Voltage drop formulas

[brother]

why are there so many different formulas for voltage drop? Ive been brushing up on some of my calcs and when I first started out I do not recall so many forumlas. Which ones do you use?? I think that the uglys book is the most simple and easy to remember, they have a standard 12.9 for copper and 21.9 for aluminum. these other formulas you have look up and they tend to vary.


vd= (2 x R x L x I)/1000 single phase

vd= [(2 x R x L x I)/1000] x .866 3 phase



uglys book formula
vd= (2 x K x I x D)/cm single phase
vd= (sqroot of 3, x K x I x D)/cm 3 phase

k=12.9 resistance for copper , k=21.9 for aluminum

 

[Dennis Alwon]

I usually use the online calculator for VD. Click Here

There are different formulas for different applications. Some formulas take into consideration Temperature and Power Factor. So I guess it depends on your application and how necessary the other factors are.

 

[brian john]

I think it depends on do you want to be in the ballpark or worried about being a decimal point off. Accurancy in any calculation is always preferred, IMO. Ask NASA as they missed the angle of landing on Plantet Mars. Our your accountant as he tells you, you have an appointment at the IRS due to a small error, as he packs his bags on a long trip to Mexico.

 

[nakulak]

or ask Morton Thiokol about the coefficient of expansion of rubber o rings

 

[Smart $]

these other formulas you have look up and they tend to vary.

All are derived from one, E=IZ, substitutimg factors mostly which determine Z—with varied degrees of accuracy—under the circumstances at hand.