480 Volt System, Wye Or Delta?

[LarryFine]

EDIT: ALERT! ~ I don't know how, but this post appeared first when I posted it.

It should be post # 3, following Charlie's link.



Charlie, nice little page. Interesting that, in this image:

. . . they refer to the un-grounded Delta as more common than the center-tapped Delta; I would have swapped them.

 

[Smart $]

EDIT: ALERT! ~ I don't know how, but this post appeared first when I posted it.

It should be post # 3, following Charlie's link.

I had a post "inserted" in another thread. Should have been #83, but instead was inserted as #76 [and it appears this particular post has been inserted as #2 instead of being #4]. What is causing this?

 

[RATLIFF]

480 Volt System, Wye Or Delta?

We Had A Question On A 480 Volt System, We Were Discussing 230 V
With A High Leg Being A Delta System. The Question Came Up About A 480 Volt System Being Delta Or Wye, One Student Installed 277 V
Lighting And Was Told It Was A Wye System. I Have Worked On A Industrial Plant That Had A 480 V With A High Leg That Read Approx.
360 V To Ground On One Phase, But This Was The Only Time In 12 Years That I Came Across This Situation.
I Need Help To Explain The Difference Between The Delta Or Wye At 480 V.
Thank You
Greg

 

[cpal]

Try this

http://www.teal.com/newsletter/AppsNote15.pdf#search='wye%20Vs%20delta%20systems'

Charlie

 

[kingpb]

EDIT: ALERT! ~ I don't know how, but this post appeared first when I posted it.

It should be post # 3, following Charlie's link.

QUOTE]

Something fishy yesterday, I noticed in the afternoon, that whomever was posting new posts, the dates were for today. Must have gotten stuck in the Twilight Zone.

 

[mhulbert]

Yes, everything is all mixed up in several threads, I posted something in another thread, and it ended up 2 pages back from the end of the thread! I promptly deleted it, but I read some other threads and it's all mixed up all over...anybody know if the webmasters are aware of this??

Let's see if this post ends up in the right area!

 

[Lady Engineer]

Hey Larry,

I've designed a center ground delta system before, but never a corner ground. I would think since you can only use corner ground delta for 3 phase loads , then it would be less common? Also, I have never done an ungrounded system, so that would not seem common. I know they used to install those back in the day, but now not sure.

That's JMHO

Lady

 

[LarryFine]

Lady, maybe you misunderstood me. I was saying that center-ground/high-leg Deltas and grounded Y's are more common than corner-grounded and non-grounded Deltas are, in my experience anyway.

 

[Lady Engineer]

oops sorry...ok, yeah then I agree.


Lady

 

[petersonra]

I have yet to run across a corner grounded system or a center grounded delta.

Most of the plants I am in use ungrounded delta because they do not want a ground fault to shut anything down.

 

[coulter]

Generally 240 delta is center grounded. I've never seen corner grounded 240 delta or ungrounded 240 delta.

Generally 480 delta is ungrounded or corner grounded. I've never seen center grounded 480 - and I can't think of a reason of why would one do that.

Disclaimer: Just cause I haven't seen one doesn't mean there aren't special cases where one might use, need, or find a screwball install.

carl

 

[wirenut1980]

The utility company I work for has some center grounded 120/240 3 phase delta secondaries, although we are trying to encourage existing customers to switch over to 120/208 V wye secondaries, and for new construction, we will generally not connect to a 3 phase delta unless for a special circumstance. It is the belief of my company that 3 phase wye secondaries are the configuration of the future...

One case I heard about was for a school that had originally been served from single phase 120/240 V. Then when they got air conditioning in the 90's, they (or their engineering firm I guess) opted (probably cheaper) to go to a 3 phase 120/240 center grounded delta service.

 

[lile001]

Utilities are trying hard to get rid of corner grounded delta systems. They were common about 50 years ago or more.

Corner grounded delta systems produce crazy voltages, and crazy ground faults. Same with "wild leg" center grounded delta, which is also becoming obsolete. The "wild leg" has a different voltage to ground, which can confuse people.

We worked on a wild leg system just last year, the utility demanded that they change out thier transformer to a Wye system, and we had to analyze the loads to see if they would still work.

--Lawrence Lile, P.E.
Project Solutions Engineering

 

[cpal]

Delta systems supplied thru 3 single phase transformers has the advantage of operating at reduced kVA (58% + or -) as a open delta if one transformer were to fail.
I've been told this was desirable at one time (manufacturing , mills warehouses) although I have not seen many (or any for that matter) for quite some time.