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Inductance and Capacitance as the Secondary Load

  1. Aug 4, 2017 #1
    What are the effects of adding inductance and capacitance as secondary load of transformer? I am using a Ring /Toroid Transformer.
     
  2. jcsd
  3. Aug 4, 2017 #2
    Hello hardy Sir,
    I used a 100VA, 230V/ 2x24V, Secondary rated current Isc=2.08A ,L=36mh/2A/250V, C=58.8micF. I increased the current upto 2A of Inductor. Is this method correct?
     
  4. Aug 4, 2017 #3

    jim hardy

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    Well, what is the impedance of a 38 mh inductor at your line frequency?
    What current do you expect per Ohm's Law?
     
  5. Aug 7, 2017 #4
    Hello Hardy Sir,
    For 38mh inductor only the impedence is 11.938. If I use both inductor and capacitor the impedence is 42.196.
    As there are two secondaries so two possible ways of connections are possible:
    a) Connecting both in parallel so V=24, But Isec=4.16.
    b) Connecting both in series so V=48, Isec= 2.08
    The current expected should me near to the load current(rated current given).
     
  6. Aug 7, 2017 #5

    jim hardy

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    Are you familiar with AC circiut analysis ? Phase angles, polar and rectangular notation and phasor notation ?

    http://www.electronics-tutorials.ws/accircuits/complex-numbers.html
    https://en.wikipedia.org/wiki/Phasor

    Connecting your capacitor and inductor in parallel to a 24 volt winding, their currents will add.
    24 volts / 11.938 ohms of inductive reactance = 2.01 amps . Do you know how to calculate its phase angle?
    24 volts / 54.134 ohms of capacitive reactance = 0.443 amps at its phase angle .

    Accounting for their different phase angles, when i add those two numbers I come up with 1.57 total.
    What do you calculate?
     
  7. Aug 7, 2017 #6
    Hello Hardy Sir,
    With inductive reactance it is lagging so -90deg.
    With capacitive reactance it is leading so +90
    So the magnitude of currents subtract each other and I get 1.567.
    Is it correct?
     
  8. Aug 7, 2017 #7

    jim hardy

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  9. Aug 7, 2017 #8
  10. Aug 7, 2017 #9

    jim hardy

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    I dont seem able to retrieve that image. Save it on your computer and use the "upload" button on the screen's bottom right.
    upload_2017-8-7_9-8-58.png


    You already know the answer to that.
    You want inductance L ?

    You know ohm's law, right ?
    You have meters, right ?
    You know frequency , right ? You used 50 hz earlier.

    Measure volts V and amps I .
    Impedance Z = V / I .

    Measure DC resistance of your inductor, Ω .
    Solve this for XL
    Z = √( Ω2 + XL2)

    And you already know XL = 2πfL
    so L = XL / 2πf
     
  11. Aug 8, 2017 #10
    Hello Hardy Sir,
    I used a signal generator and applied 300Hz frequency and amplitude 400mv. However, when I checked it on a multimeter it showed only 330mv. What can be the reason for this? What can I do about this?
     
  12. Aug 8, 2017 #11

    jim hardy

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    1. With what did you measure 400 mv ?
    2. What changed between your 400mv measurement and your 330 mv measurement ?
    for example..
    (indent ) 2a. Were the readings taken one before and the other after you connected the load ? Do you think the signal generator might sag a little when loaded?
    (indent ) 2b Were they taken with two different instruments ? Look in instruction manual for your multimeter - what is its frequency response ?

    Make both measurements with the same instrument ?
    Turn the knob up to get the output you want ?

    .
     
  13. Aug 8, 2017 #12
    Hello Hardy Sir,
    I used HP 3325A signal generator. In this signal generator I entered both values-frequency and Amplitude.
    However, when I connected the output of signal generator to a small multimeter, without any load, the multimeter showed 330mv instead of 400mv.
     
  14. Aug 8, 2017 #13

    jim hardy

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    Well then, one of them is mistaken.
    What check can you run to determine which ?


    This is at 300 hz, correct ?

    What kind of meter do you have? What is its frequency range and what is its AC accuracy?

    Lastly , did you set the HP3325A synthesizer for sine wave output? It's capable of other functions.

    upload_2017-8-8_18-53-22.png
     
  15. Aug 9, 2017 #14
    Hello Hardy Sir,
    Yes the frequency is 300Hz and I set the snthesizer for sine wave output.
    I think the meter range is not so high. I connected the output of the generator to the oscilloscope and I get perfect sinusoidal wave with correct frequency and voltage.
    In the generator the peak to peak voltage was 1.13 and in the oscilloscope it showed 1.24 V.
     
  16. Aug 13, 2017 #15

    jim hardy

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  17. Aug 14, 2017 #16
    Hello Hardy Sir,
    You are right. I did this and I am getting the output. Thank you very much for your help.
     
  18. Aug 14, 2017 #17
    Hello Hardy Sir,
    With the same transformer, I changed the load to resistive and want to make a equivalent circuit of transformer. Practically, if I perform open circuit and short circuit test, I get all the parameters of the equivalent circuit.( R1,R2', X1, X2', Rc, Xc). However, If I want to calculate these parameters mathematically, than is it possible?
     
  19. Aug 14, 2017 #18

    jim hardy

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    Well anything is possible.
    Do you know how to calculate resistance of a length of wire ?

    Do you know how to estimate leakage reactance?

    Do you know how to calculate inductance of a coil on a core ?
    Do you know how to calculate core losses ? Look up Steinmetz equations.
     
  20. Aug 14, 2017 #19
    Hello Hardy Sir,
    For resistance Of a length of a wire R=pL/A. L=(4*pi(OD^2-ID^2))/H; Is this correct?
    However, I am not ale to calculate the other parameters. If possible can you please explain me with an example?
     
  21. Aug 14, 2017 #20

    jim hardy

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    Wire is usually solid.

    I think you need to train your search engine and find tutorials appropriate for whatever is your level of familiarity, which i don't know.. Look for tutorials on transformer design. There are plenty in existence and i don't intend to write another.

    Here's my first hit from "Inductance calculation"
    http://www.rfcafe.com/references/electrical/inductance.htm
    upload_2017-8-14_8-9-26.png

    that should approximate leakage inductance.

    You'll get the hang of digging out the basics. Search on keywords in the articles that you find .

    You'll need to learn meaning of terms
    magnetic flux , the Weber
    magnetic flux density, the Tesla
    magnetizing force, the amp-turn usually abbreviated MMF
    magnetic reluctance , analogous to ohms , the ratio of magnetizing force and flux
    permability , μ , ease with which flux passes through a medium

    Magnetic circuits are like electric circuits with one exception. In electric circuits the current stays inside the wires. In magnetic circuits the flux can "leak" through the air bypassing parts of the intended circuit. Often you can ignore leakage, especially if there's a complete closed magnetic circuit of highly permeable material like a good steel transformer core..

    Suppliers of Magnetic Materials have reference libraries. Investigate Coilcraft and Mag-Inc .

    Good luck in your studies.
     
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