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. Noaha

    Core volume of 1 phase transformer

    Homework Statement The flux density in a single phase core type symmetric(length=breadth=height) transformer is B and flux is Φ. Can we find out the volume of core of transformer if the height of limb is h? Homework Equations Φ = B * Cross sectional area The Attempt at a Solution Can we say...
  2. T

    Dumb question regarding short circuit test equivalent resistance

    Hi, Silly little question about the transformer short circuit test. When I perform it with the secondary shorted and I get Req = Power / current2 is this Req = Rpri + Rsec? If I measured Rpri and Rsec with a multimeter? Thanks
  3. J

    Why is Rated Voltage Used for Full Load Voltage Regulation Calculations?

    Hi, I want to calculate voltage regulation of a transfromer. I have learned that voltage regulation is (Vnl-Vfl)/Vfl. While solving some problems for practice I came across multiple questions. In some of them where the load is given I understand how to solve them. I just find the No load...
  4. H

    Design Calculation and Sizing of a 500KVA Transformer

    I want to design the installation of a 500KVA Distribution Transformer to supply a neighborhood in Nigeria. The Existing National Grid voltage is 11KV. I want input from you guys to add to my sizing/costing. Inputs: 1. Sizing of XLPE Cable 2. Sizing of Transformer HV Protection ( Current Rating...
  5. S

    Design a flyback transformer for charging defibrillator

    how can i design a flyback transformer for the controlled charging of defibrillator capacitor(high voltage). The charging is controlled using PWM which controls the transformer switching using a MOSFET.
  6. P

    Variable 100-350VAC output controlled by PLC?

    Hello, I have a strange request from a client. He has a "burn-off" which is used to burn bits of labels that are stuck onto his products, that's a bit vague, but it's all the info I have. The request is that he wants to be able to change the voltage going through the burn-off anywhere between...
  7. G

    Autotransformer: Why does primary current go through coil?

    Hi. Why is it that in an autotransformer apparently most of the primary current goes through the winding and not through the load?
  8. I

    Calculating Input Voltage of a Step Down Transformer

    Homework Statement A pair of power transmission lines each have 0.68-Ω resistance and carry 650 Amp. If the primary voltage of the 10:1 step-up transformer is 4.6 kV, calculate the input voltage of the step-down transformer at the other end. Homework Equations P=IV V=IR IpVp = IsVs The...
  9. Vikas Kasireddy

    Primary magnetizing impedance of non-ideal transformer

    I am trying to determine the primary magnetizing inductance + core shunt resistance of a transformer. I attached the equivalent circuit of the transformer. I left the secondary open and have an AC voltage on the primary. This causes the coupling leakage inductance and coil resistance to appear...
  10. M

    Power factor of ideal transformer

    Can anyone explain why the power factor of an ideal transformer cos (phi) is equal to 1?? A simple ideal transformer is formed of 2 ideal coils. The power factor of an ideal coil is 0 since phase difference between the current and the applied voltage is - π/2. Then how can the power factor of...
  11. G

    Magnetic flux and current directions of transformer

    Hello. Let's take a transformer picture first. The basic equation explaining how the transformer work is the equation of Faraday's law of induction. \begin{array}{*{20}{c}} {{V_P} = - {N_P}\frac{{d{{\rm{\Phi }}_B}}}{{dt}}\;\;\;\;\left( 1 \right).}\\ {{V_S} = - {N_S}\frac{{d{{\rm{\Phi...
  12. G

    Transformer equation: Using Faraday's law "the wrong way"?

