Transformer - Learn and Contribute

Replies

• 

  freak16

  Questions asked in interview
  
  Q What is so special about CRGO?
  Q Which One is better : Core or shell type and why? Which one is generally used in generating stations and which one for distribution purpose? Why? Explain.
  
  ANY CEan.
• 

  freak16

  CEans , Answer the above Question. You can see that these questions are asked form the above given information only. So we can infer that we need a very strong reasoning even for minute things.
  So here We can share our knowlegde and can Blitz Our concepts.
  Lets make this effort a sucess; So Start reading and writing people
• 

  narayana murthy

  Awesome work thanks for your contribution
  i dont know much about crgo so i am answering for 2nd question i think we mostly use core type in disturbution and shall type in generation
  @freak: correct me if i am wrong i answered by observing some transformers near my home actually i never seen a transformer at generation station
• 

  shubhankar

  in CRGO, the grain orientation is used. the direction of rolling is the same as the direction of the magnetisation which makes it easy to utilize the rolling properties to a greater extent. this reduces the area of the hysterisis curve thereby reducing the core losses. in core type, the windings surround the core and hence the efficient and easy cooling of the windings is achieved. in shell type, the core appears to surround the windings and hence make the windings inaccessible and tedious to handle during repair work.
• 

  shubhankar

  What are the different types of windings (phasor groups) of a transformer. discuss.
• 

  narayana murthy

  I think types are star-delta and delta-star connection
  correct me if i am wrong
• 

  shubhankar

  yes you are partially right. they are delta star (Dy11, Dy1) and star delta (Yd11, Yd1). star star (Yy0, Yy6), delta delta(Dd0, Dd6)
• 

  shubhankar

  there are also delta zig zag and tertiary windings but are seldom used. open delta type of windings are used to vanish the zero sequence currents and scott and TT connections are also equally important
• 

  freak16

  Hello CEans!
  Some good answers!! 😀
  Shub , you are right and kudos to NM.
  My Answers :
  Ans 1
  In normal steel , Magnetic domains are oriented randomly. In CRGO , magnetic domains are oriented in one direction. It is cold rolled grained oriented steels.
  Hot rolled steels are also used. Steels are rolled at high temp with silicon quantity of 3 to 4 %.
  Resitivity of core increases due to silicon. If silicon is more than 5%. Then Core becomes brottle.
  magnetic permability = 1000 -4000.
  I am still working on other answers.
  
  Q4 What is Mitring of transformer Cores?
• 

  freak16

  In a shell-type transformer the flux-return paths of the core are external to and enclose the windings.While one large power transformer manufacturer in North America was noted for his use of shell-type designs, core-type designs predominate in the UK and throughout most of the world.
  Also Because of the intrinsically better magnetic shielding provided by the shell- type arrangement this is particularly suitable for supplying power at low
  voltage and heavy current, as, for example, in the case of arc furnace trans- formers. So core type transformer is used at most of the generating as well as distribution stations.
• 

  shubhankar

  i did not get the question no 4
• 

  sau

  i did not het the Q.4! I have 1 more question -
  what is the connection on the primary and secondary sides of a distribution transformer generally? star-delta or delta-star?
  Answer: The answer is delta star. the reason i know for the secondaries to be connected in star is that this reduces the amount of insulation required for the phase cables on the secondary sides (as we have to provide insulation for voltages which are only 58% of that line values).
  The reason for keeping the primary connection 'delta' is unknown to me. please tell. I think it has something to do with the harmonics. thus the phaser group for distribution transformers is Dy11.
• 

  shubhankar

  yes. i have mentioned it the open delta or the delta connections help in removing the sequence currents or the harmonics..
• 

  freak16

  This is the mitring of tranformers cores. It is done to provide it mechanical strength.
• 

  freak16

  Two different type of core construction is shown
  1) Square bolted
  2) Mitred
• 

  freak16

  @shubh
  Can you please explain open delta? I didnot get it.
  Also how delta connections helps in removing harmonics?
• 

  baja

  Maintainance And repairing work is easy in core type but not in case of shell type...
  Zigzag transformers is used in plants where THD is a problem. zigZag traansformer reduces HARmonics
• 

  freak16

  baja

  Maintainance And repairing work is easy in core type but not in case of shell type...
  Zigzag transformers is used in plants where THD is a problem. zigZag traansformer reduces HARmonics

  Can you explain how?
  I dont know much about zigzag transformer.
• 

  narayana murthy

  freak16

  @shubh
  Can you please explain open delta? I didnot get it.
  Also how delta connections helps in removing harmonics?

