Transformer Definition and 809 Threads

A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any one coil of the transformer produces a varying magnetic flux in the transformer's core, which induces a varying electromotive force across any other coils wound around the same core. Electrical energy can be transferred between separate coils without a metallic (conductive) connection between the two circuits. Faraday's law of induction, discovered in 1831, describes the induced voltage effect in any coil due to a changing magnetic flux encircled by the coil.
Transformers are most commonly used for increasing low AC voltages at high current (a step-up transformer) or decreasing high AC voltages at low current (a step-down transformer) in electric power applications, and for coupling the stages of signal-processing circuits. Transformers can also be used for isolation, where the voltage in equals the voltage out, with separate coils not electrically bonded to one another.
Since the invention of the first constant-potential transformer in 1885, transformers have become essential for the transmission, distribution, and utilization of alternating current electric power. A wide range of transformer designs is encountered in electronic and electric power applications. Transformers range in size from RF transformers less than a cubic centimeter in volume, to units weighing hundreds of tons used to interconnect the power grid.

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  1. T

    What is the meaning of the 5 kVa rating in a 240:120 V transformer?

    Homework Statement "A 5 kVa, 240:120 V transformer.." I am just wondering what the 5kVa refers to Homework EquationsThe Attempt at a Solution is it ##5 kVA = \sqrt{P_{total}^2+Q_{total}^2}## or is it ##5 kVA = I_1V_1 =I_2V_2##
  2. E

    What is the primary conductor size for a 3-phase 1000kVA transformer?

    Hello, this is my first post and I've been out of school for a few years and now working a job in my field at a distribution utility, but I'm just really rusty or green on a lot of things now that I'm being challenged. Seems like the simplest questions elude me! Anywho, I've been tasked with...
  3. T

    How the power transfers across the Ideal Transformer

    Hi all, I've been having a conversation with a brilliant PF memeber about power transfer, but I wouldn't be surprised if my inability for comprehension has driven them to their knees. I don't quite remember/understand how the concept of power fits into a transformer. I used to think that it was...
  4. J

    Commercial transformers for variable frequency & voltage

    I am looking to step up the voltage of a 3 phase PM generator which has variable AC output of 200 - 400 Vl-l, and 15 - 30Hz. I am looking for a step up ratio between 1:1.5 and 1:2, and need this transformer to be a commercial device. What i have been finding is that most commercial...
  5. kelvin490

    Question about transformer reflected source

    The following show the idea how a Thevenin equivalent source is used to replace the primary circuit of transformer. https://www.dropbox.com/s/0kaazx1d1srgirz/reflectedsource.jpg?dl=0 https://www.dropbox.com/s/0kaazx1d1srgirz/reflectedsource.jpg?dl=0 In textbook it is commonly stated that the...
  6. T

    Understanding Voltage Regulation in Transformers

    Hi, So I have been told on here that when you eliminate the leakage flux between coils it improves Voltage regulation, I have also read online that voltage regulation is related to inductance, but could anyone elaborate on these? 'why are these so?' [I can sort of guess something like the...
  7. kelvin490

    Understanding MMF in Transformer

    I am studying about transformer and get confused about some concept. I have learn that in an ideal simple transformer the primary has two components of current: Magnetization current i.e. the open-secondary primary current. Current that (ignoring small leakage inductances) finds it way (via...
  8. G

    Voltage Regulation - Transformer

    Homework Statement A 415V to 11 kV transformer has a rating of 200 kVA. The winding resistance and leakage reactance when referred to the primary are 0.014 Ω and 0.057 Ω respectively. (b) In designing a particular 415V to 11 kV, 200 kVA transformer, the primary winding resistance is to be 10...
  9. P

    2-switch forward converter -- transformer reset question

    Switching power converter question (FYI, this is a 2-switch forward with synchronous rectifiers on the secondary). Switching at 200kHz. The transformer stores & transfers energy during the on state (the "D" state), and then must be reset during the off state ("1-D" state). The primary...
  10. smruti

    What makes the construction of power and pulse transformers different?

    what is the difference between the construction of a power transformer and a pulse transformer used in high frequency application and what about their core and copper losses?
  11. smruti

    What is the difference between an inductor and a transformer (or solenoid)?

