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. S

    Transformer core variable reluctance

    Hi , When DC is applied to a transformer there is no secondary induction because DC current creates no changing flux in the Core. If I could change the reluctance, or permeability is another word I guess, of the transformer core while still having DC applied to the...
  2. D

    Why did the fuse blow when a DC supply was connected to a transformer?

    my friend gave a dc supply to a transformer in my college lab accidentally and the fuse went off can i get an explanation on why this happened?
  3. S

    How hot might this 3 amp transformer get?

    20 gauge copper wire is rated for 5 amps. Suppose someone use 18 gauge copper wire and wraps it 60 times around one side of a 1 inch iron ring, with the two ends then connected to a plug. A separate piece of copper wire wraps around the other side 20 times, and goes to a 13.3 Ohm resister. So...
  4. P

    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...
  5. ranju

    Transformer Frequency: No Relative Motion Explained

    We know that frequency of induced emf in secondary coil remains same as frequency of applied voltage in primary coil and I have read that its reason is " there is no relative motion between the coils..". Actually I am not getting the reason , maybe some fact or concept has slipped from my mind...
  6. T

    Open circuit short circuit (test) TX flux effect

    Hi, It's been a while but from what I remember when you short circuit a transformer, electrically it's like you've series'd up the coils and shorted the magnetisation branch. And when you open circuit a side of the TX it is like the current flows through a side then through the magnetisation...
  7. K

    Transformer help please -- AC Mains transformers of different input voltages

    Hiya Does anyone know if there's any safety or performance issues with going about the input voltage of a transformer? The spec on maplin says on just about every step down transformer that the input is (x)v-230v. As I live in the uk, mains voltages are 240v a.c. Not sure about what to do
  8. H

    Homemade diesel-electric platform truck

    Hi, this is my diesel-electric conversion for what was a battery only powered platform truck. Its got a 30hp diesel engine, a 6 Kw DC generator, and another 6 Kw AC generator. One thing to point out is that I'm running it only with the generators, no batteries. Here's some pics of it: Diesel...
  9. N

    Isolation transformer questions

    Hi I'm trying to design a circuit to be hooked upto mains ac, and it was recommended that I should use an isolation transformer for safety purposes. 1) what purpose does this server, I know that it allows power to pass without the circuits being joined, but what affect does that have/why is it...
  10. S

    Vector Diagrams for a Transformer

    Homework Statement Can anyone provide me a good tutorial link on drawing the vector diagrams for a transformer on load, when the load is a)Inductive b)Capacitive c)Resistive Capacitive ? Homework EquationsThe Attempt at a Solution
  11. P

    Power Transmission Line and Transformer Parameters

    Hi, I was wondering if it would be possible for someone to help me clarify a few things regarding transmission lines and transformers? For a Power Transmission line, what exactly is the mutual coupling between phases of a 3 phase line? Is this the same as the shunt capacitance and if not...
  12. D

    Distribution transformer short-circuit test issue

    I have a question considering the transformer's short-circuit test and the impedance (or short-circuit voltage). The transformer's general data is: Rated power: 50kVA Primary voltage: 10000V (10kV) Secondary voltage: 420V (0,42kV) Primary current: 2.89A Secondary current: 68.73A Vector group...
  13. EverGreen1231

    Questions pertaining to Transformer DGA and Duval Triangle

    Is anyone versed enough in Power transformer DGA and Duval triangles to know what the implications of the different regions might be? I've Googled and found many documents about the subject, but none really seem to mention what the implications might be for a transformer that tends towards T3 as...
  14. G

    Understanding Autotransformers for Solving Homework Problems

    Homework Statement I require some help for part i for now. :) Homework Equations N1/N2 = V1/V2 N1/N2 = I2/I1 The Attempt at a Solution I tried doing the question like a normal transformer, but the result I got was vastly different from my teacher's. I also don't understand how my teacher...
  15. D

    Energy efficiency, Transformer?

    Homework Statement A power plant produces energy at a voltage of Vi = 12693 V. Before being sent along long distance power lines this electricity is sent through a transformer with 166 turns in the primary coil and 6917 turns in the secondary coil. The voltage of the electricity sent through...
  16. I

    Help please -- what do these ratings mean on a transformer?

    Could anyone explain what the following ratings mean on a transformer? 120kw load, 1000v/500v, 60Hz
  17. Salvador

    What is the science behind DC DC plasma transformers?

    Good day , while reading about DC DC converters I stumbled upon some papers discussing a DC DC plasma transformer , the science behind it being similar to tokamak current drive or so they say , I tried to search various links for some information to get a clue about how it works but I couldn't...
  18. P

    Ideal Transformer with Superconductors?

