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

    Does the load on a transformer affect its efficiency?

    Homework Statement A transformer has 400 primary coils and 200 secondary coils. The primary voltage is 200 V, and the current is 2 A. A lamp is connected to the secondary coil. The efficiency of this transformer is 50%. Find the resistance of the lamp. Homework Equations V=IR η=P in / P out...
  2. P

    Current and Impedance in a Transformer

    My textbook doesn't cover transformers in very much detail at all, so I only have a very vague idea as to how they work... Homework Statement The secondary voltage of an ignition transformer in a furnace is 13.9 kV. When the primary operates at an rms voltage of 120 V, the primary...
  3. A

    Unable to send current through high frequency transformer

    I am building a transformer of about 9.3 gain operating at 20kHz. One would think this is saturation but if that were the case there would at least be some voltage across the load. The gain of the transformer is as expected for no load conditions but I cannot get this same voltage across a load...
  4. M

    Power transmission via Transformer.

    In transmission lines the the voltage is stepped up to a specified level thereby reducing current to ensure its transmission with minimal power loss. But we know that P=V*I so by increasing the voltage won't Powerloss gets increased?
  5. S

    Confirmation of transformer efficiency

    Homework Statement The problem at hand involved determining the equivalent circuit model of the transformer and then determining its efficiency. I for the life of me cannot get the results that he has provided us with, so perhaps someone here can either confirm my results or indeed confirm his...
  6. S

    Sizing Transformer 480V Primary 120V Secondary: ~10A 3-Phase

    480 V primary 120 V secondary. 9 temperature controllers and 2 power supplies coming off the 120VAC total Amps are ~10A This is 3-phase. How do I find the right size transformer?
  7. L

    Calculating Transformer Input Voltage?

    Homework Statement A 2400/240-V, 60-Hz transformer has the following parameters in the equivalent circuit of Figure 6.5: the high-side leakage impedance is (1.2+j2.0)Ω, the low-side leakage impedance is (0.012+j.02)Ω, and Xm at the high-side is 1800 . Neglect Rhe. Calculate the input voltage...
  8. Crazymechanic

    Efficient DC Transformer Design with Toroidal Ring and Magnetic Fluid Technology

    Hello, so I was looking at some dc to ac mechanical generators when a dc motor is used to drive a generator which in turn induced ac as was used for power conversion back in the day when semiconductor devices were not around yet.Well they had some drawbacks as the mechanical wear and etc. So I...
  9. JJBladester

    Calculating peak voltage in a center-tapped transformer

    Homework Statement Calculate the peak voltage across each half of a center-tapped transformer used in a full-wave rectifier that has an average output of 120V. Homework Equations Assuming the practical model (factoring voltage drop across diodes but not the diodes' dynamic...
  10. S

    How to incorporate core losses in an ANSOFT 2D transformer model

    I am designing a 2D model of a three-phase core-type transformer in ANSOFT MAXWELL 14.0. While doing so I have encountered a strange problem. Start of the problem:- While designing the transformer, I wanted to incorporate core losses. So, I did the following steps:- Excitations -> Set...
  11. S

    Help needed in simulating 3-phase transformer in ANSOFT MAXWELL 2D

    I am designing a 2D model of a three-phase core-type transformer in ANSOFT MAXWELL 14.0. While doing so I have encountered a strange problem. Start of the problem:- While designing the transformer, I wanted to incorporate core losses. So, I did the following steps:- Excitations -> Set...
  12. H

    Calculating leakage inductance & winding capacitance of a step up transformer?

    I am designing a small step up transformer and I'm trying to calculate leakage inductance and winding capacitance. The problem I'm having is when I search the web I find there is a ton of info on the subject. So I have no idea where to start. Can anyone explain to me how to calculate...
  13. C

    Interpretation of Linear Variable Differential Transformer (LVDT) voltage output

    Good day to all Physics Forums members, I am currently undertaking a project which involves the use of a Linear Variable Differential Transformer (LVDT) to measure the distance an object makes between two points. My setup is as follows: LVDT Type: Solartron DC50 with sensitivity of 6.158...
  14. jegues

    3 Phase Transformer Input Line Current (Δ-Y)

    Homework Statement A 25 MVA, 69kV/660V 60Hz, Δ-Y connected three-phase power transformer has an equivalent series impedance of 2.28 + j17.15Ω, a croe loss resistance of 15235.2Ω and a magnetizing reactance of 5078.4Ω all referred to the HV side. The transformer delivers 20MVA to a...
  15. B

    Can Step up transformer amplify signals?

