30A wiring advice

[Doug Miller]

In article <1DVeb.13$D93.41288@news.abs.net>, lwasserm@fellspt.charm.net (Lawrence Wasserman) wrote:

In article <+odasYAY+6e$EwRJ@jmwa.demon.co.uk>,
John Woodgate <jmw@jmwa.demon.co.uk> wrote:
...snipped...

Well, I'm a Chartered Electrical Engineer, living and working in UK, and
although your detailed explanation is correct, that IS the description
of a two-phase system.

Just as the phase angles between the conductors of a 3-phase system are
120 degrees, so that the three angles add to 360 degrees, the angles
between the phases of a 2-phase system are 180 degrees, adding up to 360
degrees.

That is just so wrong.

Maybe you could explain?

--
Regards,
Doug Miller (alphageek-at-milmac-dot-com)

 

[Gary Tait]

Whereas On Thu, 2 Oct 2003 07:12:21 -0400, "John McGaw"
<nowhere@all.xyz> scribbled:
, I thus relpy:

"Gary Tait" <seesig@xxx.yyy> wrote in message
news:1demnv87hbna8862qvtr4mrl9gvh35db7l@4ax.com...
Whereas On Tue, 30 Sep 2003 20:48:43 -0400, "John McGaw"
nowhere@all.xyz> scribbled:
, I thus relpy:
Or is CH simply a convenient posting location?

CH is the TLD for Switzerland.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

It would seem obvious that I knew that already. Why else would my reply
state "Damned difficult to believe that 10-gauge wire is unavailable in
Switzerland."

I was under the impreddsion you wern't sure if CH was indeed
Switzerland, or some poor country that sold their TLD to companies for
anonymous users.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

 

[H. R. Bob Hofmann]

not_real@nospam.xyz (Beachcomber) wrote in message news:<3f7bd671.13280393@netnews.comcast.net>...

Perhaps, personally, you are American - no born-and-bred European should
expect to find "gauge" size wire available retail within the EU - and CH
is within, though not of, the EU.

There must be a professional need for wire rated at well over 30A;
consult a friendly professional, or your local equivalent of RS
Components

Many of us Americans are indeed ethno-centric, not realizing what the
standards are or differences in other parts of the word...

However, not all of us are like that and some of us even know that the
AWG stands for American Wire Gauge, and perhaps this might not be the
standard in use for European countries. And some of us do indeed
understand that CH is geographically within the EU (mostly) except
that sometimes a CH is actually an LI.

Beachcomber

What is being overlooked here is that the non-USA way of thinking is
not nearly as do it yourself (DIY) as we have here in the USA. Much
more wiring/painting/remodeling, etc is hired out than we are used to
here in the USA. So the availability of things like heavier gauge
wire is really limited. I would suggest looking for a commercial
demolition site and scrounging the wire, if it is not against the
local law to scrounge.

H. R. (Bob) Hofmann

 

[Robert Calvert]

"H. R. Bob Hofmann" <hrhofmann@att.net> wrote in message
news:deadaa59.0310020741.63b8536f@posting.google.com...

not_real@nospam.xyz (Beachcomber) wrote in message
news:<3f7bd671.13280393@netnews.comcast.net>...
Perhaps, personally, you are American - no born-and-bred European
should
expect to find "gauge" size wire available retail within the EU - and
CH
is within, though not of, the EU.

There must be a professional need for wire rated at well over 30A;
consult a friendly professional, or your local equivalent of RS
Components

Many of us Americans are indeed ethno-centric, not realizing what the
standards are or differences in other parts of the word...

However, not all of us are like that and some of us even know that the
AWG stands for American Wire Gauge, and perhaps this might not be the
standard in use for European countries. And some of us do indeed
understand that CH is geographically within the EU (mostly) except
that sometimes a CH is actually an LI.

Beachcomber


What is being overlooked here is that the non-USA way of thinking is
not nearly as do it yourself (DIY) as we have here in the USA. Much
more wiring/painting/remodeling, etc is hired out than we are used to
here in the USA. So the availability of things like heavier gauge
wire is really limited. I would suggest looking for a commercial
demolition site and scrounging the wire, if it is not against the
local law to scrounge.