    Hi. All derivations of the (ideal) transformer equation ##\frac{U_p}{U_s}=\frac{n_p}{n_s}## use Faraday's law of induction $$U=-n\cdot \frac{d\Phi}{dt}$$ for primary and secondary and equate the change of flux ##\frac{d\Phi}{dt}##. Until now, in my textbooks it was always like this: Electrical...
  13. Nikhil N

    Current transformer for coupling noise into a cable

    I want to couple white noise to a communication cable. I am using a 50/5A CT. My idea is to connect the noise in the secondary and to couple that noise into the cable. I want to know will my idea work? Does the CT what I am using will be suitable?
  14. ZenSerpent

    Setting up the Transformer Efficiency as Objective Function

    Homework Statement To set-up an equation for the efficiency equation of single-phase toroidal transformer given the circuit with the following mesh equations (s*L1+R1)*I1 + (-s*M)*I2 = V1 (-s*M)*I1 + (s*L2+R2+RL)*I2 = 0 Homework Equations Efficiency equation(?), equation derived by The...
  15. ZenSerpent

    Relating Transformer Parameter I2 to V1 (Non-ideal) Updated

    ≪ mod note: thread moved from technical forum so template is missing ≫ Homework Statement Relate secondary current to primary voltage in a single-phase transformer having resistive load for non-ideal situation. Homework Equations KVL, Voltage across resistor and inductor, ac voltage as a sine...
  16. N

    Transformer Calculations: 200 kVA, 415V to 11 kV, 0.8 PF at 2% Regulation

    Homework Statement A 415V to 11 kV transformer has a rating of 200 kVA. The winding resistance and leakage reactance when referred to the primary are 0.014 ##\Omega## and 0.057 ##\Omega## respectively. (a) Determine the % regulation of the transformer at 0.8 power factor lagging. (b) In...
  17. BsJ SandeepA

    How to make simple transformer?

    Please help me.. how to make simple transformer to 3V up to 12V
  18. R

    Need a little help (transformer)

    I am a student of class 12. I am making a transformer for a project. I took an iron rod about 3 inches long and cross sectional area about 0.5 square centimetres as the core. The primary coil has 100 turns and the secondary has 25. I used an ac source of 16 volt. I connected the primary coil to...
  19. O

    Maximum Power Transfer Ideal Transformer

    Homework Statement Given the following circuit find the value of ZL for maximum average power transfer and find the maximum power. Homework Equations n = N2/N1 V2/V1 = N2/N1 I2/I1= N1/N2 The Attempt at a Solution move ZL from the secondary coil to the primary coil using Zs* = ZL/n^2 ZL =...
  20. Clara Chung

    Very confusing question about transformer

    Homework Statement Homework Equations Please review the question and answer of question 34. The Attempt at a Solution 1.Why does the answer take the rated power as the power output? 2.I tried to find the current like this: R=200^2 / 100 = 400 ohm I at Q = 400/[2(400)] = 0.5 A I at P = 0.5/2...
  21. J

    Earth fault in delta star (grounded) transformer

    Hi, I am studying transmission lines faults. There was a line that said In case of delta star transformer in transmission line, an Earth fault on star (grounded) side is seen as a line to line fault on delta side. There was no explanation. I tried to google solutions but couldn't find any...
  22. J

    Find V2 in Single Phase Transformer

    1. Homework Statement Find V2. Everything else is available in the picture Homework Equations r1=r1+a^2*r2 x1=x1+a^2*r2 z2=a^2*r2 I1=vp/z2+r1+x1 The Attempt at a Solution So I have used the first three formulas but it's the last one I am getting stuck on. Since my x1 is an imaginary number...
  23. Clara Chung

    B Understanding Transformer Equations and Flux Linkage in AC Power Sources

    I don't understand the concept behind equation (1). I think that the equation V=-Nd(flux)/dt is only for magnetic induction. However the power of the primary coil is usually supply by an a.c. power source. (So as to provide a changing B field.) Therefore, it is not an induction process. How can...
  24. E

    How to maximum apparent power through a linear transformer?

    Homework Statement given a linear transformer rated for 50kVA, 11000V/120V How do I find the maximum apparent power? The prompt is to maximum apparent power while keeping the Load RMS voltage between 114V and 126V. Vsource has a peak voltage of 11000*sqrt(2). The circuit looks something like...
  25. G

    Why Does My Transformer Have a Winding Disparity?