  
  #-Link-Snipped-#
  i this may help for all the explanation about the connections of transformers
  AND
  this is for zigzag transformer
  Zigzag Transformer
• 

  sau

  narayana murthy

  #-Link-Snipped-#
  i this may help for all the explanation about the connections of transformers
  AND
  this is for zigzag transformer
  Zigzag Transformer

  Everyone can search for the wikipedia links man! they can not explain. Please explain instead of pasting links..
• 

  narayana murthy

  sau

  Everyone can search for the wikipedia links man! they can not explain. Please explain instead of pasting links..

  ok then i will explain it as soon as possible
• 

  freak16

  Please CEans! Reply to my questions.Knowing a fact is not serve any purpose until you are not clear with reasoning. Comprehending the reason of the concept formulates real knowledge.
  Well I am posting some new questions to biltz your concepts again.
  Q. Tell the common name of transformer oil.
  Transformer oil performs dual functions of providing cooling and insulation within the
  transformer.
  Q What are the various gases released When decomposition of transformer oil take place due to overheating? How do these gases come out from transformer?
• 

  freak16

  A little Bit of Knowledge about Transformer oil.
  
  Oil as a coolant
  
  Iron and copper in transformer cause energy losses. These, of course,
  manifest themselves in the form of heat. This results in a rise in temperature
  of the system, be it core and windings, core frames, tank, or other anxillary
  parts. These will reach an equilibrium when the heat is being taken away
  as fast as it is being produced. For the great majority of transformers, this
  limiting temperature is set by the use of paper insulation, which, if it is to
  have an acceptable working life, must be limited to somewhere in the region
  of 100°C. Efficient cooling is therefore essential, and for all but the smallest
  transformers, this is best provided by a liquid.
  For most transformers mineral oil is the most efficient medium for absorbing
  heat from the core and the windings and transmitting it, sometimes aided by
  forced circulation, to the naturally or artificially cooled outer surfaces of the
  transformer. The heat capacity, or specific heat, and the thermal conductivity
  of the oil have an important influence on the rate of heat transfer.
  
  Oil as an insulator
  
  In most electrical equipment there are a number of different parts at different
  electrical potentials and there is a need to insulate these from each other. If this
  equipment is to be made as economically as possible the separation between
  these different parts must be reduced as much as possible, which means that
  the equipment must be able to operate at as high an electrical stress as possible.
  In addition, transformers are often required to operate for short periods above
  their rated voltage or to withstand system transients due to switching or to
  lightning surges.
  The oil is also required to make an important contribution to the efficiency
  of the solid insulation by penetrating into and filling the spaces between layers
  of wound insulation and by impregnating, after they have been dried and de-
  aerated by exposure to vacuum, paper and other cellulose-based insulation
  material.
  As an indication of the importance that is placed on electrical strength,
  it should be noted that for a long time, since the early days of oil-filled
  transformers, a test of electrical strength was the sole indicator of its elec-
  trical quality.
• 

  freak16

  I request you Guys. Please dont let this thread buried deep into other threads. Come on .
  Share your Knowledge. And If you dont have. Gain it. Atleast , Ask your doubts.
  
  Lets prepare this thread for entire Transformer Study so that you need this thread only for revision purpose.
  
• 

  freak16

  Property of transformer Oil .
  1) It is combustible
  It is interesting to know that Sometimes Mineral Oil is responsible for fire hazards at substaion.
  Therefore it is usual practice to locate these transformers outdoors and they are separated from each other by big walls (i saw at substations) So a fire is more easily dealt with and consequentially the risks are fewer.
  It is necessary to consider the need for segregation from other plant and
  incorporate measures to restrict the spread of fire.
  
  2)Low viscosity.
  3) Low pour point.
  4) High flash point.
  5) Excellent chemical stability.
  6) High electrical strength.
  7)High specific heat.
  8) High thermal conductivity.
  9) Good impulse strength.
  10) High or low permittivity, depending on intended use.
  11) High or low gas absorbing, depending on intended use.
  12) Low solvent power.
  13) Low density.
  14) Good arc quenching properties.
  15) Non-toxic.
  
  
  The purpose of a transformer core is to provide a low-reluctance path for the
  magnetic flux linking primary and secondary windings.
  Various types of steel used for constructing transformer cores are:
  1) Hot Rolled steels
  2) Grain oriented steels
  3) High permeablilty steels
  4) Amorphous steels
  5) Domain-refined steels
• 

  Arp

  Transformers are of two types based on their construction:-
  Core type
  Shell Type
  the most vulnerable part of transformer or any machine is insulation. in insulation, insulation of winding is easier in core and more good because it has better heat dissipation as windings are not sandwiched so better benefits.
  rest benefits are-easy for maintainance work,etc
  disadvantages- leakage reactance cant be reduce to any desired value, if short circuit windings of shell thpe sustain high force so benefit in shell type
  so we use core type.
  distribution-small leakage reactance as slight volt variation even not permitted
  power- more leakage reactance to have less current under sc.
  
