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. D

    Why will current decrease in a step-down transformer ?

    Why will current decrease when voltage increase in a transformer ? I 've just learned it and I get confused. Assume there are 2 solenoids, the no. of turns of coils in the left sides one(with AC current) is less than that in right sides.By conservation of energy, V(left) x I(left) = V(right) x...
  2. H

    Resonant transformer - sign of the voltage reinduced in the primary winding

    Consider a biresonant transformer with a small coupling coefficient k << 1. Let the voltage applied to the primary LC circuit be U1(t)=U*sin(2*Pi*f*t), then also the current I1 will be sinusoidal. The voltage induced in the secondary winding and the current in the secondary LC circuit will be a...
  3. Femme_physics

    Zero Point Switching with transformer

    So with my final test tomorrow I thought to sneak in another question... Homework Statement The following circuit applies switch at the load RL via Zero Point Switching. The ratio of the coil windings at the transformer is N1:N2 = 4:1. The introductory voltage is a sinusoidal type and its RMS...
  4. Y

    Where can I purchase a high frequency step-up transformer

    I need a transformer with the following characteristics that can operate at a frequency of 1MHz. Step-up ratio= 1:80 Primary L=1.55uH Secondary L=10.65mH Mutual Inductance= 62.5uH Any suggestions on what US companies might carry this kind of product?
  5. T

    Calculating Current Through Compensation Winding in Cascade Voltage Transformer

    Got cascade voltage transformer made from two completely identical units. On secondary winding, load takes I2=1A Number of compensation and secondary windings is equal. I need to find current trough compensation winding Ic . θ1 = θ2 --> θ1 = I1N1 + IcNc - I2N2 --> θ2 = I1N1 - IcNc --> I2N2...
  6. N

    Reading Transformer - Learning How to Read Non-Industrial Transformers

    I was just curious if anyone could point me in a direction on how to read transformers that are not industrial transformers? I ask this because I'm new to the field of electronics and I found an old transformer from my grandfather and the only information written on it is PT-54-A next line...
  7. S

    How Are VA Ratings Derived for Different 3-Phase Transformer Configurations?

    hello there ; I have several questions about the 3-phase transformer connections and I will be really grateful if anyone could help ... I've learned that there are several types of 3-phase transformer connections which are in general ; the (Wye-wye) , ( Wye-Delta ) , (Delta-Delta ) , (...
  8. H

    Transformer output voltage Vs turns ratio: HELP

    I just built a transformer to the specs of the original. The transformer has a turns ratio of 1:16. Input to primary is 12V. The problem I am having is a very low voltage at the secondary side. The no load voltage was the highest (40V) that I have got out of it so far. The primary coil...
  9. S

    Phasor Diagram of No Load Ideal Transformer

    For a no load ideal transformer V1 is anti phase with E1? or in phase like this?
  10. C

    How Do You Calculate Transformer Efficiency and Power Parameters?

    Homework Statement the circuit values of a 60Hz,20kVA 2400/240V real transformer: R1=3.0Ω X1=j6.5Ω R2=0.03Ω X2=0.07Ω Xm,magnetizing reactance=j15kΩ Rc,core loss resistance=100kΩ the transformer with rated load is said to be having a lagging power factor of 0.8 compute 1. primary...
  11. N

    Transformer for Heater Control

    I am looking to power a heater. According to the product specifications it will require 11.1V/26.4A to heat to 800C and 16.9V/33.1A to heat to 1000C. The manufacturer sells an expensive temperature controller which we would like to avoid using. It has been suggested to me that I use a variable...
  12. H

    Can a Zig-Zag Transformer Provide a Neutral for 3-Phase HVAC Control Circuits?

    Hi We have a project where we have to install an HVAC system but only a 3-phase supply is available. While that is fine for the motors inside the unit, it means that there is no neutral available for the control circuitry. I am aware that a "zig-zag" isolating transformer can provide a...
  13. L

    How exactly does a transformer work?

    Hi, the explanation I have been given for how a transformer works is this: The current flows through the primary coil, hence generating a magnetic field around the coil. Imagine that the coil is wrapped in the anticlockwise direction around the soft iron core (and hence current flows...
  14. R

    Information about current transformer

    hello friends...i am facing difficulties in understanding the difference between live type and deadtpe current transformer...and also the advantage of live type over dead type?
  15. M

    How the efficiency of transformer affects turn ratio

    A secondary textbook said that if there is no flux leakage, Vp/Vs=Np/Ns, no matter what is the efficiency of the transformer. May I know will the ohmic loss and eddy current contribute to the loss and modify the voltage ratio? thanks!
  16. FOIWATER

    Transformer frequency fluctuations.

