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#87349 02/18/04 10:04 AM
Joined: Mar 2003
Posts: 849
Y
Member
Question
formula for voltage drop
example 4160 mtr. distance 475 ft. full load amp (500hp) 70 . Copper wire.
22.3x distance x amps divided circular mil of cooper wire.
22.3x475x70=741477
#4=41740area cir. mills
741477divided by 41740=17.76 voltage drop
4160x3%=124.8
hows it look guys????

2017 / 2014 NEC & Related Books and Study Guides
#87350 02/18/04 05:16 PM
Joined: Dec 2003
Posts: 751
E
Member
I prefer the formula VD = 1.73xLxIxR/1,000. The R is resistance per 1,000 feet from Table 9 of Chapter 9. L is the distance from the source to the load in feet. Note that the impedance varies with the pipe type. But is not significant except with higher ampacities. For your parameters using PVC conduit I get: VD = 1.73x475x70x0.31/1,000 = 17.83 volts. Pretty close.
Use 2 instead of 1.73 for single phase.

Earl


Earl

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