wiring isolation transformer

Discussion in 'General Electronics Chat' started by Treeman, Mar 31, 2015.

  1. Treeman

    Thread Starter Member

    May 22, 2014
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    I've spent some time looking at isolation trans. I still cant work out which side goes to the wall and which to the unit - to précis an electronics text is not easy for the reader or writer. I'd rather be safe than sorry or dead so please help me get this right.
    1. I'm thinking side with earth goes to the wall and the side with 2 connections goes to unit being tested/worked on- win or lose?

    I checked for cont. in coils and there is . One reads 9ohm one is 7. There is no continuity betwixt the earth and the rest of the connections. I assume this means it will work as required; but what of the ohm difference between coils - 3.)is it negligible? I tried V=IR and the result was meaningless at 26amps and 34 - enough to run my deep fat fryer for instantly deep fried Mars Bars or Snickers.
    Yummy.

    Thanks
     
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Assuming the transformer is a 1:1 isolation transformer:

    It is reasonable to assume that the heaver (i.e. lower dc resistance) winding is the primary (inasmuch said winding must 'support' its-own magnetizing current, etc...) That said, where safety is concerned, assumption may not be advisable...

    Of course there should be no primary to secondary continuity...

    Best regards
    HP
     
    Last edited: Mar 31, 2015
  3. Treeman

    Thread Starter Member

    May 22, 2014
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    15
    Ther is no Prim/Sec continuity.

    The lower ohm coil has 3 connections and will thus go to the wall.
    The two wires will go to the unit.

    THUS -(please correct if wrong) - If the unit shorts through the chassis I have no earth path so may get a shock (be careful). But thqt shock will not be directly connected to the mains. The Unit fuse will blow and save my bacon?

    Thanks.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,498
    2,364
    If this is used an isolation transformer then the (RH) pair with the ground terminal goes to the wall socket.
    I would expect each winding to have around the same current rating.
    Max.
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,000
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    Your location in the world, other than 'home' would probably help in getting better answers. The hand written notations on the terminal blocks say your working with 200V-240V. Different areas of the world use different mains schemes.
     
  6. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Safe wiring will ground the chassis in anticipation of a primary-to-core fault --- In which case (thus wired) a fuse will open in the event of high current leakage/'dead short' --- Whereas, in the event of low current leakage, you will be protected via the effective 'shunting' of the primary to ground 'path'.

    Assuming the secondary remains ungrounded, there should be no potential difference (and, hence, no liability to shock) between the secondary of the isolation transformer and ground (earth) --- Howbeit it is folly to wager your life upon the integrity of the transformer...

    Please be advised that a fuse affords no (direct) protection against shock, its sole function is over-current protection!!!

    Best regards
    HP
     
    Last edited: Mar 31, 2015
  7. MrChips

    Moderator

    Oct 2, 2009
    12,414
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    Looks straight forward to me.

    BROWN - AC LIVE
    BLUE - AC NEUTRAL
    GREEN - EARTH

    RED-BLACK 240VAC/200VA
     
  8. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,965
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    The Brown and Blue is the primary mains supply, the Red Black is your output to the deep fat mars bar fryer.( must be from Glasgow)
     
    Treeman likes this.
  9. Treeman

    Thread Starter Member

    May 22, 2014
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    Thanks Max that's the answer I was looking for.
     
  10. Treeman

    Thread Starter Member

    May 22, 2014
    158
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    I expect it does look straight forward to you Mr Chips ! ; ).
     
  11. MrChips

    Moderator

    Oct 2, 2009
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    Isn't that what is written beside the terminal block?
     
  12. Treeman

    Thread Starter Member

    May 22, 2014
    158
    15
    Short Bus - please don't take this wrongly but if my locastion was Dunny Outer Space 97v it may not effect the modus operandi of an isolation transformer. That much I know; I think.

    Thanks everyone. I will feel safer now except for the fuse news.;)
     
  13. Treeman

    Thread Starter Member

    May 22, 2014
    158
    15
    Yes Mr Chips but that wasn't really the OP.
     
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