    How does a transformer react to a changing frequency Obviously the inductive reactance of the primary changes, which causes a decrease in the current for an increase in reactance, then so too shouldn't the output voltage be less? This seems to contradict Vs/Vp = Ns/Np What I am saying is...
  17. L

    Characteristic Diagrams: Understanding Transformer Waveform Output

    Using characteristic diagrams, describe how a Transformer produces a complex waveform from a sinusoidal input. can someone in the community please help me with this , ref. to a web informative page etc would be fantastic as any i find are way to complex for the level that i am at ( hnc ) any...
  18. K

    Transformer currents in primary and secondary question

    I'm reviewing transformers and I have some confusion over the current s is for secondary and p is for primary I know that Vs = Vp(Ns/Np) and Ip = Is(Ns/Np) So when you have a load across the secondary terminal you get your current through Vs/Rload. But does this mean for current in...
  19. N

    Magnetic Flux inside a Transformer

    I have read that when the secondary of a transformer has current flow, it will reduce the magnetic flux in the core. This then reduces the back-emf on the primary, causing a increase in current to reestablish the magnetic flux to what it once was. What I want to know is when the secondary...
  20. N

    Why Is Transformer Secondary Voltage In Phase With Primary Despite Lenz's Law?

    Why is the Voltage induced on the secondary of a transformer in phase with the primary? As far as I know, lens law states that any induced voltage on a coil is 180 degrees out of phase with the coil that generated magnetic field. Otherwise you could have infinite energy systems, lol. Is the...
  21. L

    Transformer - Calculating Output Voltage (AC Input Voltage)

    Homework Statement For a transformer, the ratio number of turns on the transformer secondary : number of turns on the transformer primary = 21 : 1200. If the input voltage is 120V AC, what is the output voltage? Homework Equations \frac {N_{P}}{N_{S}}=\frac {V_{P}}{V_{S}}...
  22. I

    How is a pole mounted transformer wired?

    I'm having trouble understanding how a pole mounted transformer is wired. I am astounded at how little information is online about one of the most common devices on the grid. The typical single phase transformer has a single wire connection from one high voltage power line. To have a...
  23. M

    How Does Efficiency Loss Affect Voltage and Current in a Transformer?

    Homework Statement A step-down transformer going from 240 V to 12 V is 95% efficient. The input current is 20 A. a) Determine the primary turns: secondary turns ratio necessary in order to maintain a 12V output. b) Determine the output current. I have solved it as if I needed an secondary...
  24. C

    The Maximum current in a transformer

    I have attached the problem. This is a practice exam and the answer Imax = (N2/N1)^2 * (Emax/R) but I have no idea why. I have been trying to manipulate the transformer equation I2/I1 = N1/N2 = V1/V2 but to no avail. Thanks
  25. R

    Ferrite magnet as toroid transformer

    Dear Experts I have a 1.5 cm ring magnet, you know, the black color type of common low magnetic power magnet. I wrapped 5 turns of copper wire around it on one side and then wrapped 10 rounds of another copper wire around it . I connected 5v battery to the 2 ends of the primary coil which...
  26. H

    Can I Measure the Output of an Unknown High Voltage Transformer?

    Hi, I have an old high voltage furnace ignition transformer with no specification plate on it, When plugged to 240v it gives about 10mm arc length; with no proper equipment to measure such high voltage I was wondering if I can plug it 50v and measure the output to calculate the ratio. I'm also...
  27. B

    An ideal (lossless) transformer has 4 times as many turns

    Homework Statement An ideal (lossless) transformer has 4 times as many turns on the primary winding as it has on the secondary winding. The secordary winding is loaded with a 10k ohm resistor and a sinusoidal voltage source having negligible resistance and a peak voltage of 10V is connected to...
  28. Evil Bunny

    Transformer Theory: No Load Current & Increasing Primary Current

    When you have no loads connected to the secondary of a transformer, what is the current in the primary? When you start connecting loads to the secondary, what phenomenon is making the current increase in the primary?
  29. F

    Transformer Short Circuit Calc

    Ok I've read a lot of articles and seen a lot of different ways of calculating the short circuit current at the transformer terminals. So I'm going to apply my own intuition and see if I can arrive at the correct value if someone could please confirm my answer. 6.6kV/400V 3 Phase 10MVA...
  30. D

    Difference between current and voltage transformer

    what is the difference between a current and voltage tranformer constructionally and functionally??
  31. D

    Resistance in a transformer

    Homework Statement This is the problem: http://i.imgur.com/MrRwi.png I'm not exactly looking for a solution to the problem, I am looking for a solution to the conflict created by different methods I've seen of doing it. Cramster's method gives an answer of 87.5 and a solution manual i have...
  32. O

    I1/I2 = N2/N1Φmax = Bmax * AcSingle Phase Transformer Calculations

    Homework Statement 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...
  33. A

    Converting 220kV to 350kV DC with HVDC: Exploring the Theory

    Hi, Something is puzzling me with the HVDC work I'm currently working with. I'm working for contracting company here in NZ contracted to complete the new HVDC converter station. We have 3 x single phase converter transformers on site converting the AC voltage. I was wondering why when...
  34. G

    Transformer Analysis: Comparing Measured and Analytical Values

    I am asked to compare analytical values of the loaded transformer with measeured values of the transformer. I have got no clue how to do that. The transformer is singl ephase 230/115V with rated secondary current 0.43 A. According to open circuit test the Rcore = 15.9kOhm, Xcore = 10.5kOhm...
  35. A

    Core loss current in a real transformer.

