zzzzzzzzzz wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.


In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.


It's a matter of semantics, I know, but the 120+120=240 system we've
been discussing actually is a 2-phase system, even though it's not
really called that. One side is 180° out of phase with the other side,
so by definition you have a 2-phase system.
It is indeed. The main advantage here is that you can combine the phases
to get a higher voltage. Less current. A 120V dryer would take some
hefty wiring.
You combine a 120V transformer winding with another 120V transformer
winding that is in-phase to get 240V. In fact, as everyone knows, it is
a single winding with a center tap.

You won't find an electrical engineer for power systems who will say
120/240V is not single phase. You are not likely to find an electrician
that deals with 3-phase who says 120/240V is not single phase. Wikipedia
is not likely to say 120/240 is 2-phase.

Only because it's not. ;-)

Fans of "2-phase" could ask for a 120/240 2-phase service from their
utility.

--
bud--

On 1/16/2011 11:36 AM, zzzzzzzzzz wrote:
On Sun, 16 Jan 2011 09:27:59 -0500, Jeff wrote:

On 1/15/2011 6:30 PM, zzzzzzzzzz wrote:
On Sat, 15 Jan 2011 17:03:24 -0600, wrote:

zzzzzzzzzz wrote:
...

How thinketh thou so?

Math engineering
...

I didn't see the above mind-boggler earlier...

It (application of math) is pretty much the definition of engineering...

What a bull****ter.


Do you have a degree in engineering? Most of the courses are math.
Been there, done that.

Yes. ...and 37 years experience as a design engineer.

A 180 degree (pi radians, one half circle) out of phase sine wave is
identical to an inverted sine wave. One half cycle is by *definition*
180 degrees. The math, if you had any regard for it, is very simple.

That's not the point. It is *ONE* phase that has been split in two by a
transformer's center tap. It is properly called "split-phase".

Call it whatever you like. I have no argument with "split-phase", but
the discussion was over the phase difference and the application
thereof. - sin(t) is indistinguishable to sin(t + pi) for sine waves

Two-phase is
something entirely different, which if you didn't get your "degree" from a
Cracker Jax box, you'd know.

If you want to throw out science and math, then we really have
nothing further to discuss here.

You generally don't.

And all your arguments are ending the same way. With insults.

Feel better now?

Jeff

On Sun, 16 Jan 2011 10:39:51 -0600, bud-- wrote:

wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.


In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.

Simpler, I agree. Whether or not the volume (of single-phase) motors exceeds
the difference in complexity is the question. Also, I suppose, it depends on
who's buying (in what quantity - inventory costs as well as manufacturing).

It's a matter of semantics, I know, but the 120+120=240 system we've
been discussing actually is a 2-phase system, even though it's not
really called that. One side is 180° out of phase with the other side,
so by definition you have a 2-phase system.
It is indeed. The main advantage here is that you can combine the phases
to get a higher voltage. Less current. A 120V dryer would take some
hefty wiring.
You combine a 120V transformer winding with another 120V transformer
winding that is in-phase to get 240V. In fact, as everyone knows, it is
a single winding with a center tap.

You won't find an electrical engineer for power systems who will say
120/240V is not single phase. You are not likely to find an electrician
that deals with 3-phase who says 120/240V is not single phase. Wikipedia
is not likely to say 120/240 is 2-phase.

Only because it's not. ;-)

Fans of "2-phase" could ask for a 120/240 2-phase service from their
utility.

;-)

On Sun, 16 Jan 2011 12:28:27 -0500, Jeff Thies wrote:

On 1/16/2011 11:36 AM, zzzzzzzzzz wrote:
On Sun, 16 Jan 2011 09:27:59 -0500, Jeff wrote:

On 1/15/2011 6:30 PM, zzzzzzzzzz wrote:
On Sat, 15 Jan 2011 17:03:24 -0600, wrote:

zzzzzzzzzz wrote:
...

How thinketh thou so?

Math engineering
...

I didn't see the above mind-boggler earlier...

It (application of math) is pretty much the definition of engineering...

What a bull****ter.


Do you have a degree in engineering? Most of the courses are math.
Been there, done that.

Yes. ...and 37 years experience as a design engineer.

A 180 degree (pi radians, one half circle) out of phase sine wave is
identical to an inverted sine wave. One half cycle is by *definition*
180 degrees. The math, if you had any regard for it, is very simple.

That's not the point. It is *ONE* phase that has been split in two by a
transformer's center tap. It is properly called "split-phase".

