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. M

    Primary voltage on a transformer

    Homework Statement a transformer with a core flux of 5 milliwebers has a primary winding of 1000 turns calcuate the primary voltage if the transformer operates at 50 Hz cycle. Homework Equations Unknown The Attempt at a Solution Im following a self paced work book, and to my...
  2. L

    How to find source current in transformer

    Homework Statement Refer to the figure attached. The single phase "exact"-equivalent circuit of a practical transformer has the following equivalent circuit parameters: Np/Ns = 2400V/240V, Rp = 14.1, Xp = 31.2, Rs = 78.5*10^(-3), Xs = 120.5*10^(-3), Rc = 156*10^3, Xm = 172*10^3. The load is...
  3. B

    Build 220V AC Transformer for Variable DC Outputs

    Hello EE, I currently have a mini project that Studiot provided me with. Project is a kind of a multi-functional tester. But I want to add another feature to that tester. That tester has a 9V DC output, which gave me an idea. I always find myself searching for batteries and other power...
  4. M

    Build Your Own Transformer: EE Student's Guide

    Hi, I was thinking of making my own power supply and I was wondering how low level I can go with it in terms of designing individual components and then putting them together to form the circuit. So, I'm looking at like a 120V to 15V transformer then through a rectifier to get 15V DC? I'm...
  5. M

    Can effective piezoelectric transformer be implemented for this application?

    Is it possible to use a piezoelectric transformer to step up voltages of 3 to 12 volts to as much as 5 kilovolts? Below are more details of what I would like to do: Input into transformer: square waves, 0 to 12-volt amplitude with frequency range of 100 Hz to 100 KHz Output from transformer...
  6. F

    Power factor of a transformer at 80%

    PF is P / S in general. If the transformer is running at 80.1% of full load, the PF should stay the same right since PF = 0.801P / 0.801S = P / S since if the transformer is running at 80.1% full load, the output S and output P would both be 80.1% right? So basically, no matter what load...
  7. F

    Calculate the transformer parameters

    Question basically asks to find the parameters of a transformer via an open circuit and closed circuit test. We were taught that for OCT, V = (I * cos(theta)) * R V = (I * sin(theta)) * X To find the core losses. This makes sense, since we are only using the component of the current that...
  8. J

    High Voltage Low current from a step up transformer

    Hi, From what I have read, if a bulb X is connected to the input voltage of a step-up transformer, and another similar bulb Y is connected to the output voltage (secondary coil), then Y will be brighter than X. From Joule's law of P = V I, it seems that the output voltage will be higher...
  9. O

    How does the configuration of two coils affect voltage readings in a circuit?

    Homework Statement given two coils one with N1 rings legnth L1 the other N2 L2, one inside the other the radius is not given.. N1 is connected to battery V1 and N2 is connected to volt-meter what will show the volt-meter? (use N1,L1,N2,L2.V1) Homework Equations Faraday's law of induction[...
  10. C

    Attempt to raise transformer current with frequency

    After some study with simulations, I've been trying to find a way to increase transformer current by increasing the operating frequency and decreasing it's size, mass, cost, and turns. It seems to make sense that I can make a much cheaper and higher current transformer by doing the following...
  11. N

    The transformer section in Flyback converter

    Homework Statement Hi everyone, I am now studying the Flyback converter as a component in a SMPS, my question is on the transformer unit on the converter. There are Primary side and Secondary side in the converter, at any given moment only either of the sides conducts, that is, when...
  12. A

    Current transformer polarity and power flow

    Hello i need to know , does the polarity of the current transformer affects the power measurements in AC systems, and if it does , how it affects the power measurements knowing that in measuring power we use the RMS values anybody have any idea about this ?? that's to say , if you have...
  13. F

    Understanding Basic Transformer Concepts

    The questions in this pre-lab are pretty basic and conceptual, and have not yet been taught in class. However, I'd like to complete this prelab early since I will be busy later on. Because it is pretty conceptual, I don't have any attempt at them except Googling around. Quick explanations or...
  14. D

    Investigating Oddball Transformer: Baffling Results

    Here is a reworked question... If i have a secondary coil and pulse a primary that is placed 90 degrees to the secondary so the magnetic flux is at a 90 degree angle to a normal winding (secondary is wound east to west primary is north to south) then how will this effect the induced...
  15. J

    Step Up Transformer: Using an Alternator to Increase Voltage

    Is it possible to use a step up transformer to increase the voltage delivered by an alternator? If so how much can you increase the voltage just depends on how many turns the copper has or what?
  16. S

    Full-Wave Rectifier w/ 2 P-N Junction Diodes & Transformer

    Show how two P-N junction diodes can be used in conjunction with a transformer that has two secondary windings, to form a full-wave rectifier. (Draw a circuit diagram including connections to the mains transformer). Explain the operation of your circuit using sketches of waveforms. (3 marks)...
  17. A

    Transformer vector group Dyn11 and Dyn1

    please i need your help to answer the following question what the difference between transformer Dyn11 and Dyn1 i know the difference is in leading and lagging of line to line voltages of primary and secondary but the question is , when i should use Dyn11 or Dyn1 as a must in the...
  18. A

    What can I do with a transformer?

