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. P

    Voltage in secondary coil of transformer

    Homework Statement A Primary coil, with ##n_1## turns, is driven with a voltage ##V=V_0sin(wt)## Find the voltage in a secondary coil, with ##n_2## turns, as a function of time Homework EquationsThe Attempt at a Solution Mutual Inductance ##M=\mu_0 n_1 n_2/l *area## ##emf=-d\phi/dt##...
  2. S

    Step Up Transformer: Current AND Voltage Increased?

    Please help! I have recently completed an experiment on transformers, using a step up transformer. I am aware of all the theory that shows that in a step up transformer, the induced voltage should increase and the induced current should decrease. However, in my experiment, my hypothesis is not...
  3. H

    Designing Your Own Transformer for Electrical Engineers

    Hello! I am studiyng for electrical engineer and i think its finaly time to build a transformer myself. I don't do this, cause i need one, but rather to learn how to design it. I'll be happy if you give me instructions how step by step to calculate one. Not how to physicaly build it, but to...
  4. J

    Calculating dimensions of a transformer on microstrip

    Homework Statement Using the graphs calculate lengths and widths of transformers (quarter wave) if they are realized as microstrip lines on a substrate that has Er=2 and height of 1.6mm at frequency 1.8GHz Z1=22.5ohm Z2=77.5ohm[/B]Homework Equations Guided wavelength = c/((Eef)^1/2)*f)...
  5. loki4000

    Quick question about transformer circuit

    Homework Statement Can someone inform me wheher my solution is correct? Homework Equations V1 = E2 * (10^-3)/2*(10^-3) = 0.001 V2 = E1 Ra = (R2+R3) = 0.02 Rb = R1 = 30 n = (1/100) n^2 = (1/100)^2 The Attempt at a Solution I1 = (V'1 - V2)/(Ra'+Rb) I1 = (0.001/n - 230)/(0.02/n^2 + 30)...
  6. T

    Quick question about inverter TX order wrt mains

    Hi, I should know better, but I'm having a mental blank. I was just wondering, if you're doing something using non-linear components on the mains, could be anything, maybe bucking to make a DC supply, whatever. Is it common practice to use an isolation transformer between mains and the...
  7. R

    A Transformer lamination thickness calculation

    I am trying to figure out the lamination thickness of a transformer to reduce eddy current loss at 10 MHz. I am new to the subject, any help will be appreciated. Also how do I calculate the size of a core to avoid saturation knowing the peak current applied to a 1:1 transformer. Thanks in...
  8. GauravU

    Open circuit test of 3 phase transformer in Ansys Maxwell

    Hi all, I am designing a three phase 11000/433 Volts Delta/Star 50 Hertz transformer in Ansys Maxwell. It has 792 turns in 6 layers on HV side (132 turns per layer) and 18 turns in 2 layers (9 turns per layer). The resistance as I have calculated is 0.1325 ohms per phase of HV winding and 5.57...
  9. T

    Single phase transformer question

    Homework Statement A 100 kVA, 2300/230V, single phase transformer has the following parameters: Rp = 0.30Ω, Rs = 0.0030Ω, Rc = 4.5 kΩ, Xp = 0.65Ω, Xs = 0.0065Ω, Xm = 1.0 kΩ The transformer delivers 75 kW at 230 V at 0.85 power factor lagging, find: a) The input current. b) The input voltage...
  10. P

    What exactly does the capacitor do in a Tesla coil?

    In all tutorials I have read on tesla coils, they have said to use a capacitor spark-gap configuration, to create a tank circuit. I want to know exactly what this means, and what is its purpose. I am not going to build a Tesla coil, I am nearly just interested in the science of it.
  11. K

    Can I Create a 15 Degree Phase Shift with Transformers?

    I was wondering how I can get a 15 degree phase shift with transformers. I know a delta wye transformer creates a 30 degree phase shift.
  12. J

    Transformer Flux and Exciting Current

    Can anyone explain in a transformer, how could a non-sinusoidal wave of exciting current produces a sinusoidal wave of flux?
  13. B

    Transformer Efficiency Problems

    Hello, My friend designs a special transformer, believing that its efficiency will rise and voltage regulation will fall compared to an ordinary one . He did a test with the same resistive load and got results below: T1(ordinary) Vp=220V 50Hz AC Vs(nl) = 99.8V Vs(fl) = 92.8V Pin = 129W...
  14. T

    Specific iron loss of transformer

    I am designing 3ph distribution transformer. So for calculations regarding to design, I want specific iron loss. I know how to find out iron loss but that requires initially specific iron loss of material, which i don't know how to calculate. I also searched it on google and in some books but...
  15. A

    Transformer current theory problem

    Homework Statement it is a long question so I have attached the question and picture Homework Equations I feel it is more theory based, which I explain below. 3. The attempt at a solution I am unsure- but I would think it is from B to A for part B, as using the RHR, if the coils are wrapped...
  16. Passionate Eng

    Transformer Efficiency - Max & Calculation

    hello there i have some confusion about transformer efficiency when it is max? and how it is calculated in different loading conditions e.g. at 80% of full load or at given PF
  17. W

    FDM simulation of an electrical transformer?

