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Parts of a Power Transformer

Updated on September 21, 2017
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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.

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    • profile image

      mahee 8 days 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 2 weeks ago

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

    • profile image

      Saddam hossain 4 weeks ago

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

    • profile image

      Kishor chandegara 2 months ago

      Dear sir

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

    • profile image

      arun kumar verma 2 months ago

      sir , how can i make my career in transformer field

    • profile image

      kuldeep kumar 2 months ago

      who many temperature of winding and oil in transformer

    • profile image

      PURUSHOTTAM KUMAR 3 months ago

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

    • profile image

      Joginder pal 3 months ago

      Please taken to knowledge for transformer

    • profile image

      Srinu 3 months ago

      Thangs

    • profile image

      sadiq suhail abubakar 3 months ago

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

    • profile image

      vairachelvam 3 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 3 months ago

      It's awesome....

    • profile image

      Rj H.S.Meena 4 months ago

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

    • profile image

      Nikunj 4 months ago

      Plz u tell me about motor concept

    • profile image

      manoranjan 4 months ago

      Deiffrsnce between kva and kw

    • profile image

      Frank mkony 4 months ago

      In like it

    • profile image

      SUMAN DEKA 4 months ago

      It is nice

    • profile image

      Nnamdi Onwuania 4 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 4 months ago

      it is so helpfull web. thnx sir

    • profile image

      tamil 4 months ago

      Very usefull sir

    • profile image

      fs 5 months ago

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

    • profile image

      saisaran 5 months ago

      what is the current value

    • profile image

      sonam (BHUTAN) 5 months ago

      Can u give more information about tabchanging

    • profile image

      Gorakh 5 months ago

      Thanks

    • profile image

      dileep 6 months ago

      thanks ur informaction

    • profile image

      Ashutosh Dubey 6 months ago

      Thank you.....Sir.

    • profile image

      Hassan Iqbal 6 months ago

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

    • profile image

      Hassan Iqbal 6 months ago

      It was helpful. Thanks

    • profile image

      NILONG 7 months ago

      Thank You and God bless!

    • profile image

      Prashant Kotkar 9 months ago

      thanks

    • profile image

      Habtamu kasaye 11 months ago

      It is really useful. thank you sir!

    • profile image

      shakeel 12 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 image
      Author

      OSBERT JOEL C 17 months ago from CHENNAI

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

    • profile image

      gokul singh 17 months ago

      Sir , the step up transformer used to step up for voltage . And why we not use it to generation of electricity , first we use 1step up . Then2nd .......... .

      I mean we step up220/440 , and 440/11kv and so on...

    • goodnews11 profile image
      Author

      OSBERT JOEL C 18 months ago from CHENNAI

      You are Welcome.

    • profile image

      jitendra gondaliya 18 months ago

      Thanks sir

    • profile image

      praveen 21 months ago

      thanks sir

    • profile image

      Shareef 2 years ago

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

    • profile image

      ashwini bidkar 2 years ago

      It is a presous information provide about transformer operation

    • profile image

      Raj 2 years ago

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

    • profile image

      AJAJ ANSARI 2 years ago

      It is very helpful for every students and teacher

    • goodnews11 profile image
      Author

      OSBERT JOEL C 2 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 2 years ago

      why dc voltage not supply in transfarmor???

    • goodnews11 profile image
      Author

      OSBERT JOEL C 2 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.

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      arjun 2 years ago

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

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 years ago from CHENNAI

      @Sahil

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

    • profile image

      Sahil 3 years ago

      What is oil temperature indicator nd it's work

    • profile image

      s.kavitha 3 years ago

      i got excellent information along with very clear pictures

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 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 3 years ago

      why the transformer rated in kva?

    • profile image

      Ravinaik.B 3 years ago

      why the transformer rated in kva?

    • profile image

      DIVI 3 years ago

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

    • goodnews11 profile image
      Author

      OSBERT JOEL C 3 years ago from CHENNAI

      I am ready to help you!

    • profile image

      Sudipt Jena 3 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 3 years ago

      Thanks a lot