    I am attempting to reverse engineer a small 1960's vintage power transformer that is employed in a vintage audio amplifier. It contains no marking to indicate operating voltage or current ratings, however I do have several sample transformers as well an an operational example of the amplifier...
  26. F

    Transformer Core Loss Lissajous

    Homework Statement [/B] A single phase transformer circuit is assembled with an RC load. A voltmeter is connected to across the capacitor and an ammeter in series with the primary. The output of the ammeter is connected to the X-channel of an oscilloscope and the output of the voltmeter is...
  27. M

    RMS value secondary voltage electronic halogen transformer

    I am trying to derive a scaling factor for an analog voltmeter for the purpose of measuring the secondary voltage of an electronic halogen transformer (EHT). http://www.ledbenchmark.com/faq/Transformers-Output-and-Compatibility.html The output voltage of these things is a "high frequency"...
  28. E

    Engineering Finding Voltage in a Transformer circuit

    Homework Statement Find Vo Homework Equations KVL, KCL The Attempt at a Solution Mesh equations: -24 + I1(2-j)-I2(1.5j)=0 I2(6+4j)+10<30degrees-I1(1.5j)=0 I1=8.69541+3.59557j I2=-1.00284+2.00908j How would I find Vo?
  29. E

    Ideal Transformer: Solve for Turn Ratio, kVA Rating, Primary Current

    Homework Statement Ideal Transformer: rated: 11000/4600 V secondary current: 30A Find turn ratio, kVA rating, primary current Homework Equations S=VI N=V2/V1 The Attempt at a Solution Are these correct? Turn ratio: N=V2/V1 = 0.418 kVA = S1*I1 = S2*I2 = 4600*30 = 138kVA Primary current: V1*I2...
  30. K

    ZigZag transformer and harmonics

    Hi again, Can/are zig zag connections used on the secondary side to avoid triplen harmonics flowing further up the power system? Let's say 3rd harmonics are flowing up the power system from some loads connected to phases a,b,c and the neutral. Since 3rd harmonic are all in phase, the...
  31. H

    Resulting magnetic flux in the core of a transformer

    In a transformer, let's say we have: I1, I2 - currents through the primary and secondary winding V1, V2 - voltages N1, N2 - number of turns F1, F2 - magnetic fluxes through core, produced by the currents I1 and I2 (they are opposing...) R - the reluctance of the core We have V1/V2 = N1/N2...
  32. G

    Isolation transformer: Potential difference to the earth

    Hi. In a normal power plug, neutral is on the same potential as the Earth and therefore, in theory, safe to touch. Line carries the full voltage difference and is dangerous if the body provides a conducting connection to the earth, since this closes the circuit to neutral. Isolation...
  33. R

    Why is my custom microwave transformer producing inconsistent voltage?

    So I was attempting to modify a microwave transformer by wrapping my own secondary coil. The first coil was standard from the microwave, around 16 gauge wire, 100 turns, so I was wrapping my coil with around a 16 gauge wire, I put it together, put a weight on the transformer to keep it together...
  34. moenste

    Power loss in the transmission system with a transformer

    Homework Statement A farmer installs a private hydroelectric generator to provide power for equipment rated at 120 kW 240 V AC. The generator is connected to the equipment by two conductors which have a total resistance of 0.20 Ω. The system is shown schematically in Fig. 1. (a) The...
  35. Biker

    Transformer and the brightness of bulbs

    Homework Statement The brightness of the bulb A in the following picture equals: A) half of the bulb B brightness B) equal to bulb B brightness C) Twice as bright as bulb B D) four times as bright as bulb B Homework Equations Ohms law Conservation of energy Faraday's law The Attempt at a...
  36. O

    Why Does a Yd1 Transformer Connection Cause a -30 Degree Phase Shift?

    Hi, I have problems understanding why, for example, a Yd1 connection introduces a -30 degree phase shift, see image below. How should I think when I want to produce vector groups like that, and derive myself what the phase shift should be? Thanks..
  37. S

    Solving Transformer Problems: Confirm My Solution?

