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. B

    Calculating the Efficiency of a Transformer for a Small Appliance

    Homework Statement The specifications of a transformer for a small appliance read "Input: 110 V, 6.4 W" and "Output: 8.9 V, 270 mA". What is the efficiency of this transformer? Homework Equations P = I * V V = I * R The Attempt at a Solution 6.4 W / (8.9*(270*.001)) ---> I think this is...
  2. I

    Understanding Audio Transformers: Passing Multiple Signals to Secondary Winding

    Will an audio transformer pass multiple signals at the same time to the secondary winding. For example if there is 200Hz 300Hz and 1000Hz on the primary winding, will there be 200Hz 300Hz and 1000 Hz on the secondary. In my opinion it will but I just wanted to confirm this.
  3. W

    Relation of I and V in secondry coil of transformer?

    One of the function of transformer is to increase the Voltage and decrease the current,It is according to P=IV.The decrease in the current will produce the loss in energy from the resistance of supply lines i.e P=I^2.R. My question is that the P=(V^2)/R is also the power loss and in case of...
  4. A

    How Is the Working Frequency of a Transformer Circuit Defined?

    Homework Statement By trying a variety of values for L_{S} and L_{L} find a transformer for which the three relationships are satisfied while, a=10. Use smallest possible inductances you need to make the transformer work properly @ 1kHz and above. Print plot with the three ratios that...
  5. S

    Transformer problem (falling off of one, that is)

    Homework Statement Which is more dangerous: the electric shock caused by falling off of a transformer, or the impact when one falls, and why? Also, what would the voltage of a 12ft (meh. might as well go with 4m) transformer be about?Homework Equations V = IR U = mgh The Attempt at a Solution...
  6. S

    How transformer loss vary with load current?

    How transformer loss vary with load current?
  7. S

    Transformer Theory: How Voltage Is Induced

    Hi How do transformers get voltage in the secondary? I am after the boring details of the "magnetism" moving and dancing in/at/around/on the core to induce that voltage? thx
  8. H

    What is the Secondary Side Current in a Transformer-Based Energy Meter Design?

    Hi Im building an energy meter and I have a doubt about the voltage channel I am using to measure voltage. Basically there is a transformer that is connected between line and neutral and on the secondary side, there is voltage dividing resistor circuit to step down the voltage to the levels...
  9. jegues

    Transformer Induction coil (COIL CONSTRUCTION)

    Hello all, I'm currently working on a project and I have a question in regards to creating an efficient induction coil for our circuit. Without going into the specific details of the circuit(We aren't given the details anyways, just the circuit itself), it basically imitates a transformer...
  10. D

    What is an intermediate frequency transformer ?

    Can intermediate frequency transformer be classified as a variable inductor ? What is its actual use in radio ?
  11. C

    Consider a transformer with winding ratio of 1 : 10

    Just out of curiosity : Consider a transformer with winding ratio of 1 : 10. What happens when AC 120 v is applied on primary and on secondary we apply DC voltage of 120 v from a battery source is series or in parallel? What will be the output in both cases?
  12. V

    Transformer ratings given a nameplate

    Homework Statement Essentially, there are 4 separate windings that are not connected. Two windings are on the top (H) and two are on the bottom (X). It is given that the rated power of the entire transformer is 5 KVA. The rated voltage is 120/240: 120/240. It also notes that the colon (:) in...
  13. F

    Is Aluminum-Aluminum wound transformer better than Copper-Copper Transformer?

    Copper-wound Transformers were proven tested to be reliable and were used by utilities years ago, because of its low-cost and capabilities. However, with their high cost nowadays, we plan to use Aluminum-wound transformers. Based on facts, aluminum's characteristics in terms of its electrical...
  14. A

    Why Does Reconnecting the Secondary Winding Affect Current Transformer Output?

    i can't seem to understand why with current transformer if the primary winding is reconnectable the rated output stays the same. but rated output depends on turn ratio if the secondary winding is reconnectable?? why??
  15. Phrak

    Transformer and inductive load

    I have a ferrite 12V to 36V transformer driving a purely inductive load near the maximum load capacity of the transformer. The inductance of the load is much less then the transformer secondary inductance. Twelve volts is placed across the primary for a period of time T1, and the...
  16. A

    How far can step up transformer inflate voltage

    How far can a step up transformer increase voltage ? Why voltage is stepped up. Is the end result output power suitable for home use after using step up transformer ?
  17. T

    Confusion open circuit transformer detector

    Hello to you all, I have seen something at a friends work place and did not understand how it worked? after asking I didn’t get an answer that satisfied me. The company produce voltage detectors and test them on a single phase 50kV transformer. One output post is connected to Earth and the...
  18. M