    Just had an idea that raised a few questions and I can't find any relevant data on after a bit of searching so thought I'd ask here. If you were to make a transformer entirely encased in superconducting material would it result in a significant step toward and ideal transformer or is magnetic...
  19. H

    Three winding transformer fault current study

    Hello all! I am carrying out the theoretical (that is, by calculation means) unsymmetrical fault calculations for three winding transformer. It is to my understanding that for the zero sequence impedance for a three winding transformer depends on the winding connections of the generator and...
  20. ZetaOfThree

    How Do You Solve a DC+AC Transformer Circuit Problem?

    Homework Statement Find ##V_{out}## for the following circuit: We are given that the transformers are ideal and ##\frac{n_1}{n_2}=a>1## where ##n_1## is the number of windings on the coil on the left and ##n_2## is the number of windings on the left.Homework Equations KVL Transformer...
  21. I

    3CR12 Steel for Power Transformer

    I live in a highly corrosive coastal environment, a major problem we have is rusting of all components of our power transformers. I have investigated the use of 3CR12 (or equivalent) for the main tank (between 31,5MVA up to 63 MVA 132kV/22 or 11kV) (YyN0) in order to prevent rust problems. It...
  22. M

    Transformer principle (induced secondary voltage/current)

    Homework Statement Draw a sketch and show/explain how the induced secondary voltage and current "moves" when the primary current "breaks" the instant the switch N is opened. See the attached image below (I apologize for my awful paint job...). Homework Equations The Attempt at a Solution...
  23. A

    Single phase transformer and net KVA output

    Homework Statement a 4 kva, 230/115 volt, 400 HZ, single phase transformer originally designed for use in air crafts, is available in a laboratory for obtaining 115 volt supply from standard 230 volt,50 HZ mains if overloading of the device is not permitted then net kva output is...Homework...
  24. H

    Is a Solidly Grounded Transformer Used in Residential Wiring?

    Hello everybody, I'm a bit confused about the concept of solidly grounded tranformers. From my understanding, the wye connection of the transformer side would be followed by a resistor of a certain magnitude. Hopeful that my doubt would be clarified. Thanks!
  25. arpansen

    Full load condition of real transformer

    What is the full load condition of a transformer. Then in reference to the equation: Vp = aVs + Req*Ip + jXeq*Ip (the very common complex equation of a simple equivalent circuit ) Should I use Vs= 230 V or Vp = 2300 V in full load load condition or will the magnitude of the primary voltage be...
  26. arpansen

    Interpretation of the rating of a real transformer

    The rating of a real transformer is 15 kVA , 2300/230-V then can we say that the primary rms is 2300 V or can we say that the secondary rms is 230 V or both. To clarify further, suppose to solve for certain characteristics of this transformer like primary current and secondary current i use...
  27. psparky

    Transformer Impedance Discussion

    I was working on trying to find the short circuit current rating of a 120 volt panel fed from a 7.5KVA transformer. Using P=IV you get 7.5KVA=120 * I I = 62.5 Amps. Then I believe you divide that current by the impedance of the transformer. .03 is the impedance in this case in the...
  28. S

    Ferrite core size and number of turns for transformer design

    hello. I'm designing a 100w 4Mhz class E amplifier. I need a ferrite core transformer for impedance transformation and load isolation but unfortunately I lack the knowledge required for designing it. if anyone could guide me to a good book or a web page, or simply give me some formulas I would...
  29. A

    Could you me what this transformer is doing in dc circuit?

    Thermoelectric generator induce DC current and I just wants to understand how can a transformer step up DC. If there is something else please make me clear.
  30. E

    Abnormal Voltages in Transformer

    Hi, Please have a look at this paper: "Abnormal Voltages in Transformers" L.F. Blume, 1919 AIEE (someone had mentioned this prior) I tried attaching the paper, did not work. The most interesting this is that abrupt pulses make transformers react as a condenser rather than an inductor...
  31. I

    Transformer Impedance: Primary Side & Secondary Load

    Hi, Since the primary side of a transformer is a closed circuit (like the cubical adapter for the iphone charger), it would make sense that even if my iphone wasn't plugged into the secondary, the primary would still draw power. I know this is the case for at least some adapters, because i...
  32. D

    Zero Impedance in Oscillating current transformer

    Hi, I have read Steinmetz books and he has a very good example of OC phenomenon that is nothing like AC case. There are certain conditions under which an OC transformer has zero impedance. Also, on his chapter of long transmission lines, he says quarter wave resonance using abrupt pulses can...
  33. M

    Frequency - Temperature characteristics of transformer winding

    Dear Sir, The rating of a single phase transformer is 230V / 230V (1:1), 5A, 50 hz, 1200W. When this transformer is operated at 230V, 5A, and 50 hz the transformer winding saturated temperature may be some value. Now when the same transformer is operated at 230V, 5A and 40 hz (reduced...
  34. M

    Change 12VDC to 12VAC, can it be done without transformer?