Could this mean that status inconsistency is more rampant here in the US

than it is in Europe? After all, in Switzerland, it might be that if my
income is higher than an electrician's income, I would probably hire
somebody to do my electrical work because it wouldn't be worth my time to do
it myself. And if my income is lower than an electrician's income, I
probably wouldn't be able to do what an electrician can do - in which case I
would probably hire this work out anyway. In the US, on the other hand, it's
not inconceivable that there are many more people who can do what an
electrician can do but who don't make as much money as an electrician. In
such an environment, you would probably find many more do-it-yourselfers.

Just a thought.

Robert

 

[Dr John Stockton]

JRS: In article <G$ck54AdO9e$Ewn9@jmwa.demon.co.uk>, seen in news:sci.e
ngr.electrical.compliance, John Woodgate <jmw@jmwa.demon.contraspam.yuk>
posted at Thu, 2 Oct 2003 08:28:29 :-

A 'two-phase' system with 90 degrees between the legs (which is really
half a 4-phase system - the angles must add up to 360 degrees) would
create a rotating field, but it is not easy to derive such a supply from
the public electricity system.

If you count 3-phase as public : It is I believe delivered in the UK as
star, with a neutral near ground.

Connect a 1:1 transformer to one leg, neutral to live wire.
Connect a Root3:1 transformer between the other two live wires.

ISTM that one then gets two outputs in quadrature, of equal magnitude.

Admittedly it is impractical to use an integer multiple of Root3 turns,
but 97:56 is within 1 in 10^4.

<URL:http://www.merlyn.demon.co.uk/js-demos.htm#App>, enter Math.sqrt(3)

Note, though, that the three supply phases are not equally loaded, and
I've not worked out whether there is neutral current. Loading could be
made to balance with an auxiliary two-input transformer, driven from the
second two legs, and connected to buck/boost the output of the first
transformer, I think.

Untested.

--
Š John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 Š
<URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang.javascript
<URL:http://www.merlyn.demon.co.uk/js-index.htm> JS maths, dates, sources.
<URL:http://www.merlyn.demon.co.uk/> TP/BP/Delphi/JS/&c., FAQ topics, links.

 

[volts500]

"jim" <email@address.net> wrote in message
news:eWIeb.2559$mg.1716@twister.nyroc.rr.com...

Wade Lippman wrote:

Don't even thing about it.

If your #10 gets disconnected, the circuit opens. No problem.
If one strand of your double #12 gets disconnected, your house burns
down.
Problem.
I thought he said he had been running it on #12 for years. I guess he
didn't notice his house had burnt down. Poor guy.
--
jim

That's _exactly_ the line of thinking that makes overloading a circuit
dangerous. Quite often takes many years for the wire to deteriorate to the
point where it can start a fire. Like a lot of people like to say, it
ain't rocket science.....but it helps to know what you're doing and WHY.

 

[s]

does four phase system exist in the real world?not very efficient i
would'nt have thought,as phases 90 degs apart would have a much smaller
potential than a similar system at 120 degs apart,otherwise a four phase
system would be used for sheer economy,would it not?
"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:G$ck54AdO9e$Ewn9@jmwa.demon.co.uk...

I read in sci.engr.electrical.compliance that s <sim.mich@cwcom.net
wrote (in <AOOeb.13$kC5.21047@newsfep1-win.server.ntli.net&gt about '30A
wiring advice - a complication?', on Wed, 1 Oct 2003:

im sorry to disagree but i dont consider this to be a true two phase
system,as only one phase is entering the transformer,one leaving.the
centre tap being there for safety/alternate voltage.