    I was thinking that the possibility may exist that I could install a fused disconnect for my line in from the power company and hook it to a 240v-to- 24v step down transformer, use a whip to connect to another fused disconnect with a 24v-to-240v before entering the panel. my theory is that my...
  19. S

    Transformer capacity based on physical size

    I once saw three very large transformers in a fenced area smaller than a typical substation fencing. They were close enough to read some numbers on a metal nameplate which gave a list of about 6 primary tap voltages in the 12000 to mid 13000 volt range. There were some other stamped numbers...
  20. Evil Bunny

    Transformer primary to secondary short?

    Let's assume a 3 phase wye distribution system with a single leg supplying a typical residential center tapped transformer (like we have in the US)... For simple math, let's say it's a 10:1 transformer with 2400V on the primary and 240V on the secondary. The center tap on the secondary is...
  21. P

    Transformer Short Circuit: Test Results and Solutions

    I have been using a 25VA transformer without any problems, but it happened to trip the elcb/mccb once I plug it in. I tested the primary windings and the secondary windings. The secondary windings seems to be short circuited with resistance of 0.3 ohm while primary with 70ohm. I tested other...
  22. J

    Transformer Operation Frequency

    Good day everyone I would like someone to tell me whether or not it is a good idea to use a 60Hz transformer at 50Hz? Thanks in advance for your response.
  23. U

    How Many Turns Requred For 220v-100v,180v 100VA Rating Transformer

    Can anyone tell me how many turns required for designing a 220v-100v,180v and 100VA amplifier? Rating : 100VA , Frequency : 50Hz Primary Secondary 220 100 220 180 Question-01: No. Of Turns in primary and secondary...
  24. L

    Need help with light fixture transformer wiring distance

    I have a low voltage light fixture with a 12-volt transformer at the top of the fixture where it mounts to the ceiling. I would like to move the transformer to the closet where the source of the wiring for the fixture and my fuse panel reside. I am wondering if the distance is too great for...
  25. S

    Transformer windings and voltage

    A transformer is constructed with 200 windings on the primary coil, and 800 windings on the secondary coil. The primary coil is connected to a car battery with a potential difference of 12 V. After a few seconds, what is the voltage across the secondary coil? The answer is 0, but why? I...
  26. V

    Finding efficiency of transformer

    Homework Statement 10kVA, 200:400 V transformer gave these test results: open circuit test (LV winding supplied): 200 V, 3.2 A, 450 W short circuit test (HV winding supplied): 38 V, 25 A, 600 W Homework Equations Calculate the efficiency when the transformer delivers its rated kVA...
  27. G

    Archived Efficiency Calculation of 10-kVA Transformer at 0.85 Power Factor Lagging

    Homework Statement A 10-kVA, 200:400 V transformer gave these test results: open circuit (LV winding supplied): 200V, 3.2A, 450W short circuit (HV winding supplied) : 38 V, 25A, 600W calculate the efficiency when the transformer delivers its rated kVA at 0.85 power factor lagging...
  28. A

    Transformers for Maximum Power Transfer

    Determine the turns ratios a1 and 12 for maximum power transfer to the 20 ohm load resistor. a=n2/n1; Rs=RL for maximum power transfer, i.e. Zsource = the complex conjugate of the load.i have try to use Z1=a1^2*Zs and Z2=a2^2*Z1 and i know Z1=-j/(2*pi*f*c)
  29. A

    Phase angle error in current transformer

    Homework Statement hi in current transformer the primary current lags the secondary current by an angle..to determine the %ratio error we need to measure the ratio of primary and secondary current...so we use a RC circuit to lead the primary current so that it could be in same phase as...
  30. D

    Calculating Single Phase Transformer Parameters and Performance

    Homework Statement Figure 1 shows the equivalent circuit of a single phase transformer and figure 2 shows the approximate equivalent circuit. Reduce the circuit to approximate form and find: rm, xm, R1, X1 Using the approximate equivalent circuit calculate- With the transformer...
  31. T

    What happens when Connecting step-up and step-down secondary Transformer coils?

    This website is a great idea. (I'm a thread vergin) Not sure if its standard but where I live 'step up' is secondary = higher voltage Opposite for 'step down'. What would the result be if you connected one secondary with a high voltage and low current in series with a secondary that had a...
  32. B

    Questions related to Current Transformer and Gauge Factor?

