What is Transformer: Definition and 807 Discussions

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. K

    Voltage measurement on a Current Transformer (CT)

    I don’t know the ratio of the CT. I’m just looking for an explanation on this. I thought in order to measure output voltage you need to pass the current through a resistor and read the voltage drop. A co worker put 400a through the CT and measured 130v. Something just seems off to me. Can you...
  2. stipan_relix

    Engineering Voltages, currents and power between a power plant and a transformer

    This is the first part of the problem, which I solved. Now to the second part which I can't manage to find the equations I need to use. Problem: This plant is connected to a 20/0.4 kV transformer of 250 kVA power, through an XP00-A cable (4x150 mm2, IN=300 A, Z1=0.26 Ω/km). a) Calculate...
  3. H

    What's the normal low-load working temperature for an SMPS transformer?

    Hi! I have question about high frequency transformers inside switch mode power supplies (SMPS). Is it normal for them to become hot under no load or low load? For example if power supply is rated for 144A at 13.8V and I only pull from it 2A at 9.6V, it normal that transformer becomes about 50C...
  4. A

    Motor / transformer variable frequency control

    few questions 1) is it true that for a 50 or 60hz induction motor maximum torque is achieved from 0hz up to design hz and if an VFD is used and frequency is increased above 50 or 60hz like 100hz the rpm will increase but the available torque will decrease? Is the reason behind this the fact...
  5. J

    Understanding Output Voltages for a Center Tapped Transformer

    While trying to understand the working of a full wave rectifier I was unable to precisely understand the working of the central tap transformer. Edit 1 : The voltages are out of phase by 180 degrees as voltage is alternating(?) So the only thing I don't understand is how the distribution of...
  6. K

    Share: Pre 1935, Vintage Rotory Transformer

    Thought I'd share this interesting old relic as I am unable to find any information about "type 28" on the Internet.
  7. P

    Why is the output current of a transformer fixed?

    Im confused about how the output current of a transformer is fixed ie can be calculated by the law of conservation of energy only...(VI)in = (VI)out ? If the secondary coil is part of a circuit, and the secondary voltage is defined by V1/n1 = V2/n2, then the current in the secondary circuit...
  8. coolboyshane88

    Halbach array arrangement for a transformer

    Can we use Halbach array for the electromagnetic field since the magnet field change with direction? What would be the disadvantage? Imagine if we use Halbach array special arrangements for the transformer instead of an iron core. Maybe it could give us the same result? Kindly Maybe we can...
  9. NIKOLA TESLA Oficial

    How to Calculate Ferrite Transformer

    Hello everyone! I am unsure how to determine the number of turns, wire size, and current of the 50 kilohert ferrite transformer thanks everyone!
  10. X

    Making a Step-up DC transformer

    For one of my scientific projects, I want to charge a couple of 450V capacitors in parallel, which I get the power from household electricity, because a lot of lithium polymer batteries can be expensive and take up a lot of space. The problem is, the power supply gives a 250V AC, and and I need...
  11. D

    How to build a flyback transformer

    I am trying to build a flyback transformer. I have a ton of questions. For example can I use a Nail as the core? If not I don't know Why not. So why not? I have already studied the design on the internet. I still have tons of questions.
  12. Buckethead

    Low Voltage to Low Voltage Transformer for <1A Output Current

    I can't seem to find a transformer that simply converts a low voltage 9V-12VAC to a center tapped output to get +/- 9v/12VDC. It seems all power transformers have a 120VAC input voltage and the lower voltage transformers are designed for high frequency switching. What is a low voltage to low...
  13. Ramazan Duzgun

    How can Center-tapped Transformer parameters be found?

    It is a common center-tap transformer which is electrically demonstrated as in figure (ideal one); In my opinion, open circuit and short circuit tests cannot be applied directly. How can I place secondary reactances ? And how can I test its all parameters in laboratory ?
  14. G

    Power supply for testing: Variac or isolation transformer first?

    This is for safely powering up devices being tested/repaired. Supply is 240V rms single phase, protected by 32A MCB and 30 mA RCD/GFCI, then fused at 13A. There doesn’t seem to be a consensus online, and my EE and repair books just say I need both, without specifying order. I think the...
  15. D

    I have been unable to build a transformer

    I have tried to build a transformer. I have tried connecting a wien bridge oscillator to a wire. That wire Formed 7 turns around a nail. A second wire was wrapped around the same nail it had 14 turns. The second wire was connected to a multimeter there was no voltage Reading. The first wire was...
  16. B

    Current Transformer Proton Accelerator

    Suppose you place a current transformer into a vacuum and flow ionized hydrogen through the center of it. The ionized hydrogen would act as the secondary winding of the current transformer. How specifically would the acceleration that the hydrogen ions experience be calculated?
  17. A

    Transformer N1V1=N2V2 works only one freq

    Hi all, Recently, I have been playing around with the Pasco Transformer Demo set of SF-8616. I have been trying to verify the transformer relationship where the "2"s mean secondary and "1's" mean primary. However, no matter what configuration I try, this relationship holds at a single...
  18. C

    Transformer, Oscillator & transposing fomulae

    But the quadratic doesn't work. I can't see where i have gone wrong. Is my approach miles off? Thanks C
  19. B

    Can energy be extracted from a proton beam using a current transformer?

