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. S

    Transformer Impedance Matching

    Homework Statement Hello, i just a have a doubt regarding the transformer impedance, my professor told me that the impedance before the primary coil should match the net impedance seen by the secondary coil, is that correct, i am not so sure about it. I would really appreciate it if you can...
  2. T

    Step up transformer + ac generator question

    Homework Statement An AC generator, originally designed to provide a peak output of +/- 155V at frequency 60Hz, is required to provide a peak output of +/- 340V at 50Hz. If the generator is connected to a transformer with 200 loops in its primary coil, how many loops should there be in the...
  3. C

    How Does Transformer Impedance Impact Primary Voltage and Current Calculations?

    Homework Statement A Single phase transformer has primary to secondary ratio of 2, its primary R1=0.05 ohms,X1=0.25ohms and the secondary R2=0.02ohms and X2=0.03ohms. The paramet of the magentizing branch referred to the primary side are Rc1=2kohms and Xm1=500 ohms. The secondary load current...
  4. neduet

    Calculating Current in a Transformer with Known Parameters and Load Impedance

    Homework Statement The prameters of 2300/230 v 50hz t/f is R1=0.286 ohm R`2=0.319 ohm Rc=240 ohm X1=0.73 ohm X`2=0.73 ohm Xm=49.2 ohm Secondary Load impedance ZL=0.387+J0.29 solve the exact equivalent circuit with normal voltage across primery.. I know every thing but i can't find...
  5. K

    Amerpage Transformer: Is There Such a Thing?

    Does anyone know if there is a such thing as an amperage transformer? Is there a device that multiplise current like a transformer multiplise voltage? If so how does it work?
  6. C

    How Does Power Factor Affect Voltage in a Three-Phase Transformer?

    Homework Statement A 2,000 kVA three-phase 33000/6600 V 50 Hz delta - star(wye) connected transformer has a primary and secondary winding resistances of 8 ohms and 0.08 ohms per phase respectively. The leakage reactance referred to the secondary is 1.5 ohms per phase. Calculate the sec...
  7. N

    Transformers in Multisim: Building a 240V to 15V Full Wave Rectifier

    Is there a normal transformer(not the center tapped transformer) in multisim that i can use to built a full wave recifier that will transform 240V @ 60Hz AC to 15V @ 60Hz AC.I am not very familiar with analog circuits and multisim and i cannot seem to find one. If anyone can help, he/she is...
  8. L

    Thanks for your help.Transformer Ratings: Questions & Answers

    Hi, I have a couple questions regarding transformers: 1. When you're told that a particular transformer is rated at 2000kVA, is that referring to the output or to the input rating of the TX? Or is it correct to say that the apparent power on both windings will be equal to that? I view...
  9. S

    Mutual inductance / coupling factor in twisted wire transformer

    I am trying to design UHF quadrature couplers from the following references: [1] 'Broad-Band Twisted-Wire Quadrature Hybrids' , http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1127996 [2] 'Twisted wire Quadrature Hybrid Directional Couplers' QST Vol 63 January 1978 pages 21-23...
  10. B

    Power transformer 60 hz to be tested on 50 hz

    The two power transformer 69/22.9kV and 230/69kV are both rated 60/80/100MVA designed for 60 Hz operation. However it will be tested on test facility were the available supply is only 50 Hz. During short circuit test at the LV side the 60/80/100MVA rating will be tested for the lowest tap...
  11. W

    Ohm's Law in Transformers: Voltage vs. Current

    In transformer when voltage increases on secondry coil then current decreases but i am confuse here that how ohm law is obeyed here. as V is d.proportiona to Current. please advise...
  12. T

    Optimizing Transformer Parameters for Efficient Substation Performance | Tims

    Hi All, I am required to assume some parameters for my research, For a new transformer worth $100 million for a substation, what likely could be sensible for these parameters? Nominal Capacity? (Example 10^5 KW) Average Repair Cost? ($1 million ?) Unsupplied energy cost? ($3 kWh ?)...
  13. R

    Transformer notation confusion?