    Hello friends.I was just wondering if a step up transformer can be used to amplify voltage signals like a transistor,as it step up input voltage at its output.?
  16. S

    How can I design and make a 1750khz IF transformer

    I am in need of some 1750khz intermediate transformers for an old tube project. I can find a few 455khz but not 1750khz. Removing turns from a 455khz IF transformer would raise the frequency but what would that do to the impedance? I thought I would be able to find quite a bit on the...
  17. I

    Transformer Radiator Design and Calculations

    Hey guys I'm BRAND SPANKING new to posting anything an any forum ever...this is a last resort at the end of much research, brainstorming and desperate googling... My problem: We've built a transformer tank to house the core and this will be filled with oil, a radiator was built as well...
  18. B

    Calculating turns in a primary coil of a transformer

    Homework Statement A 100 W transformer (Ns = 1500) has an input voltage of 9.0V and an output current of 0.65 A Homework Equations P = IV Np/Ns = Is/Ip = Vp/Vs The Attempt at a Solution The problem is that I'm not sure what a 100 watt transformer means. Assuming it means that it...
  19. K

    Induced emf and flux in a transformer, conceptual question

    Hey Folks, I am a third year electrical engineering student and just want to clarify a concept involving electromagnetics/transformers. When supplying magnetization current to a transformer (assume sinusoidal), this induces a time changing magnetic flux in the core. The time changing magnetic...
  20. W

    Mutual inductance of transformer with coils of different area and length

    Hello, I am trying to derive the mutual inductance between the two coils of a transformer. I want to do this for two coils with different lengths and different cross-sectional areas (assuming that one side of the transformer core is thicker than the other). The parameters are therefore: I1...
  21. D

    Transformer Dilemma: Solve the Mystery

    Hi, I have a dilemma about transformers that I want to discuss. Say that I have connected an AC source to a step-up transformer with Np turns in the primary winding and Ns in the secondary winding. Say that the secondary winding is connected to a resistance R. We know that the voltage in...
  22. P

    How to tell if a transformer is wye or delta

    I'm going through a list of 12 transformers and trying to determine if they are wye or delta. The schematics I have come across are for power engineering and don't go into too much detail other than the following: The transformers step down ~400V 60Hz AC (three-phase) to ~120V 60Hz AC (single...
  23. Hardik Batra

    Why Are Primary Turns Fewer and Thicker in Step-Up Transformers?

    WHY in step up transformer, the number of turns are less in primary and copper wire is thick. Whereas in secondary number of turns are more and copper wire is thin. In step-down transformer the situation is reversed. I want the reason for this?
  24. E

    How does current flow in the primary coil during transformer self induction?

    I am having trouble thinking about self induction in the primary coil... My text says in standard situation the self induction voltage is same as the primary voltage... My question is how does current flow in the primary coil then? Please tell me where I am getting this wrong?
  25. E

    Testing Transformer: What is the Top Metal Thing?

    Hi everyone. What is the metal thing on the top of the testing transformer (figure below)? It looks like electrode, but what is the use? I find it ubiquitous in many HV equipments.
  26. C

    Excitation current & primary current in transformer

    Transformer equivalent circuit shows that excitation current is just a tiny friction of the primary current. I always thought the pricinple of transformer was like this: voltage on the primary winding generates the current there, then flux in the core, then voltage on the secondary winding and...
  27. M

    Can you calulate a transformer secondary resistance by using load regulation %

    If I had a step down transformer of 300 VA in size at 45-0-45 Volts@3.3 Amps with a regulation of 10% could I do the following to calculate the internal resistance of the secondary winding for my power supply circuit? Voltage * Regulation 10% to work out the voltage difference between noload...
  28. A

    Transformer Calculations - determining turns/current/maximum flux

    The Question A single phase transformer has the following rating: 120 kVA, 2000 V/100 V, 60 Hz with 1000 primary turns. Determine: (A) the secondary number of turns (B) the rated currents on the primary and secondary (C) The maximum flux (D) given a maximum flux density of 0.25 T, the...
  29. T

    400v Transformer for Geiger circuit

    I'm trying to find a transformer for this circuit: http://www.pocketmagic.net/wp-content/uploads/2011/03/geiger-simple-1b.jpg I don't really know what to look for but I did find this: http://www.goldmine-elec-products.com/prodinfo.asp?number=G13599 If that outputs 200v can I just...
  30. S

    High frequency noise in smps transformer

    I have assembeled one smps circuit for 25volts, 40 amps. Circuit gives unwanted high feaquency noise at part load. It is silent at no load. What could be the problem. I am not electronic engineer, Electronics is my hobby. Any body can help me.
  31. R

    Transformer output indepedent of core permeability

    I am having trouble pinning down why the relative permeability of a transformer core will not directly affect the output voltage. In fact the voltage is determined by the turns ratio and is independent of mu of core material. Given this where is the flaw in the following reasoning: Induced...
  32. T

    Transformer, flux linkage and emf short question

    http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Physics%20%289702%29/9702_s05_qp_4.pdfHomework Statement 6b Homework Equations flux linkage = BA B=F/iL The Attempt at a Solution from my understanding, if B=F/iL , if the current is zero...
  33. F

    Practical use of a quarter wave transformer

    Hi guys. I have some questions about the practical use of a quarter wave transformer to match loads. For my question please refer to the figure below... According to my reading the input inpedance fo a quarter wave transformer is: Zin = Z12/ZL and to properly match the line with...
  34. H

    How difficult is it to design a broadband transformer?