    Is a Transformer Considered a Machine?

    why transformer is a machine?
  19. N

    Neon sign, transformer failure

    Hi all- Can anyone offer any insight into a problem I've noticed for years but don't know how to solve? I'm a self taught neon tube bender. I am not an electrician or electrical engineer. Through the years, I've noticed neon tube, fluorescent lamp, transformer and ballast failure more often...
  20. L

    Understanding 110/220V Transformers and Designing Linear 24V 3A DC Power Supply

    I can't figure out how those 110/220v transformer work. Like the ones in cell phone chargers. Say for example, if the primary voltage is 110v, the secondary will be 24v. But if the primary is connected to 220v, the secondary should be 48v. Are the stages after the secondary designed for up to...
  21. O

    How to estimate the Rating of Transformer

    T/F=Transformer usually T/F is used according to the load of the area, street etc. How they estimate that 50 KVA transformer is enough for this load,street? any formula or method please explain ::Thanks
  22. O

    Re-conditioning of Transformer oil

    What is the procedure to recondition the mineral oil used in transformer so that it become useable again. Any helpful link or... Thanks
  23. S

    Transformer Voltage vs. Frequency

    Homework Statement Using two solenoids on a ferromagnetic core, I made a primitive transformer and graphed this graph of voltage against frequency which is attached. Homework Equations [What I'm looking for.] The Attempt at a Solution What I am having trouble is, what equation...
  24. M

    Engineering Finding impedance in an ideal transformer circuit

    Homework Statement This is a review question for my test, but I can't get the right answer, the problem is to find the impedance ab. Homework Equations Zin = 1/a^2 * ZL The Attempt at a Solution The 10 ohm resistor and the capacitor are in parallel and then add the 50 ohm resistor...
  25. B

    Relation between un-balanced loading and transformer loss

    Hi all, Is there a definite relation between un-balanced loading of a 3 phase transformer and increase in transformer loss? If so, how? Does un-balanced loading affect variable (copper) loss or fixed (core) loss? Pls. explain in detail. If I carry out load balancing between the o/p phases...
  26. F

    Understanding AC Step Up Transformers: Common Issues and Solutions

    I've been running some tests on some simple AC step up transformers, and I can't seem to justify something to myself: I hook up 12 VAC to the primary coil, but the voltage on the coil is actually more like 1 VAC, when measured with a voltmeter. It's not an issue with the supply--it puts out...
  27. K

    What Could Be Causing My Transformer to Fail During Exciting Current Test?

    Hi Folks, We've been use one of the linear transformer in our product for a while and suddenly in one lot the transformer has failed the exciting current test limit at higher votage(132V). This is a 120AC/20VAC@750mA linear transformer. Supplier is trying to figure out what went wrong but...
  28. neduet

    Understanding Transformer Core Loss under Increasing Load on Secondary

    1.If we increasing load on secondary of transformer core loss is same or not ? 2.what is the most common lamination thickness of transformer core? 3.some kind a paper we used in winding for insulation what is the name of this material?
  29. L

    How do high voltage surges affect lightbulbs?

    The bulb connected to the input of a step-up transformer is less bright than a similar bulb connected to its output. Why?
  30. P

    Question: What Determines the Number of Turns in a Transformer's Secondary Coil?

    Transformer HELP! A small transformer with 1200 turns In the primary coil is used to power a appliance that has a output voltage of 6V. The label o the transformer says that the input is 5W at 120V. What will be the output power of the transformer? Given: V output= 0.6*10V (6V)...
  31. C

    Where can i find a US standard AC err transformer or something?

    i have a vent that is too fast and too loud, and it runs off of US standard ac. i was wondering if there is a (good brand name) device that could limit the rms voltage. i don't want a pair of resistors, that would heat up real fast. i need the voltage cut in half, approximately. an analog...
  32. H

    Flux Linking in secondary coil for Toroidal Transformer problem

    Homework Statement A toroidal transformer has been built. It has a square section 'doughnought' shaped non-magnetic core, inner radius 'a' and height 'h' around which the secondary transformer has been wound 'n' times. Calculate the flux linking the secondary due to a time dependent current...
  33. A

    Temperature rise in Power Transformer

    The following transformer gets overheated and I was looking for most probable the causes associated with it. 1. Rating : 7.5 MVA, 0.85 power factor, Power Transformer (Manufacturer - Kirloskar) 2. Connected Load : Upto 6 MW 3. Oil Natural Cooling System 4. Normal Atmospheric Temperature ...
  34. W

    Uses of an Isolation Transformer

    I want to know what do we use an isolating (1:1) transformer for. My book says it is to "protect against electric shock". It doesn't say how. I tried to ask my teacher but he didn't know. I also have looked at http://en.wikipedia.org/wiki/Isolation_transformer" , but I could not...
  35. S