    Homework Statement For a transformer, I need to get the ratings on the meters (wattmeter, ammeter, voltmeter) when it is put through an open circuit test and a short circuit test. Primary 240/480 Secondary 120/240 1KVA 60Hz The Attempt at a Solution Now I am not sure what is...
  14. teroenza

    Tokamak Transformer Properties

    Hello all, I am a layman who is interested in nuclear fusion via magnetic confinement (the Tokamak setup). I recently read in a book about how the (a) transformer in the device could operate only for some number of "volt-seconds" before it had to be "recharged". This requires an additional...
  15. Terocamo

    Transformer concepts (magnetic induction)

    Homework Statement The transfromer equation is given by\frac{Vp}{Vs}=\frac{Np}{Ns} for an ideal transformer. This equation is correct only if there are perfect flux linkage, the resistance of both primary and secondary coil is small and carries negligible current. The notes mention here if the...
  16. T

    Total load using step-up transformer

    Hi all. I'm hoping someone can help me out on a (for me) tricky little issue. We are to use a communication module that we know will draw 5amp and must be supplied via a UPS. Tricky bit is that its 3.5km away so we need to step up the voltage at source and step down again at load. 400Vac is to...
  17. neduet

    Understanding Transformer Capacity: 250 kva, 440 input, 220 output

    Hi friends If I have three phase 250 kva Transformer, 440 input and 220 output then Can I say that it can bear 568.2 amp current or 1136.3 amps?
  18. R

    Solving a Problem with Transformer Load Resistance and Source Resistance

    Weird Transformer Problem :( Homework Statement "In the transformer shown in the figure below, the load resistance RL is 44.0 Ω. The turns ratio N1/N2 is 2.10, and the rms source voltage is ΔVS = 77.0 V. If a voltmeter across the load resistance measures an rms voltage of 26.5 V, what is...
  19. J

    Resistor to trick 12v transformer

    Hi guys, new here. I was wondering if anyone knew of a way to trick a 12 volt transformer into seeing more load. I have these lights http://www.lowes.com/pd_172832-24969-800CBL5N_0_?productId=1207073&Ntt=tiella&Ntk=i_products&pl=1&currentURL=/pl__0__s?newSearch=true$Ntt=tiella$y=0$x=0" and it...
  20. D

    Ideal transformer problem, angular frequency w

    Hello, I have some doubts in the following problem of a transformer, specially on parts 2 and 4. I would be very grateful if someone could please give me any ideas specially about those parts... Homework Statement The Attempt at a Solution 1) Applying KVL in each mesh...
  21. T

    How to convert dc voltage into higher dc voltage using transformer?

    how to convert dc voltage into higher dc voltage using transformer? i am tring to convert 9 volt dc into 120 volt dc , and i ve to use transformer ,,, the problem is the transformer must have input ac voltage as it work on flux variation . i think the solution is to convert the input dc into...
  22. M

    Where Can I Find a Simple Guide to Transformer Design?

    Does anyone know of a good link to basic transformer design? I keep seeing the standard equations but they don't seem like much help. I can't seem to find any good guides for designing the most basic transformer For example, I will see equations relating the ratio of turns to the ratio of...
  23. Z

    Transformer efficiency conversion

    Greetings physics gurus Im getting bogged down on conversion of the VA to A Homework Statement A small transformer used to power a laptop computer has the following characteristics printed on it: • input AC 220 V, 50 Hz, 15 VA. • output DC 5.0 V, 1.0 A. Is this transformer...
  24. I

    Understanding Impedance Matching with Audio Transformers

    I have a question about impedance matching with transformers. If I have a source impedance of 20 K ohms, to step up the voltage does the primary have to match 20K ohms with a secondary of 40K ohms for a step up of 1:2. Or can I change it so the primary is 50 Ohms with a secondary of 40K ohms...
  25. S

    Calculating Transformer Parameters

    Homework Statement see attachment The Attempt at a Solution for part a): I tried to use the equation N2/N1= I1/I2 I got 12A, instead of the answer (24A) can someone please show me how to do this? I missed class one day, and now I'm lost
  26. A

    Power Transformer Control: Generator or Cable?

