# Voltage at service

1. Apr 21, 2014

### rozilla

Hi guys,

If there was a voltage drop of 20V on a 3ph line of 347/600, is the voltage at the service 327V or 580V, or both? Thanks you for reading.

RozilΩ

2. Apr 21, 2014

### phinds

Is this a homework problem? What do YOU think the answer is, and why?

3. Apr 21, 2014

### Baluncore

Who observed a voltage drop of 20V ?
How did they measure it ?

4. Apr 21, 2014

### rozilla

Hi guys,

This isn't school related. That isn't the actual voltage - I'm trying to understand the concept of which would be the operating. With the concept, I can apply it accordingly. I assume it is 580 as it is three phase.

5. Apr 21, 2014

### Baluncore

The specified voltage is 347V / 600V.
The three phases are separated by 120°. 1 / Tan(30°) = √3 = 1.73205
If you multiply 347V by √3 you get 600V.
You cannot change one without changing the other.

When combined with a common neutral you have three single phase supplies of 347V, relative to the neutral. The voltage between the phases is 600V.

A 20V single phase drop is a 34.6V three phase drop.
A 20V three phase drop is an 11.5V single phase drop.