    I was recently going through electric machinery fundamentels by Stephen Chapman and noticed the graph of the core loss current. I need help in understanding the nature of the current graph plotted against time, like how its value stays constant for some fixed time then varies linearly.
  36. B

    Current and Voltage in a transformer

    Homework Statement The primary coil in a transformer has a power of 100W. The flux through a single loop in the primary is changing at a rate of 25 Wb/s. The primary has 100 loops and the secondary has 500 loops. Assuming a perfect transformer (no losses), determine the current and...
  37. L

    Step-Up Transformer Conceptual Problem

    Homework Statement Even for an ideal transformer, we can't get "something for nothing". If this transformer steps up the voltage, what must be decreased? a) power b) current c) resistance The Attempt at a Solution Ep/Np=Es/Ns I believe it's power or current, but these two are related. So...
  38. E

    EMF Induced on Secondary Coil of a Transformer

    Homework Statement http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9702%20-%20Physics/9702_s02_qp_4.pdf <------ CLICK ON THE LINK The Attempt at a Solution Is the above diagram the correct answer ? Please note that the diagram in the question paper is for COIL...
  39. C

    10kV Flyback Transformer, 2W possible?

    Is it possible to build/purchase a 10kV (nominal) flyback transformer which runs on about 2 Watt or less?
  40. C

    Modified microwave transformer- rneed advice for rectifiers and wire ratings.

    Modified microwave transformer- need advice for rectifiers and wire ratings. Hello everyone. I've been doing a lot of research as to how to go about purifying copper. There are two approaches I'm considering. Electrolysis and Smelting. The electrolysis method requires I have a DC output of low...
  41. S

    Using wattmeter with current transformer

    Hey guys, Just looking for some reassurance as to whether I have visually depicted the wattmeter and current transformer correctly in the image I have provided. Needed to step down current to satisfy current ratings of wattmeter. One thing I cannot seem to see is how it detects the voltage...
  42. S

    What Power Values Are Used in Transformer Efficiency Calculations?

    When I calculate efficiency of a transformer, I use output power/imput power x100%. Then what are these power values? Is the power the power in a load or the total power coming out of the transformer (meaning it includes the joule heating)? Then also what about the input power, which values do I...
  43. C

    Light bulb & photovoltaic cell & power transformer combo for FREE energy

    Does anyone think that it's possible to have a perpetual motion machine electricity generation of a combo of a light bulb shining light on photovoltaic cells that are connected to power increase transformer coils to power that light bulb? I suppose there would have to be some kind of way to...
  44. P

    Solving Transformer Per Unit Questions

    [b]1. attached is the question i am trying to solve. I do not know how to do per unit questions. [b]2. Part a) of the question ask to convert into per unit and then per phase equivalent circuit. I do not understand how to do it. Please guide. Also, how to calculate the bus1...
  45. P

    Ideal Transformer Homework Solution

    Homework Statement See attachedHomework Equations V2/V1=I1/I2=n n=2The Attempt at a Solution \begin{array}{l} {\rm{Mesh 1: }} & 4{I_1} + {V_1} = 60 \\ {\rm{Mesh 2:}} & 10{I_2} - {V_2} - 2{I_3} = 0 \\ {\rm{Mesh 3:}} & - 2{I_2} + 10{I_3} + {V_2} - {V_1} = 0 \\ {I_1} = -...
  46. C

    What is the Number of Turns in the Secondary Coil of a Transformer?

    Homework Statement Hello everybody, am confronted with this question: A transformer with 5500 turns in its primary is used between a 240V a.c supply and a 120V kettle. Calculate the number of turns in the secondary. Homework Equations The equation Es/Ep = Ns/Np can be applied in...
  47. B

    Transformer Mathmatical Modelling

    I would like to do the mathmatical modelling then apply it in matlab. This is my trailier. Vp-ip*Rp-Lp*(dip/dt)-Rc*ic = 0 ----- 1 Vp-Lm*(dim/dt) = 0 ------2 i need the modelling of the secondary voltage to the primary and the flux Vs= ? flux= ? I did apply it in MATLAB but didn't work.
  48. S

    Solenoid + Transformer + Current buildup interval

    I decided to make a couple solenoids. Not too many loops on them though as I need higher gauge wire. After getting that I put one in the other and in that a core of metal that had some iron in it. I tried inducing a bit of current in the outer winding by driving DC current through the inner coil...
  49. 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...
  50. 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)...
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