  mitring- process of cutting the core sheets
  done to have better flow of flux(and to avoid sat) across corners and to reduce wastage of material.
  generally done 35/55 degree mitring. and we have ultimately reduce core loss.
• 

  Arp

  here come the turn of transformer winding:
  cylindrical,helical,diuble helical,multilayer helical, cross over, disc and cont disc, aluminium foil windings
  based on current rating, temp rise, sc strength,etc
• 

  freak16

  Continuing with series of Questions :
  
  Q What is % impedance of transformer?
  Q What is the condition for parallel operation of transformer?
  Q Why does core saturation increase the iron losses?
• 

  ISHAN TOPRE

  
  
  We use to change values of three phase voltage and current. Since three phase power is the most common way in which power is produced, transmitted, an used, an understanding of how three phase transformer connections are made is essential.
  
  We can easily construct a three phase transformer when we wound three single phase transformers on a single core. These transformers are put into an enclosure which is then filled with dielectric mostly a kind of oil.As we are using a dielectric, it provides electrical insulation between the case and the windings. This dielectric cooling and to prevent the formation of moisture.
  
  P.S: The original source is #-Link-Snipped-#
  I am not in to much of electrical stuff but tried to write it in my own words.
• 

  ISHAN TOPRE

  Q1) answer: It is the voltage drop on full load due to the winding resistance and leakage reactance expressed as a percentage of the rated voltage.
• 

  freak16

  sau

  i did not het the Q.4! I have 1 more question -
  what is the connection on the primary and secondary sides of a distribution transformer generally? star-delta or delta-star?
  Answer: The answer is delta star. the reason i know for the secondaries to be connected in star is that this reduces the amount of insulation required for the phase cables on the secondary sides (as we have to provide insulation for voltages which are only 58% of that line values).
  The reason for keeping the primary connection 'delta' is unknown to me. please tell. I think it has something to do with the harmonics. thus the phaser group for distribution transformers is Dy11.

  Primary is in delta as Line current is 1/Sqrt(3) of phase current. So Amount of copper required is less.I asked my prof. He said that its a matter of debate always to decide delta -star or star delta which is to be preferred. Depending on the load and other factors it is decided.If you have any query Do ask.
• 

  freak16

  Yes Ishu ! You are right. Yet I would like to add additional information.
  The normal method of expressing transformer impedance is as a percentage voltage drop in the transformer at full-load current and this reflects the way in which it is seen by
  system designers. For example, an impedance of 10% means that the voltage drop at full-load current is 10% of the open-circuit voltage, or, alternatively,
  neglecting any other impedance in the system, at 10 times full-load current, the voltage drop in the transformer is equal to the total system voltage. Expressed
  in symbols this is:
  (I_full_load*X/Open Circuit voltage)*100
  X=Leakage reactance
• 

  frodo.rok

  what is the difference between floating neutral and earthed neutral of transformer?
  in which cases and why we ask for floating neutral?
• 

  PraveenKumar Purushothaman

  freak16

  Q What are the various gases released When decomposition of transformer oil take place due to overheating? How do these gases come out from transformer?

  Dissolved Gas gets released from the transformer oil. They are used for checking the faultness in the transformer. The faulty gases are Hydrogen, Nitrogen and Oxygen Oxides of Carbon: Carbon Monoxide and Carbon dioxide Hydro Carbons: Acetylene, Ethylene, Methane and Ethane.
• 

  narayana murthy

  praveenscience

  Dissolved Gas gets released from the transformer oil. They are used for checking the faultness in the transformer. The faulty gases are Hydrogen, Nitrogen and Oxygen Oxides of Carbon: Carbon Monoxide and Carbon dioxide Hydro Carbons: Acetylene, Ethylene, Methane and Ethane.

  yes i am adding one more point here buchholz relay in transformer protection to protect while when these gases are released and it activates C.B when it reaches gases in the oil
• 

  PraveenKumar Purushothaman

  And I wanna ask my long time doubt... 😔
  
  We all know that DC cannot be stepped... But how in my remote car, there is a tx??? PS: I have no core ideas about electronics... 😔
• 

  narayana murthy

  praveenscience

  And I wanna ask my long time doubt... 😔
  
  We all know that DC cannot be stepped... But how in my remote car, there is a tx??? PS: I have no core ideas about electronics... 😔

  sorry praveen i can't able to understand your doubt
  i dont used a toy car so can i know what is tx your saying
• 

