Wacky measurement vid?

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ritelec said:
I'm confused.
This is not me.
Curious

https://docs.google.com/file/d/0B8y9ZDgOR7fJc0t2d3dZcXIxZE0/edit?pli=1
Click to expand...
I do not see any big problem.
The bus conductor on the left is near the same potential as the conductor in the middle. The difference between L and Mid plus the difference between Mid and R equals the difference between L and R (or close enough for meter accuracy.
The potential each of them to ground is about 120, which is what I would expect as a phantom voltage if the other three conductors were part of an ungrounded system. Or the magnitudes of the three voltages could be very close to equal and still have the vectors sum to each of the three line-to-line measurements recorded.

It does look like the system is not really a three phase source though, otherwise the ~120 + ~120 = ~240 would not hold true. So why the three wires?
Could be a high leg with the open delta pot for the high leg defective or open.
 
Does it look like single phase and someone doubled up phase b to a?

I see the green bond screw so it looks like service.


open delta with a high legg?

I guess that looks the same as a closed delta with high legg but open ???

the 120v doesn't work. ?
also in the pic enclosed, what should voltage be from the top of 240v to bottom right of 240v ? 480v??
 
ritelec said:
Does it look like single phase and someone doubled up phase b to a?

I see the green bond screw so it looks like service.


open delta with a high legg?

I guess that looks the same as a closed delta with high legg but open ???

the 120v doesn't work. ?
also in the pic enclosed, what should voltage be from the top of 240v to bottom right of 240v ? 480v??
Click to expand...
Nice drawing.
The voltage from top to right will be 240, within the regulation accuracy of the two pots. Instead of that pot you put in a jumper, or a 2 volt output transformer, you should be pretty close to the measurements in the video.
The high leg would normally be on B in the panel, but that was not always true and may not be true in the video case even if modern. Clearly something is screwed up.
Also possible that somebody put a single phase 120/240 into a three phase panel, but in that case the 2 volts is a little hard to explain unless the 120 to ground there is a phantom voltage rather than hard wired.
 
The center to the left leg / phase was reading 2.65 volts not 265.

Roger
 
B phase is dead coming from the POCO. He's only seeing a reading between B and C and B and ground because the breakers are closed. If he shut the main and checked line side, he would get very different readings.
 
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