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

    Electrical energy transmission and transformer

    When transferring electricity from a generator to a factory or anything we would use a transformer to step up the voltage right? As P=VI and P is constant in the primary and secondary transformers (ideal case), with an increased V as compared to the primary transformer it will in turn result in...
  2. F

    What Voltage Does Voltmeter V1 Read in a Transformer with Tapped Secondary Coil?

    Homework Statement 27.An alternating current power supply rated at 120 V is connected to the primary coil of a transformer. The coil has 200 turns. The secondary coil has 600 turns, and is tapped 200 turns from the top end, as shown. What is the reading on voltmeter V1? (diagram attached)...
  3. D

    About transformer configuration

    i may need your help for following question. 15kva, 2300/230v, 50Hz transformer has voltage drop of 2% and 4% of load voltage, due to winding resistance and leakage reactance respectively, at full load. 230v is maintained at the secondary terminal. The full load copper loss is equal to the...
  4. M

    Practical transformer question-3ph/single phase.

    I need a 10-15 : 1 step-down transformer for an electrolysis project. It needs to be capable of about 150A. I have an old ex-military transformer/rectifier, but it outputs 200A at upto 230V DC. It has a humungous transformer in it , and some banks of BIG diodes, so if I get a variac from ebay...
  5. L

    What's wrong with my transformer model with Ansoft Maxwell

    Hi, I had modeled a simple transformer with Maxwell 3D (one closed iron and 2 coils), all seems all right except the output voltage, I have only 300 mV and I must have 12V ! I join the files, if someone can help me ? A strange thing is the StrandedLoss which up to 350 kW ! where's come from...
  6. H

    Can I Design a Transformer Coil with These Specifications?

    I am in need of a transformer which has the following characteristics: Operating frequency 20kHz Turns Ratio 1:8 Primary 12V square wave @ around 100mA max Dual secondary coils (wound together with equal turns) (Note: Only 1 secondary coil will operate at any given time) Secondary 96V...
  7. C

    Calculation of core losses of a transformer

    Hello! I am a grade 12 student. If you are familar with the IB program, I am writing an extended essay (it's a 4000 word research essay) on how transformer losses are affected by temperature. Through two experiments I was able to determine how the losses of the primary and secondary windings...
  8. B

    Impedance Voltage of a transformer.

    I know what impedance voltage is. I will state it just make sure we are talking about the same thing. Impedance voltage is relative short circuit voltage, when secondary of a transformer is short circuited, and we are slowly raising the primary voltage "Vpr" until the current at the secondary...
  9. J

    Need help finding high voltage transformer

    I am trying to find a high voltage transformer with the configuration shown below. The guy that took the picture says that it is an x-ray transformer that he modified slightly, but after all my searching, I can't find a transformer like it. Has anyone seen this type of transformer or know...
  10. L

    How simulate a transformer with Maxwell Ansoft?

    Hi, I would like to simulate a standard transformer (2 coils + 1 closed iron) with Maxwell 3D (V15) but I don't find tutorial or example. Maybe someone can explain how can I do ? I want to see the flux in primary and secondary. And I want to put a tension in primary and see the current in...
  11. S

    Looking for split-phase step-up transformer

    I am looking for a step-up isolation transformer (not an autotransformer) with an input of 120V and an output of 240V where the ground reference for the secondary is half way between the two hot line outputs so each is 120V relative to ground with opposing phase angles so they are 240V relative...
  12. J

    Transformer Primary and secondary currents

    Homework Statement A single phase transformer has the following rating : 120kVA. 2000v/100v, 60 Hz with 1000 primary turns. Determine: a.Secondary turns b.The rated primary and secondary currents Homework Equations Vp/Vs = Np/Ns The Attempt at a Solution a. I have used...
  13. E

    Making a 3-Phase Transformer with 2 Single-Phase Transformers

    Well we can make a three-phase transformer using THREE single-phase transformers, but is it possible to make one, using only TWO single-phase transformers?
  14. Y

    Why Doesn't Current Flow in an Isolation Transformer Secondary?

    Hi, Maybe this is a stupid question, but I've been wondering about this all day. In my book, they only explain the isolation transformer really brief. As far as I understand, the main of the transformer has a neutral which is grounded, if you touch that, the current will flow through...
  15. G

    Overunity Device Using Transformer - Need HELP with theory

    Overunity Device Using Transformer -- Need HELP with theory Ok, so if you had a transformer with a single primary winding and multiple secondary windings - let's just say 10 secondary windings - what could you do with this? Say if all of these windings were 1:1 with the primary to the...
  16. jegues

    Power Factor OCT of Transformer

    Homework Statement See statement below. Homework Equations The Attempt at a Solution I've been reading through the notes for my course and in the section where we are determining the parameters for transformers. For the OCT they give, 240V, 1.066A, 136.6W From this they...
  17. jegues

    Transformer Confusion (Simple, Help)

    Homework Statement See first figure attached. Homework Equations The Attempt at a Solution For this question I understand parts 1) and 2) entirely and have obtained the correct answers from the solutions. I am confused about part 3) and I think my confusion stems out from...
  18. C

