Transformer step up or down

Discussion in 'Power Electronics' started by quique123, Feb 3, 2018.

  1. quique123

    Thread Starter Member

    May 15, 2015
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    So I need a transformer for a small spark. The only one i have lying around is a hefty 5lb one about the size of a baseball that I think came out of a UPS unit. I understand the basics of a transformer but while reading up I got to thinking about the differences between a stepUP and a stepDOWN transformer. So I have a couple of questions:

    1. if i take any transformer and I connect the power source on 1 side for steup and on the opposide for step down?

    2. In any transformer that has a 2:1 winding, will 9V produce 18V and then 18 produce 9V the other way around?
     
  2. Alec_t

    Expert

    Sep 17, 2013
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    In principle, yes to both questions: but transformer windings are designed for certain current and voltage maxima which have to be taken into account. For example, the insulation on a low voltage secondary winding may not be adequate to cope with mains voltage.
    Stepping up voltage also steps down available current, since the transformer can handle only a certain power. Vin x Iin = Vout x Iout.
     
  3. quique123

    Thread Starter Member

    May 15, 2015
    344
    5
    Ok so if I take that transformer and connect a 3.7V or 9V battery I might get 7.4 or 18 V but the current would be super low right?
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Yes if you pulse the Secondary side with 9v, the Primary will give out a larger voltage depending on the turns ratio.
     
  5. Alec_t

    Expert

    Sep 17, 2013
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    No, you wouldn't. Transformers require AC energisation.
     
  6. quique123

    Thread Starter Member

    May 15, 2015
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  7. Reloadron

    Distinguished Member

    Jan 15, 2015
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    While I do not know your location the simple way to go about this would be to find a junk yard and scavenge a automotive ignition coil. When we apply a voltage, say 12 VDC nothing will happen, the field lines of flux will extend outward from the transformer. When we remove power the magnetic field will rapidly collapse and the secondary will give you your wanted spark. Before automotive systems went to electronic ignition systems a set of points in the old distributor would open and close driven by a cam, all mechanical, and each time the points opened a spark plug would fire.

    These coils could also be driven with a typical lamp dimmer. Applying a sine wave to these coils won't work as you want the field to collapse rapidly. This is why the points worked so well on the old automotive ignition coils, points would Make or Break as in right now.

    Ron
     
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