  PraveenKumar Purushothaman

  narayana murthy

  sorry praveen i can't able to understand your doubt
  i dont used a toy car so can i know what is tx your saying

  tx is transformer dude... I had a remote car... It operates on 4 AA batteries. The remote is powered by a 9V Battery... Both have a transformer circuit in them... Like, that piece of element has two input and two outputs.. 😛
• 

  narayana murthy

  praveenscience

  tx is transformer dude... I had a remote car... It operates on 4 AA batteries. The remote is powered by a 9V Battery... Both have a transformer circuit in them... Like, that piece of element has two input and two outputs.. 😛

  but battery is DC power i think we are using stepper motor in it
  anyway i don't want to keep hand in it because i dont know much about them and one thing we are reading transformer as t/f or t.f in books but not tx so small misunderstanding sorry
• 

  freak16

  Thanks Praveen and Ishu. Feelong good after seeing your replies. Thanks a zillion.
  @Praveen
  Yes. You are right.I like to add a bit. It is 80% of hydrogen which emits and other are hydrocarbons like Methane ,ethane ,etc. They come out through breather.
  Transformer Breathing Systems
  Because of the high thermal expansion of transformer oil, it is necessary, for all but the smallest transformers, to provide a mechanism to accommodate this
  expansion. Air and other gases which are released are expelled out through the breather.
  Common name of transformer oil is ASKAREL ( MINERAL OIL)
• 

  freak16

  praveenscience

  And I wanna ask my long time doubt... 😔
  
  We all know that DC cannot be stepped... But how in my remote car, there is a tx??? PS: I have no core ideas about electronics... 😔

  Dc can be stepped up only using SMPS and DC-DC converters. May be the transformer is making a rectifier which produces DC ( full wave rectifiers).And this dc is steeped up using choppers.
  Full Wave rectifiers are of two types:
  1) Bridge type
  2)Transformer type.
  Praveen , you must be supplying AC to transformer.
  Are You directly supplying DC to transformer?
• 

  narayana murthy

  freak16

  Dc can be stepped up only using SMPS and DC-DC converters. May be the transformer is making a rectifier which produces DC ( full wave rectifiers).And this dc is steeped up using choppers.
  Full Wave rectifiers are of two types:
  1) Bridge type
  2)Transformer type.
  Praveen , you must be supplying AC to transformer.
  
  Are You directly supplying DC to transformer?

  lol freak its really impossible to give DC supply to transformer as i think you had seen a question what happens if DC is given to transformer as it is basic question in transformer
  but you given answer for this
  @praveen: the ckt of t/f given is not transformer it is ckt of rectifier i think
• 

  freak16

  praveenscience

  tx is transformer dude... I had a remote car... It operates on 4 AA batteries. The remote is powered by a 9V Battery... Both have a transformer circuit in them... Like, that piece of element has two input and two outputs.. 😛

  It just not possible by the best of my knowledge. Dc with transformer.NO MEANING. It may be converting DC into AC then stepping it up then converting it again into DC.
  Wild guess. I am just trying to reach to some conclusion.
  @Praveen
  Sorry for above post. I saw this post late.
• 

  PraveenKumar Purushothaman

  Hey guys, cool, have you people seen the inside of a remote car??? I am saying about that!!! 😛 How can a transformer be 1cm x 1cm??? 😲
• 

  narayana murthy

  praveenscience

  Hey guys, cool, have you people seen the inside of a remote car??? I am saying about that!!! 😛 How can a transformer be 1cm x 1cm??? 😲

  dude i never heard about a t/f in remote car i think this discussion should be continued for best knowledge
  @freak and all: don't give up i concentrate on it and give my answer may be after 1 day if you all know please post soon
  @praveen: size of t/f can be decided on its rating
  ofcourse you may be right it can't be at such a small size
• 

  freak16

  narayana murthy

  lol freak its really impossible to give DC supply to transformer as i think you had seen a question what happens if DC is given to transformer as it is basic question in transformer
  but you given answer for this
  @praveen: the ckt of t/f given is not transformer it is ckt of rectifier i think

  Yes NM
  You are right. I am not saying to feed dc to transformer. I said " YOU MUST BE PROVIDING AC TO TRANFORMER' then i asked praveen if he is feeding remote car with dc
  Did you read the full wave rectifiers with transformer?
  In which you supply AC and DC is produced. I am talking about that only. You produce DC and step it up.
  Any further interjections will be entertained.
• 

  narayana murthy

  freak16

  Yes NM
  You are right. I am not saying to feed dc to transformer. I said " YOU MUST BE PROVIDING AC TO TRANFORMER' then i asked praveen if he is feeding remote car with dc
  Did you read the full wave rectifiers with transformer?
  In which you supply AC and DC is produced. I am talking about that only. You produce DC and step it up.
  Any further interjections will be entertained.

  do you seen total ckt in bridge and in all rectifier ckts we use transformers because for rectifier we need 24v only but from supply we are getting 230v
  hope i am right
• 