    Solve Transformer Question: V1/V2=N1/N2

    Homework Statement http://i.imgur.com/DBoKH.png Homework Equations The Attempt at a Solution V1/V2=N1/N2, that means there shouldn't be a current. Why it is 0? Thanks!
  19. R

    Wattage requirement for step-up transformer

    Hello,I want to investigate the feasibility of buying a step-up transformer(110/120v to 220/240v)in order to plug in a 20 amp 240v portable electric heater that is rated at 4000 watts.The 110/120 comes from a standard wall outlet in a home built in 1995.I want a portable heater set-up that is...
  20. G

    Square wave into a transformer, low impedance output needed

    I need to connect the transformer to an 5V open-collector source as shown below, but the load must not see a larger impedance than 50Ω. The 5V source is an internal source to the driver and not available outside of it. As it stands, the seen impedance will be 5k when the bjt is off, so this will...
  21. T

    Air Core Transformer design help

    I am building a 400W power amplifier that is designed to work between 10MHz to 15MHz. I have a schematic that uses a set of isolation transformers and a set of step-up transformers. I ordered some powdered ferrite transformers from Magnetics (www.mag-inc.com). The isolation set is a...
  22. S

    Transformer dot prob don't understand (with sol)

    The problem: Solution in the spoiler: I don't know how to do the problem (a), but I also don't understand the answer (top of coil 3?). Can you give me the process on how to do the problem (a), i.e. in general how do I assign dots to coils in circuits? :)
  23. A

    Understanding Autotransformers and Dot Convention: A Question on V1 and V2

    Hello, I have the following question regarding autotransformers and dot convention (please see attached). Can anyone give any guidance? I think I have an answer for part (a) but not completely sure if this is correct as I haven't come across a similar example before, sorry about the lack of...
  24. I

    Can a Step Down Transformer Handle Universal Input for a Linear Power Supply?

    Building a simple linear power supply for a project and need to spec out a transformer. I have no idea how they're built and used in the industry. I was instead handed a 120VAC input with a 24VAC output and 2A max step down transformer. I am content with it for the moment. But I'm looking to...
  25. S

    Classical Physical Explanation for Turn Ratio in Transformer

    Hello. I'm trying to understand why, in terms of Maxwell's Equations, the ratio of the number of turns in a transformer converts an input voltage to an output voltage. EE explanations only seem to go as deep as this article: http://en.wikipedia.org/wiki/Transformer#Basic_principles They state...
  26. U

    Electrical Winding 1st toroidal transformer for my DIY Geiger counter

    First post! :) I am building a Geiger counter with this circuit: http://www.pocketmagic.net/wp-content/uploads/2011/03/geiger-simple-1b.jpg in the blog the author used a regular EI transformer from a power supply, but I tried disassembling them and broke the ferrite core 4 time now, so I...
  27. B

    Maximum flux in a single phase transformer

    A single phase transformer has the following rating: 120 kVA, 2000 V/100 V, 60 Hz with 1000 primary turns. Determine: (a) the secondary turns (b) the rated primary and secondary currents (c) the maximum flux (d) given a maximum flux density of 0.25 T, the cross-sectional area of the core...
  28. N

    Transformer Voltage Regulation and efficiency determination?

    A transformer is rated at 2300/230 V, 15 kVA and 50 Hz. Assume that the transformer is operating at 80% p.f., leading and at rated output the secondary terminal voltage is 230 V. The following parameters for the transformer are given: N1 = 1500 turns N2 = 150 turns r1 = 2.7 ohms r2 = 0.024...
  29. R

    Transformer Load: Do I Need to Worry?

    Hi physics forum, I'm going to use a transformer to step down 240V AC mains to 24V AC. I remember my physics teacher telling me about matching the load between the power supply and the load. Do I have to worry about this in my case? Regards, Richard
  30. J

    Magnetic Flux analysis in transformer design.

    Hello everyone, I'm currently at third year of EPE and this software is totally new for me so i would to ask a few questions. I have been asked to use infolytica MagNet using Field Sampler tool to analyse a flux behavior in the air-gaps and in the transformer core for 2 different core...
  31. D

    Transformer, AC Source, and a Battery

    Homework Statement Using an AC signal generator vs, a transformer with turns ratio n = 1, and a battery VB, sketch a circuit that will generate the output signal vout = vs + VB Homework Equations \frac{V_2}{V_1} = \frac{N_2}{N_1} The Attempt at a Solution Here's my sketch...
  32. R

    Can Paraffin Oil Improve Transformer Insulation?

    Hi Gents. I've to use a transformer ( "R" Core), primary to mains and secondary (2 X 9 V) connected to high voltage source of about 8 kV. I am going, in order to improve primary to secondary insulation, to place this transformer in a paraffin oil "bath". Is it a good idea ?
  33. C

    Current Transformer Phasor Diagram Explained

    can anybody explain me the phasor diagram of a current transformer. it would be a great help
  34. C

    Using a Matching Transformer for 50 Ohm to 75 Ohm Coax

    hello, good afternoon. I'm a little bit confused about the use of matching transformer. I made a 50 ohm tv antenna, and i connected it to a 50 ohm coaxial line. However, I've found out that for tv applications, 75 ohm coax should be used. my question is, if i will replace my 50 ohm coax, can i...
  35. C

    What are the numerical values of a1 and a2 in this AC transformer circuit?