    what is the difference between inductor and a transformer...or a solenoid and a transformer
  12. D

    Stuck on a flyback transformer project

    i have a question if i may i have a flyback I am trying to turn into a power source but all the tutorials show a flyback that is way different than mine there's only has one wire out of the top mine has three one from the top and two on the side labeled screen and focus i really need a high...
  13. kelvin490

    Understanding Inductor Behavior in Transformers: Voltage and Current Phasing

    In an inductor, a current waveform 90o out of phase with the voltage waveform creates a condition where power is alternately absorbed and returned to the circuit by the inductor. If the inductor is perfect (no wire resistance, no magnetic core losses, etc.), it will dissipate zero power. I...
  14. C

    Delta-Delta 3 phase transformer HNC help

    << Thread moved from the technical engineering forums to HH >> I'm currently studying for a HNC in electrical engineering and am currently stuck on a question on one of my assignments. The question is: A Delta-delta, 3 phase transformer steps down the system line voltage of 132kV to a local...
  15. ranju

    Three winding transformer

    while studying the purpose of tertiary winding in the this 3-winding transformer , I'hv gone through a statement that " the zero sequence component caused by line-to-neutral load on secondary side cannot be balanced by primary currents as the zero sequence currents cannot flow in isolated...
  16. cnh1995

    Switching transient in current transformer

    If a purely inductive circuit is excited with an AC source, a transient occurs before reaching the steady state 90 ophase shift i.e. the current takes some time to shift the phase depending on the switching instant. Is there any such transient in CT?? Suppose the primary circuit is initially off...
  17. Z

    Finding a Low-Cost Way to Step-Down Voltage for DIY Power Supply

    Hi. I have made a 12Vdc 3A unregulated power supply for my projects. I want to do some electrodeposition, and the 12V are a bit too high (It starts to electrolyze water and the deposited copper breaks very easily). I'm looking for a way to step-down the voltage without using too much money...
  18. mishima

    Rough lab measurement of transformer inrush current?

    Hi, Id like to measure inrush current for various salvaged transformers (unknown windings, but probably 120/24) to the nearest 10 mA. I only have a simple DMM and soundcard scope. It seems that a clamp meter has this capability; if a clamp meter is the best approach, can I construct my own...
  19. Salvador

    Rotary Transformer: Transferring Current & Power?

    If I have a rotary transformer in order to transfer some current o or from a rotating part, I wonder doesn't it add some extra power induced from the rotational motion to the secondary side of the transformer , since atleast one part of it is rotating with respect to other.? Like for example I...
  20. M

    Calculating Transformer Input Voltage

    Homework Statement Calculate the primary current, and hence the voltage at the transformer input winding, V1. Transformation ratio, a = N1/N2 = 0.1 R1 = 0.12 Ω; R2 = 12 Ω X1 = 0.4 Ω ; X2 = 40 Ω RC = 560 Ω V2 = 2300 V RL = 1 kΩ 'Xm = 800 Ω' Homework Equations R1eq = R1 + a2R2 X1eq = j(X1 +...
  21. D

    Help with Transformers: Understand Step-Up Coils & Voltage

    Hello everyone, I need some help with transformers as I am very confused... I understand the role of a step up transformer - the secondary coil has more turns thus has a higher voltage induced. This in turn reduces the current and the overall heating effect is reduced. This is why transmission...
  22. R

    Engineering Where is the bandpass filter in this circuit?

    Homework Statement I am doing a project on the Elenco AM/FM superheterodyne radio kit. I have been stuck for ages trying to figure out how the two common emitter amplifiers are tuned to filter out anything that is not around 455 kHz. I tried to find a bandpass filter, or a high-pass and a...
  23. K

    Engineering Shady data from a transformer’s short-circuit test

    Homework Statement Data from the short-circuit test of a 60-Hz, 100-kVA, 4600–230-V transformer are: VSC = 172.3 V ISC = 20.2 A PSC = 1046 W Get the per-unit parameters. 2. Relevant equations ISC ≠ Irated, so how will I solve the problem? The problem is from the book with ISBN 0130612103.
  24. cnh1995

    Current Transformer Magnetic Behavior

    Hi friends..I am very confused with the magnetic behavior of a CT. CT secondary should never be left open.Okay I understand why. But how exactly does a shorted secondary cancel the primary flux? For that the primary and secondary currents must be 180 degrees out of phase while Lenz's law states...
  25. T

    Quadrature Booster or Phase shifting TX

    Hi, Does anyone know about these? Specifically I'm trying to figure out changing the tap on the Delta effects the series voltage: source wiki: http://en.wikipedia.org/wiki/Quadrature_booster Any vector diagram or word explanations will help. Also, what size diameter coils must be used on the...
  26. A

    Transformer with open iron core?

