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Registered Member #157
Joined: Sun Feb 12 2006, 08:00PM
Location:
Posts: 76
Before I cut up my precious copper tubing. Can i make a junker coil primary out of the aluminum wire used in HV lines? im only asking because i always see copper wire/tubing used.
Registered Member #55
Joined: Thu Feb 09 2006, 04:56AM
Location:
Posts: 149
This is a question I asked on the old forum. Sulaiman's explanation is exactly what we concluded from it. Skin depth pretty much cancels out the lower conductance so the difference is neglegiable (just slightly negative compared to copper) I have built a few SGTCs using aluminum primaries (for ease of bending and shaping) and have had good results.
Registered Member #358
Joined: Sat Apr 01 2006, 06:13AM
Location: UCSB
Posts: 28
It does not completely cancel it out; it's actually a square root.
When you quadruple the resistance, the skin depth doubles (just check the skin depth calculators :P), giving you 2x the area and 4x the resistivity, so the overall resistance is double.
Aluminum's resistance is 2.65 micro ohm centimeters, and copper is 1.673. At DC, aluminums resistance is 58% higher by volume. When skin effect dominates, its SQRT(2.65/1.673), or only 26% higher.
Primary resistance typically isn't the limiting factor anyway (especially when you got a spark gap in there), so as the others have said, aluminum is fine.
When I had problems with primary resistance, I actually switched to aluminum.
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TC Primary, copper or aluminium?
