is their a difference between the surface area of the weir that i use for 1A AC voltage source and 1A DC voltage source ?
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3\$\begingroup\$ I think you mean the the cross section. Yes. It depends on the AC frequency and the material. Usually this only affects frequencies in the MHz range, but there are exceptions. For example, you should not use iron wires even for 50/60Hz AC. The skin effect is extreme for iron because of its high µr. \$\endgroup\$– JankaDec 15, 2016 at 4:09
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Skin effect and proximity effects are caused by AC magnetic fields affecting the usable part of a conductor for passing current. As frequency rises skin effect worsens but only as a square root of the frequency increase.
This means that DC resistance is lower than AC resistance (and I'm not talking about inductive reactance here). Skin effect: -
Skin effect is not negligible at 50 Hz for power transmission systems. At 50 Hz copper has a skin depth of about 9 mm making it very problematic for power distribution: -
Proximity effect occurs when AC currents are flowing in side-by-side conductors - the interactions between the magnetic fields produced tend to reduce the usable conductive part of a cable even more: -
The picture above is when the AC currents in each wire are in-phase (as happens in power distribution cable bundles. The picture also shows a level of skin effect.
This is a useful link for understanding both effects.
answered Dec 15, 2016 at 11:59
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\$\begingroup\$ I can state authoritatively that commercial aircraft use the same wire size for 400Hz AC and DC power distribution of equal RMS AC and DC current. Of course, "power distribution" can mean anything depending on the circumstances. OP asked about a 1A example. A skin depth of 9mm means a solid core wire of at least 18mm diameter for full skin effect mitigation at 50Hz. That wire would be comically oversized and a ludicrous choice for carrying 1A. \$\endgroup\$– vofaDec 15, 2016 at 14:56
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1\$\begingroup\$ @vofa I've never been one to limit my answers to the constraints of the question if I feel there is a wider relevance that is of interest. \$\endgroup\$– Andy akaDec 15, 2016 at 15:25
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Wires are sized to make sure they don't get too hot. AC currents are typically specified in units of RMS Amps. AC RMS and DC are equivalent for calculating wire heating (\$P_{WIRE} = I_{WIRE}^2 * R_{WIRE}\$)--for low frequency AC current. As Janka said, a wire's current carrying capacity lowers at high frequencies due to the skin effect. If you're transmitting 50/60Hz AC mains current, the skin effect is largely irrelevant, and the wire size will be the same for 1A DC or 1A RMS. Wire type affects current capacity as well, but copper wire is by far the most common type.
