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Building a isolation transformer...

Discussion in 'Electronic Design' started by Default User, Jan 12, 2009.

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  1. Default User

    Default User Guest

    Hi,

    I've got an old tripplite power conditioner box and while it may be an
    isolation transformer of some sort, I am not exactly sure what it is so I am
    going to rewire it so I know for sure. I have a isolation transformer or I
    could possibly use the transfer in the conditioner box.

    My question is:

    What do you do with the ground? The primary ground comes in and is
    connected to the chassis.

    The secondary winding will become the outlet's hot and neutral.

    What about the outlet's ground?

    If you leave it open, it isn't a ground.

    If you connect it to the line ground, then it is a ground, but really will
    it function as one considering that the hot/neutral are isolated (if there
    is a fault)?

    If you connect it to the line ground and also connect it to the secondary
    windings neutral (bonding the secondary winding neutral to line ground),
    then is it truly isolated?

    What do commercial units do?

    I'm planning on using this for hobbiest type use...

    Thanks,

    Alan
     
  2. Phil Allison

    Phil Allison Guest

    "Default User"

    ** They carry the supply ground wire through to the outlet socket - for
    obvious safety reasons.

    It is *characteristic* of all AC supply isolation transformers that
    connection either of the secondary wires to safety ground will blow no fuse
    nor trip any protection devices.

    Such transformers should be used only when it is necessary to make bench
    tests and measurements on live, non-isolated line voltage devices.

    Then put it away.


    ...... Phil
     
  3. Default User

    Default User Guest

    Hi Phil,

    So you are saying I should carry the ground from the input line cord to the
    chassis and to the output receptacle ground as well? But, leave both the
    secondary outputs hot and neutral unbonded?

    Wouldn't it be better if I just used a 2 conductor receptacle with no
    ground? I mean is it really a real ground since neither the hot nor neutral
    coming off the secondary can deliver any current to it?

    Thanks

    Alan
     
  4. Phil Allison

    Phil Allison Guest

    "Default User"

    ** They carry the supply ground wire through to the outlet socket - for
    obvious safety reasons.

    It is *characteristic* of all AC supply isolation transformers that
    connection either of the secondary wires to safety ground will blow no fuse
    nor trip any protection devices.

    Such transformers should be used only when it is necessary to make bench
    tests and measurements on live, non-isolated line voltage devices.

    Then put it away.

    ** Yep.


    ** It still functions perfectly as a safety ground, since nothing ( like
    some chassis) connected to it can become live.

    What the hell do you think a protective ground conductor is for ??

    And NEVER delete ALL the prior posting

    - like you just did.



    ...... Phil
     
  5. Jasen Betts

    Jasen Betts Guest

    the last two isolating transformers I inspected closely had 2
    conductor line cords cast into the potting compound.

    the boilerplate on the one I have now says "NZSS1379 Class 2"
    but I don't know what that means.

    this is an old 1300VA transformer for power tools, It dates
    from before ELCB type protection

    bye.
     
  6. Phil Allison

    Phil Allison Guest

    "Jasen Buggers Sheep


    ** The last two sheep Jasen shagged were dead


    ** Cos Jasen is a GOD ALMIGHTY total fucking RETARD.


    Baaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhh.....





    ...... Phil
     
  7. GregS

    GregS Guest

    Commercial units can be called isolation transformers and the ground
    goes straight through and one leg of the output is tied to ground
    forming a new neutral. This gets rid of common mode noise to ground.
    I think many times you have to isolate ground and any connections
    to the secondary, for test purposes. There can be at least two
    scenarios. Its either noise control or true isolation. Got to be carefull.
    All tripplite isolations tranformers have the ground tied to secondary
    as per NEC.

    greg
     
  8. JosephKK

    JosephKK Guest

    Try an Internet search on "grounding separately derived systems"
    (without the quotes).
     
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