Voltage Drop 3 Wire

[bassbum71]

I know the voltage drop for a two wire system, but what is the voltage drop formula for the 120/240 V 3 wire system. I know it differs a little.

 

[peter d]

There are 2 voltage drop formulas- single phase and 3 phase.

1 ph = 2KIL/Vd

3 ph =1.723KIL/Vd

For more, check out this link:

http://www.mikeholt.com/mojonewsarchive/EC-HTML/HTML/Voltage_Drop_Calculations~20030326.htm

 

[Smart $]

I know the voltage drop for a two wire system, but what is the voltage drop formula for the 120/240 V 3 wire system. I know it differs a little.

Actually voltage drop calculations are all performed with the same formula. However, most formulas use a length/circuit-type multiplier to shortcut calculating each conductor separately. For instance, in a two-wire circuit one commonly uses the one-way circuit length with a 2? length multiplier, instead of just entering the total circuit length from what is considered to be the source (most often it is technically not the source).

Additionally, for a 120V three-wire MWBC circuit or feeder, the neutral only carries the current imbalance. Caution should be taken if calculating voltage drop with only the imbalance on the neutral, for it does not take into consideration one line of the circuit may not be conducting while the other is. In this case, the voltage drop as seen at the load would be identical to a two-wire circuit. Only where it can reasonably be expected that both line conductors will be conducting, or not, concurrently can you use the reduced voltage drop on a three-wire MWBC or feeder.

 

[George Stolz]

Here's the FAQ on VD.

 

[bassbum71]

Thanx

Thanx

Actually voltage drop calculations are all performed with the same formula. However, most formulas use a length/circuit-type multiplier to shortcut calculating each conductor separately. For instance, in a two-wire circuit one commonly uses the one-way circuit length with a 2? length multiplier, instead of just entering the total circuit length from what is considered to be the source (most often it is technically not the source).

Additionally, for a 120V three-wire MWBC circuit or feeder, the neutral only carries the current imbalance. Caution should be taken if calculating voltage drop with only the imbalance on the neutral, for it does not take into consideration one line of the circuit may not be conducting while the other is. In this case, the voltage drop as seen at the load would be identical to a two-wire circuit. Only where it can reasonably be expected that both line conductors will be conducting, or not, concurrently can you use the reduced voltage drop on a three-wire MWBC or feeder.

Thanx for the info.