230V Delta?

[synchro]

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.

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.

 

[Little Bill]

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.

1.414, isn't that Pi?

 

[don_resqcapt19]

1.414, isn't that Pi?

No. That is the square root of 2. Pi is 3.1416

 

[Little Bill]

No. That is the square root of 2. Pi is 3.1416

Well I had the "1" and "4" right!
It's been so long since I used it I forgot. But when I saw the 1 & 4, my mind went to Pi.
I always think when I hear PiR², "pie are round, cornbread are square"!

 

[GeorgeB]

1.414, isn't that Pi?

Are you thinking about Pi day on Sunday? <grin>

 

[hbiss]

I can’t seem to find a good image of how ground fault lighting detectors are wired, anybody got any good pictures or references?

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

 

[synchro]

1.414, isn't that Pi?

No. That is the square root of 2. Pi is 3.1416

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.

 

[ptonsparky]

My oldest is a Pi Day baby and she has celebrated with a round one in the past. That has become popular enough that she had to start ordering in advance at her local bakery.

 

[kwired]

1.414, isn't that Pi?

it is the square root of 2, rounded at the thousandths.

 

[LarryFine]

 

[Little Bill]

it is the square root of 2, rounded at the thousandths.

I believe post #63 and #67 made that clear already.

 

[kwired]

I believe post #63 and #67 made that clear already.

Square root of pi is 1.7724538509055160272981674833411...

 

[LarryFine]

Square root of pi is 1.7724538509055160272981674833411...

But, pie are round.

 

[winnie]

But, pie are round.

Round root of pi is 2

 

[zbang]

But, pie are round.

Never seen Sicilian-style pizza? (They're usually rectangular, and rather good.)

 

[LarryFine]

 

[sparkselec]

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

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.

 

[LarryFine]

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.

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.

I agree that those voltages suggest a floating system, whether intentional or not.

 

[kwired]

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.

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.

 

[hillbilly1]

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.

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.