If you look at it like that, you get the confusion that troubled the OP.
You have chosen the explanation of the centre-tap to 'prove' your
assertion. But one 120 V supply behaves exactly as a single-phase
supply, and so does the other. When you look at the two together, the
important phase-difference comes into consideration. Your explanation
'hides' the phase-difference.

if this were a true
two phase,then it could be fed straight into a squirrel cage motor
without the need of a starting capacitor to phase shift the feild,or am
i missing something quite fundamental here??

Yes, you are missing something. A two-phase system does not create a
rotating magnetic field, as a 3- or higher- phase system can do. So the
motor won't start. The starting capacitor and the second winding DO
create a rotating field.

A 'two-phase' system with 90 degrees between the legs (which is really
half a 4-phase system - the angles must add up to 360 degrees) would
create a rotating field, but it is not easy to derive such a supply from
the public electricity system.
--
Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go
to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[s]

did anybody actually answer this one eventually?
"Joe 90" <donot@usethisaddress.com> wrote in message
news:3f79f827$1_4@news.bluewin.ch...

I am making some changes to an electrical dryer. Where I live, I cannot
get
hold of 10 gauge wire for the 30A circuit - I know, don't ask why, pls.
Can
I use two 12 gauge wires connected in parallel? Based on my electrical
knowledge, this would split the max current between the two wires allowing
the wires to run cooler and well below max capacity.

 

Joe 90 wrote:

It MUST be two phase between the two hot wires, because if it was in one
(the same) phase then the heating element would not heat up.

- +ve 120V
- -
- -
- -
- -
- -ve 120V

+

- +ve 120V
- -
- -
- -
- -
- -ve 120V

= no potential difference between the two hot wires and so no current flow.
Waves are in a single common phase.

- +ve 120V
- -
- -
- - -
- - -
- - -ve 120V

+

- +ve 120V -
- - - -
- - - -
- -
- -
- -ve 120V

= 180 deg phase shift, 240V potential difference at peaks therefore current
flows therefore heater heats up.

Lets go to the understanding of how it heats up and avoid
the controversy that surrounds what you label it.
Consider:
+ - + -
A--Battery1--B--Battery2--C
Let each battery provide 120 volts.
A to B = 120v; B to C = 120v; A to C = 240v
or in other words, a simple series circuit (the
circuit being completed by the voltmeter). Either
battery can be used independently of the other, providing
120v DC, or they can be used in series to provide 240v DC.

Now, substitute the secondary of a center tapped transformer
for Battery1 and Battery2. Again, it is a simple series
circuit. Either half of the secondary can be used independently
of the other half, and provide 120v AC, or the two halves
can be used in series to provide 240v AC.

In the US, the dryer uses points A and B (or B and C) to
provide 120 volts for lighting, timer circuit, motor circuit,
electronics, and points A and C to provide 240 volts to the
heating coil circuit. The dryer does not give a rat's ass
what we call it - single phase, two phase, split phase
or anything else - as long as it "sees" the required
voltage at the necessary current.

 

[John Woodgate]

I read in sci.engr.electrical.compliance that Dr John Stockton
<spam@merlyn.demon.co.uk> wrote (in <GhltEHBBnIf$Ewfe@merlyn.demon.co.uk

) about '30A wiring advice - a complication?', on Thu, 2 Oct 2003:

If you count 3-phase as public : It is I believe delivered in the UK as
star, with a neutral near ground.

Well, the distribution itself isn't really either star or delta, but no
neutral comes with it. The neutral is earthed at the sub-station.

Connect a 1:1 transformer to one leg, neutral to live wire.

So you would need this transformer to have three secondaries in star,
with only one used.

Connect a Root3:1 transformer between the other two live wires.

I'm not sure whether you could incorporate such a secondary on the same
three-phase core as the first transformer, by winding it round two
'legs'. Possibly. Many such arcane transformer configurations exist.

ISTM that one then gets two outputs in quadrature, of equal magnitude.

Admittedly it is impractical to use an integer multiple of Root3 turns,
but 97:56 is within 1 in 10^4.

