Diff elec systems

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liquidtite

Senior Member
Location
Ny
I remember a few years ago I was in a factory and the voltage system was new to me .
The mechanic I was working with said the system was a corner grounded delta .

I forgot the exact voltages phase to ground and phase to phase ,but I remember that one of the phases was grounded so if you were to put tester on that phase and on ground you would read 0 .

When I was explaining the voltage to a Forman at work recently he said that the system I was explaining was a highleg delta but I think it is a diff system than highleg .

I tried looking up all the diff systems wye and delta online but only could find
a few .


If some one could put down the diff systems I would really appreciate it.
also is the corner grounded delta diff from the high leg like I thought or is it same

thanks for your time
 

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I believe a corner grounded delta will have the zero volts from one phase to g
round but a high leg delta will have a High leg to ground
 
Corner-grounded delta:
Just like the name, one of the three "phase" leads is bonded to the EGC, so for a 240v delta system, you'll see 240v between each phase but 0v from the grounded phase to the grounding leads/system. Since one phase is grounded, it's identified as grounded with white or gray insulation. Note that it's NOT a neutral. Take a look at http://forums.mikeholt.com/showthread.php?t=145700&page=3

High-leg delta:
I'm not sure that corner grounding an otherwise high-leg system is legal. See also http://forums.mikeholt.com/showthread.php?t=146083

Then there are the common 3-phase wye connected with a grounded center point (also a real neutral point), and the somewhat rare ungrounded systems (which have their own special requirements).

The wikipedia article is pretty good, too.
 

Smart $

Esteemed Member
Location
Ohio
Also note these systems may not have OCP on the grounded leg. Panels and disconnects may appear identical to ones for a 120/240 1? 3W system.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Also note these systems may not have OCP on the grounded leg. Panels and disconnects may appear identical to ones for a 120/240 1? 3W system.
I believe that although OCP on the grounded conductor only is not allowed, it is still permissible to use breakers with a common trip that also interrupts the grounded conductor. I am not sure why you would want to do it though unless you had the three pole parts left over from another job.
 
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