    I've 3 batteries ( each 3kw X3= 9kw ) and If Inverter for 9kw is too expensive, I just want the 12V AC, so it can be done without transformer? So, in this diagram: http://www.aaroncake.net/circuits/inverter.gif Can I just remove the transformer and put powerful transistors to withstand 9kw input...
  35. dwn

    How Is Average Power Calculated in a Transformer Circuit?

    Homework Statement Please see the image attached. We are asked to find the average power (P) delivered to ZL. 2. Relevant Questions (My observation of the circuit) The circuit on the left is as follows: V + I1*(5 + jwL) = 0. For the circuit on the right: V = I2*(Z + jωL) Is a=...
  36. H

    Can You Change a 10-Pin Transformer to an 8-Pin One Without Affecting Quality?

    Hello everyone! Firstly, I have very basic knowledge of pcb design and in electrical engineering in general :confused: I want to ask you if I want to change a 10 pin transformer into a 8 pin one. Would that effect the quality or sth? what consequences does it have ? are pins with more...
  37. C

    Current in secondary of transformer

    I am trying to get a better understanding of transformers. Assuming the transformer is ideal, and the secondary is connected to a high impedance load such as an oscilloscope, would there essentially be no current in the secondary? In this case the turn ratio is one. So ideally, the voltages...
  38. T

    Confusion about transformer and flux

    Lets consider an ideal transformer in no-load state, i.e. with the primary side connected to a voltage source, and the secondary side in open-circuit. Now, this is what I believe; the voltage Vp in the primary produces a current, which lags the voltage by 90°, as would be in an inductor. This...
  39. P

    Transformer for a power supply

    I am going to make a power supply. I understand the smoothing capacitor and the full-wave bridge rectifier. I am trying to make a 60V, maybe 10A power supply - maybe only 5A, but I would prefer 10A. I don't have a transformer for it, though. I have researched a fair bit on transformers...
  40. N

    Transformer powering Heating Element

    This one has me puzzled... using a variable power pack to heat an element - the powerpack is way overrated for the element (120A @ 12V secondary of transformer) so decided to build a smaller version. To get the element to about the right heat (glowing red) i set the large PP to about 25A and...
  41. C

    Transformer & Mesh Current Problem

    Hello people, I ve recently started to solve questions about magnetic coupled circuits, but I am stuck at a question that I ve seen for first time. I want to write the mesh equations but I simply don't know what should I do with the transformator in the middle when writing the equation for upper...
  42. L

    Engineering Short circuit calculation small network: gen motor transformer cables

    Hello guys, I have to make a short circuit calculation for school but I am a bit lost.. I have a copy off the IEC61363 and internet connection as my help lines. Homework Statement The network consists of a generator feeding to switchboard A with a cable in between, on the same...
  43. Q

    Transformer Capacitive Coupling

    I had a 4:1 single phase step-down transformer. Primary winding was provided the mains supply (225V) and output (secondary) was 57V. I was under the impression that capacitive coupling b/w primary and secondary was noticeable only in high-voltage transformers, and thus in this case (low voltage)...
  44. F

    Differential Protection for transformer

    Hi just wondering does differential protection protect against turn to turn faults? Does it protect against all phase to phase faults or is there special circumstances where it won't protect the transformer?
  45. L

    Magnetic Disturbances Affecting a Transformer Question

    Homework Statement Part A: A 250kVA, 11kV/50Hz supply single phase transformer has 80-turns on the secondary coil, calculate: i. The approximate values of the primary and secondary currents: ii. The approximate number of primary turns iii. The magnitude of the flux in Wb I think I...
  46. johann1301

    How Does COS Ø = 0.99 Affect Transformer Efficiency?

    On a trafo i just bought, it says COS Ø = 0,99. What does this mean? Is there some angle involved in changing the voltage?
  47. johann1301

    Effect of Transformer AC/AC: 27W Ingoing, 20VA Outgoing

    I have a transformer AC/AC which says that the ingoing effect is 27W and the outgoing effect is 20VA. Wich means it loses about 7 J every second to heat. (?) Any idea as to why it is written as VA instead of W on the outgoing line?
  48. J

    Physical Reason For Reduced Current In Step Down Transformer

    Hi everyone, I've been reading transformers and this question came in my mind. I'm unable to find a satisfactory answer. Why does the current increase in a step down transformer? I am aware of V1I1 should be equal to V2I2, but I was looking for a physical reason for the current to...
  49. F

    Power Factor and Single Phase Transformer

    What is the secondary current in a single-phase distribution transformer that is attached to a 480v line when the transformer is supplying 120v to a 16kW reactive load with a power factor angle of 40°. So I have kVA = 16kW/cos 40 = 20.89kVA Is = 1000 * 20.89kVA / 120v = 174A. I don't...
  50. H

    Quarter wave impedance transformer?

    Hi everyone, I keep trying to understand how impedance transformation works using a TLT but I'm stumped. There seems to be something I am just not understanding. Can someone explain in different ways how a line that is a quarter wave long cause an open circuit to look like a dead short and...
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