Maximum Field Current for Delco 10SI Alternator? - Page 3

 

So a 120V 1000 hour bulb run at 240V would last 1000/(2^13) = 0.12 hours?


For how long? :-)

Nick

  On 30 Mar 2008 16:32:31 -0500, nicksanspam@ece.villanova.edu wrote:


Maybe, if the voltage is brought up slowly or unless it instaflashes.  OTOH,
since a
regular household runs at a fairly high temperature already for good color
rendering
and since it has a short design light, maybe not.  Run the lamp at 130 or 140
volts
and see how it conforms to Westinghouse's heuristic.

If you're actually interested in how incandescent lamps behave at overvoltage (I
suspect you're not and that you're just being your usual chickensh*t self but
just in
case anyone else is), go to http://www.candlepowerforums.com  and look for a
member
called Luxluthor.  He's done a very extensive several year study of mostly
portable
lighting-related lamps operated on over-voltage.  He includes performance curves
and
instaflash voltages.  His work includes many small low voltage high wattage
quartz-halogen lamps, typically AV lamps.  

Many lamps will go 3X nominal voltage before instaflashing.  Many of those will
operate for satisfactory time periods at the instaflash voltage if brought up
slowly,
as with a PWM controller.


Probably 20 to 30 hours on mine.  I've had 2 or 3 fail but all those failures
were
infant mortalities.  Once the lamp gets past the first few minutes of operation,
it
is good for many hours.  I use those cheap chicom "5 for $5" harbor freight
special
lamps.  they've turned out to last as long as brand name ones.

I bring the lamps up on about 145 volts (variac-controlled) for modeling and
framing.
I have a push button on a cord that I press just before the exposure.  The button
operates a contactor that switches to the full 240 volts.  They stay at that
power
only long enough to meter the light, set the exposure and take the picture.

If you're interested in the details - again, I'm sure you're not - then you can
look
around the net for an article I wrote several years ago for a glass art
newsletter.
It was a paper publication then but I'm sure it's online by now.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
It isn't Global Warming.... It's Jerry Falwell arriving in hell.

 

slowly,

 If I remember  properly from years back, Tungsten Halogen (or metal
halide) bulbs behave differently than standard incandescents due to
the "halide cycle". Tun at too low a voltage the tungsten boils off
and does not form a proper metal halide and does not redeposit on the
filament, causing severely shortened lamp life at moderate
undervoltage. Moderate overvoltage has much less effect , from what I
remember. Big problem with overvoltage on halides is from reduced
filament durability - so vibration and shock kill halide bulbs faster
when moderately overvoltage. This is why low voltage halogens stand up
better - as they have a heavier (higher current meand thicker
fillament) tungsten fillament than high votage bulbs, so they are
physically more robust.

Again, it's been 35+ years since I worked with the AV stuff on a daily
basis, and the halide bulbs were pretty new tech back then - and I've
forgotten a lot

--
Posted via a free Usenet account from http://www.teranews.com

 

Interesting. Don Klipstein says:


So if a 120 V bulb lasts 750 hours at 120V, Don might expect it to last
(120/240)^12x750 = 0.18 hours (11 minutes) at 240V.

Nick

 On 30 Mar 2008 22:54:16 -0500, nicksanspam@ece.villanova.edu wrote:


Only to folks like you who know just enough about a subject to argue.  The
original
paper, a copy of which I have, addresses only conventional tungsten lamps.  I'm
not
sure if the halogen cycle had been discovered at the time of publication.

I'm curious whether you'd find it equally interesting to note that a 4 hour
photoflood lamp and a quartz heat lamp designed to operate at maybe 2000 deg K
behave
quite differently in response to over-voltage?  Kinda Captain Obvious to me.  It
would probably surprise you to learn that a staple of the studio in the bad old
days
was the Sola transformer that made sure the photofloods were getting their exact
rated voltage while no one seems to care much about heat lamps.


I probably need to send Don a copy of the paper.  Don's a collator of
information so
he publishes only what he's found elsewhere.  He doesn't do original research.
12
and 13 seem to be bandied about the net about equally but the original paper
says 13.

Here's a page referencing GE's heuristic.  You might notice that GE's exponent is
13.1 for gas-filled and 13.5 for vacuum.  

http://www.zap-tek.com/webpage/Elect/lsn_4/014_lamp_res.html

Can I please, mas'a Nick, champion of all nitpickers, be permitted to round 13.1
to
13 for the purposes of idle conversation?

OTOH, the nomograph (by any chance know how to use one of those, Nick?) here
seems to
be using exp 12.

http://www.squidoo.com/tungstenlamps

A master nitpicker might also notice that Squidoo claims that the same exponent
applies to all lamp types while the GE heuristic shows different exponents and
the
Westinghouse paper addresses only "incandescent" lamps, presumably
nitrogen-filled,
given the vintage.  

I'm sure you'd agree with me, nick, that none of this has any relevance at all
to the
question of whether an alternator field coil in any way behaves like an
incandescent
lamp.  



BSIBSO (Nick's version of GIGO, BS in/BS out). Or what happens when one knows
just
enough to do the math but not enough to apply the data.  Hint: You might note in
the
URL above that the GE heuristic is useful for no more than +-10% from the
nominal.  

BTW, any particular reason you chose 750 hours this time and 1000 hours on the
last
round?  Just pullin' numbers out of yer nether region again?

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com  <-- best little blog on the net!
Tellico Plains, Occupied TN
Save the whales, collect the whole set!