A case for downgrading to PCs (was: WARNING: RANTING COMPUTERNUT...

From: Joe R. <rigdonj_at_cfl.rr.com>
Date: Thu Jun 17 21:56:28 2004

At 09:44 PM 6/17/04 -0400, you wrote:
>
>> Most know about motor rotation but he was talking about delta versus
>> Y. This can be quite different.
>
>What _is_ the difference between delta and Y?

  There's a BIG difference. In delta the windings are arranged like a
triangle with the power lines connected at the apexs so there isn't a
neutral leg and the hot legs all work against each other. In Y, the
windings are arranged like a Y with the neutral at the junction and the
power lines at the ends of the legs therefore neutral is connected to one
end of each of the three windings. There's also a significant difference in
the voltages between the hot legs. IIRC the hot leg of a Y is 240 VAC WRT
to neutral and about 300 VAC between the legs (it's the sum of the voltages
on each leg times the SINE of their phase angles). In Delta there doesn't
need to be a neutral but if there is it's isolated from the hot legs so
there's no voltage difference. Also the voltage between the hot legs is
fixed at 220VAC. Delta only needs three lines to work effectively, Y needs
four (three for power plus neutral). Ideally the neutral in Y connection
should be at 0 VAC WRT to ground but if you get a heavy power draw on one
leg of a Y then it can shift the neutral away from 0 volts.

   The point is that there's a big difference in the voltages between the
legs and also from the legs to neutral or ground in the two systems. I may
not be exactly right about the exact voltages but it doesn't matter since
they vary from country to country and region to region but you get the idea.

    Joe

 A while ago we had a
>discussion that ended up revolving around what point is grounded
>("neutral"). As far as I can see, delta and Y are basically
>equivalent, provided you don't try to refer anything to ground (or
>anything else beyond the three phases), and provided you don't overload
>anything.
>
>Am I missing something?
>
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Received on Thu Jun 17 2004 - 21:56:28 BST