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Electronics Equipment Wire Specification

Discussion in 'Modding' started by Big Elf, 22 Feb 2012.

  1. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    I'm looking at 2 wires from different suppliers each supposedly to the same specification but with different amperage ratings.

    Can anyone explain why they should have a substantial difference in the amperage they can handle. Also when it comes to PSUs how is the current rating for each wire calculated. With a PSU that can deliver, say 50A, is it the amps divided by the number of cables supplying power or something more complicated than that. I've been doing a fair bit of reading and haven't been able to come to any conclusions.

    Wire -1
    AWG 18 24/0.2mm (0,75²) tinned copper conductor
    Overall diameter 2.3mm
    Rating 1000V 4.5A at 70°C
    DEFT61-12 (part 6) approved

    Wire – 2
    24/0.2mm copper (Nom. conductor area: 0.75mm²) - Stranded core, single
    Overall diameter: 2.05mm
    Maximum current: 6A
    DEF61-12 (Part 6) Type 2 and BS4808 Part 2 A flexible wire for general purpose extra heavy duty interconnections within apparatus.
     
  2. SuicideNeil

    SuicideNeil What's a Dremel?

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    I do know that a cable made from a greater number of smaller strands ( strand count ) is a better conductor ( greater cross sectional area ) & more flexible than the same gauge of cable made from fewer, thicker strands.

    If you have multiple wires in parallel delivering current to the same component, then that current is divided equally between the wires, yes. Since PSUs often have a single rail & you can only use one connector going to a certain component, then you have to be sure that component isn't going to draw more current than the wire can handle ( more of an issue with power hungry fans or fan controllers- seen a few burnt fan connectors lately ).

    Ofcourse, things like GFX cards have multiple wires and connectors to deliver power, so the odds of melting the wires is somewhat slim so long as the stuff you are looking at isn't any smaller gauge than what you'd normally find on a half decent PSU..
     
  3. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    Thanks for that. They both have the same number of strands as AWG 18 wire so should be OK. I was just wondering why the one that has the thicker insulation has a lower amperage rating.
     
  4. Dreamslacker

    Dreamslacker Minimodder

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    It depends on how they word the specifications.

    There's a marked difference between continuous and peak/ max current.

    Notice that the 2nd spec says max current, not average continuous. The thickness and type of the insulator plays a part here.

    When the wire carries current, it heats up somewhat.
    Depending on the ambient temperature, the insulation may actually melt due to the heat generated.

    If you look at the specs of the first, they do actually tell you what voltage, current and temperature the testing is conducted at. You probably won't be using the wire at 1kV and 70'C so it can probably do much more. A typical PVC insulated 18GA wire should actually do about 16-18A max for lower voltages in a chassis. For non-chassis use such as for power line transmission, this actually goes down to about 2.3A.

    IMO, the first wire's manufacturer is much more honest about the rating and you should go for that instead.
     
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  5. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    Thanks, just what I needed. I've ordered a reel of Wire 1.
     

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