URL:http://www.merlyn.demon.co.uk/js-demos.htm#App>, enter Math.sqrt(3)

Note, though, that the three supply phases are not equally loaded, and
I've not worked out whether there is neutral current. Loading could be
made to balance with an auxiliary two-input transformer, driven from the
second two legs, and connected to buck/boost the output of the first
transformer, I think.

Untested.

Ingenious, though. Simple, for sufficiently difficult values of simple.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Dr John Stockton]

JRS: In article <uCZ+mJAMqQf$Ew5J@jmwa.demon.co.uk>, seen in news:sci.e
ngr.electrical.compliance, John Woodgate <jmw@jmwa.demon.contraspam.yuk>
posted at Fri, 3 Oct 2003 06:35:08 :-

I read in sci.engr.electrical.compliance that Dr John Stockton
spam@merlyn.demon.co.uk> wrote (in <GhltEHBBnIf$Ewfe@merlyn.demon.co.uk
) about '30A wiring advice - a complication?', on Thu, 2 Oct 2003:

If you count 3-phase as public : It is I believe delivered in the UK as
star, with a neutral near ground.

Well, the distribution itself isn't really either star or delta, but no
neutral comes with it. The neutral is earthed at the sub-station.

Connect a 1:1 transformer to one leg, neutral to live wire.

So you would need this transformer to have three secondaries in star,
with only one used.
...

I think you did not read as much into "delivered" as I tried to write
into it. I meant it as four wires, one being almost safe to touch.

ISTM that any 3-phase transformer must contain (at least) three distinct
pieces of iron capable of being wound. As ISTM you suggest, with a
winding on one, and windings on the other two in series, one can get the
desired quadrature-phase output.

Sometimes I wonder what could be done with a winding around each edge of
a skeleton iron tetrahedron, using one face for input and the other
edges for output, or vice-versa, or ...

--
Š John Stockton, Surrey, UK. ?@merlyn.demon.co.uk / ??.Stockton@physics.org Š
Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
Correct <= 4-line sig. separator as above, a line precisely "-- " (SoRFC1036)
Do not Mail News to me. Before a reply, quote with ">" or "> " (SoRFC1036)

 

[Spehro Pefhany]

On Thu, 2 Oct 2003 18:36:42 -0700, the renowned "s"
<sim.mich@cwcom.net> wrote:

does four phase system exist in the real world?not very efficient i
would'nt have thought,as phases 90 degs apart would have a much smaller
potential than a similar system at 120 degs apart,otherwise a four phase
system would be used for sheer economy,would it not?

There exist 5-phase synchronous motors (steppers). They run more
smoothly than the more common 2-phase type. Of course the power for
them does not come directly out of a plug in the wall.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Gary Tait]

Whereas On Fri, 3 Oct 2003 06:35:08 +0100, John Woodgate
<jmw@jmwa.demon.contraspam.yuk> scribbled:
, I thus relpy:

I read in sci.engr.electrical.compliance that Dr John Stockton
spam@merlyn.demon.co.uk> wrote (in <GhltEHBBnIf$Ewfe@merlyn.demon.co.uk
) about '30A wiring advice - a complication?', on Thu, 2 Oct 2003:

If you count 3-phase as public : It is I believe delivered in the UK as
star, with a neutral near ground.

Well, the distribution itself isn't really either star or delta, but no
neutral comes with it. The neutral is earthed at the sub-station.

Connect a 1:1 transformer to one leg, neutral to live wire.

So you would need this transformer to have three secondaries in star,
with only one used.

Connect a Root3:1 transformer between the other two live wires.

I'm not sure whether you could incorporate such a secondary on the same
three-phase core as the first transformer, by winding it round two
'legs'. Possibly. Many such arcane transformer configurations exist.

ISTM that one then gets two outputs in quadrature, of equal magnitude.

Admittedly it is impractical to use an integer multiple of Root3 turns,
but 97:56 is within 1 in 10^4.

URL:http://www.merlyn.demon.co.uk/js-demos.htm#App>, enter Math.sqrt(3)

Note, though, that the three supply phases are not equally loaded, and
I've not worked out whether there is neutral current. Loading could be
made to balance with an auxiliary two-input transformer, driven from the
second two legs, and connected to buck/boost the output of the first
transformer, I think.

