# line voltage

Discussion in 'General Electronics Chat' started by matt11111, Jun 17, 2009.

1. ### matt11111 Thread Starter Member

May 12, 2009
11
0
I have done measurments on some three phase machines. I have measured the line to ground voltage while monitoring the line to ground current to determine things such as PF and starting current.

Would I be right to assume that if I wanted the line to line voltage all I would do is multiply the line to ground voltage for a single phase by 2?

Also, my panel says it is a 600v supply but when I measure from line to ground it gives a value of 350 v RMS. Multiplying by 2 to get the line to line voltage gives 700 v. Most of the machines are rated for 575v or 550v.
Am I taking the measurement wrong? How can a panel rated for 600v handle 700v, and how can a machine that is rated for 575v (on the nameplate) be running on the higher 700v supply?

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
This is not true.

The line-line voltage is the line-ground voltage multiplied by the sqrt(3).

3. ### alim Senior Member

Dec 27, 2005
113
1
Hi the line to line voltage called the line voltage is 1.732 times the phase voltage , conversely the phase voltage is 0.577 times the line voltage thus 600* 0.577equals 346.2 approx. 350v.

fraz.kharal likes this.