    Homework Statement Homework Equations I've used these formulas (VH/VX) = (TH/TX) = (IX/IH) for solving the turns although I'm not quite sure if 2400 V is the VH same as for 480 V for solving the ampere-turns, I = kVA/V where: V= either the VH or VX then multiplied the current I got to its...
  38. BjornFanden

    5th and 7th Harmonic mitigation (D-yd transformer)

    Hi, I do not see how this method (illustrated in the figure below), can completely remove the 5th and 7th harmonic? I know that in a wye-delta connection a 30 degree phase shift is introduced. But to fully remove the 5th harmonic we need a phase shift of 180/5 = 36, and for the 7th harmonic we...
  39. H

    Calculating Pulse Transformer Frequency at Voltage

    Hi. I need some help in explaining in a simple way how to calculate the minimum allowable frequency at a certain voltage when selecting a pulse transformer. The one I'm looking at has an ET value of 45Vusec. I'm feeding it 22.5KHz at +/-6VAC square wave. It seems to work fine but I fear it is...
  40. putta

    Clarification transformer circuit

    attached image: the transformer taping is correct 120+120=240V? where i take taping of transformer nuetral point? the both are consider is 240V out put in two different faces? please if any wrong in circuit help me or it good i will proceed. here i attached circuit .pdf
  41. nishant mudgal

    Is Powerline Voltage Always an Integral Multiple of 11?

    Why is the supplied voltage in the powerline wires an integral multiple of 11 from the supplier? Example -- That line is 11,000V
  42. G

    220V 50Hz Equipment vs. 230V 60Hz Equipment compressor

    If If you have a compressor designed for US 60 HZ 230 V what are the risks with applying it in 220 V 50 HZ ? I understand there will be a ~20% derate in power but are there any safety or failure concerns ? would the lifespan of equipment change? Do I need a transformer ? This equipment...
  43. Umar Awan

    Is it current or voltage that is fixed in transformer output

    In a transformers output, is it the current that is fixed or the voltage? I have been trying to resisitively heat some tungsten foil and I am stuck at trying to find out the amount of current I need in my transformers output. The problem I am facing is that I know that the tungsten resistivity...
  44. U

    Why the efficiency of air core transformer changes (up and down)

    The graph below shows the efficiency of an AIR CORE transformer at different voltages (from MAINS). At low voltages, it has high efficiency and gets lowers because of high magnetising current causing heat loss. But why is it higher at some points again? I do not understand this pattern. Please...
  45. Umar Awan

    What is the reason for using high KVA transformers in electrical heaters?

    Note: I have a feeling this is below Electrical Engineering requirements, but I couldn't find a more suitable category, so I think I'll extort the advantages of a forum base with electrical understanding more than I think may be required(ofcoarse I know very little about the field, so I may fall...
  46. Clara Chung

    Transformer and power question mutiple choice

    Homework Statement The turns ratio of a transformer is 20:1 step down and the primary coil is connected to a 220V a.c. supply. If the secondary coil is connected to a '36W, 15V' light bulb and the efficiency of the transformer is 80%,find the current in the primary coil. Homework Equations...
  47. Clara Chung

    A question related to transformer

    Homework Statement Electricity generated in the power station is stepped up by a transformer X from 25kV to 400kV before transmitted by overhead cable. Then it is stepped down to 200V through another transformer Y before entering domestic circuits. Assume all transformers are ideal. Given the...
  48. Salvador

    SMPS transformer core getting hot advice

    I had a bit of rattle about this here before but I hope you folks ain't fed up with me yet.:) So after some trial and error I've built a working smps for my amplifier , it's pretty high power ,when testing dummy loads i got up to 2KW , since I don't need more for my project I never went further...
  49. A

    Snubber for a 3kVA 240V to 110V transformer

    Hey... how's it going? I've built a step down box to run 110 VAC appliances off incoming 240 VAC (Malaysia). The only components in the box are a cooling fan (240 V) and a great big transformer. It's a single phase 30A output aluminium cored 240V->110V 50 Hz transformer that weighs about 25 kg...
  50. I

    Half wave rectifier with ideal transformer

    Homework Statement Determine the rms values of the currents of primary and secondary windings of transformer in the network circuit diagram. Transformer is perfect, with ratio 6: 1,and negligible AC component of magnetizing current, is connected to the sinus supply network U1 = 220 V, f = 50...
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