    Current transmitted control by the input power from the generator or control by the resistance of the transmission cabel?
  27. M

    Transformers for High Frequency: Size and Step-Up Ratio Considerations

    How small can I make a transformer and still get 1:30 or preferably higher step-up ratio ? I have been reading a lot about transformers and I know using higher frequency will reduce the size, and I need to use ferrite core for high frequency. I don't want to use really high frequency, probably...
  28. V

    Ideal Transformer: Vp/Vs, Ip/Is, Np/Ns Ratios

    Hi, http://en.wikipedia.org/wiki/Transformer related picture: Above link, says: "If the voltage is increased, then the current is decreased by the same factor." I didn't understand. Is this means, if I increase Vp, Ip will decrease? Or means Is will decrease? One more... Suppose...
  29. C

    Transformer qs, find turns ration & primary current

    Homework Statement A step up transformer is designed to operate from a 12V supply and to deliver energy at 240V. If the secondary winding is connected to a 60W, 240 V lamp, determine: a) the turns ratio of the transformer b) the primary current Homework Equations P primary = P...
  30. L

    Transformer Problem Homework: Building a 1:1 Isolation Transformer

    Homework Statement I'm working with a stripped-out microwave oven transformer core. I've split off a stack of laminations 1.25" thick, and cut out the middle leg of the "E" lams. I want to build a hollow-core 1:1 isolation transformer, and input a slow (about 3 Hz) pulsed DC current...
  31. M

    Transformer Efficiency Calculations

    Hey. I am currently doing a bit of revision for an exam and I am struggling on the following question: I understand the whole voltage/current/power/impedance ratio stuff, but can't seem to find any information on calculating efficiencies using the resistances or the transformer core losses...
  32. S

    I'm having trouble calculating inductance values in a transformer

    I have to figure out the two inductance values for a transformer; L2 and L1 where L1 is the inductance that sees the primary voltage and L2 is the secondary. i'm working with the formulas; n^2 = Z2/Z1 (8/1000) roeL2>>Z2 (roe= angular freq= 1kHz) n^2= L2/L1 basically i use this...
  33. M

    Quick transformer regulation question - Please help

    Homework Statement Tests are performed on a 50Hz transformer which yield the following results: Short circuit test: V1 = 40V, I1 = 10A, Power input = 20W Open circuit test: V1 = 240V, I1 = 1.2A, Power input = 70W Here are the equivalent circuit parameters from the above tests. Rc = 823...
  34. T

    Transformers: Calculating Base Rating and Per-Unit Values - 100 kVA, 1 kV

    Hello all, I am new to the forum and hope my question is appropriate for this section. My question is about per-unit notation and calculations. Basically I've been given the resistance, reactance at the primary and secondary windings of a transformer, core losses and inductance, etc. The...
  35. P

    Transformer primary-to-secondary turn ratio problem

    Homework Statement A step down transformer has a primary to secondary ratio of 4:1. If the peak current in the secondary is 12 A, the peak current in the primary is what? Homework Equations Vp/Vs = Np/Ns The Attempt at a Solution (4/1) = (Ip/12 A) what is the relation...
  36. M

    How Can I Boost the Voltage Without Increasing the Current Rating?