    Hello Friends, Kindly tell me the formula/values for the following: 1. Gauge Factor in the primary winding of a transformer with voltage 5 MVA 2. Voltage Drop in the Secondary Side of a Current Transformer with 100:5 Please help Thanks
  33. PainterGuy

    How does a centre tap transformer enable full wave rectification?

    hello everyone, 1:- in the below video i think the transformer used is called centre tap transformer. someone was telling me that the input voltage of 12V is divided between two voltages of 6V across the secondary coils. But at one time only one secondary coil is really conduction because the...
  34. I_am_learning

    3 phase Vs 1 Phase Transformer Cost

    I have just completed a course in Transformer Design. But I am now surprised at a result I found. For Handling Same Power (Say 15 Kva) at around same efficiency, 3 phase transformer are more heavier and costlier than single phase transformer. Although, The Copper Weight Decreases in case of...
  35. S

    Calculating Secondary Terminal Voltage for Single Phase Transformer Problem

    Homework Statement Hey, I'm a bit stuck with this tutorial problem: A single phase transformer operates from a 230 V supply. It has an equivalent resistance of 0.1Ω and an equivalent leakage reactance of 0.5Ω referred to the primary. The secondary is connected to a coil having a resistance of...
  36. G

    Transformer Efficiency: Why Does Direct Loading Not Determine It?

    Why is the efficiency of a transformer not determined by direct loading?
  37. A

    AC transformer earth connection

    I am helping out with the installation of an alarm system and need some info regarding earthing of low voltage transformer lead. The alarm system has a 3 wire 12 volt AC output power supply as well as a back up 12 volt DC battery which also contributes to the AC supply to the main ciricuit...
  38. G

    Transformer Help: Immediate Effect of Short Primary Winding

    If the primary winding of a transformer is shorted, what will be its immediate effect to the transformer?
  39. G

    What if a 60Hz Transformer is Connected to a 6Hz Source?

    What would happen if a transformer designed for operation on 60Hz were connected to a 6Hz source of the same voltage?
  40. H

    Is the Back EMF of a Transformer a Dynamic Equilibrium?

    Why the back emf of the primary coil always equal to the supply voltage but no greater than supply voltage(because of the large number of coil turns) when no loaded?Or it is a kind of dynamic equilibrium?If yes,how it reach equilibrium? Thank you.
  41. Y

    Question on Q of a quarter wave transformer using lossy transmission line.

    I don't know whether this is the right place, should actually belong to EE but my experience is you really don't get a lot of help in EM over there because I notice there is only one or two people that attempted answer these. This is regarding to finding the Q factor of a lossy tx line using...
  42. A

    Three-phase transformer DC-resistances

    Homework Statement Three-phase transformer, 20/0.5 kV, dyn11. Not connected to the grid. DC-resistance between two primary windings is measured to be 80 ohm. What is the DC-resistance of ONE primary coil Homework Equations The Attempt at a Solution I thought I could just...
  43. R

    Why Did I Feel a Shock from a High Voltage, Low Current Transformer?

    A small doubt in transformer... Hi friends A transformer (say step up one) increases the output voltage. However, power input is equal to power output so output current should be small. Now yesterday I took a spark circuit(from an electric gas lighter using a 3 volt battery) and allowed the...
  44. neduet

    Help for electrical transformer?

    Hello friends: I need answer of my question please Q.1 In electrical transformer polarities must be same or not Q.2 if transformer under normal condition load is also normal. Is there power of input feed equal to power output? (My teacher said input power = to output power) Q.3 Must...
  45. M

    From Israel: what are these recently added transformer discs?

    This woman in Israel is spooked by the clear, brown and green discs just added to transformers in her Israeli townas seen in this clip http://img128.imagevenue.com/img.php?image=82134_ScreenHunter_02Feb.0403.03_122_415lo.jpg She writes: "What are The new installations on the Pylons...
  46. Phrak

    Asymmetrically Driven Transformer Primary

    Take as an example a 120VAC 60 Hz primary, soft iron core transformer. Fed it with 120VAC with a 2VDC offset, what will happen?
  47. F

    Transformer - the inductive resistance

    As I recently learned, the inductive resistance and capacitor resistance in a circuit are opposite and therefore need to be subtracted. And since transformers are basically big coils of wire, where I assume there's inductive resistance, shouldn't adding capacitors to the circuit lessen the...
  48. F

    Electrical Can I Build a DIY Welding Transformer From Scratch?

    I built a welder using Microwave oven transformers, but I keep melting the secondary coil, and they are a pain to rewrap. So I was thinking about building a transformer from scratch using available materials. My first obstacle is the core material, I know laminated core material is...
  49. I_am_learning

    Turns / Core size optimization for Transformer

    Say, I want to design, 220 / 12 V 100VA transformer. We have V = 4.4BfNA (V is applied voltage RMS, B is peak flux Density, N is no. of turns, f is frequency, A is core cross section) so, B = V / (4.4 f NA) If i use iron core, there is limit to the maximum value of B without excessive...
  50. I_am_learning

    Exciting Current harmonics in Transformer

    Due to non-linearity of magnetic core of large transformer, Which is excited by pure sinusoidal voltage source, the exciting current isn't perfectly sinusoidal. It can be thought to be composed of pure sinusoidal plus mainly 3rd harmonic component. But does this current flows in the primary...
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