230V Delta?

Status
Not open for further replies.
kwired said:
You need a separate EGC for corner ground and ungrounded systems as well beyond the service or first means of disconnect. So yes you run 4 wires with branch circuits and feeders, or 5 if there is a neutral.

Corner ground and ungrounded systems are still referred to as three phase three wire systems though. If you have a three phase four wire "system" that means there is a neutral conductor involved even if it has no load connected to it.
Click to expand...


Main disconnect- sorry .

But yes, I agree.
 
MTW said:
Many old plants with busway systems that operate on ungrounded delta, have a custom busplug installed with this lamp ground detection system installed. Easy to readily see when a phase has faulted from the plant floor. Some 25W 130V rough service lamps would be a good selection for reliable long life use. I think I have a plug with these lamps installed on the shelf, At a future time I could check if others are interested.
Click to expand...
For those who have never seen one, Ground Detection Lamp Busplug, antique Bulldog from the hometown. 480/240V capable, 120V 7.5W lamps

BulldogFront.jpg

BulldogInterior.jpg

BulldogInsideCover.jpg
 
Little Bill said:
Last we heard, you were trying to find a job with a POCO. Care to share what POCO you are working with now that you are designing systems for?
Click to expand...

Don't think POCOs would have a need for 138/240Y. From what I'm told they just start at 13,800 volts and go up from there.
 
MTW said:
For those who have never seen one, Ground Detection Lamp Busplug, antique Bulldog from the hometown. 480/240V capable, 120V 7.5W lamps

View attachment 2555680
Click to expand...

This is an example of the resistor style bus plug I described earlier. Those are tapped resistors not fuses. The resistors help deal with the system charging currents found on ungrounded systems.
 
jim dungar said:
This is an example of the resistor style bus plug I described earlier. Those are tapped resistors not fuses. The resistors help deal with the system charging currents found on ungrounded systems.
Click to expand...
I was going to ask if that is what we were looking at, then saw your post.
 
jim dungar said:
This is an example of the resistor style bus plug I described earlier. Those are tapped resistors not fuses. The resistors help deal with the system charging currents found on ungrounded systems.
Click to expand...
Yes those are wirewound resistors. Probably made by Ward Leonard based on their light olive green color.
 
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
Click to expand...
Are there any 3 phase motors still on this system?
 
ptonsparky said:
Why wouldn’t there be? Is there something I’m missing?
Click to expand...
PA was known for 3 wire two phase. If this is just some unused storage building, those photos on the roof could be of a scott T transformer. The voltage relationships are closer to two phase than three phase.
 
IMG_20210309_173443.jpg

The last two phase systems I have seen were all 5 wire (6 with egc) and only ever in PA. They are quite the interesting rare bird.
 
The primary is 3-phase, secondaries are 3-phase, and this is far enough from Philly that I really doubt there's ever been two-phase in the building. The only motor loads I saw are the elevators and a few exhaust fans, at least some of which I know are 3-phase. There are a lot of transformers throughout the facilities to provide 120V power as well, which would have included lighting and circulating fan loads. I wasn't able to get into the oldest part of the factory to see that, but the 3-phase primaries drop to that side as well.
 
tortuga said:
View attachment 2555687

The last two phase systems I have seen were all 5 wire (6 with egc) and only ever in PA. They are quite the interesting rare bird.
Click to expand...
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.
 
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.
Click to expand...
I never have seen a 3 wire 2 phase system in the wild.
It can in theory be made with two single phase transformers off a delta 240 system.( But dont ask me how)
I have seen and worked on 5 wire two phase way back during my Philly years.
From what I recall the 3 wire variant was used in more rural areas, and the main reason building owners would keep it around is hard to replace motors like elevators (and the utility would have provided transformers when it converted to three phase).
 
Status
Not open for further replies.
Top