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. Q

    Grounding the Transformer Neutral

    I observed the following configuration in a factory: Power supply from a generator (400 V line-to-line) is stepped up to 11 KV (line-to-line), which is then fed to another transformer that produces a stepped-down, 2-phase output. The step-down transformer has 3 input terminals. Step-up...
  2. A

    Polarity of 3p core transformer

    I have a 380V,3 phase core type transformer which is being used as AC line choke in the incomer of a VFD.As we are using only the inductance property of the transformer,I was just wondering whether we could connect R phase of the supply to any winding and then follow the phase sequence...
  3. P

    Transformer Current Drops with Load

    Hi, I have observed that as the load applied to a transformer secondary is increased (i.e. Increased Impedance), the current drawn by the transformer seems to decrease. Is this purely due to the fact that because the voltage remains fairly constant and the impedance is increased, the current...
  4. E

    How Do You Calculate Transformer kVA Rating Based on Site Measurements?

    Hi, I've just got into my electrical engineering course and I need some help with a question of mine here. During a site visit, we were shown a main LT panel which has switchgears, ammeters and different kinds of relays and the distribution network from that panel. In the main LT panel...
  5. A

    Step input to loaded transformer

    I am trying to calculate the response of a loaded ideal transformer to a step input. For example a step input in voltage from zero on the primary coil with a resistor connected across the secondary coil. I already understand that with the second coil disconnected (for all practical purposes not...
  6. E

    Transformer connected in parallel question

    Homework Statement The question is as per my attachmentHomework Equations The Attempt at a Solution I found the following help of the internet but do not know where to start any assistance would be appreciated: you don't need to be concerned about matched turns ratio. You can assume that the...
  7. Crazymechanic

    Lowest frequency of a transformer

    Hi , I've been wondering about this one thing. Well a transformer works on indcution , so a increase/decrease in voltage amplitude and/or periodical polarity reversal is needed to induce a current and voltage in the secondary. Now if we leave the current reversal aside for a bit and look at...
  8. Faraz Murtaza

    Current Direction at 'P' Point in a Transformer

    what will be the direction of current at 'P' point in the transformer?
  9. D

    Transformer model in power system

    Hello I am interesting in transformers lately, and I noticed that most commonly used method for representing transformers in power systems is by symmetrical components. Now, I am wondering - is there any way that we can represent and calculate transformer in phase system, totally without...
  10. E

    Piezoelectric transformer efficiency

    Dear all, How is the efficiency of piezoelectric transformer higher than electromechanical coupling factor? Thank you, Husain
  11. andrewkirk

    How does a laptop transformer avoid using energy?

    I've been idly wondering about this question on and off for many years. In an AC transformer the load on the source side comes from the work it has to do to generate currents in the other side via inductance. I imagine that if the circuit on the other side were suddenly broken, there would be...
  12. Q

    Transformer Voltage in case of Short-Circuiting

    Consider a distribution transformer: The primary winding (HV) has a nominal voltage of 14.4 KV, whereas secondary (LV) has a nominal voltage of 120 V. One terminal from each of the primary and secondary windings is solidly grounded. A HV line (14.4 KV) is connected to the primary. Now, if the...
  13. amjad-sh

    The induced current in transformer

    Hello, I know that in ideal transformer the law I2/I1 = N1 /N2 I know that I2 is the induced current in the secondary coil, so I1 is the induced current in the primary coil or the current generated from the generator?? where N1 is the number of turns in the primary coil. and N2 is the number...
  14. Crazymechanic

    Maximizing Efficiency: Back EMF and Transformer Behavior in an Ideal Circuit

    Hello , I have a question , assuming ideal devices here without losses for the sake of simplicity. Imagine I have a circuit like the one attached. Now if I would manage to flip either one of the switches fast enough that the switch is cut off right when the magnetic saturation of the...
  15. P

    Transformer winding resistances R1, R2 and Re1 and inductances

    Hi, If there are no resistance and impedance parameters given for a single phase transformer, is it possible to work out the values of primary and secondary winding inductance and resistance (r1,r2,re1, x1,x2,xe1 etc) without the use of a short circuit test. The transformer can be tested...
  16. J

    Can a microwave transformer be used for other purposes?

    I have the transformer from a microwave that has the few turns and big windings on one side and the other side must have smaller turns I was just wondering if you apply 115 volt ac to the larger number of windings what would come out the heavier windings? I am just wondering if this can be used...
  17. Q

    Transformer Delta Configuration

    I have a few confusions related to the delta configuration of a transformer (single-phase transformers used to make a 3-phase transformer): 1) In a closed delta, the windings are connected such that H2 end of one winding is connected to H1 of the other winding. What will happen if one of the...
  18. P

    Voltage drop through a transformer

    Hi, I understand that for a real transformer there will obviously be a current drop through the transformer due to winding resistance, core losses hysteresis etc. For the sake of power system analysis, however, do you still assume that the secondary and primary voltages are linked by terms of...
  19. S

    How Do You Calculate Induced EMF in a Single Phase Transformer?