    Hello everyone, I am working on a project in which I need to make a broadband/pulse transformer. The transformer will operate in the 20-80kHz range. The transformer will use about 20 watts of power. I need a turns ratio of 1:3. 20V input 60V output It's just for hobby use. I don't have...
  35. S

    Does Flux Density Affect the Weight per KVA of a Transformer?

    Homework Statement Cold-roiled steel of high silicon content enables the designer to use higher operating flux densities with lower loss per kg. The higher flux density reduces the weight per kVA. Can anyone explain how & why does weight/KVA depends on flux density Homework Equations...
  36. T

    Formulas for Transformer Calculations

    I am an EET student. The professor I have is not very thorough in his examples and if you can't keep up with him or have x-ray vision to see through him to the board while he is working the problems then you just don't get the information needed. That said, I am currently trying to do a take...
  37. P

    Ideal Transformer current relationship and problems of B-H relationship

    When I read the lecture notes about the ideal transformer, I have some problems about the proof of current relationship i1/i2=N2/N1=1/a.The proof is shown below. Current Relationships of ideal transformer: To get the current relationships use ampere's law mmf= ∫H•ds= N1i1+N2i2’ H x length =...
  38. J

    Transformer output current question

    hello, I'm super noob. My understanding is not yet clear. it sounds like folks here are describing current as something that's output by the transformer, but i thought current does not exist until there's a load. so my question is, how big of a load can it handle (not sure what 'big' really...
  39. J

    Transformer Core: Questions About Lamination & Soldering

    hello i have a question about the transformer core.when we make it's core,we usually make it laminated to reduce eddy currents.but i saw that there is a soldeing in the corner of the transformer core.why we do this ?
  40. B

    Help with transformer 220V - something

    Hello, I am planning on making a PSU for my home project. I got this probably 30 year old transformer from an old machine used for printing. Now this machine is very big and it had pumps and all that, and this transformer was in it. It has no marks, no info, nothing. It has one small...
  41. Y

    Where Does the Formula for L_0 in Audio Output Transformers Come From?

    I am reading audio output transformers. This is a paragraph from RDH4 and I don't understand where the formula of L_0\; come from. Please see attachment.
  42. E

    How Are Transformer Turns Calculated Using Voltage Measurements?

    Question: The nameplate on a 50 kVA transformer shows a primary voltage of 480 V and a secondary voltage of 120 V.We wish to determine the approximate number of turns on the primary and secondary windings. Toward this end, three turns of wire are wound around the external winding, and a...
  43. C

    Why do laptop transformer sizes vary so much?

    Why laptops transformer size varies so much? Also, the little cylinder right next to the cable connector to the laptop is there to avoid that the laptop works as an antenna? How does that work? Thank you Regards
  44. G

    Step down Transformer is it possible?

    Step down Transformer is it possible?? 20,000 Volts 4 Amps its something very simple. There is a "free energy" device that generates the above voltages and currents. What I want is to drive it into a step down transformer reducing it ro 240 V and 10 A (EU household power ratings). Would...
  45. R

    Can the EM Spectrum Be Converted to Electricity Using Transformer Coils?

    The EM field of a magnet or electromagnet can be converted to electricity with the use of a transformer (coil). My question is... Does that hold up for the whole EM spectrum... IR through Gamma?
  46. Y

    Looking for small 110V to 220V transformer.

    Believe it or not, I have problem finding a small 110V to 220V isolation transformer! No matter how I typed in the search, I get solid state converters. This is true on ebay and Amazon and Digikey! What happened? It used to be so common and cheap to buy a small isolation transformer, it's...
  47. R

    Linear transformer and coupling coefficient

    Homework Statement The coupoing coefficient of K' of a linear transformer is adjusted so that Zab is purely reissitive when ω= 25k rad/s. What is Zab? Homework Equations Not sure The Attempt at a Solution I'm not sure how to being this problem. For one, from what I've been...
  48. M

    Using Voltage Regulation to find load capacitance (Transformer)

    Hi, I did an experiment, involving transformers. Where we did open circuit and short circuit tests then test with a resistor, capacitor and inductor. For the last question it asks Calculate the load capacitance and inductance from the voltage regulation readings. Voltage regulation...
  49. T

    I'm currently stuck on a transformer question and require a little clarification

    Homework Statement A 50 kVA 6360 V/240 V, 50 Hz, transformer is tested on open circuit and short circuit to obtain its efficiency. The results of the tests are as follows: Open Circuit: Primary Voltage 6360 V, Primary current 1.0 A, Input power 2 kW. Short Circuit: Voltage across primary...
  50. W

    Can a transformer operate until maximum load?

    Hi, I have one 2500KVA transformer with 11kV/433V. The maximum current at low voltage side for this transformer provided by producer is up to 3333.49A. Currently, this transformer is running with 2700A which is about 80% of transformer usage and the temperature of the transformer has reached to...
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