    I want to convert ac 50V, 1.8A into 100V, 1.8A. The voltage is doubling, while the current rating is required to be the same. How can I achieve this? A transformer action step ups the voltage, but does it lowers the current rating? Thanks
  37. S

    Calculating Secondary Amps in Step Up Transformer Problem

    I am having a problem with the following problem: A step-up transformer increases 10V to 170V. What is the current in Amperes in the secondary as compared to the primary? Assume 100% effiiency. The only formula I can see that has Amps in it is the turn ration...
  38. B

    Inductive interference from two EM coils (aka a transformer)

    I've been wondering about this for a long time. The little black box that you plug into the wall so you can power your electronic devices contains a general run-of-the-mill transformer. But if the power is completely shut off to the device: not draining any current waiting for a power button...
  39. N

    Volatge regulation of a single phase transformer

    A 10 kVA, 2200/220 V, 50 Hz single phase transformer is tested and the following results are obtained. Open circuit test (LV) Short circuit test (HV) Voc = 220 V Vsc = 150 V Ioc = 2.5 A Isc = 4.55 A Poc = 100 W Psc = 215 W Calculate: (i)The transformer parameters and...
  40. K

    Transformer with attached load: required source voltage

    1. A large power transformer has a turns ratio N1 / N2 of 1:5. When the primary voltage is 400v and it is connected to a resistive load its secondary current is 100A. Calculate the required value of source resistance of the supply to give a maximum power trnasfer 2. Vp = 400v, Ratio 1:5...
  41. N

    Vector diagram for no load single phase ideal transformer

    hey there.. how am i going to sketch a vector diagram of the given diagram? is it same like phasor diagram?
  42. Q

    Residual-current device & isolation transformer

    Hi guys, I don't understand why when one touches both the live wire and neutral wire in the secondary of an isolation transformer, the current in the live wire and the neutral wire in the primary will be the same. This is described in my book as the reason why a residual-current device in the...
  43. Y

    Generator connected to transformer- Find angular speed of coil

    Homework Statement A generator consists of a circular coil of radius 0.2 meters wrapped 10 times and is spun in a uniform magnetic field of 0.38 Tesla. It is connected (on the primary side) to a transformer with 7 turns on the primary side and 20 turns on the secondary side. If the secondary...
  44. E

    Isolation Transformer: Protecting Circuits & People

    Hai all, How does an isolation transformer protects the circuit and the person from shock. Please explain in detail.
  45. N

    Using Google Sketchup for CAD Modeling in FEMM Transformer Simulations?

    hi there, i'm trying to simulate a ETD core http://www.ferroxcube.com/prod/assets/etd29.pdf" transformer using FEMM free software but I'm not getting it...i've done some simulations with pot cores and had no problem with that, using the axissymmetric mode. bue this type of core is not...
  46. C

    Build Transformer: 110V-1V, 2 Electrodes | DIY

    Is it possible to build an adjustable transformer that can take 110/120 and dial it all the way down to 1 volt? I'd like to build one if possible to aid in physical development so it's very important to be able to take it as low as possible in the beginning. I'd like it to have 2 electrodes as...
  47. neduet

    Transformer and watt or VA relation?

    Hi friends it is not ( problem or numerical) just i want know friends if i have 15kva transformer . then can i say it can carry 1500 watt 10 (split AIR conditioners) as a load. and what happened if i add 5 more (split AIR conditioners) in same case. just give me idea...
  48. C

    Is the coil in a car's ignition system functioning as a transformer?

    like in a car when electrons flow through the battery to the coil , the coil is like a transformer using coiled copper wire to up the voltage to give the spark plugs a hotter spark. I am not sure where this energy is coming from , so are we actually getting more electrons to flow per second...
  49. S

    Transformer questions - primary, secondary, gaaaah

    Transformer questions - primary, secondary, gaaaah! Hello, I really need help with this. Much appreciated! Thank you so much in advance for any help!Homework Statement A step-up transformer has exactly 100 turns in the primary and exactly 200 turns in the secondary. If the voltage in the...
  50. S

    Primary coil of an ideal transformer. I need an equation.

    Homework Statement The primary coil of an ideal transformer is connected to a 120-V source and draws 1.0 A. The secondary coil has 600 turns and supplies an output current of 5.0 A to run an electrical device. A) What is the voltage across the secondary coil? B) How many turns are in the...
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