    Homework Statement A step down transformer, 2400/240 V, 50Hz has the following resistance and leakage parameters. Z1 = R1 + jX1 = 4 + j12 Ω Z2 = R2 + jX2 = 0.04 + j0.12 Ω The transformer is operating at 80% of its rated load. The power factor of the load is 0.866 leading. Determine the...
  20. P

    Transformer input Voltage question

    Hi, Just to clarify, If a real transformer is being supplied with let's say 100V rms from a generator, and a load is connected to the secondary via a line containing both reactance and resistance, the input voltage at the transformer primary terminals should always be 100V, no matter what is...
  21. Q

    Negative Voltage Regulation in Transformer

    How can a transformer have negative voltage regulation? A few texts state that a leading power factor can give rise to negative power factor, but I have not been able to figure out how this is possible. One vague explanation in my mind is that capacitance across the secondary terminal will...
  22. U

    Ignition coil as Hvdc transformer

    Can a large scale ignition coil drive type circuit can be used for stepping up the dc voltage
  23. X

    Transformer equivalent circuit open and closed circuit test

    I see the open and closed circuit test on the transformer section I don't understand why we doing that(open and closed circuit test) can anyone explain and give some example?
  24. Superposed_Cat

    Plasma wakefield acceleration. Why is plasma the perfect transformer?

    Hi all, I recently read the wiki article on Plasma wakefield acceleration and it states that plasma is "The most efficient transformer known" but does no explain how (or maybe it does electrodynamics and induction are not my strong suit) and when I google it the only things that come up are...
  25. P

    How Do You Calculate Turns and Current in an Ideal Transformer?

    Homework Statement The Mag FLux Density in the core of a 4.4kVA 440V/4400V step up TX is 0.8T (rms). If the induced emf per turn is 10V, find: a) the primary and secondary turns, b) The cross sec area of the core, c) the full load current in each winding. Homework Equations The...
  26. E

    Is My Understanding of Star Delta Transformer Voltages Correct?

    Hi, From the basics of 3 phase power, I believed that if you had a delta source which had Line Voltages and Phase Voltages of 100V, if you converted this into a star source, the Equivalent Star Line voltage would still be 100V and the equivalent star phase voltage would then be 100V/sqrt(3)...
  27. Tesladude

    How can I cut out 60hz reception from transformer?

    I just made an amp for a friend giving about 30 watts x2. but it is in a small project box and I am receiving 60hz coming into the input of the amps. I have done tests and it is the EM field of the transformer, I have 2 trimpots on the inputs to the amplifier and have been able to cut out this...
  28. A

    Line Current in a 2 phase transformer

    I am a graduate engineer and have been set a small task to work out the current (primary side) in a 2 phase 30kVA 415:650 transformer. The 2 phases have been utilized from a 3 phase source and are hence 120 degrees out of phase. I understand had it been a 3 phase 30kVA transformer I could...
  29. Drakkith

    Transformer Q: What Limits Current Flow?

    When stepping up/down voltage in a transformer, what limits the current flow through the secondary? Is it the impedance of the windings/circuit?
  30. smokingwheels

    Whats the rule for a Secondary of a transformer VS Rectification metho

    I seem to remember my lecturer talking about Transformers and Rectification methods and there ratings for different modes of operation (25 Years ago). I bought a book called Understanding DC Power Supplies By Barry Davies and I can't find any reference to my question in it. The question is...
  31. Low-Q

    Can a DC Capacitor Transformer Transform Direct Current Voltage?

    DC "transformer" I just had an idea not using induction as in regular AC transformers, but using the electric field in a capacitor using DC in order to transform DC voltage directly without advanced electronics. The idea is using a special capacitorl. The capacitor have a primary pair of foils...
  32. F

    Quarter Wave Transformer: Understanding Formula

    Hi, The quarter wave transformer, as I understand, is supposed to allow matching an input impedance to an output impedance. The formula pertaining to a quarter wave transformer transmission line is $$Z_\mathit{in} = \frac{Z_0^2}{Z_L}$$ I thought that the condition for a line being matched to...
  33. B

    Secondary voltage on transformer

    120 v ac primary and turn ratio of 5:1 I came up with 600v ac is this wrong
  34. S

    Detection of inter-turn winding-short fault in 1-phase transformer

    Hi all, I have simulated (both in software and experimentally) inter-turn winding short-circuit fault in a single-phase transformer (working as a stand alone unit). I have the following observation but don't know the reason behind it:- The fundamental component in the no-load current is...
  35. D

    Inrush in Transformer at no load

    I am trying to simulate the inrush current in a transformer when it is at no load, using the software Powerfactory. I get the Magnetization current, and it is what I was expecting. But I get confused when I draw the phase current, because as the trafo is at no load... should not be the same...
  36. Crazymechanic

    Electric field , sphere , transformer.

