal 

        17 months ago

        It was helpful. Thanks

      • profile image

        NILONG 

        18 months ago

        Thank You and God bless!

      • profile image

        Prashant Kotkar 

        21 months ago

        thanks

      • profile image

        Habtamu kasaye 

        22 months ago

        It is really useful. thank you sir!

      • profile image

        shakeel 

        23 months ago

        why dont we make the core simply from 1 sinlge metal...is there any reason to use the cut to length parts like yoke, centre limb or side limb?

        kindly explain

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        2 years ago from CHENNAI

        Transformer can stepup voltage alone not power. Input power will be equal to the output power ( neglecting losses).

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        2 years ago from CHENNAI

        You are Welcome.

      • profile image

        jitendra gondaliya 

        2 years ago

        Thanks sir

      • profile image

        praveen 

        2 years ago

        thanks sir

      • profile image

        Shareef 

        3 years ago

        Use full information to me......thanks a lot.

      • profile image

        ashwini bidkar 

        3 years ago

        It is a presous information provide about transformer operation

      • profile image

        Raj 

        3 years ago

        wher is tpmo switch is used in the transformer.??

      • profile image

        AJAJ ANSARI 

        3 years ago

        It is very helpful for every students and teacher

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        3 years ago from CHENNAI

        @Manoj.

        When DC voltage is connected across the transformer terminals the constant flux will be produced. The current through the windings increases rapidly, overheating and thereby damaging the windings.

      • profile image

        manoj 

        3 years ago

        why dc voltage not supply in transfarmor???

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        3 years ago from CHENNAI

        @ Arjun

        Function of a transformer is to either step-up or step-down the applied voltage level based on its turns ratio. Current purely depends on the load.

        For an ideal transformer input power = output power

        Power = VI CosØ.

        From this, you can quote that to maintain the power constant, as the voltage is increased the current should be decreased and as voltage is decreased current should increase.

      • profile image

        arjun 

        3 years ago

        In the case of current why low voltage windings is higher than that of high voltage windings

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        4 years ago from CHENNAI

        @Sahil

        Oil temperature indicator used to indicate the temperature of oil inside a transformer.

      • profile image

        Sahil 

        4 years ago

        What is oil temperature indicator nd it's work

      • profile image

        s.kavitha 

        4 years ago

        i got excellent information along with very clear pictures

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        4 years ago from CHENNAI

        Ravinaik.B

        Transformer Losses : the Iron loss and the copper loss are independent of the power factor. These losses depends on the voltage and current only. Power factor has no effect on the losses occurring on the transformers. That's why it is rated in kVA.

        More info:

        https://hubpages.com/technology/Losses-in-Transfor...

        https://owlcation.com/stem/EASY-UNDERSTANDING-OF-W...

      • profile image

        Ravinaik.B 

        4 years ago

        why the transformer rated in kva?

      • profile image

        Ravinaik.B 

        4 years ago

        why the transformer rated in kva?

      • profile image

        DIVI 

        4 years ago

        Can you please give me more information about tap changing in transformers

      • goodnews11 profile imageAUTHOR

        OSBERT JOEL C 

        4 years ago from CHENNAI

        I am ready to help you!

      • profile image

        Sudipt Jena 

        4 years ago

        The above article stands very useful for me for working in power grid and dealing with power transformers. I hope I can get more helps from this site.

        Thanks .

      • profile image

        Ahmed said 

        4 years ago

        Thanks a lot

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