Design and Zs

[trebor]

Hi can anyone advise me please, I am studying in preparation for 2391-20

If i want o calculate max R1 + R2 for circuit do i correct for both conductor and ambient temps or conductor only, the problem is ive seen both methods in different books only one can be right ?

for example 30 m of 2.5 t&e iwhich is 19.51 mohms per mtrs could be;

19.51 x 30 x (1.2 for condutor temp)/= 702 mohms/1000 = 0.70 ohms

or 19.51 x 30 x 1.20 x (1.04 ambient to 30deg c) = 730mohms/1000 = 0.73


thanks my learned friends, i hope

 

[Mark.W]

This is probably one for Lenny!

 

[Guest123]

Hi.

I only allow for ambient temp when I do R1+R2 calcs, not conductor temp. The conductor operating temp factors are used when the maximum operating temperature under load is going to be close to the maximum rating of the cable insulation, i.e 70 degrees C for thermoplastic T+E.

I was just typing my reply