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How much current can a 3 mm wire carry?

  1. Jun 13, 2013 #1
    how much current can a 3 mm wire carry???


    I was wondering how much current can a wire with of 3 mm diameter can carry?

    Considering the maximum temperature of the wire doesn't change considerably, to melt the insulation...

    Unfortunately I don't know which gauge wire this is...

  2. jcsd
  3. Jun 13, 2013 #2
  4. Jun 13, 2013 #3
    I pretty much agree with Runei using different data.
    3 mm diameter is 0.118" dia
    From book Reference Data for Radio Engineers
    #9 AWG is 0.114" dia
    Book gives fusing current of #9 AWG as 396 amp for copper.
  5. Jun 14, 2013 #4
    highly appreciate your comments,

    Considering this wire is used as the primary wire of a transformer, how many amps do you think it can carry for continuous duty??? Because I didn't quite understand what you mean by "fusing current"... & how many kVA would you guess?

    Is it the current which will fuse copper metals which have no insulation??!
  6. Jun 14, 2013 #5
    A completely different issue in a winding since the inner most winding - is "surrounded" by other winding, all of which are giving off heat. In this case the mechanical design, insulation thickness and type, as well as the transformers core heat - all play a role. This needs to be looked at from a total system perspective.
    From the most basic analysis - if you can calculate the core losses and the winding ( restive) losses - estimating total watts, then calculate the temperature rise of the whole assembly ( Thermal resistance to the ambient- air etc) , this T rise needs to be well below the insulation rating (class) used on the wire. An then have some concern for hot spots - e.g. the temperature will not be uniform throughout the whole transformer - if this is for a one off or low volume build I would oversize the wire significantly - if for a school project, perhaps contact/visit a custom transformer shop and discuss - there is an art + skill + experience + technology to transformers.
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