  PraveenKumar Purushothaman

  I will try to provide a screenshot if possible... 😀 Its something awesome I wish to share... 😛
• 

  narayana murthy

  actually friends in my view we use t/f to reduce voltage and for remote cars we use DC and battery is also DC
  so no need of rectifier and t/f i am confused in it
  @praveen: please post soon i can got answer for it i think he given the ckt of internal diagram
  and if it is chargable from supply we must use rectifier but the rectifier will be build in charging cable so no need of internal ckt
• 

  freak16

  Please Praveen Do tell us. It will add to our knowledge and boggle our concepts.
  Will be a test.
• 

  Arp

  percentage impedance gives the total power loss and represents the per unit impedance
  conditions- correct polarity, same volt ratio and same volt rating, samex/r and same per unit impedance(desirable not necessary)
  increasing in furthur current after knee point would not increase the flux and ultimately increase iron loss as no more furthur grains can be orient in the particular direction
  
  correct me wherever i'm wrong or whenever you have better answer
• 

  PraveenKumar Purushothaman

  I searched it throughout the internet... Couldn't get... 😔 Will take a photo and send you!!! 😀
• 

  Mr.Don

  @NM
  
  In a small remote car with micro controller arrangement, we can use AA batteries for power supply and a bridge rectifier later connected to a small filter circuit and it's connected to a regulator.A 5v regulator which allows only 5v through the supply because the micro controller will operate with 5v only. A crystal oscillator will be arranged for producing frequency for the micro controller.
  
  In the case of taking the power directly from the supply, then we can use a 9-0-9 transformer to step down the voltage then it connected to the bridge rectifier and the connection follows same as above.
  
  Note: Transformers only work with AC supply.
• 

  ISHAN TOPRE

  Can anyone explain me micro-controllers, I have read something about the motorola IC. But don't know about it too well? Can anyone help to explain its block diagram?
• 

  PraveenKumar Purushothaman

  OKi guys, I got that transformer stuff... I took a pic of it... 😀
  
• 

  PraveenKumar Purushothaman

  Behind the two disc capacitor, it says ANT... See right of it... That's TR1!!! 😀
• 

  freak16

  frodo.rok

  what is the difference between floating neutral and earthed neutral of transformer?
  in which cases and why we ask for floating neutral?

  Floating neutral is neutral whose potential of the common point is not constant. As in the earthed neutral , Common point has the potential zero i.e. ground potential.
  If we have floating neutral than triplens will be absent i.e. harmonics will be less.
  Any further clarification will be welcomed
• 

  Arp

  some brain storming transformer questions just for quick revision
  
  Q1 why we use transformers? you are not suppose to tell only for step up and step down.
  Q2 why we cant use anything else in place of step up or step down transformer? like bjt amplifier,etc which even amplifies power?
  Q3 have you noticed any difference in transformers one at generating station and other at distribution station. other than their size and capacity and voltage levels.
  Q4 discuss different types of bushing?
  Q5 where in hv winding tap changer should be placed.? give answer with reasons.
• 

  PraveenKumar Purushothaman

  Guys, any improvement in my question / case???
• 

  Mr.Don

  Arp

  some brain storming transformer questions just for quick revision
  
  Q1 why we use transformers? you are not suppose to tell only for step up and step down.
  Q2 why we cant use anything else in place of step up or step down transformer? like bjt amplifier,etc which even amplifies power?
  Q3 have you noticed any difference in transformers one at generating station and other at distribution station. other than their size and capacity and voltage levels.
  Q4 discuss different types of bushing?
  Q5 where in hv winding tap changer should be placed.? give answer with reasons.

  AU or JNTU or ANU question paper 😛
  
  Jokes apart.
  
  Answers for Q1 & Q2
  
  Transformers can step down or step up the power without the change of its frequencies.
  
  A big difference. A transformer converts power into more useful means of transportation or matching to the end results.
  
  Pincoming = IPVP = Poutgoing = ISVS.(the ideal transformer equation)
  
  then as the outgoing voltage of the transformer increase, the outgoing current will decrease. An amplifier adds power. For example, voltage amplifier add voltage (amplify) independent the amplifier current.
• 

  PraveenKumar Purushothaman

  Q4 discuss different types of bushing?
  
  Transformer bushings are a very integral part of transformers and the way they function in different types of capacities. The bushings are necessary to complete the conductive energy output of the volts that are transformed within the transformer so that they can then move through mediums such as air and gas, including the grounding barriers that each unit is designed with.
  