    Suppose there exists a proton beam that is pulsed on and off. If this beam is aimed through a current transformer as in the attached image (the proton beam would act as the main primary conductor in this case), what would be the output of the transformer, and how would it affect the beam...
  20. M

    Simulink: Saturation characteristic of saturable transformer

    I'm trying to get saturation characteristic of current transformer in simulink... In simulink, there was an example of a current transformer : https://www.mathworks.com/help/physmod/sps/examples/current-transformer-saturation.html And in this document, it said : the CT is assumed to saturate...
  21. Redio

    Electrical Can a Transformer Be Converted into a Welder Transformer?

    Hello can anyone how to convert this transformer in a welder transformer
  22. Sudalai

    I have some technical questions about a toroidal transformer core

    I have 150 x 100 x 60 M4 grade toroid core and same grade slit coil, I need to 180 x 100 x 60 in my design purpose.i would like to add OD 20 mm. my suspicion is a slit that can be added should be on the same grade?
  23. yecko

    Understanding Load kVA and Power Factor in Three Phase Transformers

    For question 2.28, the load kVA requires the use of power factor before calculating the line current, while eg 2.7 do not. May I ask why do they have the difference of using PF or not? Thank you.
  24. B

    Biot Savart Law with Different Magnetic Permeabilities

    I would like to make a program that produces a 2D heat map showing the magnitude of the magnetic field produced by a finite length solenoid. The heat map would show the field strength along the radial and axial directions of the solenoid. I plan to divide the conductor into "infinitessimally"...
  25. K

    B How a Secondary Resistor affects the Transformer Primary Side?

    Let's assume a 2:1 transformer which has a 100V Source connected on the primary circuit and has no/negligible resistance, on the secondary circuit a 5 Ohms resistor is connected. Using the 'Impedance Transfer/Reflection' method, the primary circuit would act as if there was a 25 Ohms resistor...
  26. E

    Can a transformer be grounded and any point in the winding?

    Conceptual question here. Not really positive if it should be asked here or in general physics... In U.S. grid power supply could the secondary winding in a step-down transformer providing split phase power be grounded at any point in the winding? Instead of calling the center tap neutral, if...
  27. Jason-Li

    415V to 11kV Transformer Voltage % regulation

    1. 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. (a) Determine the % regulation of the transformer at 0.8 power factor lagging. (b) In designing a...
  28. alan123hk

    Nonlinear transformer model for simulation in LTSpice

    I am looking for a comprehensive nonlinear transformer model, which should be available free, readily available for simulation in LTSpice and able to take account of various factors of nonlinear transformer including hysteresis characteristic, skin and proximity effect, leakage inductance...
  29. Manoj Sahu

    Why do Current Transformer cores have different knee point voltages?

    I have to test a Current transformer. I read knee point is a point at which 10% increase in voltage leads to 50% increase in current. As there are different classes of current transformer (cores), how it is decided what/how much will be the knee point voltage of that core.
  30. G

    Engineering Parameters of transformers: open and short-circuit tests

    Homework Statement Ok I have the following circuit and data (when the subscript is "ef" it means "rms" values): I am asked to determine the parameters of the transformer r1 L11, L22 and LM with the given experimental data. Homework Equations 3. The Attempt at a Solution [/B] I had no...
  31. G

    Transformer equations under load

    My question is about the theory when a current is drawn from secondary coils ... So ac in the primary produces a changing field that links itself producing a back emf in primary (in ideal transformer back emf equals Vp from the supply but in a real transformer the is a small net current in...
  32. M

    Applying Ampere's Law to a Transformer

    Homework Statement I was wondering if and how we can apply Ampere's Law to a transformer? I am just thinking about the bog standard transformer with a core, primary coil, and secondary coil. 1) How do I deal with the current from both coils? 2) Do I need to think about the opposing magnetic...
  33. Helmholtzerton

    Balun Transformer vs. 180 Degree Hybrid Coupler?