Call it whatever you like. I have no argument with "split-phase", but
the discussion was over the phase difference and the application
thereof. - sin(t) is indistinguishable to sin(t + pi) for sine waves

There's that Cracker Jax degree talking again. As "bud--" says, ask your
power company for "two-phase power" and see what you get.

Two-phase is
something entirely different, which if you didn't get your "degree" from a
Cracker Jax box, you'd know.

If you want to throw out science and math, then we really have
nothing further to discuss here.

You generally don't.

And all your arguments are ending the same way. With insults.

Just speaking the truth.

Feel better now?

Talking to an idiot? Nah, it's a dirty job.

On Jan 16, 11:39*am, bud-- wrote:
wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. *One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The *voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.



In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.





It's a matter of semantics, I know, but the 120+120=240 system we've
been discussing actually is a 2-phase system, even though it's not
really called that. One side is 180° out of phase with the other side,
so by definition you have a 2-phase system.
It is indeed. The main advantage here is that you can combine the phases
to get a higher voltage. Less current. A 120V dryer would take some
hefty wiring.
You combine a 120V transformer winding with another 120V transformer
winding that is in-phase to get 240V. In fact, as everyone knows, it is
a single winding with a center tap.

You won't find an electrical engineer for power systems who will say
120/240V is not single phase. You are not likely to find an electrician
that deals with 3-phase who says 120/240V is not single phase. Wikipedia
is not likely to say 120/240 is 2-phase.

Only because it's not. *;-)

Fans of "2-phase" could ask for a 120/240 2-phase service from their
utility.

--
bud--

Bud
Would you please guide me out of this morass these folks have
constructed for themselves. You know how the dry transformers that we
install all the time have output voltage selection taps to compensate
for the variations in utility input voltage so we still end up with
120 volts for the general purpose receptacles? What do you say we wire
one with a conductor off of each voltage selection tap. Do we know
have six phase or eight phase. Dam I cant keep my tongue that far out
in my cheek without it starting to hurt.

I just thought of another question for the two phase crowd. How many
phases on the output of a high leg center tapped phase delta
transformer? By there logic it must be four. Dam my cheek is
starting to hurt again!
--
Tom Horne

"This alternating current stuff is just a fad. It is much too
dangerous for general use." Thomas Alva Edison

On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman
wrote:

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you have
the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center, you
still have 240 total, but the fraction of 240 changes as you move the
center tap.

This sentence is the one that doesn't ring true.
"The two insulated wires each carry 120 volts, but they are 180
degrees out of phase so the difference between them is 240 volts. "


Ok everyone. Without any explanations included. Weigh in on the
final answer. In phase or 180 out? You are allowed only yes or no.
Is the sentence in question correct?

I vote no.

On Sun, 16 Jan 2011 14:22:42 -0500, Metspitzer
wrote:

On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman
wrote:

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you have
the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center, you
still have 240 total, but the fraction of 240 changes as you move the
center tap.

This sentence is the one that doesn't ring true.
"The two insulated wires each carry 120 volts, but they are 180
degrees out of phase so the difference between them is 240 volts. "


Ok everyone. Without any explanations included. Weigh in on the
final answer. In phase or 180 out? You are allowed only yes or no.
Is the sentence in question correct?

I vote no.

I forgot to include my tag line.........
If you can't dazzle them with brilliants, baffle them with bull****.

On Sun, 16 Jan 2011 11:31:08 -0600, "
wrote:

On Sun, 16 Jan 2011 10:39:51 -0600, bud-- wrote:

wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.


In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.

Simpler, I agree. Whether or not the volume (of single-phase) motors exceeds
the difference in complexity is the question. Also, I suppose, it depends on
who's buying (in what quantity - inventory costs as well as manufacturing).


Well, all I know is I can buy 2HP 3 phase motors for considerably
lower cost than 2HP single phase here in Waterloo and they are
generally smaller as well. When you get to 5HP and higher, the
difference REALLY becomes obvious.
Not sure how 1/2 HP compares.

Also, lots of decent used 3 phase motors are available CHEAP, while
good used single phase are less common (because 3 phase only burn out
or need bearings, while single phase can also have starter problems,
bad caps, etc - and are also more prone to burning out when starter
problems occur.)

On Sun, 16 Jan 2011 14:22:42 -0500, Metspitzer
wrote:

On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman
wrote:

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you have
the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center, you
still have 240 total, but the fraction of 240 changes as you move the
center tap.

This sentence is the one that doesn't ring true.
"The two insulated wires each carry 120 volts, but they are 180
degrees out of phase so the difference between them is 240 volts. "


Ok everyone. Without any explanations included. Weigh in on the
final answer. In phase or 180 out? You are allowed only yes or no.
Is the sentence in question correct?