    Hi , one of my electric field and how it works questions. My friend made a drawing that will help you visualize what i mean better. So we have a sphere made from wire or metal beams etc doesn't matter.Now we wrap wire around it and leave the ends separate, we attach a circuit of a resistor...
  37. R

    Understanding Flyback Transformers: Exploring Voltage Induction and Turn Ratios

    Hey everyone, I'm a bit confused about how exactly the transformer works. What I have gathered from wikipedia is that basically what is happening is a low voltage DC is pulsed through the primary winding via a transistor, causing current build-up. When the pulse is through, the current in the...
  38. A

    Meggar a Transformer: Step-by-Step Guide w/ Pics

    Could you kindly show me as to how to meggar a transformer step by step with relevant pictures ...?? Very urgent..kindly reply.
  39. V

    Measuring air transformer at resonant frequency

    Hi, I am in the process of trying to develop an air transformer but encountering unusual behaviour which I hope can be explained with some fundamental theory I don't yet know. My set up is as follows; - Two identical wound 13.3uH inductors designed to resonate at 4.364MHz. They are 10...
  40. G

    Question: Why does AC current change through a transformer?

    Hello physics friends! I have a question about AC current I hope you can help me understand. So I know that putting AC through a transformer will raise or lower the voltage, but because power has to be kept constant, the current changes in the opposite direction. But according to Ohm's law...
  41. B

    Is a inverter the same as a transformer or marx generator?

    so i was looking up solar inverters (for solar panel setup) and i saw this picture and i thought it looked kinda the same how the marx generator is setup with a bunch of capacitors and on the schematic it looks like a transformer ... are these three similar in anyway? or do they use some of...
  42. M

    The lesson of electric machines and drivers - transformer questions

    the lesson of electric machines and drivers -- transformer questions question: the data of a single phase transformer are as following; nominal primary voltage U1n= 230V nominal secondary voltage U2m= 12V line frequency f= 50 Hz apparent power S=50 VA loading...
  43. Y

    Understanding Transformers: The Relationship Between Voltage and Amperage

    here is something I do not understand when a transformer increases voltage it lowers amperage that way there is no free energy as power is Volt * amps (watts)but amperage is not preset as it depends on ohms (the resistance to the current or amperage) as amperage = volts / ohms so what...
  44. H

    Transformer in electric generation plant

    Hello, I was looking into some drawings for electric generation plant, and i figured out a high voltage transformer 13.6kv/380KV 600MVA that connects the plant to distribution line. My question is why they use only one transformer 600MVA? Why they don't use 3 transformers 200MVA each so in...
  45. A

    Change in flux of a transformer

    Hello, As I understand, a simple transformer works by using the Input AC in the primary coil to generate magnetic field in the iron core, which then generates an AC in the secondary coil. My question is: how does this process change the voltage? I've searched for answers on other websites but I...
  46. S

    Why Are There Notches Instead of Square Wave Voltage in My Flyback Transformer?

    Hi friends, I am trying to design a Flyback converter(Vin=15 volts, Vout=15 volts, fsw=140kHz) in general purpose PCB. The Mosfet(IRF510) is being driven from TL494. I have checked that the mosfet is being successfully driven by TL494. But after connecting the transformer(E 16/7/6) in sec...
  47. D

    Forced cooling method of transformer

    What is exactly the control system employed for forced cooling of transformer? 'If the load on transformer increases,then temperature rises & the mass flow rate of coolant has to be increased' is it true? So is there any sensor/transducer for sensing (taking the feedback) of flow rate of...
  48. G

    Transient oscillations in transformer?

    Hello, I calculated the transient response of a weakly coupled transformer (M ≠ L1L2), for a heaviside step function input. I get a decaying oscillatory response, even though I didn't include any capacitance, can this be? If interested here is the angular frequency I get...
  49. K

    Solving Transformer Problems: Primary and Secondary Coils

    Transformer problem, Please Help! Please help with this problem. A transformer consists of 300 primary windings and 804 secondary windings. a) If the potential difference across the primary coil is 21.0 , what is the voltage across the secondary coil ? Found this part, Vs = 56.3 V...
  50. deedsy

    Physics - transformer / resistance question

    Homework Statement In the transformer shown in the figure below, the load resistance RL is 46.0 Ω. The turns ratio N1/N2 is 2.65, and the rms source voltage is ΔVS = 85.0 V. If a voltmeter across the load resistance measures an rms voltage of 27.5 V, what is the source resistance Rs? I've...
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