It is refered to as electromigration at least within the semiconductor
design industry. It is an issue we take into consideration when
designing the wiring of our circuits.
--
73 es God Bless de KK1L...ron (kk1l@arrl.net)
ASIC PE IBM Microelectronics
<><
QTH: Jericho, Vermont
My page: http://www.qsl.net/kk1l
stuart benner wrote:
The reduction in life of an incandescent lamp when operated on DC versus AC is
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
sensors.
Stu Benner
W3STU
Quoting Martin Ewing <martin@aa6e.net>:
OK, I've heard this said before. But inquiring minds want to know: why
should DC be worse than AC for lifetime in lighting applications?
I seem to recall it was an issue for vacuum tube filaments, presumably
because having a DC gradient on the filament led to unequal
concentration of emission on the filament. (On the other hand, AC
supplies could lead to hum.) But in a lighting situation?
I can think of a couple reasons why DC might be better: no AC-induced
vibration, unity peak to average power, etc.
73 - Martin, AA6E
Subject:
Re: [RFI] 120v halogen lights
From:
"Tom Rauch" <w8ji@contesting.com>
Date:
Sun, 4 Apr 2004 10:23:22 -0400
To:
<rfi@contesting.com>, "Pete Smith" <n4zr@contesting.com>
I assume that there is no reason why any real transformer that delivers
12.6vac couldn't be used -- perhaps even an AC wall wart.
That's right, as long as it is AC. If you run DC bulb life is shorter.
73 Tom
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