I vote no.
no

On Sun, 16 Jan 2011 15:23:20 -0500, wrote:

On Sun, 16 Jan 2011 11:31:08 -0600, "
wrote:

On Sun, 16 Jan 2011 10:39:51 -0600, bud-- wrote:

wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.


In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.

Simpler, I agree. Whether or not the volume (of single-phase) motors exceeds
the difference in complexity is the question. Also, I suppose, it depends on
who's buying (in what quantity - inventory costs as well as manufacturing).


Well, all I know is I can buy 2HP 3 phase motors for considerably
lower cost than 2HP single phase here in Waterloo and they are
generally smaller as well. When you get to 5HP and higher, the
difference REALLY becomes obvious.
Not sure how 1/2 HP compares.

Fractional-HP motors are what I was really thinking about. Certainly above a
couple of HP the numbers go the other way. A single-phase 100HP motor would
be a rare thing indeed. ;-)

Also, lots of decent used 3 phase motors are available CHEAP, while
good used single phase are less common (because 3 phase only burn out
or need bearings, while single phase can also have starter problems,
bad caps, etc - and are also more prone to burning out when starter
problems occur.)

A lot of those things that burn out on a fractional-HP motor are pretty easy
to fix, making the motors a lot cheaper (scrap yard cheap).

On Sun, 16 Jan 2011 15:30:48 -0600, "
wrote:

On Sun, 16 Jan 2011 15:23:20 -0500, wrote:

On Sun, 16 Jan 2011 11:31:08 -0600, "
wrote:

On Sun, 16 Jan 2011 10:39:51 -0600, bud-- wrote:

wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.


In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.

Simpler, I agree. Whether or not the volume (of single-phase) motors exceeds
the difference in complexity is the question. Also, I suppose, it depends on
who's buying (in what quantity - inventory costs as well as manufacturing).


Well, all I know is I can buy 2HP 3 phase motors for considerably
lower cost than 2HP single phase here in Waterloo and they are
generally smaller as well. When you get to 5HP and higher, the
difference REALLY becomes obvious.
Not sure how 1/2 HP compares.

Fractional-HP motors are what I was really thinking about. Certainly above a
couple of HP the numbers go the other way. A single-phase 100HP motor would
be a rare thing indeed. ;-)

Also, lots of decent used 3 phase motors are available CHEAP, while
good used single phase are less common (because 3 phase only burn out
or need bearings, while single phase can also have starter problems,
bad caps, etc - and are also more prone to burning out when starter
problems occur.)

A lot of those things that burn out on a fractional-HP motor are pretty easy
to fix, making the motors a lot cheaper (scrap yard cheap).
When a 3 phase motor ends up in the scrapyard because it outlasted
the machine it was on, you only need, at worst, a pair of bearings.
When a single phase motor ends up in the scrapyard you likely need a
$16 starting cap as well as the bearings - and may also need to
cleen/repair the starting switch.

The big problem is you need a 3 phase supply to run the 3 phase motor
- and outside of industrial plants 3 phase is "relatively" rare.

On Sun, 16 Jan 2011 16:55:12 -0500, wrote:

On Sun, 16 Jan 2011 15:30:48 -0600, "
wrote:

On Sun, 16 Jan 2011 15:23:20 -0500, wrote:

On Sun, 16 Jan 2011 11:31:08 -0600, "
wrote:

On Sun, 16 Jan 2011 10:39:51 -0600, bud-- wrote:

wrote:
On Sat, 15 Jan 2011 10:48:33 -0600, bud-- wrote:

Jeff Thies wrote:
On 1/13/2011 4:36 PM, David Nebenzahl wrote:
On 1/12/2011 7:22 PM Ralph Mowery spake thus:

"Dean Hoffman" wrote in message
...

Metspitzer wrote:

It is considered single phase. If you remove the center tap, you
have the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center,
you still have 240 total, but the fraction of 240 changes as you
move the center tap.
This sentence is the one that doesn't ring true. "The two insulated
wires each carry 120 volts, but they are 180 degrees out of phase
so the difference between them is 240 volts. "
The common 240 volt system in the US is only single phase. A true 2
phase system will have the the voltages only 90 deg out of phase. In a
240 volt single phase system , the center, neutral or whatever you
want to call the wire will carry only the unballanced currents and can
be the same size as the other two wires. A true 2 phase system usually
has 4 wires, but it it is wired up with only 3 wires, the 'center'
wire has to be the largest wire.