    Is there a big difference between these two devices? It appears a signal can be applied to one port of a balun, which will generate two signals 180 degrees out of phase with respect to each other on two of the other ports of the device. The results can be achieved with a 180 hybrid coupler...
  34. E

    How do transformers work, and how to read dot notation

    <Moderator's note: Moved from a technical forum and thus no template.> Hi all, I have attempted this question but have a few queries on how transformers work, and what the dot notation represents. (a) The flux would be clockwise around the iron core. (b) This is the question where it gets a...
  35. Wrichik Basu

    Why are there three wires in secondary coil of transformer?

    This is a 12-0-12 transformer that I intend to use in my circuit: Why are there three wires in the secondary? One is of course the neutral (in black). Why are there two live wires? As an additional question, can I use four 1N5408 rectifier diodes to convert the output of this transformer to...
  36. B

    Transformer: single primary coil and multiple secondary coils

    If I have a coil with 10 turns and a primary voltage $$V_p$$ and primary current $$I_p$$ and a single secondary coil with 10 turns, I understand the power in the secondary will be $$P=V_pI_P$$ and hence voltage and current in the secondary coil will be the same. If I now bring a 3rd coil with...
  37. R

    How to understand the Rating of this transformer

    Hello How to know the rating of this transformer
  38. Paola Flores

    Question about Magnetic Circuits in a Transformer Core

    Hello community, I can't find an explanation for something and I thought I'd come and ask you. I'm studying for a test I have tomorrow and I came across a problem of a three legged steel core with 400 turns on the center leg, the magnetization curve is given, the first part of the problem asks...
  39. J

    Transformer question: 50Hz versus 60Hz

    Will a transformer with 60 Hz being fed to a 50 Hz supply work?
  40. J

    Bench test AC transformer from stereo tube equipment

    I would like to disconnect the secondary windings from a stereo preamp to test the voltages of the secondary windings. The transformer has a 330 - 0 - 330 volt center tapped secondary and a 10.9 volt secondary. It is to be used with house current - 110 or so in Virginia. I have measured the...
  41. M

    Help with building this transformer in ltspice

    Hi, everything oko_O i just want to tell, can somebody, who have time just to read this file, you understand direct, if you know about fm detection, i just don't know how to make a transformer in ltspice, can somebody told how to make it this circuit with transformer and tuned please
  42. V

    Can we accurately model transformer oil degradation with mathematical equations?

    As the major contribution to degradation is due to the oxidation of oil which adds more polar constituents to the oil and thus increase the effective dielectric constant of the mixture.Can we assess the oil degradation just by looking at the effective dielectric constant changes over time? TIA
  43. R

    How to calculate the cable size between QRM and transformer

    cable size calculation between QRM and 11kv to 400v transformer (1500 kva)
  44. Peter Alexander

    Understanding Transformer Phasor Diagrams: A Step-by-Step Guide

    Hello everyone! I'm currently studying transformers and a task related to phasor diagrams shows up. I'm having lots of problems with comprehension of the subject, so I'd like to ask for some help. I don't understand how the phasor diagram given as a solution could possibly be drawn out of the...
  45. C

    Engineering Simple transformer circuit with 3 resistors

    Homework Statement 2. Homework Equations [/B] V1N2=V2N1 I1N1=I2N2 The Attempt at a Solution For a part[/B] I try to draw 3 mesh but I cannot write down the equation. Can someone help me out?
  46. Muhammad Danish

    Calculating Current in Primary Coil: Where Does P = V^2/R Formula Come In?

    Homework Statement Homework Equations How will we calculate the current in primary coil? The Attempt at a Solution The current in the secondary coil will be 2 Amperes by I = V/R. So in the primary coil by using ratio proportion method, the current in the primary coil will be 5 Amperes. But...
  47. I

    Leakage Reactance of a three phase power transformer using Ansys Maxwell

    Hello all; I am trying to calculate leakage reactance of three phase power transformer . I am using Ansys Maxwell final element solution to analyse it. The software gives me total energy and linkages and self and mutual inductances.By using this quantities how can ı compute leankage reactances...
  48. O

    Transformer Load Regulation Old Exam Question Help

    Hi, I was wondering if anybody would be willing to point me in the right direction for solving the following question. The questions is as follows: A 10000V RMS (primary) to 415V RMS (secondary) transformer rated 400kVA has the following resistance and reactance: Rs = 3 ohms Xs = 10 ohms A...
  49. OldWorldBlues

    Easy way to calculate losses for re-purposing a transformer?

    Hi everyone! This is my first thread :) I've been working a bit with AC and radio, and would like to make a simple(-ish) circuit in which a 1-volt peak audio signal is stepped up to around 5 volts with a transformer, and is fed into a crystal oscillator to make a crude-but-effective AM...
  50. carllacan

    Transformer under an external magnetic field.

    What happens to the current through a transformer windings if the whole system is under a uniform magnetic field in the direction of the coils and with frequency equal to that of the AC in current? I think the current induced in the primary solenoid should generate a field that would make up...
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