    My goal is to program a FDM simulation of a transformer. So, we have the coupled inductor model to start with ... However, if L1 = 1, L2 = 9, and coupling is perfect then M = sqrt(1*9) = 3 and L1 - M = -2. So, this seems problematical to me. Also, if I try to simulate this model using SPICE...
  18. D

    How to solve a voltage issue in a 25 kva transformer?

    I need an urgent help. I have a 25 kva transformer in my house. Without load the volt metter indicates 114 volts. Which dould be fine for my house. But when I put the house on the transformer I have no electricity and the volt metter indicates less than 1 volt. Can anybody help me out please?
  19. U

    Variable Voltage Transformer for Wind Turbine Battery Charging?

    We are trying to build a wind turbine which will charge a battery. Since wind speed varies (which affects the generated current and voltage), we were going to integrate a transformer in. My question is does such a transfomer even exist where the input voltage varies while the output voltage is...
  20. Yam

    What should be the power rating of the StepDown Transformer?

    Dear Forum Members, I imported an electrical equipment from the US which uses 110v, my country used 220v and as such i need to pirchase a step down transformer. The equipment is a piece of antique and doesn't come with much instructions. I could only get a circuit diagram and i am puzzled by...
  21. R

    Single-phase Transformer Calculations

    Homework Statement I'm a bit thrown at this problem as I am unsure if firstly my equations so far are correct and secondly where/how I need to factor in the 50 Hz part. Or is this a red herring? Also, am I correct in thinking that the emf means voltage? Any help would be appreciated A...
  22. A

    Star/delta transformer - single phase fault on secondary

    Homework Statement A three-phase distribution transformer is configured as follows: -primary side = star with solidly grounded neutral -secondary side = delta, grounded via zigzag earthing transformer A single phase-earth fault occurs on the secondary (delta) side of the circuit...
  23. AstroJMT42

    Voltage drop and transformer improvement

    Homework Statement Power station produces AC power at 2.5Mw, I = 100A. Transferred along 100km line with a resistance of 50 ohms to a factory. Calculate power lost and % efficiency Homework Equations P=VI P = I2R The Attempt at a Solution Initial power at the station is 2.5x106 . Using I2R...
  24. T

    What is the problem with leakage inductance?

    The thread name is probably misleading, but I just want to make sure I'm clear in that: Are the only two problems caused by leakage inductance (stray magnetic flux causing imperfect mutual coupling) in a transformer, that of; - poorer voltage regulation & - EMI noise on other equipment (?)...
  25. G

    How is current direction in transformer determined and why?

    Hello. Please see the attached picture first. For typical battery (nothing but capacitor), current direction is clear as electrons can't not flow across the two plates in battery so they only choose wire as a path from cathode to anode. But in transformer (+ and - sign represents voltage at...
  26. V

    What causes screeching noise in phone adapter transformers?

    My phone adapter makes a screeching sound when switched on, but not too loud to be audible to everybody. I know there are eddies within the transformer, but other adapters do not seem to be noisy. What is that?
  27. M

    Transformer for CDI ignition power supply

    I have an old motorcycle which I would like to fit with a modern CDI ignition. The ignition would be of the type typically fitted to dirt bikes and which require a high voltage AC source. They have a permanent magnet alternator with a separate high voltage stator for the ignition in addition...
  28. ZenSerpent

    Single Phase Transformer Losses -- Hysteresis, Eddy Current Constants

    Hi. My colleagues and I are doing a research on transformers (single-phase) and we stumbled across the following equations involving hysteresis and eddy current losses: Wh = ηBmaxxfV where Wh = hysteresis losses η = Steinmetz hysteresis constant Bmax = maximum flux density x = constant...
  29. tech99

    Transformer core considered as a waveguide

    Has anyone considered the iron core of a transformer to act as a transmission line or waveguide, where it conveys energy from primary to secondary? The core seems to resemble a "magnetic version" of the single wire Goubau line.
  30. Aryan Andaleeb

    Homework help: Transformer Current

    Homework Statement If we denote: Alternating current in the primary coil as I1 Alternating current in the secondary coil as I2 Similarly, we denote, Number of turns in primary coil as N1 Number of turns in secondary coil as N2 And, we denote, Voltage generated across primary coil as V1...
  31. Nahian

    Paralleled Transformers: Why Overload & How to Prevent It?

    When transformers with the same turns ratio, but different kVA ratings are paralleled , it is possible for the smaller transformer to be overloaded and the larger transformer to be lightly loaded.Why is it so? Can anyone please show mathematical and theoretical explanation?And what can be done...
  32. Nahian

    Rated Conditions of Transformer & Electrical Components

    What is actually meant by the rated conditions of a transformer or any other electrical components??
  33. neduet

    What is this in power transformer 60 MVA

    Dear all, hi what is this pipe thing in new transformer 60MVA and what is its use. ?
  34. Marcis Rancans

    Can a transformer handle more current than its specifications?

