Current ampacity for small swg conductors

Discussion in 'Physics' started by amilton542, Feb 7, 2012.

  1. amilton542

    amilton542 Thread Starter Member

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    I want to calculate the current carrying capacity of small copper enammelled wire guages.

    Everything I look at is AWG, and their cross-sectional areas are too big. I'm after an swg table but can't find one.

    Is there a formula I can use to determine the current ampacity?
  2. bertus

    bertus Administrator Staff Member

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  3. amilton542

    amilton542 Thread Starter Member

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    Thank you.
  4. Kozmyk

    Kozmyk New Member

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    A lot of the data in tables giving ampacity per wire size is application related. Mainly to mains power installation.
    These include safety margins for heat dissipation, cable bundling, insulation melting points etc. and are not the maximum ampacities for a single conductor in free air.

    The ultimate maximum would be at the point at which the conductor fails i.e. melts or breaks.
    Clearly you have to work back from that state. :)
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  5. studiot

    studiot E-book Developer

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    You will find the information you seek in publications by

    The Radio Society of Great Britain (RSGB)

    eg

    The Radio Data Reference Book by Jessop, p221 references current ratings and other data for SWG copper.

    What SWG are you interested in?
  6. amilton542

    amilton542 Thread Starter Member

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    I'm interested in 24 SWG, but after looking at the conversion table Bertus gave me, the closest approximation in wire diameter was 24 AWG; which was close enough.

    For 24 AWG i've got 577mA.
  7. studiot

    studiot E-book Developer

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    My tables have the following data for 24 swg

    diameter 0.022 inch

    resistance of 1000 yards 63.16 ohms

    length in yards per pound 228.3

    current rating 0.4561 amps at 1200 amps per sq inch

    Turns per linear inch

    Enamel 41.6
    Single silk 42.1
    double silk 40.0
    Single cotton 36.7
    Double cotton 31.0

    Turns per square inch

    Enamel 1731
    Single silk 1772
    double silk 1600
    Single cotton 1347
    Double cotton 961

    Nearest american wire guage 23
  8. amilton542

    amilton542 Thread Starter Member

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    Thanks studiot.

    I don't suppose you know a good method on how get your hands on the other end of the conductor that is embedded inside a bobbin of coil like this http://www.maplin.co.uk/enamelled-copper-wire-44

    I can do it buy hand and get it nice and tight so it looks exactly how it did before, but to do it by hand to eight bobbins of 24 SWG copper wire will take me days.

    I was thinking of a drill set-up, but I think it could prove awkward trying to get the windings tight.
  9. studiot

    studiot E-book Developer

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    Both the RSGB and Babani publications had practical amateur coil winders based on hand drills and sewing machines etc. I have also seen Knitmaster hand cranked wool winders pressed into service.

    The main issue is a turns counter. Some electronics mags of yesteryear had designs for this. You can also modify a bikeometer or wheeled pedometer mechanism for this.
    amilton542 likes this.
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