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9v DC from 3 phase power line

Discussion in 'Electronic Basics' started by Guest, Oct 7, 2004.

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  1. Guest

    Guest Guest

    I have a machine with 1kW, 3 phase motor.
    I also have a sensor board measuring temperature, humidity and rotation
    speed. This board operates with 9v, 100mA DC.
    How can I obtain 9v from the 3 phase power line?
    Can I use any two line of the 3 phase power line to connect an ordinary 240v
    to 12 v transformer?
     
  2. Yes, if the 3 phase power has 240 volts line to line.
     
  3. Externet

    Externet Guest

    Yes, you can use an adapter with the same primary tension as two of
    the phases tension. Measure voltage across 2 phases first.
    Miguel
     
  4. John G

    John G Guest

    The above seems to originate in Australia where there is almost
    universally 3phase Y connected 230/400 volt supplies.
    In a motor situation there may not be a handy neautral but general
    purpose power is always 230 volts phase to neautral and the only
    trnsformers (Wall Warts) readly avaiable are 230 to whatever.
    Of course it may be expedient to buy a special transformer with a 400
    volt primary if there is no neautral at the actual location this 9 volts
    is required.
     
  5. James

    James Guest


    Thats the usual way here in aus. Transformers with 415 volt primaries
    aren't too hard to find here, its very common in industrial control.
    An industrial supply shop should have the transformer you want. If you
    try and connect a transformer designed for 240 onto 415 volts it will
    saturate and you will quickly burn it out. If a neutral is present
    just connect it between an active and neutral. Be careful of colour
    codes too, machines seem to use a wide variety of colours for various
    things - black isn't necessarily neutral.

    Check the voltage first :)


    cheers
     
  6. Ross Herbert

    Ross Herbert Guest

    On Fri, 8 Oct 2004 00:12:29 +1000, <Johnietta> wrote:

    |I have a machine with 1kW, 3 phase motor.
    |I also have a sensor board measuring temperature, humidity and rotation
    |speed. This board operates with 9v, 100mA DC.
    |How can I obtain 9v from the 3 phase power line?
    |Can I use any two line of the 3 phase power line to connect an ordinary 240v
    |to 12 v transformer?
    |
    Listen only to swanny.....

    The fact is that if you measure between ANY 2 PHASES you will read 415
    V nominal. If you measure between ANY ONE PHASE and NEUTRAL you will
    read 240V nominal. Since this is what you require for a readily
    available wall-wart transformer then that's how you obtain the primary
    input voltage for the wall-wart.
     
  7. If you have to ask that, you shouldnt be doing any such thing!
     
  8. carl

    carl Guest

    bust out one of the phases and neutral. you can run this to the
    appropriate transformer with some filter caps in front of and behind a
    7809 voltage regulator ic.
    any of the phases to neutral will be about 120vac but if you go across 2
    phases then the voltage goes up to about 208vac or so
    be careful
     
  9. carl

    carl Guest

    oops....i'm thinking you are in america but i'm thinking now australia?
    my response would work in america but i'm not sure what the voltages are
    in australia.
    be careful
     
  10. Whilst no doubt you could make it work in that manner (Aus supply being 415v
    phase to phase) it would not be a good method. Far better to have a seperate
    supply for the monitoring eqt. I am assuming that the motor runs off an
    outlet ??
    If it has a control cabinet or motor starter cubicle then mounting the
    tranny with a fuse in the supply line would be the best approach.
     
  11. carl

    carl Guest

    a separate supply would be better, i agree, but with the exception of
    the confused voltages, i gave him what he was asking for. i'm not here
    to tell him what he's asking for.
     
  12. Oh OK now I understand.
     
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