Interesting, if OT. The effect may be real, but I am trying see the
physics. The E-field seems too small to push W atoms around. They are
neutral. But maybe there's a slight ionization. Or momentum transfer
from the electrons? Which end gets the "notch"? Hmm...|
Whatever it is, lifetime should improve dramatically if you reduce the
temperature -- run at reduced voltage, AC or DC.
Anyway, on the original topic -- old-fashioned iron-core transformers,
variable transforms and/or rheostats (do we still use that word?) are
the way to go.
73, Martin AA6E
Re: [RFI] 120v halogen lights
stuart benner <firstname.lastname@example.org>
Mon, 5 Apr 2004 12:55:06 -0400
The reduction in life of an incandescent lamp when operated on DC versus AC
attributable to a phenomenon known as "DC notching." With DC applied, the
tungsten molecules migrate within the filament and the filament takes on a
"notched" appearance. The increased local resistance at the notch points along
with the reduced physical strength result in decreased life. If AC is applied to
the filament, this condition is avoided. A lamp operating on DC may have 20% to
50% of the same lamp operated on AC.
Much research was done on this at NASA-Goddard by their lamp expert Dr. Henning
Leidecker. One of the life-limiting factors on the earlier GOES spacecraft (and
others) was the life of the black bias (incandescent) lamp in the satellite
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