Hi Bill and everyone else interested!
My comment "surprising it's working at all" is among other things relating
to a typical house installation in North America. A cobb web of wires
criss-crossing through beams and joists, no conduits for the wires, cheap
components and generally cheap installations. Everything in order order to
save a buck or two. Electrical safety here has still a long way to go.
At one point in 1970s the house builders went totally crazy and installed
aluminum wiring to save even more money. Fortunately they had to stop that
practise as it caused too many house fires and the insurance companies
refused to cover damages.
Some basic facts about 3 phase.... Most of the electric power in the world
is 3 phase. The concept was originally conceived by Nikola Tesla and was
proven that 3 phase was far superior to single phase power.
3 phase power is typically 150% more efficient than single phase in the same
power range. In a single phase unit the power falls to zero three times
during each cycle. In 3 phase it never drops to zero. The power delivered
to the load is the same at any instant. Also, in 3 phase the conductors need
only be 75% the size of conductors for single phase for the same power
output.
Using three conductors (rather than two, as used for single phase power)
allows for lower current levels in each conductor, again facilitating the
use of smaller conductors. For this and other reasons, three-phase power
simply provides a more efficient means of supplying power to large
electrical loads as well as typical residential dwellings.
Likewise, if one is running, say, 5-10 kVA, it's a lot easier to find
components to
handle the 15-20 amps per phase, rather than handling the 50 amps you'd need
for single phase. When handling currents over 20-25 amps, everything gets a
LOT more expensive: switches, variacs, fuses, fuseholders, plugs and
sockets, etc. There's a good reason why three phase is popular for loads
over a few kW, especially if you start pricing good plugs and receptacles
to handle 10 kVA, (i.e. not stove/dryer plugs which are really designed to
be plugged or unplugged a few dozen times, at most).
3-phase power doesn't "have it's advantages" it's superior to 1- and 2-phase
systems.
There is a lot more to be said about 3 phase power. Maybe some other time.
73s Bert, VE3OBU
-----Original Message-----
From: Bill Turner [mailto:wrt@dslextreme.com]
Sent: Monday, November 17, 2003 7:50 AM
To: Bert Almemo
Cc: Karl-Arne Markström; amps@contesting.com
Subject: Re: [Amps] Benefits of 3-phase power?
On Sun, 16 Nov 2003 20:05:07 -0800, "Bert Almemo"
<balmemo@sympatico.ca> wrote:
>As an example, to get 120V and 240V to the house, which by the way is the
>same phase, the power distributor uses "pole pigs" or other type of
>transformers for 240V with a center tap to get 2x120V. It's really
>surprising that it's working at all.
_________________________________________________________
"Surprising that it's working at all"? Could you please explain that?
I've worked with both two and three phase for years, and while I see
that three phase has it's advantages, I wouldn't want it for ordinary
home use.
Comments welcome.
--
Bill, W6WRT
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