| Tomi Holger Engdahl 2006-06-26, 3:25 am |
| moroney@world.std.spaamtrap.com (Michael Moroney) writes:
> What I would do:
>
> Everything would be made to operate from 240V.
>
> The 240V would be supplied from center tapped transformers, with the
> center tap grounded. In other words, the current American system.
> The center tap would be used for nothing but grounding. No 120V devices.
>
> 3 phase would be 240Y/139, with the Y center point grounded. Again,
> everything uses 240V either single phase or 3 phase, nothing gets
> connected to the center point except the ground.
>
> This gives the best of both worlds. Devices draw less current thus more
> safety there. Touching any hot by a grounded person will only give you
> a 120V shock, unless touching 3 phase where you would get zapped with 139V.
> You'd need to manage to touch 2 hots at once to get zapped with 240V.
> GFCIs could be used everywhere. No 4 wire 240V circuits, 2 hots+ground
> everywhere. 3 phase has 3 hots+ground.
>
> The big drawback is all light switches need to be double pole, and 3 way
> switch circuits get "interesting".
There are some wiring systems that somehow reseble your ideas:
230V between phases and no neutralin the supply (also called 230V
delta). Houses are then fed two phase wires, neither of which is
necessarily anywhere near earth potential. This is used in at least in
Norway in some locations. Light switches are double pole here.
Some places in Belgium three phase 220 across the phases (= 127 phase
to earth/neutral, 230V Y output on transformer) is used on older
domestic dwellings (new installations are 400/230V 3 phase, neutral,
earth). For this reason all Belgian fuseboards (whether actual fuses
or circuit breakers) protect both current carrying wires irrespective
of supply type.
--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
|