Voltage Drop

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Benton

Senior Member
Location
Louisiana
In the section of the code book under the Tables, Conductor Properties, which of the resistance percentages do I use when calculating voltage drop? I have been taking a quiz and my answers seem off.:-?

Single Phase VD= Amps*Length*ohms*2?

3Ph VD=Amps*2L*R ?

Thank for your help in advance
 

BJ Conner

Senior Member
Location
97006
In the section of the code book under the Tables, Conductor Properties, which of the resistance percentages do I use when calculating voltage drop? I have been taking a quiz and my answers seem off.:-?

Single Phase VD= Amps*Length*ohms*2?

3Ph VD=Amps*2L*R ?

Thank for your help in advance

Are you using table 8 or 9. IF it's Ac current you should be using reactance (table 9) not DC resistance (table 8).
 

klnorth

New member
Location
Singapore
Resistance Value used for 3-phase voltage drop

Resistance Value used for 3-phase voltage drop

From the voltage drop formula (Mike Holt WireGuide99), the "Equiv CCT AC Resistance" value used in the 3-Phase voltage drop calculation is (1.732) x the AC resistance value from NEC Chapter 9 Table 9.

The "Effective Impedance" (Z) is also listed in table 9 for Ohms to N (1000 ft).
Why would the effective impedance not be used for this calculation?
 
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