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Combining Two Transformers

Discussion in 'Hobby Electronics' started by Dave, May 7, 2004.

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  1. Dave

    Dave Guest


    I have two 9 amp 12 volt dc (output) transformers that I would like to use
    together to provide the same voltage but at a higher amp rating. Is there a
    way to do this.

    Any assistance would be appreciated.

  2. Phil Allison

    Phil Allison Guest

    ** Is this a question on some sort of test paper OR do you *really* have
    two DC supplies ??

    If you do - then kindly tell us all about them.

    The devil is in the detail you know.

    IGNORE any fool who tries to answer your question as posted.

    .......... Phil
  3. It sounds like you want to run the transformers in paralell. Yes you can do
    that. With them both powered connect one output of one transformer to the
    output of the other. Measure the outputs of the other two wires (AC) and if
    you get zero volts then the transformers are connected in phase. if you get
    double the voltage then the transformers are out of phase and you need to
    swap the two outputs over. If you don't they'll go bang when you connect
    them together.

  4. Dave

    Dave Guest


    I gave up doing exams years ago. The two transformers in question came from
    a garden lighting set and were given to me. I thought they may be of some
    use particularly if they could be combined to provide a higher current.

    They are described on the case as being Arlec 61130, Input 240V, 0.5A,
    Output 12V, 9A, 108VA. I have an interest in electronics but my knowledge is
    limited - hence my request.

  5. bruce varley

    bruce varley Guest

    Dave, Transformers of the same type can often be parallelled without
    problems, but you need to be aware of the potential safety hazards in doing
    this. If you isolate the primary of one, then it will still be live at 240
    Volt, being backfed via the other. I'm not sure what the regs say about
    this, maybe someone else can advise...? You shouldn't proceed until this
    has been clarified, some other poor person working on such a system
    unawares could be killed..
  6. Phil Allison

    Phil Allison Guest

    ** Good.

    ** What ***ever** made you decide they were DC ?????????

    They can probably be wired together in parallel to give 12 volts at 18
    amps AC !!!

    But is 12 volts AC any good to you ??

    ............. Phil
  7. bruce varley

    bruce varley Guest

    On further reflection, let me be a bit blunter. It's a bloody dangerous
    procedure, don't do it. There have been many near misses, and undoubtedly
    fatalities as well, due to backfeed electrocutions.
  8. Hi Dave, Could you please tell me where I can get some dc
    transformers? I'm sure they would come in handy one day.
  9. If you put them both in a common box so that it's obvious that they're
    connected together it would be safer. Paralleling two transformers was in an
    electrical test I did at the end of my apprenticeship. It's not particularly
    difficult but you do have to get the phasing right.

  10. Kevin

    Kevin Guest

    Is it possible to connect a few transformers to a 7Amp PS, to boost the
    output amps?
  11. KLR

    KLR Guest

    If the transformers are in the same enclosure - and BOTH primaries are
    connected to the SAME mains power cord (permanently wired via a common
    terminal block in the enclosure with the transformers etc) and both
    have a common mains fuse/switch etc - then the setup should be just as
    safe as with a single transformer.

    I dont know about the regulations - but common sense would tend to
    suggest that this method is fine. Actually on one occasion SC did
    publish such a design for a car battery charger with 2 paralleled 12v
    transformers (as 2 smaller ones fitted into the compact case used
    where one large one of the same VA rating wouldnt) .

    If they are these "consumer" type transformers with a mains cord and
    plug already fitted (as I would imagine to be the case with a garden
    light transformer) - and you plan on using 2 separate mains plugs
    into 2 power sockets etc - then DONT DO IT. It IS a serious safety
    hazard as if one plug is plugged in and another isnt - then its pins
    would be LIVE !
  12. KLR

    KLR Guest

    LMAO :)
  13. Dave

    Dave Guest

    Thanks to everyone who responded. I think I will put this idea aside until
    I get more experienced in electronics.

  14. Arpit

    Arpit Guest

    It strikes me that they just may be switchmode supplies. In which case
    putting them in parallel might not be such a great idea. The
    switchmode supplies i tried that with when I was littler just
    activated teh safety cutoff if I remember correctly.
  15. Phil Allison

    Phil Allison Guest

    "Arpit" <

    ** There is a very obvious difference in weight - even a novice could
    not miss that.

    ........... Phil
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