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#71907 - 11/10/06 12:09 AM 240 Grounded B phase distribution  
Almost Fried  Offline
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Joined: Sep 2006
Posts: 98
Madison County, Ark. USA
I am curious to know how common this configuration is? I first ran into it in KC, where it is all over the place. They use 2 pole gear, makes for some simpler setups where you have a lot of meters and gear for a single building.


Work Gear for Electricians and the Trades

#71908 - 11/10/06 03:07 AM Re: 240 Grounded B phase distribution  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,057
Estero,Fl,usa
I saw it on sewer lift pumps. That was just a motor load in a remote area so it made perfect sense. Simple and cheap.


Greg Fretwell

#71909 - 11/10/06 02:36 PM Re: 240 Grounded B phase distribution  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
KC = Kansas City?

I find corner-grounded delta an interesting configuration, as it's something we've never (to the best of my knowledge) used over here, at least not unless it was perhaps employed in the very, very early days.

It makes perfect sense for saving extra switch poles, fuses, etc.


#71910 - 11/10/06 02:45 PM Re: 240 Grounded B phase distribution  
SteveFehr  Offline
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Joined: Mar 2005
Posts: 1,198
Chesapeake, VA
We have a term for corner-grounded delta around here... "ground fault!"


#71911 - 11/10/06 04:00 PM Re: 240 Grounded B phase distribution  
gfretwell  Online Content


Member
Joined: Jul 2004
Posts: 9,057
Estero,Fl,usa
I don't know why corner delta seems so strange to people. We ground transformer taps and use them as current carrying legs all the time.


Greg Fretwell

#71912 - 11/11/06 11:18 PM Re: 240 Grounded B phase distribution  
WFO  Offline
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Joined: Sep 2005
Posts: 202
Cat Spring, TX
We use corner grounded 3 wire 3 phase xfmrs. all the time on pump jacks in the oil field.


#71913 - 11/12/06 01:41 AM Re: 240 Grounded B phase distribution  
Almost Fried  Offline
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Joined: Sep 2006
Posts: 98
Madison County, Ark. USA
Pauluk-Yes, the one and only Kansas City.

Steve F. please explain what you mean?

[This message has been edited by Almost Fried (edited 11-12-2006).]


#71914 - 11/12/06 09:09 AM Re: 240 Grounded B phase distribution  
SteveFehr  Offline
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Joined: Mar 2005
Posts: 1,198
Chesapeake, VA
I've never seen a corner-grounded delta used, but I have seen a lot of floating deltas on numerous switchboards. Naval ships use floating delta exclusively- even for single-phase circuits, both wires are "hot" legs of a 110/63V Delta. The idea is that if there happens to be a single phase ground fault, it won't interrupt power to the loads, and the worst a single-phase shock could be is 63V, which is especially important when you might be half-submerged in salt water at the time. I see it a lot in buildings, too, even some floating wye (with X0 ungrounded)- the reasoning is always the same; that a ground fault won't cause an unplanned outage.

So, when I hear talk of corner grounding a delta, I immediately think "Ground Fault!"


#71915 - 11/12/06 09:18 AM Re: 240 Grounded B phase distribution  
iwire  Offline
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Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Quote
I see it a lot in buildings, too, even some floating wye (with X0 ungrounded)- the reasoning is always the same; that a ground fault won't cause an unplanned outage.


What kinds of buildings?


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#71916 - 11/12/06 11:18 AM Re: 240 Grounded B phase distribution  
SteveFehr  Offline
Member
Joined: Mar 2005
Posts: 1,198
Chesapeake, VA
IT and communications. Often the switchboards and generators are 480V delta with local power supplies providing 208/120Y to the electronics. This creates some problems, as TVSSs and UPSs don't work properly on floating delta, and can malfunction if the delta drifts too far from center.

[This message has been edited by SteveFehr (edited 11-12-2006).]


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