  Types of Bushing
  i) Alternator bushing
  ii) Transformer bushing
  iii) Bushings for switch gear
  iv) Wall bushing or roof bushing
  v) Cable end and joint box bushing
  
  Other Types
  i) Stem type
  ii) Pull-through type
  Core
  i) Condenser core type
  ii) Non-condenser core type (Hollow Porcelain type)
  iii) Gas filled bushing
  iv) Solid Bushing
  Others
  i) Solid Ceramic Bushing
  ii) Epoxy Bushing
• 

  freak16

  Kudos to Arp!!
  I will answer after some time.
  Here is one more question paper ( Comparatively Easy though 😛)
  Instructions
  1) No negative marking
  2) Each question carry 1 Like or 5 marks😁
  3) No time Limit.
  Questions
  .
  Q What is the function of wind pipe in transformer?
  Q What is the silica gel? Discuss its properties.Why do we use it?
  Q Difference between vectoe group Dy11 and Yd0?
  Q Why do we need cleaning or purification of transformer oil?
  Q Discusss different types of relays used for the protection of transformers
  
  Shoot CEans.
• 

  freak16

  @ Praveen I got the answer.😀
  
  We can use transformer with DC if there are changes in flux. Like we can have multiple switching operation with Dc supply so a transformer can be used provided we dont allow it to saturate.
  You must see the ckt diagram of SMPS. We use inductor there and dont allow it to saturate.
  This achieved by multiple switching ( of Mosfets).
• 

  PraveenKumar Purushothaman

  In a remote car???
• 

  freak16

  Arp

  some brain storming transformer questions just for quick revision
  
  Q1 why we use transformers? you are not suppose to tell only for step up and step down.
  Q2 why we cant use anything else in place of step up or step down transformer? like bjt amplifier,etc which even amplifies power?
  Q3 have you noticed any difference in transformers one at generating station and other at distribution station. other than their size and capacity and voltage levels.
  Q4 discuss different types of bushing?
  Q5 where in hv winding tap changer should be placed.? give answer with reasons.

  Ans1 Transformer are of various types
  1) Phase shifting transformer
  2) Regulating transformer
  3) Generating transformer
  4) Distribution transformer
  4) Instrument transformer
  5) Pulse transformer
  Thanks to transformer that today AC transmission is possible to each nook and cranny of the India. We generate at or near the coal mine and transmit it to Delhi or other areas.
  (Because of its step up and step down only ) Besides that It isolates the control ckt from the power ckt so that any fault in power ckt doesnot harm the control cktry.
  It is also used in instumentation , measurement and indicating purposes like potential transformer and current transformer.
  It helps to maintain voltage profile also like by tap changing and phase shifting transformer that improve the power angle.
  Pulse transformers is used in power electronics for gating SCRs and numerous other purposes.
• 

  freak16

  praveenscience

  In a remote car???

  What did you want to ask?
  I read it in video of power electronic ( By B.G Fernades iit bombay) He explained the concept nicely.
• 

  freak16

  Ans 2 Because first they need some sort of biasing like bjt amplify only when you proide dc biasing to it.Second their efficiency is very poor as they operate in linear region.
  
  Ans3 Yes in cooling system In GTS we use forced cooling. They operate on Online TAP CHANGERS. In Insulation class also GTs will be superior.
  Bushing Design also will be different.
• 

  PraveenKumar Purushothaman

  freak16

  What did you want to ask?
  I read it in video of power electronic ( By B.G Fernades iit bombay) He explained the concept nicely.

  Mind sharing the link here???
• 

  Arp

  for Q3, all difference freak u say is due to the capacaity difference. if one is of higher mva then we have to use forced cooling.
  and for your info, we use on load tap changer in distribution transformer.
  for Q2, freak u r very close to the answer, but think if there is something thats amplifying power means we generate 10kw and amplify it to 25 kw. isn't it good.
  Q1 and Q4 are correctly answered one by praveen one by freak.
  Q5 still left..
• 

  freak16

  I am afraid if On load tap changer is used in distribution only. It is used in high capacity transformer and GTs are high capacity transformer.Also Gts are always working .If if you want to change taps in GTs you can do it on load only. You willnot go to shut off whole power plant first and then change the tap . Again start the plant ( which may take 2 days).It just not possible. SO On load tap changer must be used in GTs.
  Sorry ! For giving the difference based on capacities. Okay . In GTs ( as they are working all the time ) , Core losses will be high. Their vector group may be different. Please you explain more.
  I am working on Q5.
• 

  freak16

  praveenscience

  Mind sharing the link here???

  #-Link-Snipped-#
  In the mid of this lecture , you will get the same concept.
• 

  Arp

  freak, distributing transformer can be of high capacity even. although we dont have to stop plant,etc but we have to switch off power supply of all those area whenever we want to use tap changer. we always want to have a better and easier way. look out at any major distributing substation like one at maharani bagh or at constitutional club's you'll find the on load tap changer.
• 

  freak16

  Agreed.
  Can you please post the answer of question 2and 3?
  