There are always some on here that do not understand the differance in
a split phase 120/240 volts system ususally used in the homes and a
true 2 phase system. I doubt that hardly anyone here has seem a true 2
phase power system.
I haven't seen one.
(Weren't the original Westinghouse/Tesla AC generators at Niagara falls
2-phase?)

I have seen Scott (or T connected) small 3 phase transformers that
essentially convert 3-phase to 2-phase to 3-phase (2 transformers for
480/277 to 308/277).

A Scott-T needs two phases to get a third. One split phase won't do it.

For a 3-phase transformer, you use 2 transformers in a Scott connection
for the primary, and with a Scott connection on the secondaries. The
primary is 3-phase. The secondary is also 3-phase. The voltage in the
transformers is at 90 degrees - 2-phase. A disadvantage is the
transformer currents are not in phase with the voltage so the
transformers can't be used at their full rating. It is practical for
small 3-phase transformers.


In particular starting torque. All motors need a push in the right
direction to get them going. Often this is an artificial phase made by
the starting cap. You really want 3 phase for the big motors. In fact
the power company generates 3 phase power (sort of the reverse of a
synchronous motor), barring electronic means it is hard to get otherwise.

Three phase motors are probably cheaper than single phase starting at
somewhere less than 1 HP.

Simpler, but I doubt cheaper (volume).

I am too lazy to look up prices (which also requires matching quality).
My notes say over a 1/2 HP motor is cheaper in 3-phase. You don't need a
winding that is only used to start the motor. And you don't need the
start switch paraphernalia and often a capacitor. Motor control is
likely more expensive.

Simpler, I agree. Whether or not the volume (of single-phase) motors exceeds
the difference in complexity is the question. Also, I suppose, it depends on
who's buying (in what quantity - inventory costs as well as manufacturing).


Well, all I know is I can buy 2HP 3 phase motors for considerably
lower cost than 2HP single phase here in Waterloo and they are
generally smaller as well. When you get to 5HP and higher, the
difference REALLY becomes obvious.
Not sure how 1/2 HP compares.

Fractional-HP motors are what I was really thinking about. Certainly above a
couple of HP the numbers go the other way. A single-phase 100HP motor would
be a rare thing indeed. ;-)

Also, lots of decent used 3 phase motors are available CHEAP, while
good used single phase are less common (because 3 phase only burn out
or need bearings, while single phase can also have starter problems,
bad caps, etc - and are also more prone to burning out when starter
problems occur.)

A lot of those things that burn out on a fractional-HP motor are pretty easy
to fix, making the motors a lot cheaper (scrap yard cheap).
When a 3 phase motor ends up in the scrapyard because it outlasted
the machine it was on, you only need, at worst, a pair of bearings.
When a single phase motor ends up in the scrapyard you likely need a
$16 starting cap as well as the bearings - and may also need to
cleen/repair the starting switch.

$16 is still a cheap motor.

The big problem is you need a 3 phase supply to run the 3 phase motor
- and outside of industrial plants 3 phase is "relatively" rare.

A lot of woodworkers use a three-phase motor as a rotary converter.

On 1/16/2011 8:36 AM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 09:27:59 -0500, Jeff Thies
wrote:

On 1/15/2011 6:30 PM, zzzzzzzzzz wrote:

On Sat, 15 Jan 2011 17:03:24 -0600, wrote:

zzzzzzzzzz wrote: ...

How thinketh thou so?

Math engineering
...

I didn't see the above mind-boggler earlier...

It (application of math) is pretty much the definition of
engineering...

What a bull****ter.

Do you have a degree in engineering? Most of the courses are math.
Been there, done that.

Yes. ...and 37 years experience as a design engineer.

A 180 degree (pi radians, one half circle) out of phase sine wave
is identical to an inverted sine wave. One half cycle is by
*definition* 180 degrees. The math, if you had any regard for it,
is very simple.

That's not the point. It is *ONE* phase that has been split in two by
a transformer's center tap. It is properly called "split-phase".
Two-phase is something entirely different, which if you didn't get
your "degree" from a Cracker Jax box, you'd know.

OK, I know this has devolved into a semantic argument, but you're really
giving us a distinction without a difference.

By now we all know that what is *called* 2-phase electric service is
that obsolete arrangement with one phase lagging the other by 90°. Fair
enough.

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or not it
is usually called that (yes, it's called "split phase").

