Another Voltage Drop Question

[U2cy2]

Installing a 50A circuit 1500' from 480V distribution panel, will accept a 5% drop. I understand the need to step up the size of the wire to reduce the voltage drop but am having a little bit of trouble wrapping my head around why, in my case, I am running single phase 277V, my wire needs to be (copper) 250 kcmil vs 480V which will require 2/0 ... I'm still dealing with 277V per phase, does the affect of each phase really help reduce the voltage drop that much?

 

[ptonsparky]

The neutral on a 3 phase 4 wire system will carry only the imbalance of the line to neutral loads. So...you are using the 480 to its full advantage.

 

[ptonsparky]

Why 277v only load?

 

[LarryFine]

If you're running only two conductors, and there will be a transformer at the load end, it makes all the sense in the world to supply 480v line-to-line instead of 277v line-to-neutral.

 

[Ingenieur]

allowable 5% v drop for 480 is 24 vac
allowable 5% v drop for 277 is 14 vac
10/24 x 1.732/2 ~ 36%, hence wire must be much larger

3 ph v drop = 24 = 1.732 x L x R x i
1 ph v drop = 14 = 2 x L x R x I
assuming L and I are the same, R for the 1 ph must be smaller, ie, larger wire