  On load tap changer is located over the top as their will be many tapping so all are located on the top of HV windings.
  As it will provide ease in changing. I am not sure. A wild conjecture.
• 

  freak16

  Kudos to Arp!!
  I will answer after some time.
  Here is one more question paper ( Comparatively Easy though )
  Instructions
  1) No negative marking
  2) Each question carry 1 Like or 5 marks
  3) No time Limit.
  Questions
  .
  Q What is the function of wind pipe in transformer?
  Q What is the silica gel? Discuss its properties.Why do we use it?
  Q Difference between vectoe group Dy11 and Yd0?
  Q Why do we need cleaning or purification of transformer oil?
  Q Discusss different types of relays used for the protection of transformers
  
  Shoot CEans.
• 

  Arp

  Q1 The tank is connected to the atmosphere through the wind pipe. on which brether,etc are placed. its function is to exchange the air with atmosphere.
  Q2 it is dehydrating material in breather to absord moisture which can damage the winding insulation.
  blue when dry and whitish punk if moist.
  Q3 Dy11- hv in delta lv in star and angle b/w line voltages is 30 with lv lag hv line volt
  Yd0 hv in star lv in delta no phase diff
  Q4 as transformer's oil disintegration , sparking carried out on a regular basis so we need to cleaning purification.
  Q5 bucholz relay- gas actuator relay.
  differential protection
  core leakage balanced protection.
• 

  PraveenKumar Purushothaman

  Arp

  Q1 The tank is connected to the atmosphere through the wind pipe. on which brether,etc are placed. its function is to exchange the air with atmosphere.
  Q2 it is dehydrating material in breather to absord moisture which can damage the winding insulation.
  blue when dry and whitish punk if moist.
  Q3 Dy11- hv in delta lv in star and angle b/w line voltages is 30 with lv lag hv line volt
  Yd0 hv in star lv in delta no phase diff
  Q4 as transformer's oil disintegration , sparking carried out on a regular basis so we need to cleaning purification.
  Q5 bucholz relay- gas actuator relay.
  differential protection
  core leakage balanced protection.

  Omg!!! Cheating!!! But you wud be getting only one like instead of five!!! 😛 he he... 😀
• 

  freak16

  He got atleast 4 if he had answered each Answer in separate post Praveen..
• 

  Arp

  freak we are waiting for your next set of questions.
  @ praveen, 😀
• 

  PraveenKumar Purushothaman

  Arp

  freak we are waiting for your next set of questions.
  @ praveen, 😀

  I second Arp... 😀 Send us the next set of questions... Give US a chance... 😛
• 

  narayana murthy

  i think these may be good questions
  
  1.what are harmonics? how they effect efficiency and regulation?
  2.does even harmonics present on transformers if yes how they effect?
• 

  PraveenKumar Purushothaman

  What are harmonics? how they effect efficiency and regulation?
  
  In wave, for a certain period, the frequency repeats itself. That fundamental pattern is called Harmonics. We have studied that, a wave is generally made up of a fundamental frequency f and repeats itself n times. The wave which comes after the fundamental frequency is called as an overtone. Eg. 2f, 3f, etc.
  
  Hope my answer is right!!! 😀
• 

  narayana murthy

  praveenscience

  What are harmonics? how they effect efficiency and regulation?
  
  In wave, for a certain period, the frequency repeats itself. That fundamental pattern is called Harmonics. We have studied that, a wave is generally made up of a fundamental frequency f and repeats itself n times. The wave which comes after the fundamental frequency is called as an overtone. Eg. 2f, 3f, etc.
  
  Hope my answer is right!!! 😀

  it may be right praveen upto some extent by my knowledge frequency will not be repeated it multiplies and that frequency will be added to fundamental frequency this is known as harmonics
• 

  shubhankar

  yes it is the multiple of the fundamental frequencies. and even harmonics are not present as they cancel out each other
• 

  shubhankar

  for more details..here is my voice article for harmonics..
  #-Link-Snipped-#
• 

  Arp

  harmonics are those waves which oscillates with different speeds and thus having different frequency as compared to that of fundamental. even harmonics are not present in transformers as they cancel out and only oo harmonics are present as a result. harmonics result in excessive power loss in lines, malfunctioning of motors due to crawling, harmonic current flows in line which increses reactance drop and regulation becomes more poor and it also has an adverse effect on efficiency. but at the same time haromics are useful particularly in heating loads where harmonic can create excessive heating and in the transformer where it is necessary to produce the sinusoidal voltage.
  
  Hope its clear..
• 

  Arp

  freak last answer we would like to have from u!! regarding protection relays for transformer.
  reply it soon... 😀
• 

  Arp

  some brain storming transformer questions just for quick revision
  
  Q1 why we use transformers? you are not suppose to tell only for step up and step down.
  Q2 why we cant use anything else in place of step up or step down transformer? like bjt amplifier,etc which even amplifies power?
  Q3 have you noticed any difference in transformers one at generating station and other at distribution station. other than their size and capacity and voltage levels.
  Q4 discuss different types of bushing?
  Q5 where in hv winding tap changer should be placed.? give answer with reasons.
  