Untested.

Ingenious, though. Simple, for sufficiently difficult values of simple.

FWIW, the UK MV distribution system is 11KV delta, and is transformed
to a 230/380V Wye, with one phase per home.

The US usually uses a Wye system for the MV, with one phase (hence
single-phase) Hot-Neutral, with a center tapped 240V transformer, the
center tap being gorund/neutral.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

 

[Gary Tait]

Whereas On Thu, 2 Oct 2003 18:36:42 -0700, "s" <sim.mich@cwcom.net>
scribbled:
, I thus relpy:

does four phase system exist in the real world?not very efficient i
would'nt have thought,as phases 90 degs apart would have a much smaller
potential than a similar system at 120 degs apart,otherwise a four phase
system would be used for sheer economy,would it not?

You could do that with two genuine 2 phase supplies.

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:G$ck54AdO9e$Ewn9@jmwa.demon.co.uk...
I read in sci.engr.electrical.compliance that s <sim.mich@cwcom.net
wrote (in <AOOeb.13$kC5.21047@newsfep1-win.server.ntli.net&gt about '30A
wiring advice - a complication?', on Wed, 1 Oct 2003:

im sorry to disagree but i dont consider this to be a true two phase
system,as only one phase is entering the transformer,one leaving.the
centre tap being there for safety/alternate voltage.

If you look at it like that, you get the confusion that troubled the OP.
You have chosen the explanation of the centre-tap to 'prove' your
assertion. But one 120 V supply behaves exactly as a single-phase
supply, and so does the other. When you look at the two together, the
important phase-difference comes into consideration. Your explanation
'hides' the phase-difference.

if this were a true
two phase,then it could be fed straight into a squirrel cage motor
without the need of a starting capacitor to phase shift the feild,or am
i missing something quite fundamental here??

Yes, you are missing something. A two-phase system does not create a
rotating magnetic field, as a 3- or higher- phase system can do. So the
motor won't start. The starting capacitor and the second winding DO
create a rotating field.

A 'two-phase' system with 90 degrees between the legs (which is really
half a 4-phase system - the angles must add up to 360 degrees) would
create a rotating field, but it is not easy to derive such a supply from
the public electricity system.
--
Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go
to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

 

[daestrom]

"s" <sim.mich@cwcom.net> wrote in message
news:Uwifb.521$Sz5.321@newsfep3-gui.server.ntli.net...

does four phase system exist in the real world?not very efficient i
would'nt have thought,as phases 90 degs apart would have a much smaller
potential than a similar system at 120 degs apart,otherwise a four phase
system would be used for sheer economy,would it not?

I guess it depends on how you 'count' four phases. Obviously you could call
it 'two phases' with center-taps tied together I suppose. But you're right,
three phase on a watt/wire basis is more economical. Do the math assuming a
fixed current capacity and you'll find three phase is the most economical on
a watt/wire basis. Five, seven, nine, eleven, any higher number of phases
do not do as well as three. Kind of a geometry/math thingy.

IMHO, anytime one phase is exactly 180 out from another, I don't count that
as a separate 'phase'. So a 'four phase' system is really just a two phase
system with some center-taps. Kind of like residential supply in US (the
so-called Edison connection). Whole flame wars have gone on for days over
whether to call that a two-phase system, or just a single phase system with
center-tap. FWIW, if one wire is exactly 180 out from another wire, isn't
that just like the two wires of a single phase AC supply? Well, don't want
to start another war over that, but just pointing out there are differences
of opinion.

There have been two phase systems where the two phases are 90 apart. They
can produce a rotating field for self-starting machinery. Conventionally,
this would take four wires to distribute. But an obvious economy is to tie
one leg of each phase together so you only need three wires. This requires
a larger conductor for the common conductor and is 'unbalanced' with respect
to ground. Causes some problems with telephone service and the like.

daestrom

 

[daestrom]

"Dr John Stockton" <spam@merlyn.demon.co.uk> wrote in message
news:mgq10UC8zZf$EwLH@merlyn.demon.co.uk...

