On 07/02/2021 13:20, Andrew wrote:
On 07/02/2021 09:04, Jeff Layman wrote:
On 06/02/2021 23:43, Steve Walker wrote:
On 06/02/2021 23:20, newshound wrote:
On 06/02/2021 23:14, Theo wrote:
While I was on the TLC website I was doing a thought experiment.

Twin and earth cable comes in a variety of sizes:
1, 1.5, 2.5, 4, 6, 10, 16 mm2.

But what if you want to wire three phase?Â* TLC only have 1 and 1.5mm2
three
core and earth.Â* Doncaster Cables also have 2.5mm2 but not larger.Â* CEF
likewise.Â* There's some three core in SWA but I assume that's
primarily for
external use?

I understand that using three phase you can get 3x the power
compared to
single phase - so a 32A radial would get you 7.3kW single phase or 22kW
three phase.

But how should you wire that?Â* For a 32A single phase radial the TLC
calculator indicates it needs 6mm2.Â* What cable do you use for three
phase?

I suppose you could run a pair of 4/6/10mm2 T&E but that would seem
'surprising' - one of those pairs carries two phases instead of live
and
neutral, and anyone who mixes up a phase for neutral may be in for a
shock.
Plus the colour scheme is confusing (two brown and two blue, which
phase is
which again?Â* You can sleeve, but what if you mix up the cables?)

You could use SWA, but that's fairly unwieldy and pricey for an
internal
installation.

So what's the 'proper' way to do it?

Thanks
Theo

IME at the domestic / light industrial level 3 phase is usually wired in
single core.

And for heavier industrial use, you could use something like:

https://www.vwcable.com/nyy-nyy-j-ny...h-power-cable/


Although the biggest I have seen myself (while testing a gas turbine
generator set) used singles - 3 pairs of 500mm2

Somewhat coincidentally, and further to the thread which I started last
week with the subject "At what low mains voltages do devices stop
working?", there have been two 500kVA generators running locally while
work was being done on a substation (I thought one was 300kVA as it was
smaller than the other, but was informed by a guy from SSE that both
were 500kVA). Both had 5 cables from them, four were yellow and seemed
to be about 25mm diameter, the other was yellow with a green stripe and
was somewhat less - maybe 20mm in diameter. A rather poor close-up photo
of connections made to the overhead line (440V?) is shown he
https://ibb.co/vBgFpj3
I think it is possible to just make out the colours, and assume the
other ends hidden in the generator are also colour coded. Does the earth
carry less current, or it it just there in case the neutral fails as a
temporary backup?

I guess those 25 mm cables have about 300 - 350mm^2 wire in them, and
are rated at 500 - 1000A.

Not far form me is a house with a Tesla parked in the drive. There is a
shoe-box sized wall charger unit with a cable about 20 - 25 mm diameter
going into it. I assume that's 3-phase.


Sounds more like a single phase charger. The chap near me who had a
new supply to the house, requiring the road to be dug up, has a charger
box on his house wall that looks to be about 2 to 3 foot high by 18
inches wide. I assumed he has had a 3phase supply connected to the house
from the other side of the road (which being a slight curve, has all
the street lamps).

The box is this one:
https://www.smarthomecharge.co.uk/chargers/tesla/tesla-wall-connector/

That can be single or 3-phase. This is a new estate still being built.
The house in question was built three or four years ago, so could well
have a 3-phase supply.

--

Jeff