3 Phase Voltage Drop - Wye vs. Delta Feeder to Panel 1

[djr3203]

I was under the assumption that for calculating voltage drop on a 3 phase, 4 wire (Wye) feeder from a distribution panel to a panel you only take into account the 1-way distance from the distribution panel to the panel because the assumption is the loads are balanced resulting in no current on the neutral to produce a voltage drop. I was under the assumption that this is the same for a 3 phase 3 wire (Delta) feeder from a distribution panel to a panel.

I was in a discussion today where someone said you do take into account the return distance on a wye feeder but not on a delta feeder. I disagreed, but taking a closer look at my voltage drop calculator, I realized the voltage drop was slightly different for a 3 phase 3 wire than a 3 phase 4 wire feeder. The interesting thing is that my calculator comes out with a slightly higher voltage drop for the 3 phase 3 wire than the 3 phase 4 wire. So I still think I may be correct? Anyone know why the voltage drop for a 3 wire feeder would be slightly more than a 4 wire?

Thanks for the input.

DJR

 

[davidbeach]

Does your calculator assume the same power factor in both cases? Wye sourced circuit with no current in the neutral is indistinguishable from a delta sourced circuit.