    Homework Statement The sinusoidal voltage source in the circuit shown in Fig. 2 is developing an RMS voltage of 2000V. The 4ohm load in the circuit is absorbing 4 times as much average power as the 25ohm load. The two loads are matched to the sinusoidal source that has an internal impedance of...
  36. D

    Transformer short circuit test ?

    Hi guys, After doing some reading on transformers and reading solved examples there was one thing I couldn't quite figure out. There was a transformer with all the nominal data (10k/0.4k kV/kV, 100kVA), it said that they made a transformer short circuit test when one side is shortened and...
  37. L

    Cancel secondary flux (reaction) from transformer

    hi, The drawing show 2 transformers T1 and T2. Each primary of transformer is at fixed voltage (110 volt for example), but one transformer is with 0° phase and other with 180° phase. The secondary of each transformer has the same charge and the same current. The idea is to cancel the flux from...
  38. B

    How to calculate transfer function when there is a transformer

    Homework Statement Calculate the transfer function, H(s) = Vo(s)/V1(s), of the given circuit.The Attempt at a Solution I see there is an inverting amplifier with gain A = -10. However, I don't know how to complete the analysis with this ideal transformer. How can I substitute it? Thank you.
  39. P

    How to know the VA rating of a transformer

    Hello to all I am an electrical engineer and in an interview I was asked to tell the MVA rating of a transformer of few KV , and nothing was given means neither the power factor and nor the current , so I want to ask you people is there any way to determine the MVA rating of the...
  40. S

    Selecting the Right Transformer Turns Ratio for a Given Voltage

    Considering a practical transformer, We can get a given voltage and corresponding current ratio by selecting a particular turns ratio. ie. V1/V2=N1/N2=i2/i1 Say that I want to make a 240V/60V. Now 240/60 volts ratio can be acheived by considering different no. of turns on primary(P) and...
  41. S

    How Do Core Construction and Amp-Turns Affect Transformer Performance?

    Off and on, I have been messing with making a little transformer. My first attempt was last winter. They never seem to really work very well. Is there any sort of rule regarding the amp-turns needed around a core with a particular permeability? My earliest attempts used a straight rod...
  42. D

    Single Phase Transformer: Short Circuit Experiment Results and Calculations

    hi guys, this is a question from an exam about a single phaze transformer and it goes like this, I am sorry for the bad translation in some parts i couldn't find the correct terms: A single phaze transformer is given with nominal data of - 10k/0/4 kV/kV , 100kVA A short circuit experiement...
  43. D

    How Does Electron Spin Orbit Influence Ferromagnetic Transformer Functionality?

    I have been working on a transformer that has a potential difference out but no current. it uses of electron spin orbit to work. here is a brief explanation with some references i have uncovered that iron is unique in that each atom has a magnetic moment, that is each atom has a north...
  44. R

    What is an isolation transformer

    Does anyone know what is meant by electrical isolation? From this schematic: url=http://upload.wikimedia.org/wikipedia/en/1/12/Swer.gif I don't see the significance of calling the transformer an "isolation transformer". What is the difference between a transformer and an isolation...
  45. H

    Bifilar Winding & Transformer Secondary Voltage

    If a transformer has a bifilar wound primary coil will the secondary voltage still be equal to the transformer's turns ratio? Bifilar coils when connected together in the proper way have a much higher voltage between turns. Instead of the voltage across each turn being equal to the total...
  46. T

    Potential Transformer of a 3-phase

    Ive got a problem related about potential transformers in 3 phase. Are they measured in line-line or line-neutral? My connection is wye-delta. Thanks!
  47. teroenza

    Why transformer voltages in phase?

    Homework Statement Why are the voltages of the primary and secondary coils of a transformer in phase? The transformer is a simple one with two coils, and an iron core. A.C. voltage applied to the primary, no load on the secondary. Homework Equations The Attempt at a Solution...
  48. Y

    How to calculate power loss from a transformer

    I am currently trying to figure out how much power loss there is with a small transformer we have running VERY hot. XF info: 5kVA 120/208 to 277V %Z:5% I can't recall any power equations dealing with real transformers.
  49. F

    Voltages and Turns in a Transformer

    In a step-up transformer, should the ratio of the voltages be approximately equal to the ratio of the number of turns? Why? Same for a step-down transformer: should the ratio of the voltages be approximately equal to the ratio of the number of turns? Why? Thanks
  50. F

    Connecting a transformer backward

    An electric doorbell requires a 12 V, 60 Hz ac supply. If the transformer is connected the wrong way around the circuit, what voltage is supplied to the doorbell? If figured the voltage ratio would now be 120/12, or 10, and 10 x 120 = 1200V. Is this right? My other idea was that...
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