  Guys only Q1 and Q4 are correctly answered so far..
• 

  PraveenKumar Purushothaman

  Arp

  some brain storming transformer questions just for quick revision
  
  Q1 why we use transformers? you are not suppose to tell only for step up and step down.
  Q2 why we cant use anything else in place of step up or step down transformer? like bjt amplifier,etc which even amplifies power?
  Q3 have you noticed any difference in transformers one at generating station and other at distribution station. other than their size and capacity and voltage levels.
  Q4 discuss different types of bushing?
  Q5 where in hv winding tap changer should be placed.? give answer with reasons.
  
  Guys only Q1 and Q4 are correctly answered so far..

  Wow!!! Q4 was mine!!! 😀
• 

  PraveenKumar Purushothaman

  freak16

  What did you want to ask?
  I read it in video of power electronic ( By B.G Fernades iit bombay) He explained the concept nicely.

  Hey I asked a question, like there was a transformer in a remote car, which is totally powered by DC. How will that work???
• 

  freak16

  Arp

  freak last answer we would like to have from u!! regarding protection relays for transformer.
  reply it soon... 😀

  Sur Arp..
  I will post as soon as possible.
• 

  freak16

  You didnot get the answer yet???
  Didnot you watch the video i gave the link of?
• 

  narayana murthy

  Arp

  some brain storming transformer questions just for quick revision
  
  Q1 why we use transformers? you are not suppose to tell only for step up and step down.
  Q2 why we cant use anything else in place of step up or step down transformer? like bjt amplifier,etc which even amplifies power?
  Q3 have you noticed any difference in transformers one at generating station and other at distribution station. other than their size and capacity and voltage levels.

  i think i had a answer for 2nd question noise is main problem for these electronic devices but there is no such problems in transformers i think i am right correct me if i am wrong
  for 3rd question i have observed change in losses
• 

  Saandeep Sreerambatla

  I guess this post will help you!
  
  #-Link-Snipped-#
• 

  maraitamilan

  in crgo (cold rolled grain oriented steel the permeability is higher.the molecules are regularly arranged and hence the intermolecular friction is less.The hysteresis loop is narrow hence the hysteresis loss is less
• 

  chaitanyagymnast

  What happens in transformer when we change the supply frequency??
  
  i.e the change in voltage, current, flux and etc..??
• 

  freak16

  chaitanyagymnast

  What happens in transformer when we change the supply frequency??
  
  i.e the change in voltage, current, flux and etc..??

  There are many possibilities considering the constraints.
  

  E= 4.44*N*f*g​

  where N = number of turns​

  f = Operating frequency​

  g = maximum flux​

  1) If E remains contant​

  then flux will increase as f decrease and vice versa.​

  2) If no constraints, E will decrease​

  ​

  So from above equation the effect of frequency can be studied on emf induced which affects other parameter accordingly.​

  ​
• 

  chaitanyagymnast

  freak16

  There are many possibilities considering the constraints.
  

  E= 4.44*N*f*g​

  where N = number of turns​

  f = Operating frequency​

  g = maximum flux​

  1) If E remains contant​

  then flux will increase as f decrease and vice versa.​

  2) If no constraints, E will decrease​

  ​

  So from above equation the effect of frequency can be studied on emf induced which affects other parameter accordingly.​

  ​

  
  We know induced emf is directly proportional to change in flux i.e "e=dg/dt" where g is function of flux..
  
  suppose the frequency is increased, change in flux increases so E should also increase...
  But E should not increase beyond the applied primary voltage V1..
  So from above emf equation may be magnitude of flux should decrease..
  
  My doubt is, is E is more, less or same as the previous applied voltage??
• 

  freak16

  E= 4.44*N*f*g
  

  Here E=induced emf​

  This equation is obtained by "e=dg/dt" only. So you see everything in the context of refined equation.​

  Frequency about which you talking about is supply frequency?​

  Vapplied= E +ir + j(i*2*pie*f*L)​

  Where L = inductance​

  Can you elaborate your question so that i can explain in more depth? 😀​

  ​
• 

  chaitanyagymnast

  by increasing in the frequency leakage flux increases, in the form of leakage reactance "XL"
  
  so may be magnitude of the flux wave is decreasing, and it causes the decrease in "E"
  
  Simultaneously increase in change in flux causes increase in "E"
  
  
  My doubt is which one effects the "E" more than other and why??
• 

  Naman Agarwal

  shubhankar

  yes you are partially right. they are delta star (Dy11, Dy1) and star delta (Yd11, Yd1). star star (Yy0, Yy6), delta delta(Dd0, Dd6)

  i think there are 11 types of connections...