Posted: Tue May 06, 2008 11:19 pm Post subject: Re: The Abundance of Copper
I'm not an electrical engineer but I don't think that we're looking at it correctly in terms of mere resistance, but should look in terms of how much current a wire can carry. Resistance losses for copper versus aluminum are tiny, and even superconductors with zero resistance have current limits.
I do know that many long range high voltage wires are now aluminium.
Posted: Tue May 06, 2008 11:48 pm Post subject: Re: The Abundance of Copper
The typical thing that limits the amount of current a given wire can carry is voltage drop. Voltage drop is determined by the diameter of the wire and its characteristic resistance. At higher frequencies, skin effect also plays a role, but not at 60hz.
Heat dissipation can also play a role in some circumstances if a bunch of wires are running through the same conduit. _________________ "So while you sit and whistle Dixie with your money and your power.
I can hear the flowers a-growin in the rubble of the towers.
I hear leaders quit their lying
I hear babies quit their crying.
I hear soldiers quit their dying, one and all." - OCMS
Posted: Wed May 07, 2008 12:33 am Post subject: Re: The Abundance of Copper
Quote:
I do know that many long range high voltage wires are now aluminium.
Almost all.
Quote:
In the early days of electrical transmission, copper was used extensively as a conductor, but now virtually all conductors are aluminum. Each conductor is made of many strands (1-5 mm in diameter) combined to give an overall diameter of 4-50 mm. In most conductors, steel or a high-strength aluminum alloy is used for the core strands to give the conductor added strength. In a transmission line, up to 4 conductors may be used in parallel to form a conductor bundle.
line loss decreases with the inverse of the voltage increase squared.
ie. As voltage doubles line loss drops by 75%. The higher resistance of Al becomes less of a factor and other metal characteristics like weight,tensil strength, and cost take over.
Posted: Tue May 13, 2008 10:03 pm Post subject: Re: The Abundance of Copper
Aluminum can be used in many places, even most of the distribution lines in aircraft are aluminum. However, in cases where dissipation is key to sizing equipment, copper rules the day. changing to aluminum may save you a significant portion of the conductor mass, but you are hit with the need for increased size of everything, which makes the damned thing heavier than with copper windings. Current ratings of wire are dependent on temperature rise, at a system level you look at voltage drop, but if your insulation goes over rated temp, your systems dies a premature death.
Hope this helps... _________________ "Sometimes one pays most for the things one gets for nothing."
Albert Einstein
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