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Re: Aluminum magnet wire?

Hi Aric,

	I have seen magnet wire made every imaginable way.  However, I never
imagined it made from aluminum ;-)

Aluminum is one of those metals that always fatigues when bent.  So it may
be weaker or more likely to break when wound on the form.  

Aluminum cannot be "easily" soldered so you need to clamp it with a screw
or something like that.  The connection must be "gas tight" or use that
special grease for aluminum electrical connections.  Aluminum oxidizes VERY
quickly and easily.  Aluminum oxide is an excellent insulator and, when it
makes a resistive contact, can withstand giant temperatures and still
provide a high resistance connection perfect for starting fires...

The DC resistance of aluminum is 66% that of copper which probably will not
make a noticeable difference.   However, the AC resistance needs to be
checked...  At 200kHz the "skin depth"* of copper is 0.148mm while aluminum
is 0.182mm  That actually gives you back a bit of conductivity.  It may run
a little hotter than copper, but that should not be a big factor at all.

Bare aluminum is definitely not a good choice.  Aluminum will quickly
oxidize far into the skin depth layer making a nasty semi-conducting region
and raise the AC resistance drastically.  Thus, it is very poor for the
very high currents in primaries where even clean copper can get pretty warm
and where reducing losses is critical.  Only wide strap (large surface
area) would be minimally useful in the primary.  I assume your wire was
enameled while the aluminum was still fairly free of oxidation and is well
protected.  Nicks or scrapes into that enamel may cause a hot spots however.

So...  If you make good connections and don't break the wire, it should
work fine.  Of course, I have never "really" tried it so there may be
hidden problems.  I would think it would be a bit experimental.  However,
If you have a bunch of spare aluminum wire around, I would give it a go.
If you could make an identical secondary from copper, the comparisons would
be definitive.

*BTW - AC currents tend to travel in a thin layer just below the surface of
a conductor for electrostatic reasons.  "Skin depth" is a measure of how
deep that current layer is.  Since these depths are usually very small, a
thick conductor may have just as much AC resistance as a thin conductor
since the skin depth is independent of how think the conductive material
actually is unlike DC resistance.

Cheers,

	Terry



At 03:25 PM 09/15/1999 -0400, you wrote:
>     Is aluminum magnet wire an acceptable substitute for copper magnet 
>     wire in a secondary?
>     
>     Aric
>