Re: [CAD_CAM_EDM_DRO] Re: U.S. 220 vs Euro 220

info.host@... wrote:

> What is Star and Open Delta (?Wye?)? Do you remember where abouts it was
> that uses 440V raw in the house? I'm off to get my multimeter. `.^)
>
> John H.
>
>

Hello John,

On an true Delta you put 3 transformers beween all 3 primaries. and get
240 V between lines.Each line has this way 2 transformers connected.
The voltages are two times 120 V against ground and
the third leg 208V against ground..

On an open delta you connect only 2 transformers between only the 2
primary lines and get the
third line out of the connection of the 2 transformers. Its value
against ground depends strongly from the load. So some people call
it the floating line. It is supposed to be 208 V but it nearly never
gets achieved,.

In Europe it makes more sense. They connect of all 3 transformers one
leg on primary line and the other leg of all three to ground.
It looks like a star.
If one primary fails the motor stops and will not pull current through
the other windings or transformers.
At least as long it is connected in star too. If it is connected in
delta there is a change to continue
turning.
This is the reason why in America so many threefase motors burn and
transformers explode. If the one transformer from the power supply fails
a big motor pulls current from small ones and fries the small ones.
This can't happen in Europe, because there is no
way to pull current from. The line is dead.
I have this in my shop and never got trouble. When one line fails all
motors stop immediatly
and make a lot of noise.
And I can switch them of if the their contactors didn't do it
themselves.
I hope I could explain it well enough.
Good Luck
Sven Peter from Costa Rica

W


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