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220 to 110 autotransformer being given away

Discussion in 'Electronic Repair' started by micky, Dec 16, 2013.

  1. micky

    micky Guest

    Someone on Freecycle is giving away an autotransformer. with
    220/240-volt input and single 110-120-volt output. 1-Amp fuse. Made in
    England.

    Do I have any use for that for repair work or anything? Since there
    is already 120 in the house, I don't think so, but in the picture it
    looks like new. ;-)

    What are they used for?
     
  2. Leif Neland

    Leif Neland Guest

    micky forklarede den 16-12-2013:
    In civilized countries with a modern electric system, we have 230v,
    allowing for using less copper/alu in the cables.

    When we get equipment from backward countries with only 110v, we use an
    autotransformer to step down the voltage.

    An autotransformer use less wire than a "normal" transformer, but does
    not give isolation between primary and secondary.

    Leif

    .... with 230 and 400v in the house.
     
  3. RobertMacy

    RobertMacy Guest

    LOL! Thanks, I needed that today.

    Of course, here in the US we should be happy that Edison LOST out
    regarding his DC distribution system. Wasn't Edison the one who invented
    the Electric Chair just to discredit his competitor [Tesla, Westinghouse]?
    He wanted to show how lethal these high voltages were, but alas, his first
    three testers died rather badly, inhumanely.
     
  4. Check whatever else is being offered by the guy.

    I found a nice 120 to 220 transformer in a pile of garbage earlier this
    year, thought about, and couldn't think of a reason to bring it home,
    especially with that weight.

    I dig a bit more in the pile, and find a sander, one of those ones with a
    sort of shovel part at the front for the sandpaper. So i bring that home,
    not really paying attention to it.

    I get home, and I then notice the plug is wrong, and the label says it's
    for 220v.

    There was a reason that transformer was there, it was for the sander.

    Michael
     
  5. Leif Neland

    Leif Neland Guest

    John G sendte dette med sin computer:
    Why should that be dangerous?

    Surely you do not rely on the which wire is live and which is neutral,
    and have the neutral connected to the cabinet or something?

    Or are your insulation so bad it cannot withstand 240 volt to ground?

    Leif
     
  6. Phil Allison

    Phil Allison Guest

    "Leif Neland"
    ** Old US made items ( audio, radio TV etc ) have no connection to ground so
    the chassis floats at some mid voltage OR is linked to one side of the
    incoming AC line with a capacitor. The cap is usually either 0.1uF or 0.05
    uF @ 400V DC.

    The plug can be reversed so the user is supposed to find the way that links
    that cap to neutral and so brings the chassis down to a low voltage. This
    will result is less hum and noise in the sound.

    If used with a auto tranny from a 240V supply, the cap ( aka " death cap" )
    can bring the chassis to 240V or itself experience 240 VAC if the chassis is
    grounded by another item. 240VAC is more than such caps can stand and they
    often fail short.

    With guitar amps, this situation is particularly lethal - hence the title
    "death cap"'.

    FYI:

    An auto tranny will deliver full AC line voltage on BOTH output wires
    simply if the neutral is not connected at the supply end.



    .... Phil
     
  7. Leif Neland

    Leif Neland Guest

    John G har bragt dette til verden:
    Yeah, but do you say "This is the neutral connection, I can touch this
    safely"?

    Assume everything is "hot". Just like my father taught me: Check it is
    unloaded, and then treat it as if it was loaded.
     
  8. Leif Neland

    Leif Neland Guest

    Phil Allison formulerede spørgsmålet:
    So no voltage across the device connected.

    Just as any device will have full AC line voltage on both inputs if the
    neutral is not connected in the wall socket. But no power.

    Heck, if you have two/three-phase supply, and the ground is
    disconnected, you can get double or 1.7*line voltage. WITH power.
     
  9. don't forget you waste more iron in magnetics with that 50Hz stuff.
     
  10. micky

    micky Guest

    There was a picture and it clearly said autotransformer, no capital a,
    in big letters.

    I'm in the US btw, if anyone thought otherwise.
    Yeah, I've wanted one of those for a long time. I'm still alive so
    no harm done. ;-)
     
  11. Leif Neland

    Leif Neland Guest

    dave skrev den 16-12-2013:
    You are confusing autotransformers with variotransformers.

    Actually, most variotransformers are also autotransformers, a subset
    with a movable tap.

    Some variotransformers come with an isolation transformer, so you are
    relative safe as long as you only touch the hot circuit with one hand.

    Leif
     
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