# AC Resistance & Reactance of SINGLE conductor? (NEC)



## countrytoad (Sep 22, 2013)

NEC TABLE 9: Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75 C - Three Single Conductors in Conduit

Stupid Question: What about AC SINGLE-PHASE (Single) Conductors?

Is there a table?

Thanks!


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## Ship Wreck PE (Sep 22, 2013)

I think that you would use NEC table 9 for 1, 2, or three conductors. All of the sample problems that I have seen use this table.


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## PE blues (Sep 22, 2013)

You take 3phase R, X, multiply by 2.


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## countrytoad (Sep 22, 2013)

So Table 9 gives R and X for 3-phase.

And Table 9 gives R and X for 1-phase, but you multiply by 2 because of the return path (Correct?).

Seems odd that 3 phases would have the same impedance.

Is this because we're only using the impedance in per-phase calculations?

(same as how current only refers to a single-phase; i.e., we don't add up total current of 3 phases)


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## iahim (Sep 22, 2013)

countrytoad said:


> So Table 9 gives R and X for 3-phase.
> 
> And Table 9 gives R and X for 1-phase, but you multiply by 2 because of the return path (Correct?).
> 
> ...


Correct. The table is for 3 phase circuits, but the values are given per conductor. So you can use them on single phase circuits. You just need to account for the return path, like you said.


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## iwire (Sep 30, 2013)

Multiply by 2 for return path if is single phase is what my understanding so far


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