Voltage Drop Equation

[eanton22]

From where is the following equation derived from?

Vdrop = 1.732 *K * Q* D * I/ CM

is this the NEC equation?

 

[raider1]

There is no NEC voltage drop equation, as adjusting for voltage drop is not an NEC requirement just a suggestion.

Chris

 

[eanton22]

I understand. But where is the above equation from?

 

[bob]

From where is the following equation derived from?Vdrop = 1.732 *K * Q* D * I/ CM

is this the NEC equation?

From where is the following equation derived from?
Vdrop = 1.732 *K * Q* D * I/ CM
is this the NEC equation?

This is basically ohms law VD = I x R

Q = adjusts DC resistance for AC. Usually not use for sizes smaller than 2/0
K = volume resistivity in ohms-cmil/ft 12.9 CU 21.2 AL 75C 10.5 17.3 25C
D = conductor distance ft
I = amps
CM = conductor area in cmils

Rearrange the formula VD = I amps x [K ohms-cmils/ft x D ft /CMils]
The units Cmils and Ft cancel and you are left with
VD = Iamps x [ K ohm x D ] /value of CM = I amps x R ohms
I left out the Q factor. D = 2 for single phase 1.73 for 3 phase.

Check this post http://forums.mikeholt.com/showthread.php?p=1111384

 

[eanton22]

Thank you..........Oh yeah War Eagle!