    Hello everyone, I'm not sure if the title makes sense, but I'll try to explain it a bit better here. So, if we have a transformer with an open iron core (U shaped iron core, with coils wrapped around each side, same number of coils, same thickness), why is the electromagnetically induced emf in...
  27. R

    How Do You Calculate Primary Current in a Step-Up Transformer?

    Homework Statement An 5kVA ideal step-up transformer having a turns ratio of 200:1700 and is connected to a primary voltage of 1000V. Determine the primary current at full load. Homework Equations Vs/Vp = Ns=Np = Ip/Is The Attempt at a Solution I think it is 1700/200=Vs/1000=8500V But, I do...
  28. S

    Detecting a ground fault on the secondary of a transformer

    I work on a ship, and we have a 440V ungrounded distribution system. We have load centers that have transformers bumping that 440V down to 120V for recepticles and other services. This standard ship setup always has ground fault detection on the 440V side (at the switchboards) and at each...
  29. S

    Is the Transformer in My Adapter Damaged? A Question for Physics Assignment

    Hi guys, I am rather new here and would like to pose a question about transformers. As physics assignment I am supposed to make a model of an AC transformer, for which I grabbed an AC/AC step down adapter (something like these here...
  30. Salvador

    Transformer generator question

    Say I have a soft iron piece which somehow has a changing flux in it (for simplicity take 50hz) for the question doesn't matter how the flux got there. Now I have a coil and I now take the iron piece and move it back and forth through the coil 50 times a second to be the same rate as my flux...
  31. B

    Can Voltage Division Be Used to Solve Transformer Line/Load Ratio?

    Homework Statement (in picture) Homework Equations V=IZ The Attempt at a Solution So last time I had to do KCL to find voltages, so I want to make sure I'm doing this one right. Can I do voltage division and do Vload/VG? My division would be VG(500<36.87)/(500<36.87 + 60<53.13) But that...
  32. B

    Find transformer primary and secondary voltage/current

    Homework Statement (in picture) Homework Equations V=IZ All the ratio formulas (i.e. V2/V1 = N2/N1) The Attempt at a Solution I thought V1 would be 1000 Vrms. Well the answers are shown and it's not. So I thought maybe I would multiply Vrms (1000) by root 2 to find Vpeak (Vrms = Vpeak/root...
  33. I

    Can't tell if I made a chaotic circuit or if I broke the sim

    So, I was playing around with a couple of voltage multiplier circuits a few months ago, and while optimizing one design, I came up with a pretty neat (not to brag) way of converting a sine wave to a square wave by using transformers in a completely different way than normally. A little while...
  34. ironsword

    What is the Significance of Half Crest Time in Power Transformer Data Sheets?

    Dears, during reading power transformer (0.71/33) kv data sheet, I found term "half crest time" which equals to 0.8 s, the question is: what is that time and why is important? thanks and kind regards.
  35. blooperkin

    Transformer question (between substation and home)

    Homework Statement A power station generates 100kW of power at a voltage of 10kV. Given that the connecting cables in the primary and secondary circuit each have a resistance of 10Ω, find the turn ratio required for an ideal step-down transformer to bring electrical energy to the home at 240V...
  36. B

    Current transformer for protection question

    Homework Statement Determine RR value if the relay current has not to exceed 20mA. Neglect relay resistance. 2. The attempt at a solution I believe the solution is behind Merz-Price theorem, where the voltage system is balanced. CT1 and CT2 are identical current transformers, however, RL2...
  37. T

    Transformer inductance a function of mu only?

