core saturation on homemade transformer

Discussion in 'The Projects Forum' started by Gated, Jul 7, 2010.

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  1. Gated

    Thread Starter New Member

    Jul 7, 2010
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    Ive built a homemade transformer,

    here is a quick video of it in action: http://www.youtube.com/watch?v=0jqUkzCWAss&feature=related

    at the moment it is kept under a bath of oil and barely overheats, however, when at its full power, I notice that the core becomes saturated as the transformer goes under load, and it just draws more and more current until it finally stabalizes at around a 30A draw.

    seems that the current draw is so low because im using a bank of non-polarized capacitors to provide power factor correction and make the primary behave more as resistive rather then inductive.

    does anyone here know just how the saturation of the core is inherent on the current draw? can anyone explain?

    on a side note, here are some specs:
    input: 120V - 15-30A
    output: 6kV - 700-850mA

    thanks.
     
  2. Dx3

    Member

    Jun 19, 2010
    87
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    Iron is added to a coil to increase its inductance, therefore increase its inductive reactance (Xl). When the iron saturates magnetically, it no longer contributes to the inductance and the coil becomes more like an air core coil. The inductive reactance becomes much less and the current becomes much more.
     
  3. Gated

    Thread Starter New Member

    Jul 7, 2010
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    I see, is this a linear draw? or only inherent on my load?

    say you have a dead short on your secondary, then the current draw should be very high. and compare the current draw to an open secondary, or a load,

    if the secondary is left open, then the transformer quitly idles at around 5-8A
     
  4. Dx3

    Member

    Jun 19, 2010
    87
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    The change from being an iron core transformer to a saturated core is rather sudden...not linear.

    Your second sentence does not make sense.
     
  5. Gated

    Thread Starter New Member

    Jul 7, 2010
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    yeah, I may have worded it wrong,
    what im refering too, is that if the secondary is left without a load, or open circuit, then the current draw is minimal, compared to a high draw if the secondary is shorted.
    if that makes more sence.
     
  6. Dx3

    Member

    Jun 19, 2010
    87
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    Your statement is true. "No load" allows less current flow than a shorted load.
     
  7. Gated

    Thread Starter New Member

    Jul 7, 2010
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    okay,

    seems there is an issue and i cant edit the previous posts :confused:

    I just had a run with this HV transformer and was arcing it, this time however I placed a meter on the primary side
    seems the further you draw an arc and it becomes unstable, the more frantic the current draw is, jumping up and down between 20-25A rapidly.

    if on a dead short, the current remains constant however.
     
    Last edited: Jul 7, 2010
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I hope you realize that what you have made is extremely dangerous.

    High-power high voltage projects are not something that should be considered or attempted by inexperienced persons, as one mistake could get you killed instantly.

    This is not an appropriate discussion for these forums
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    The transformer has a claimed input of up to 3600 watts, so the claimed 5100 watt output is not likely. Nevertheless, that is a very dangerous voltage. The isolation of primary to secondary is not known, not is the insulation certified. This is awfully lethal to be nothing more than making loud arcs. There does not seem to be much application for this transformer.
     
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