Electronics > Projects, Designs, and Technical Stuff
Mains cable size
TimFox:
I was careful to start my post with "in American usage". Yes, we still use "conventional units" in engineering in the United States, even though the country is legally metric. "Imperial units" is a British term.
However, if a European or British engineer were working in my lab (before I retired), I would not expect him to use "mils" in the American sense, but would show him what sizes of wire are commercially available here.
I still oppose the use of "mil" or "mm" to mean "mm2".
It can take a long time to learn all the slang terms used in a foreign country.
By the way, on that multi-week business trip to UK, I ran up a 2240 GBP hotel bill (including meals), which I reported back to my company in the US as a "ton of money", which is approximately a "tonne of money". In the US, we call that a "long ton", while 2000 lb av is a "short ton" or just "ton". I still don't understand the British definition of a cwt = hundredweight as 8 stones, which is less than 100 lb.
tooki:
--- Quote from: ricko_uk on August 04, 2020, 03:05:30 pm ---Hi,
I just had someone supposedly expert insist that when someone says "1.5mm mains cable" it refers to the copper diameter because it says mm not mm^2.
That does not make any sense for two reasons: first and foremost it is the area that matters when carrying current and secondly you cannot measure the diameter of a multi stranded wire accurately because it varies depending on how much you twist the strands
But he is adamant he is right and his colleague supports his point too.
Can someone confirm that is not correct and despite the fact that in normal parlance it is say 1.5mm it is supposed to be 1.5mm^2 (i.e. square)?
Thank you
--- End quote ---
What might also confound the issue is that a 1.5mm2 solid wire has a diameter of 1.38mm. So if someone measured it roughly, they might have incorrectly assumed it was 1.5mm diameter. (4/pi, or about 1.27, is where the diameter and area of a circle are the same value.)
But it’s more likely that they’ve simply gone all this time without understanding it correctly, never realizing that there are two systems for measuring wire.
This could be considered a theoretical advantage of the AWG system: since the gauge is an abstract number not directly correlated to the cross section (at least, not in a trivial way), it doesn’t ever lead you down the path of attempting to perform math on the gauge. :P
vk6zgo:
--- Quote from: TimFox on August 04, 2020, 10:17:34 pm ---I was careful to start my post with "in American usage". Yes, we still use "conventional units" in engineering in the United States, even though the country is legally metric. "Imperial units" is a British term.
However, if a European or British engineer were working in my lab (before I retired), I would not expect him to use "mils" in the American sense, but would show him what sizes of wire are commercially available here.
I still oppose the use of "mil" or "mm" to mean "mm2".
It can take a long time to learn all the slang terms used in a foreign country.
By the way, on that multi-week business trip to UK, I ran up a 2240 GBP hotel bill (including meals), which I reported back to my company in the US as a "ton of money", which is approximately a "tonne of money". In the US, we call that a "long ton", while 2000 lb av is a "short ton" or just "ton". I still don't understand the British definition of a cwt = hundredweight as 8 stones, which is less than 100 lb.
--- End quote ---
Sorry, no, an Imperial hundredweight is 112 lbs, a stone is 14 lbs, (8x14 =112).
JohanH:
Over here (EU, Finland) electricians I know always talk about "square" (as in mm2) about cables. I have never observed that this would have been misinterpreted. Cables and labels are always clearly marked. Then again I haven't worked as a real electrician (even though I've done some work in the field).
TimFox:
Oops about the "cwt"--it can be confusing when the answer is not "100".
With respect to AWG: the gauge number is logarithmic, and -3 gauges doubles the area to a good approximation.
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