Single Phase Voltage Drop Calculation

[Alaktrical_Gingineer]

I want to compute for the Single Phase Voltage Drop of a THHN wire using the formula from IEEE Std 141-1993:

Vd = I * (R cos [theta] + X sin [theta]) * 2

My issue is I don't have the R and X data from the manufacturer so I would like to visit NEC's tables for recommendations. Table 8 shows DC Resistance and Table 9 shows AC Resistance and Reactance but only for 3-phase systems. Is there anything I can do? Getting the data from the manufacturer is out of discussion.

(I know VD is not always an NEC requirement but I still would like to calculate it.)

Thank you.

 

[winnie]

The information is buried in this document: https://www.eaton.com/content/dam/e...us-ele-tech-lib-voltage-drop-calculations.pdf

Buried in the sense that they don't provide separate single phase and 3 phase X and R values, but rather provide a table that gives voltage drop per amp for different combinations of conductor, phase, and power factor. You might be able to back out the X and R values from this pre-done calculation.

I _think_ you can simply use the L-N values for X from table 9 as the 'one way' values for a single phase calculation, but I by no means certain of that.

-Jon

 

[MyCleveland]

I want to compute for the Single Phase Voltage Drop of a THHN wire using the formula from IEEE Std 141-1993:

Vd = I * (R cos [theta] + X sin [theta]) * 2

My issue is I don't have the R and X data from the manufacturer so I would like to visit NEC's tables for recommendations. Table 8 shows DC Resistance and Table 9 shows AC Resistance and Reactance but only for 3-phase systems. Is there anything I can do? Getting the data from the manufacturer is out of discussion.

(I know VD is not always an NEC requirement but I still would like to calculate it.)

Thank you.

Found a great paper on-line 3 or so years ago that is basically a con ed class document where all the various VD methods are broken down.
The paper ends in describing the IEEE, or EXACT method, you are describing. I added this method to my excel calculator,
I don't recall any discussion of different X values for 1P vs 3P and quickly looking through the paper I am not seeing anything.
If you discover any write ups you can share...please do.

 

[NewtonLaw]

My understanding is that the three phase values are given on a per phase basis, I.e., for a balanced system no return current. If you have single phase load, then you must add the neutral impedance. If the neutral is the same size as the phase wire, you are back to the equation you want to use.