cctalk Digest, Vol 88, Issue 2

Grant Taylor cctalk at
Tue Jan 4 09:49:28 CST 2022

On 1/4/22 8:06 AM, Jonathan Chapman via cctalk wrote:
> Yes, that's open delta. There are one or two small commercial buildings 
> here in town that still have open high leg delta service -- that's 
> 240V delta, and one of the 240V transformers is center-tapped to give 
> 120/240 split phase for small loads.

I'm having trouble reconciling that with my current mental understanding.

First I have to bring up line vs phase.  My understanding is that the 
line is the actual wire, and a phase is what runs over the two lines.

I can see how you might use two lines combined with a "corner ground" 
for as the third line for a delta configuration.  Thus you have three 
three distinct line parings ~> phases.  L1+G, L1+L2, L2+G.

If that is not what's being discussed in this case, then I have no idea 
what it is.

> My guess is, aside from saving on wire, insulators, etc. (not 
> significant in town), the real savings is on disconnects and the 
> extra transformer.

I apparently need to do more reading.  I'm not seeing how corner ground 
delta will save a transformer.  Or I'm completely misunderstanding 
things.  --  Time to research "open delta".

Grant. . . .
unix || die

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