    How large current does go through resistor (how to calculate it?) and can it draw more current than written on specs of transformer (in this case burning it down)? Do they mean 0,5 amps are max current safe to draw without burning down? Transformer is connected to wall power (220 V, 60 hz). On...
  35. J

    What is D.F and How to Calculate It for Transformer Load?

    I have seen an excel sheet in calculator to calculate the size of transformer. There are option to put the vales of Kw,PF,Qty and Equipment D.F. I could not understand what is D.F. What is the equation to calculate the D.F and equation to calculate the total load D.F?
  36. A

    Finding Turns Ratio for Different Transformer Configurations

    So I was studying on transformer calculations and understand it all pretty well until coming across these questions that I don't really understand. There's about 6 of them but if someone could work out 2 for me so I can understand it and finish it off it would be much appreciated. Thanks...
  37. T

    Electrical meter and efficiency question

    Q1. I know a DMM will anticipate a sineusoidal supply, thus there can be problems with spiky supplies. Even if you have a true RMS meter, it it's a spikey supply, non-sineusoidal, you still can't calculate the peak of a spiky supply? Does a DMM measure the peak, then calculate from THAT the...
  38. Y

    Engineering Electrical Circuits - Three Phase Power - Y-Y transformer

    Homework Statement I took a few pictures of the circuit, it went across two pages so I took a few pictures, and closeups of certain parts to ensure that all the details can be seen For the circuit: http://s7.postimg.org/ywd4nrmsq/IMG_20150905_140403187_HDR.jpg Figure 1. Overview of Circuit...
  39. L

    Engineering Transformer open/short circuit test

    Hi guys, The problem isn't with the question itself its more to do with the fact about how they got Z and R. Just need some clarification. In every other AC power question. I have always worked out impedance with whatever parameters I had be it P/I^2 or V/I. I'm confused as to what the...
  40. A

    Transformer and potential difference

    Homework Statement So i was in a course yesterday and the "teacher" told us the following (which i had a hard time believing/understanding) There is a load connected to a transformer. Applied potential difference is 230V. The load is malfunctioning and the insulation isn't working anymore. The...
  41. R

    Utility Metering Current Transformer

    The electric utility has a digital wattmeter that seems to be measuring the power usage at the high voltage side of our distribution transformer (11 kV - 420 V 3 phase, 250 kVA) via a Current Transformer. How exactly does this work? Specifically, what I'm confused about is that transformers...
  42. D

    Car Amplifier Mod: Can It Be Used Practically?

    Hello, I am new to this site as well as to electrical theory. I recently took a second semester physics course and stumbled upon a great deal of curiosity in the electricity and magnetism portion of the class. I am taking a few courses pertaining to electricity&magnetism as well as engineering...
  43. R

    Splitting power between cables by rating

    How are power distribution cables parallel-ed to split loads optimally? If the cables were exactly identical this would be easy but how is it achieved in general? e.g. Say there's a 11 kV to 420 V distribution transformer but the primary load is some distance away. Assume the load increases...
  44. J

    Three single phase transformer with different %Z's

    Hello everyone, I have a three phase circuit that consists of a three-phase transformer bank feeding a balanced three-phase delta load. The transformer bank consists of three single phase transformers connected in delta. Each transformer is rated at 333kVA, 2400V. Two of the transformers...
  45. J

    Emulating car battery output through home power?

    I'm setting up an amplifier which is intended for use in a car, and I'm not using it in one. I'm trying to power it through a typical DC 250 volt wall outlet. What kind of transformer should I use? (I'm also trying to power a car stereo with it as well)
  46. Guidestone

    What is the Purpose of Current in a Transformer?

    Ok guys so I have to purchase two transformers with certain voltage value and current. I think I know what voltage in a transformer means when it comes to look for one, it's only the input and the output voltage, please correct me if I'm wrong. But I can't understand the current value, is it...
  47. cnh1995

    Induction motor as transformer

    It is observed that the stator current of IM increases on loading. In transformers, the increase in primary current due to loading is significant . Is it same in induction motor? Does the air gap affect it?
  48. S

    Does a Step-Up Transformer Really Increase Light Bulb Brightness?

    theroteically using transformers can't create power then why a light bulb connected with a step up transformer can become brighter
  49. S

    Power of Transformer: Primary & Secondary Light Bulb

    when i compare the brightness of the light bulb in the primary transformer and the secondary transformer (step up transformer) the secondary light bulb is brighter . teacher say because of v^2/r after step up the v increase and so the power. however if i use i^2r after step up i decrease power...
  50. A

    Tapped Transformer With a Capacitor

    The question is the following: a) Determine all load voltages and currents b) Determine the resistance reflected into the primary. Answer a) R(l): 35V, 2.91A, X(cl): 15V, 1.5 A The answer to part (b) is apparently 34.5 Ohms. How did they arrive at these answers? I am not sure...
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