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Question about blown fuses.

  • 01-02-2011 12:22pm
    #1
    bridgetown1
    Registered Users, Registered Users 2 Posts: 150 ✭✭


    I was doing some JC experiments on light and 2 transformers blew on me. When I investigated the fuses I discovered that the blown transformers had fuses marked 'F1AL250V' while the others were marked 'T1AL250V'. While the transformers were blown, the fuses remained intact!! What is the difference between the 'T' marked fuses and the 'F' ones, which seem to be the cause of the problem?

    Thanks in advance!


Comments

  • #2
    bridgetown1
    Registered Users, Registered Users 2 Posts: 150 ✭✭bridgetown1


    I hope I have put this question in to a suitable forum.


  • #3
    watty
    Registered Users, Registered Users 2 Posts: 32,417 ✭✭✭✭watty


    Speed at which they blow, Surge rating. But either way sounds like transformers underrated or fuses overrated. Correct value fuses even of slowest kind should fail before transformer does. If there is no other fault, then the Transformers are under specified.

    I nearly lost a transformer due to some idiot replacing fuse with nail wrapped in foil. Note to self. Always check correct fuses fitted.
    I unplugged it when I saw the smoke (which was vapourising varnish!) I poured some polyurethane varnish into transformer while it was still roasting hot, a bit more 30min and 1 hr later. Left it a day, and repaired the fault (missing -90V rail to feed P.A. grids etc). Transformer was fine and running cool with P.A. off.

    If a transformer gets a shorted turn or two due to insulation failure, it will run hot on no load.

    1A Fuses. What Power where you taking from Transformers and what rating are they? You'd want 250VA / 250 Watt rated transformers for 1A mains fuses and only be taking 180W to 200W max. Roughly.


  • #4
    brownmini
    Registered Users, Registered Users 2 Posts: 177 ✭✭brownmini


    bridgetown1 wrote: »
    I was doing some JC experiments on light and 2 transformers blew on me. When I investigated the fuses I discovered that the blown transformers had fuses marked 'F1AL250V' while the others were marked 'T1AL250V'. While the transformers were blown, the fuses remained intact!! What is the difference between the 'T' marked fuses and the 'F' ones, which seem to be the cause of the problem?

    Thanks in advance!


    T = timelag
    and I think that F = fastblow (opposite to timelag)

    If you get two of the fuses together, you'll see one
    looks like its a fine spring of fusewire with a slender heatsink along its middle
    or will have someway of soaking heat away from the fusewire,

    Whereas the Fastblow will just be a fine piece of straight wire, maybe
    with a spring on one end putting it under tension to make sure it pulls apart fast.


    The Timelag allows for surges and peaks without blowing...it'll start to glow first.
    The Fastblow will do ''exactly what it says on the tin" - if it sniffs the possibility
    of over-current it will blow, it doesnt hang around.

    see "http://en.wikipedia.org/wiki/Fuse_(electrical)" for some more.

    Personally - if I dont see the T then I consider it to be a fastblow.
    And years ago, the T used to be on the end not at the front.


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