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Mr Fizzion
 
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Default Resistance per Meter for copper cable (R1+R2)

On Tue, 25 Oct 2005 17:16:15 GMT, "dennis@home"
wrote:


"Slurp" wrote in message
...

"dennis@home" wrote in message
o.uk...

wrote in message
oups.com...
Hi

Can someone help out with this Electrical problem.
(I'm doing a CG2330 course)

Table 9A of the IEE On site guide only goes upto 50mm csa cable for the
values (R1+R2)

Eg
50mm Phase+CPC = 0.774 mOhms/m

What would you do if the conductor was say 70mm ???

Is there a formula I could use ?


50/70 x 0.774 mOhms/m?


Nope, nothing like.
Its cross sectional area you need to use (pi * r^2)

So for 50mm = approx 1962 sq mm, 70 mm = approx 3846 sq mm.

i.e. it will be arount HALF the resistrance or about 385milliOhms/metre.


Cables are usually quoted in mm2.
It correct for 50mm2 and 70mm2 is it not.


The OP stated 50mm csa - csa = cross sectional area. For a direct
current, resistance is inversely proportional to the cross sectional
area of a material so doubling the area halves the resistance.

Mr F.