230V Delta?

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kwired said:
Seems to me if two phase three wire were connected like shown there would be excessive current flow through the upper and left two coils, unless there is no physical connection at the center point, which it might be trying to show that I guess.
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Yes, there would be no connection at the center point.
However, the common conductor in two phase three wire ( line C in post #55) will carry 1.414 times the current on lines A and B (assuming equal loads across A-C and B-C). So the common conductor would need to be sized proportionately larger than the other two.
 
synchro said:
Yes, there would be no connection at the center point.
However, the common conductor in two phase three wire ( line C in post #55) will carry 1.414 times the current on lines A and B (assuming equal loads across A-C and B-C). So the common conductor would need to be sized proportionately larger than the other two.
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1.414, isn't that Pi?
 
Dsg319 said:
I can’t seem to find a good image of how ground fault lighting detectors are wired, anybody got any good pictures or references?
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Simple. Each light goes from a phase to ground. If a phase faults to ground, ground gets energized and the light that isn't lit is the one that's grounded.


-Hal
 
Little Bill said:
1.414, isn't that Pi?
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don_resqcapt19 said:
No. That is the square root of 2. Pi is 3.1416
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Both √2 and Pi are "irrational" numbers which means that they can't be expressed as a ratio of two integers, and their decimal representation goes on forever. However, the approximate values given above are more than sufficient in most cases.
Pi is also a "transcendental" number which means that it is not a solution (aka "root") of a polynomial equation with rational coefficients.

 
PetrosA said:
I've been trying to wrap my head around a system I recently worked on in an old factory in York, PA. It's a 230V high-leg Delta system from what the on-site electrician explained, but the readings are unlike anything I've ever seen and I'm trying to figure out what's going on. There are three hots and a ground on site, no neutral. Phases A and C read 137V to ground, while phase B reads 157V to ground. Between any phases I get 248V. The open knife switches make it really interesting ;)View attachment 2555618
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I have serviced many delta services in the last 50+ years. There are 4 basic configurations of delta services. There is the ungrounded delta (very rare). The corner grounded delta where B phase is tied to ground and the B phase fuse is a special fuse which is actually a solid copper bar or just a copper bar. A closed delta, And an open delta. or a closed delta where the center between B and C is neutral (and is derived by grounding that center point). In a 240 volt system, the voltage should be 240 volts between any 2 points of the delta, is 120 volts from neutral/ground and B or C and 277 volts from A to neutral/ground. The neutral point should have been grounded at the transformer and the 4th wire carried with the service conductors. Given the obvious age of this instillation, I suspect that the ground was separately derived and has degraded over time and needs to be re-established.
 
sparkselec said:
In a 240 volt system, the voltage should be 240 volts between any 2 points of the delta, is 120 volts from neutral/ground and B or C and 277 volts from A to neutral/ground.
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208v, but who's counting. ;) And, we usually refer to the high-leg as B phase here.

The neutral point should have been grounded at the transformer and the 4th wire carried with the service conductors. Given the obvious age of this instillation, I suspect that the ground was separately derived and has degraded over time and needs to be re-established.
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I agree that those voltages suggest a floating system, whether intentional or not.
 
LarryFine said:
208v, but who's counting. ;) And, we usually refer to the high-leg as B phase here.


I agree that those voltages suggest a floating system, whether intentional or not.
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add the voltages he mentioned up, then divide by square root of three and you get ~248. Neutral point is not solid and has drifted from the true neutral point.
Add: maybe better wording would be grounded point has drifted away from the actual neutral point.
 
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LarryFine said:
208v, but who's counting. ;) And, we usually refer to the high-leg as B phase here.


I agree that those voltages suggest a floating system, whether intentional or not.
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C phase on utility, moves to B on our stuff per code. Something about correct metering on utility side is the reason they have it on C.
 
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