    Hi, I know that the permiability (mu) changes as the core material saturates and I would have thought L1 = N12 / reluctance L2 = N22 / reluctance and they'd both share the same reluctance length, this would indicate to me that L1 and L2 are only a function of mu. Is this correct? I know also...
  38. T

    Magnetising current of inductor and transformer, onformation

    Hi, I've never thought of an inductor actually consuming any real power, however the other day I was concidering an open circuit secondary, transformer. This should be the same model as just an inductor should it not? (or rather this is how we can model an inductor too?) If this is so all the...
  39. A

    Why are larger transformers more efficient than smaller ones?

    Homework Statement Transformer efficiency loss Homework Equations Larger transformers are more efficient than smaller The Attempt at a Solution I understand the basics of energy loss through heat etc but i don't understand why it would be different for the sizes of transformers. Is it to do...
  40. P

    Tap Changing (ULTC) Transformers and Reactive Power Control

    So I am trying to understand how a ULTC operates in the Reactive Power Control mode (it adjusts taps to control the reactive power in a line). What equation is governing it's operation, and what variables does it adjust in order to increase/decrease reactive flow? Is it just the simple reactive...
  41. P

    Overall Power Factor of three motors for transformer voltage drop calculation

    Hi Suppose I have three motors connected to a single busbar which is fed by a single transformer and suppose that the current into the busbar (i.e. the total current of the transformer secondary) is known. If I wish to calculate the transformer voltage drop the I will obviously need the load...
  42. S

    Troubleshooting Transformer Core Loss Simulation Error

    Hello Engineers, while simulating transformer core losses in transient Maxwell sollution, I have got an error: Current leak to the air. does anyone ahev idea to solve this problem Thank you
  43. G

    Why doesn't a center tap from a transformer short when grounded?

    Hi everyone, Basic question here. Residential pole mounted transformers and many other transformers that produce a neutral have that neutral "center taped" from a current carrying coil in the transformer and bonded to ground. My question is why doesn't the current in the coil short threw that...
  44. S

    Brightness of lamp connected to transformer

    Homework Statement A lamp is connected to the secondary part of an ideal transformer. What will happen to the brightness of the lamp if the number of turns in secondary coil is increased? Homework Equations Vs / Vp = Ns / Np = Ip / Is P = V.I = I2R = V2/R The Attempt at a Solution I have...
  45. P

    How Do You Calculate Voltage Drop in a Transformer?

    Homework Statement A 3MVA 11kV/415V 3 Phase Transformer has the following parameters +ve sequence resistance = 0.00355pu +ve sequence reactance = 0.0901pu Primary PHASE current to the transformer is 55A and the load power factor on secondary is 0.85 lagging. Calculate voltage Drop The...
  46. P

    Voltage Regulation for three phase Dzn Transformer

    Hi, I need to calculate the voltage regulation of the 3 ph Dzn transformer. I have knowledge of the current going into the primary winding of the transformer (Delta winding) and hence need to calculate the current in the secondary (load current) so that I can use this in the voltage...
  47. M

    Engineering Using the Short Circuit Test on a Single Phase Transformer?

    Homework Statement A short circuit test is performed on a small single phase transformer. The results are: Primary Voltage 5V, 60Hz Primary Current 2A Secondary Current 10A Primary Power 8W a) Making suitable approximations deduce the primary/secondary turns ratio (single number)? b) Making...
  48. X

    Solenoid vs transformer inductance

    When they teach transformers, they give you the Ampere's law, the Faraday's law, etc. and then derive this well known formula L = μ * N^2 * A / ℓ. And everything is no nice, all these parameters are used to define some other relationships, like the concept of reluctance in magnetic circuits...
  49. H

    Voltage Regulation transformer

    Homework Statement 5. A 415V to 11 kV transformer has a rating of 200 kVA. The winding resistance and leakage reactance when referred to the primary are 0.014 Ω and 0.057 Ω respectively. (a) Determine the % regulation of the transformer at 0.8 power factor lagging. (b) In designing a...
  50. ranju

    What is the impact of increased magnetizing current on transformer power factor?

    In a transformer , we know that the no-load current has two components , one magnetizing component I0sinphiand other one is the winding loss component i.e. I0cosphi.. if the magntizing current increases in the transformer what is the effect on the power factor??
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