# Ampacity question/problem

OK, let's make sure I've got it right:
lamp operates at around 1500W 260V, with the current around 4.2A (steady state)
Transient of 15A at startup. Thickness 0.000254 meters stainless steel 304, a length of .012 meters area of 836e-006 meters squeared. ( is this the cross sectional area, or the surface area of one side, or what?)
resistivity of 7.2e-007 ohms per meter (is this right?)
So it's not a wire, its a piece of thin (0.254mm) stainless sheet metal 12cm long and how wide?
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I think I figured it out from equations I found here: http://www.polarinstruments.com/support/cits/AP144.html
If I'm guessing at your numbers right, then the below should be true:
cross area 0.000836 m^2
thickness 0.000254 m length 0.012 m
resistivity 7.20E-07 R = r*L/A 1.03E-05 Ohms of track
where
R is the end-to-end track resistance in Ohms r is the resistivity of the track material in Ohm Metres L is the track length in metres A is the track cross sectional area in square metres
I^2 R = 2.33E-03
2.33 milliwatts will be dissipated at 15A
I think you're safe if the above is true, by an order of magnitude
Also I found this: http://hypertextbook.com/facts/2006/UmranUgur.shtml
6.897E-07 ohm-m for 304 steel, even better!
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Cr500,
Thanks so much for the help. The explination of the subject and the references provided were very helpful. This will be very helpful if the piece is redesigned with different dimensions or for any reason we use a different type of metal. I will continue to check new threads in hope of providing help to others as you did for me.
Thanks,
-Erik
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The .836e-006m^2 is the surface area of the metal. The resistivity value is 7.2e-007 ohm-m at 20 degrees celcius. The length is actually 12 mm (I wrote the wrong unit before) and width is 5.3mm. It is a very thin, small piece of stainless sheet metal, which is why I think i'm having so much trouble. It is much easier to figure out the amount of current a wire can carry, mainly due to the fact there is tons of information out there about wire ampacity. Once again I appreciate all your help on this topic.
Thanks,
-Erik
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OK, updated with the new numbers:
width 0.0053 m thickness 0.000254 m length 0.012 m cross area=width*thickness 1.3462E-06 m^2 resistivity 7.20E-07 R = r*L/A 6.42E-03 Ohms of track
where
R is the end-to-end track resistance in Ohms r is the resistivity of the track material in Ohm Metres L is the track length in metres A is the track cross sectional area in square metres
I^2 R = 1.44E+00
1.44 watts will be dissipated at 15A
1.13E-01
0.113 Watts will be dissipated at 4.2A
A little higher, but still not bad.
wrote:

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On 8 Mar 2007 12:36:52 -0800, snipped-for-privacy@yahoo.com Gave us:

The stainless would have to be an eighth inch bar stock to get hot at 4.2 amps.
Still, I would insulate it along its length with a shroud of non-conductive sheathing.
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Methinks you're just being retarded now.

Ever use the term "Voltage" or "Wattage"? Technically, neither of those are real terms either. You need to face the fact that you terms list is not the be all end all fact sheet, dumbass.
Hey... I got one... describe for me what a "dry solder joint" is, if you have any balls, boy
I'll bet you can't, yet it has been in use in the industry for decades.
This should be funny...
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Fuck off, jack-off. Not your buddy.
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On Mar 12, 6:41 pm, MassiveProng

make up ur mind....i can't do both at the same time.......................buddy
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Gave us:

Certainly not due to any retarded asswipe assessments a dipshit like you makes.
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On Thu, 08 Mar 2007 18:07:25 GMT, "cr500r"
Top posting, TOFU Usenet retard!
http://en.wikipedia.org/wiki/Top-posting
Learn and obey, dipshit.
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us:

Sure, bub. Except that the term has been used for over a century, and is taught in electronics around the world.
You were likely sleeping when it was referred to, and DEFINED as "current carrying capacity".
You see, dipshit, some folks just like to make single word terms that define a specific aspect of operation.
Even E=MC^2 has a far longer definition.
So get with the program, dingledorf.
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The Neher McGrath Paper published by IEEE in 1957 has information on materails other than copper and aluminum used as conductors.
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On Thu, 8 Mar 2007 12:31:23 -0900, "Gerald C Newton"

Cool call/reference, G.