JRS: In article <uCZ+mJAMqQf$Ew5J@jmwa.demon.co.uk>, seen in news:sci.e

I think you did not read as much into "delivered" as I tried to write
into it. I meant it as four wires, one being almost safe to touch.

ISTM that any 3-phase transformer must contain (at least) three distinct
pieces of iron capable of being wound. As ISTM you suggest, with a
winding on one, and windings on the other two in series, one can get the
desired quadrature-phase output.

Sometimes I wonder what could be done with a winding around each edge of
a skeleton iron tetrahedron, using one face for input and the other
edges for output, or vice-versa, or ...

That's an interesting thought. Wonder which way the flux would align in it.

I have seen three-phase transformers that were three vertical irons tied
with cross bars at top and bottom. Kind of like 'III'. The primary and
secondary were wound on top of each other, one phase per leg. Took up less
space than three conventional single phase units. It was were 'space and
weight considerations' were more important than money (i.e. military).

daestrom

 

[John Wilson]

John Woodgate wrote:

I read in sci.engr.electrical.compliance that s <sim.mich@cwcom.net
wrote (in <AOOeb.13$kC5.21047@newsfep1-win.server.ntli.net&gt about '30A
wiring advice - a complication?', on Wed, 1 Oct 2003:


im sorry to disagree but i dont consider this to be a true two phase
system,as only one phase is entering the transformer,one leaving.the
centre tap being there for safety/alternate voltage.

You're right; it's a single-phase system with a center tap.

If you look at it like that, you get the confusion that troubled the OP.
You have chosen the explanation of the centre-tap to 'prove' your
assertion. But one 120 V supply behaves exactly as a single-phase
supply, and so does the other. When you look at the two together, the
important phase-difference comes into consideration. Your explanation
'hides' the phase-difference.


if this were a true
two phase,then it could be fed straight into a squirrel cage motor
without the need of a starting capacitor to phase shift the feild,or am
i missing something quite fundamental here??

You're right. There were two-phase power systems before there were
three-phase systems, and they are still used for a few special purposes.

Yes, you are missing something. A two-phase system does not create a
rotating magnetic field, as a 3- or higher- phase system can do.

Yes it does.

So the
motor won't start. The starting capacitor and the second winding DO
create a rotating field.

A 'two-phase' system with 90 degrees between the legs (which is really
half a 4-phase system

No, it's a two-phase three-wire system. A four-phase system has
conductors with phase angles that differ by 45 degrees. More explanation
below.

- the angles must add up to 360 degrees) would
create a rotating field, but it is not easy to derive such a supply from
the public electricity system.

It's trivial, using a standard device called a Scott-connected
transformer. It consists of two transformers, one connected between
phases A and B, and the other connected between the center tap of the
first one and phase C. If you choose the ratios of the two transformers
correctly, the other windings of the two transformers are 90 degrees out
of phase, giving you two-phase power. How you make the connections on
the two-phase side determines whether you're dealing with two-phase
three-wire, two-phase four-wire, or two-phase five-wire. Being a
transformer, this can pass power either from the three-phase system to
the two-phase system, or vice versa.

The US standard center-tapped single-phase system is just that; single
phase. Three-phase systems can have either three or four wires,
depending on whether the neutral is carried along with the phase
conductors to allow phase-neutral loads to be connected.

Two-phase systems are more complicated. It can be done with three wires;
call them X, Y, and Z, with VXZ leading VYZ by 90 degrees. If VXZ=VYZ=1,
then VXY=1.414. With this system, Z is normally grounded and called the
"neutral". Two-phase four-wire can be done, too, with no neutral.
Calling the wires W, X, Y, and Z, VWY leads VXZ by 90 degrees. If
VWX=VXY=VYZ=VZW=1, then VWY=VXZ=1.414. The phase angle between any two
adjacent wires is 90 degrees. To make it more complicated, you can do
two-phase five-wire, which is just like two-phase four-wire with the
addition of the neutral.

