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Wattage of large 4-terminal 0.01 ohm resistor, want to know

Discussion in 'Electronic Design' started by L Chung, Apr 29, 2004.

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  1. L Chung

    L Chung Guest

    Hi,

    I have bought a high wattage 4-terminal Dale resistor from eBay. I
    could not determine the wattage from the markings on the body and no
    luck from the Vishey Dale website either.

    Its gold in color, made of two rectangular flat aluminium blocks
    bolted together by 10 countersink screws, with 8 holes for mounting
    onto a heatsink. Dimensions of the body are WxHxD=8"x2"x1".

    Current connection is at either ends(C) and two wires(P) exit near
    each end.

    The date code 7339 probably refers to year 1973 and week 39th.

    Does anyone knows the rated wattage of such resistor when fitted on a
    heatsink?

    DALE, SPR-390-3, 0.01ohm, 1%, 7339.

    Note: o:hole, +:screww

    -------------------------------------------------
    |o + o + o + o|
    C |+ +| C
    ===| @ @ |====
    |+ \ / +|
    |o | + o + o + | o|
    -----|-------------------------------------|-----
    | |
    |P |P


    Thanks

    L.Chung
     
  2. L Chung wrote...
    As you noted, Dale is now Vishay. They still make the SPR-2213 and
    SPR-2214, which appear to be similar but smaller. The '2214 version
    is 4.5" long and is rated at 50W, or 100W when on a heat sink.
    http://www.vishay.com/docs/30224/spr.pdf


    Thanks,
    - Win

    whill_at_picovolt-dot-com (use hill_at_rowland-dot-org for now)
     
  3. R.Legg

    R.Legg Guest

    SPR indicates special-purpose wirewound. The parts are derated to 0W
    at 275DegC.

    Dale metal-clad parts are typically rated at 25W per linear inch of
    resistor body length with 1"width heatsink interface, and 50W/linear
    inch with a 2"width heatsink interface. At 8"x2" your part will be
    book-labelled in the region of 400W.

    SPR part numbers do not normally indicate a wattage rating.

    RL
     
  4. legg

    legg Guest

    SPR prefixes were used for a wide variety of special power resistor
    styles and configurations. It was a wild-card prefix, denoting
    products that were not currently in high-volume production, and
    required a special order.

    For example, the SPR-1002 is an NH250 with a central pipe intended to
    allow water cooling and SPR-2093 is a through-hole-solderable
    4-terminal solid-wire shunt.

    Ceramic resistors are probably different beasts altogether.
    SPR-2213/4 are SPR because of optional constructions offered - with
    added terminals, more rugged element materials construction and
    winding styles.

    Metal-clad parts use a silicone filler and have welded element
    terminations. The larger clad parts are derated to 40% or less in free
    air, without the heatsink. There may also be restrictions for the part
    number that do not follow the general clad case, given it's apparent
    high-current shunt function.

    RL
     
  5. L Chung

    L Chung Guest

    400W! That's huge. I guess this type of resistors fill the needs where
    a common current shunt can't because open current shunts do not have
    heatsinking and so must not gets too hot. Below 20W for most?

    Thanks all for the valuable information.

    L.Chung
     
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