Isolation transformer

Discussion in 'General Electronics Chat' started by robertogc, Jul 9, 2013.

  1. robertogc

    Thread Starter New Member

    Jul 9, 2013
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    Hi,
    I have an isolation transformer with a 2A time delay fuse on the primary and also same type of fuse at the seconadary. The secondary fuse blows after certain time. Is is possible to be a transformer problem or more likely a problem on the cicuitry after the secondary?

    Thanks
     
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
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    The easiest way to find that out is to disconnect the load from the secondary, then power it up. If the fuse doesn't blow, the transformer is probably ok. Have you measured the load? Is it more than 2 amps?
     
  3. crutschow

    Expert

    Mar 14, 2008
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    I don't see how a transformer problem can blow a secondary fuse, since the only current going through that fuse is from the load.
     
  4. gerty

    AAC Fanatic!

    Aug 30, 2007
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    He may have it overloaded or a problem with the load..
     
  5. robertogc

    Thread Starter New Member

    Jul 9, 2013
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    I will disconnect the load first and see what happens but the question arose because one of my colleagues said it is not possible that the transformer blows the secondary fuse. He says only the primary fuse will blow due to a problem in the transformer.
    What do you think? Is any chance to blow a secondary fuse due to a transformer problem? Or is it always related to load problem? The latest makes more sense to me.
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Did you ask him why he stated this?
    Can he explain his logic to you?
    What is the load?
    If the transformer is bad, it will blow the fuse with nothing connected to the secondary.
     
  7. WBahn

    Moderator

    Mar 31, 2012
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    I'm trying to think of how any type of fault in the transformer could result in current flowing through the secondary's fuse when no load is connected. Remember, the OP specifically said that it is only the fuse in the secondary that is blowing. The only thing I can think of would be something associated with the secondary's contacts/plug/cord such that it is shorting the secondary.
     
  8. gerty

    AAC Fanatic!

    Aug 30, 2007
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    +1
    That's why I suggested he disconnect the load, to totally eliminate the load and associated wiring.
     
  9. WBahn

    Moderator

    Mar 31, 2012
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    Oh, I absolutely agree with that suggestion. It's the very, very first thing that should be done. The second thing, if the unit passes that test, is to power something else that only places a light load on it. The thing after that would be to use something that should put a load on it that is a good fraction of the fuse current. This is, assuming of course, that he has no reasonable way to actually measure the current that is present load is actually drawing.
     
  10. Duane P Wetick

    Active Member

    Apr 23, 2009
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    The first question should be to measure load AC current (I) with an ammeter...then size your fuse to 150 to 200% of that load...and also pick the right type of fuse...Fast-Acting, Slo-Blo etc. If you don't know how to pick an appropriate fuse...give this forum an idea of what the load is and you will get an answer.

    Cheers, DPW [Everything has limitations...and I hate limitations.]
     
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