AIUI, the original Niagara Falls system was two-phase. The beauty of a
three-phase system is that the voltage between any two wires other than
the neutral is the same.

73,
JohnW

 

[John Woodgate]

I read in sci.engr.electrical.compliance that John Wilson
<johnwilson@alum.mit.edu> wrote (in <tJofb.399729$2x.134818@rwcrnsc52.op
s.asp.att.net&gt about '30A wiring advice - a complication?', on Sat, 4
Oct 2003:

No, it's a two-phase three-wire system. A four-phase system has
conductors with phase angles that differ by 45 degrees. More explanation
below.

You've just chosen definitions that suit your denials.

- the angles must add up to 360 degrees) would
create a rotating field, but it is not easy to derive such a supply from
the public electricity system.

It's trivial, using a standard device called a Scott-connected
transformer. It consists of two transformers, one connected between
phases A and B, and the other connected between the center tap of the
first one and phase C. If you choose the ratios of the two transformers
correctly, the other windings of the two transformers are 90 degrees out
of phase, giving you two-phase power. How you make the connections on
the two-phase side determines whether you're dealing with two-phase
three-wire, two-phase four-wire, or two-phase five-wire. Being a
transformer, this can pass power either from the three-phase system to
the two-phase system, or vice versa.

That is TRIVIAL?
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[daestrom]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:gK69UVADjof$EwZ8@jmwa.demon.co.uk...

I read in sci.engr.electrical.compliance that John Wilson
johnwilson@alum.mit.edu> wrote (in <tJofb.399729$2x.134818@rwcrnsc52.op
s.asp.att.net&gt about '30A wiring advice - a complication?', on Sat, 4
It's trivial, using a standard device called a Scott-connected
transformer. It consists of two transformers, one connected between
phases A and B, and the other connected between the center tap of the
first one and phase C. If you choose the ratios of the two transformers
correctly, the other windings of the two transformers are 90 degrees out
of phase, giving you two-phase power. How you make the connections on
the two-phase side determines whether you're dealing with two-phase
three-wire, two-phase four-wire, or two-phase five-wire. Being a
transformer, this can pass power either from the three-phase system to
the two-phase system, or vice versa.

That is TRIVIAL?
--

Given that most service comes from one, two or three stepdown transformers
(single, open-delta, delta) anyway, reconnecting them into the Scott-T
connection isn't much of a difference. Many commercial transformers have
the center tap and one at 86% (the tap needed on the single-phase to center
transformer to get the same voltage).

So, reconnecting a set of service transformers is kind of trivial when you
think about it.

daestrom

 

[John Wilson]

John Woodgate wrote:

I read in sci.engr.electrical.compliance that John Wilson
johnwilson@alum.mit.edu> wrote (in <tJofb.399729$2x.134818@rwcrnsc52.op
s.asp.att.net&gt about '30A wiring advice - a complication?', on Sat, 4
Oct 2003:

No, it's a two-phase three-wire system. A four-phase system has
conductors with phase angles that differ by 45 degrees. More explanation
below.


You've just chosen definitions that suit your denials.

See ANSI Standard C1, where the nomenclature of US electrical systems is
defined. This is not a matter of opinion.

- the angles must add up to 360 degrees) would
create a rotating field, but it is not easy to derive such a supply from
the public electricity system.

It's trivial, using a standard device called a Scott-connected
transformer. It consists of two transformers, one connected between
phases A and B, and the other connected between the center tap of the
first one and phase C. If you choose the ratios of the two transformers
correctly, the other windings of the two transformers are 90 degrees out
of phase, giving you two-phase power. How you make the connections on
the two-phase side determines whether you're dealing with two-phase
three-wire, two-phase four-wire, or two-phase five-wire. Being a
transformer, this can pass power either from the three-phase system to
the two-phase system, or vice versa.


That is TRIVIAL?

Another poster addressed this.

73,
JohnW