    Mutual Inductance and Transformer Question

    Hi, I would like to ask a question about Mutual Inductance and Transformer. Suppose I have two coils N1 and N2, where N1 is the primary coil and N2 is the secondary coil that is connected in series with some resistance Rx. If I place a voltage V1 across the primary coil, the output voltage V2...
  36. Y

    Solution: Find Full-Load Primary Current in Polar Form

    Homework Statement A single phase 500V/250V transformer that supplies a rated load current of 10 A with a power factor of 0.8 lagging. At no load, the supplied current is 0.25 A with a power factor of 0.10 lagging. I am supposed to find the full-load primary current and express it in polar...
  37. Y

    Solve Transformer Question: Find Full Load Primary Current

    Homework Statement A single phase 500V/250V transformer that supplies a rated load current of 10 A with a power factor of 0.8 lagging. At no load, the supplied current is 0.25 A with a power factor of 0.10 lagging. I am supposed to find the full-load primary current and express it in polar...
  38. S

    Modeling of toroidal transformer

    I want to model a toroidal transformer with a given permeability and saturation flux density. Specifically, I want to model a split core toroid clipped onto a power line, to simulate coupling, so it is really a one turn secondary and a primary of arbitrary turns. Any software packages out...
  39. C

    Can a 220v transformer store electiric charge?

    i turn off the transformer i assembled its from a 220v power source i touched the primary windings and surprisingly it gave an electric shock. i never know this things store charges like capacitors, how does this happen? any explanations?
  40. J

    Switch on a transformer but with no load connected

    If i switch on a transformer but with no load connected to the secondary path.Is the transformer will burn?
  41. U

    When the primary of a transformer is connected to A.C. mains

    When the primary of a transformer is connected to A.C. mains, the current in it... a) is very small if the secondary circuit is open, but b) increases when the secondary circuit is closed. PLEASE EXPLAIN THESE FACTS.
  42. J

    Is Oversizing Current Transformers Necessary for Timed Overcurrent Protection?

    I am using a digital genset controller that to run and protect a generator. This controller has, in addition to other functions, timed overcurrent protection (1-30 seconds). The controller uses 5 amp secondaries. The generator is 83 amp. The 100 amp breaker I plan to use has a...
  43. T

    Transformer and Generator in Per Unit System

    Homework Statement A 3-phase generator rated 100 MVA, 13.2 kV, X = 20% is connected through a Δ/Y transformer to a transmission line whose series reactance is 40 ohms per phase. Assume that the base values in the line circuit are 200 MVA and 115 kV. Find the generator and transformer...
  44. B

    Solving Transformer Issue with 160KVA SOCOMEC UPS

    I new here at the forums. I have a situation in an office building I'm handling. Just want to know if someone could help me out. Here's the problem: 3 units of 160 KVA SOCOMEC UPS connected to 3 units 200KVA 3 phase 4 wire 460V/380V transformer connected in parallel. Configuration is...
  45. R

    Can electrical curents flow from generator to transformer

    Hi, got a doubt this mng, when I heard the power will be shutdown in my office tomorrow to repair a faulty circuit b/w transformer and my office. when the transformer is shutdown, and generator/ups/battery is used to keep the power supply to critical components, will the current flow into...
  46. T

    Transformer copper loss calculation

    Hello guys have a little problem see if anyone can help Homework Statement Q the primary winding resistance is 125Ohms, Secondary is 0.7ohms calulate the transformers copper loss at full load. now the transformers name plate is 240V 50Hz 28VA the earlier question explains...
  47. I

    Problem with air core transformer

    I have two inductors, one as a primary and the other as the secondary. I am trying to transfer the radio signal from the primary inductor to the secondary inductor. But I am getting no signal on the secondary inductor. The radio signal is a voltage signal with very little current. The inductors...
  48. S

    What are load calculations for a transformer?

    what are load calculations for a transformer? A 44kv line is distributed into the industry using around 8 transformers 3750kva, 2500kva and 1500kva. What does this mean and what are the load calculations for this? Also how is it distributed?
  49. B

    Calculating magnetomotive force in a transformer

    If I have a transformer with a known primary inductance and number of turns, and the output is open circuited, how would I go about calculating the magnetomotive force created by the magnetizing current?
  50. A

    Can a Variac handle the current output of a 2300V microwave oven transformer?

    If one had a microwave oven transformer (MOT) from a microwave that was said to be 1200W, and the transformer itself had an output of 2300V, would that mean that the current would be: Power = Current * Voltage 1200W = Current * 2300V Current = 0.52A The reason I ask is because: I'm...
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