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Reliability of transformers

Discussion in 'Electronic Design' started by Fred, Jul 12, 2004.

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  1. Fred

    Fred Guest

    A transformer winding / supply company has suggested a failure rate of 1% of
    its products over what I presume to be a year period. The sort of size we
    are talking of is around the 100VA.

    Can anyone enlighten me if this is typical, just that it seems rather poor?
     
  2. That is absolutely insanely horribly bad. Ordinary mains-frequency
    low-voltage power transformers used well within their ratings will
    outlast most any other part in your design. It's also hard to kill
    them even by moderately abusing them (cook them at extremely high
    temperature or arcing them will do them in). I don't know how you'd
    make a transformer that bad.

    Of course if you're talking about a cheaply made 10kV transformer run
    at 125°C, that's maybe a horse of a different color.

    Best regards,
    Spehro Pefhany
     
  3. That's a spec written by a marketroid. 1% over 10 years might be more
    realistic, but I'd be disappointed. I'd expect a World War 2 100 VA
    transformer kept in a benign environment to still work.
     
  4. I read in sci.electronics.design that Spehro Pefhany <[email protected]
    Battery-charger transformers that are not varnish-impregnated fail after
    a few years, but that's probably intentional, and is due to the bad
    environments (especially very high humidity) they experience. A
    varnished one will last forever.
     
  5. Joerg

    Joerg Guest

    Hi Fred,

    To add to Spehro's and John's concerns: Just imagine if every part in
    your design had a "reliability level" that would cause 1% to fail in a
    year? How many systems would still work after one year? How soon would
    the warranty overhead on this design eat up a corporation's assets?

    Regards, Joerg
     
  6. legg

    legg Guest


    Perhaps it's your presumption of 'a year period' that is in error.
    Obviously you'd need to find out for sure, however.....

    Early mortality prior to shipping, shipping damage, and 'returns for
    other reasons' can sometimes all be lumped into the same 'total
    defects' category. This does not provide any meaningful representation
    of device reliability or failure rate, nor does it give anyone a clue
    as to possible methods of avoidance/improvement without more serious
    analysis.

    But it's what a bean counter wants, and he has every right to it.

    RL
     
  7. Mr TUBEAMPS

    Mr TUBEAMPS Guest

    some power transformers have a thermal
    fuse hidden under the primery winding
    tape, when thay blow, winding is open.
    the fix is to peal back the tape to fined
    it, and then brige it with wire and use a
    external fuse. use silicon or hot glue
    to reseel.

    john
     
  8. Ian Stirling

    Ian Stirling Guest

    I'd replace thermal fuse, and improve ventilation, if possible.
     
  9. Tim Shoppa

    Tim Shoppa Guest

    Most 1940's era transformers have had an insulation failure since then.
    Not all... and a lot of insulation failures go undetected.

    A good fraction of transformer failures are due to the stuff it supplying
    failing catastrophically, taking out the transformer with it. Rectifier
    and filter capacitor failure does this. I wouldn't attribute this as a
    failure due to the transformer, but maybe the manufacturer does in counting
    totals. The "1% over maybe a year" is not a real spec in any event.

    Tim.
     
  10. Tim Shoppa

    Tim Shoppa Guest

    Most 1940's era transformers have had an insulation failure since then.
    Not all... and a lot of insulation failures go undetected.

    A good fraction of transformer failures are due to the stuff it supplying
    failing catastrophically, taking out the transformer with it. Rectifier
    and filter capacitor failure does this. I wouldn't attribute this as a
    failure due to the transformer, but maybe the manufacturer does in counting
    totals. The "1% over maybe a year" is not a real spec in any event.

    Tim.
     
  11. Fred

    Fred Guest

    Just found out the 1% is the failure rate after 1st test. Had me worried
    for a moment.

    Thanks for all the replies. Will keep you posted on any further figure.

    I also thought it was worryingly poor. My experience is they tend to be one
    of the last things to fail.
     
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