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Insulating hardware, esp.washers

Discussion in 'Electronic Design' started by [email protected], Dec 21, 2013.

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  1. Guest

    Handy--I passed on some, thinking they wouldn't be stiff enough.

    Thanks.

    James
     
  2. Guest

    I was mostly wondering what people do between the bolt and the
    semiconductor--sorry I didn't make that very clear. I saw the
    various offerings at DigiKey, but some of them looked cheesy.
    I didn't prep them. Trapping grit would be my main concern, but even
    that shouldn't make much difference as long as the grit's non-conductive.

    That depends. If the screw's not touching the TO-220, it doesn't matter.
    I've seen old nylon, yes, yellow-brown, and brittle.
    It won't run continuously, and in normal operation it shouldn't
    even get hot. But, abused, it will, and the customer's hammering
    the heck out of it.

    So, I'm trying to protect the semis under fault conditions.

    It already has instantaneous current limiting with a limit inversely
    proportional to switch temperature. That and the heat sinks were really
    just meant so the unit would survive long enough to take out its input fuse.

    I might make that thermal overload cutoff a lot more aggressive. Or
    possibly not--blowing sacks of fuses might get old, and enforce a
    certain amount of discipline.
    Per John, Teflon cold-flows. Nylon would probably work here. As it is
    I'm using Kapton, 'cause that was handy locally, intruding into the hole
    to keep the bolt clear of the TO-220 tab.
    Removing burrs is essential--burrs are NOT allowed. Having done that,
    the Al2O3 works great--no problems at all.

    Cheers,

    James Arthur
     
  3. One check always worth doing when you have assembled everything is an
    insulation integrity check to ensure what should be insulated remains
    insulated.

    --
    ********************************************************************
    Paul E. Bennett IEng MIET.....<email://>
    Forth based HIDECS Consultancy.............<http://www.hidecs.co.uk>
    Mob: +44 (0)7811-639972
    Tel: +44 (0)1235-510979
    Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
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  4. Den lørdag den 28. december 2013 05.02.28 UTC+1 skrev John Larkin:
    and can be stacked in "parallel" or "serial"

    -Lasse
     
  5. josephkk

    josephkk Guest

    A new material for my list, cool. I was going to recommend diallyl
    phthalate for the job, i have used it enough at temperatures as high as
    125C for years in a test lab. No problems.

    ?-)
     
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