3 phase wye/delta bank with wild leg?

[rcdallas]

Subtractive or additive it doesn't matter the hook up is exactly the same...what gets different is when you use an additive mixed in with some subtractive.

That or feed in an H2 for some odd reason while the others are fed in H1...BUT I won't go there.

Here it's not uncommon to see one fed in H1 and the other H2 on a open delta.

[Trbl639]

That's right RC.......see that a lot in S Arkansas in the oil patch!!

Good post sully, but ya forgot...some places are using wye pots......2 bushing secondary...some of the youngsters might get lost when they see em the first time! Around here, it's not unsual to see 3 pot wye banks, with the hot (secondary) on the right, and the bank next pole down is cut to the left..if I remember right our spec called to cut em center to right....but it just depended who built it..hell they might be cut center/right...center/left....or even outside to outside!!


When I was at Little Rock AFB, working nights, many years ago........got a voltage complaint call, from the A/C guys... Y/Y bank,voltage was good all the way across, but none of the 3 phase air units would run! Scratched my head some on that one!! Turns out day crew had replaced the bank pole (deadend)...removed everything, put the new wood back in the same hole and then put everything back in the air.....they weren't paying attention when they wrecked it out, and I had to figure it out! all pots were 2 bushing primary, all were marked Additive, but one had been re-wound years earlier and put in that bank.........but the name plate had NOT been replaced, and that pot was wound Subtractive!!! I'll be honest on that one, I scratched the crap outta my head, I couldn't figure out squat and was ready to give up, but decided to call my resident expert, My Old man, and he suggested checking polarity and Bingo, there it was.........before the day crew came in the next day, in 4 inch high RED letters, SUBTRACTIVE was painted on that can!!!

[rcdallas]

When I was at Little Rock AFB, working nights, many years ago........got a voltage complaint call, from the A/C guys... Y/Y bank,voltage was good all the way across, but none of the 3 phase air units would run! Scratched my head some on that one!! Turns out day crew had replaced the bank pole (deadend)...removed everything, put the new wood back in the same hole

I remember asking something similar to this once in a class about slapping the ground strap in a different position from the other two cans on a wye/wye and was just told that it wouldn't work.

I have seen where on a delta bank if you hooked up the tie bus wrong, say x3-x3 - x1-1 you'll just get some crazy voltages, like 340 on a 120/240...what I'm getting at is when you checked voltage, everything was still made up and you where still getting 208 phase to phase? I can see that.

I can't remember exactly off the top of my head how to check polarity, it's something where you put 120 on the primary side and you check voltage on the secondary if its + so many volts or - so many volts it's one or the other.

edit:

I wonder what the rotation meter was doing to ya when you came across this...probably wasn't marked before ya got there.

[lewy]

I remember asking something similar to this once in a class about slapping the ground strap in a different position from the other two cans on a wye/wye and was just told that it wouldn't work.

I have seen where on a delta bank if you hooked up the tie bus wrong, say x3-x3 - x1-1 you'll just get some crazy voltages, like 340 on a 120/240...what I'm getting at is when you checked voltage, everything was still made up and you where still getting 208 phase to phase? I can see that.

I can't remember exactly off the top of my head how to check polarity, it's something where you put 120 on the primary side and you check voltage on the secondary if its + so many volts or - so many volts it's one or the other.

edit:

I wonder what the rotation meter was doing to ya when you came across this...probably wasn't marked before ya got there.

Yea you were pretty close when it came to checking polarity
The H1 bushing is connected to low voltage bushing directly opposite with a jumper
A volt meter is connected across the other high voltage bushing & low voltage bushing
the high voltage windings are energized with low ac voltage (120)
If your reading is above 120 the trans is additive below 120 subtractive.
Of course you can bank additive & subtractive transformers together.