Look at it this way: with 3-phase service, there are 3 separate phase
conductors, each with 60-cycle AC starting at a different point: 0°,
120° and 240°, right? With the transformer, there are 2 conductors with
two phases: 0° and 180°. So how is this any different from the 3-phase
system (let's assume that the 3-phase setup comes with a common ground
conductor). One has the phases 120° apart, the other 180° apart. In both
cases, there are multiple conductors with different phases of the same
frequency current. Right? (You could just as well have 4 phases 90°
apart or 6 phases 60° apart, if you wanted to stretch the example.)

You seem to object to calling the center-tapped transformer "2-phase"
because you say that one side is just the inverse of the other (negative
when the other side is positive and vice versa), but hey, that's what
you get with a 180° phase shift, right? Can you say "push-pull amplifier"?

So just to be absolutely clear: a center-tapped transformer with all 3
conductors feeding circuits is not normally *called* "2-phase" power; it
is in fact, however, delivering 2-phase power.

I look forward to your argument to this.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

David Nebenzahl wrote:

OK, I know this has devolved into a semantic argument, but you're really
giving us a distinction without a difference.

By now we all know that what is *called* 2-phase electric service is
that obsolete arrangement with one phase lagging the other by 90°. Fair
enough.

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or not it
is usually called that (yes, it's called "split phase").

Look at it this way: with 3-phase service, there are 3 separate phase
conductors, each with 60-cycle AC starting at a different point: 0°,
120° and 240°, right? With the transformer, there are 2 conductors with
two phases: 0° and 180°. So how is this any different from the 3-phase
system (let's assume that the 3-phase setup comes with a common ground
conductor). One has the phases 120° apart, the other 180° apart. In both
cases, there are multiple conductors with different phases of the same
frequency current. Right? (You could just as well have 4 phases 90°
apart or 6 phases 60° apart, if you wanted to stretch the example.)

You seem to object to calling the center-tapped transformer "2-phase"
because you say that one side is just the inverse of the other (negative
when the other side is positive and vice versa), but hey, that's what
you get with a 180° phase shift, right? Can you say "push-pull amplifier"?

So just to be absolutely clear: a center-tapped transformer with all 3
conductors feeding circuits is not normally *called* "2-phase" power; it
is in fact, however, delivering 2-phase power.

I look forward to your argument to this.


It's been awhile since I asked any silly questions. Probably at
least two minutes so I'm behind on my quota. Isn't the distinction
also about timing? There is no time with three phase power when the
voltage is zero on all three lines. There is in single phase.
Did that happen with the old two phase systems?

On Jan 17, 6:46*am, Dean Hoffman wrote:
David Nebenzahl wrote:
OK, I know this has devolved into a semantic argument, but you're really
giving us a distinction without a difference.

By now we all know that what is *called* 2-phase electric service is
that obsolete arrangement with one phase lagging the other by 90 . Fair
enough.

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or not it
is usually called that (yes, it's called "split phase").

Look at it this way: with 3-phase service, there are 3 separate phase
conductors, each with 60-cycle AC starting at a different point: 0 ,
120 and 240 , right? With the transformer, there are 2 conductors with
two phases: 0 and 180 . So how is this any different from the 3-phase
system (let's assume that the 3-phase setup comes with a common ground
conductor). One has the phases 120 apart, the other 180 apart. In both
cases, there are multiple conductors with different phases of the same
frequency current. Right? (You could just as well have 4 phases 90
apart or 6 phases 60 apart, if you wanted to stretch the example.)

You seem to object to calling the center-tapped transformer "2-phase"
because you say that one side is just the inverse of the other (negative
when the other side is positive and vice versa), but hey, that's what
you get with a 180 phase shift, right? Can you say "push-pull amplifier"?

So just to be absolutely clear: a center-tapped transformer with all 3
conductors feeding circuits is not normally *called* "2-phase" power; it
is in fact, however, delivering 2-phase power.

I look forward to your argument to this.

* * * It's been awhile since I asked any silly questions. *Probably at
least two minutes so I'm behind on my quota. * Isn't the distinction
also about timing? * There is no time with three phase power when the
voltage is zero on all three lines. * There is in single phase.
Did that happen with the old two phase systems?- Hide quoted text -

- Show quoted text -

My understanding is that the ancient two phase had a phase difference
of 90 deg, so there would also not be any time when there is no
voltage
difference between the conductors.

I have to join dpb, David, and Jeff in saying that krw is totally
wrong.

To address some of the specifics:

krw: "No they,(2 hots in 240V service) in fact, aren't. One is the
negative of the other. "

One is the negative of the other and it's also 180deg out of phase
with the other.
Take a sine wave centered around zero, shift it by 180deg and it
becomes the
negative of the other.


From dpb: "There are two meanings of "phase" here which is the
difficulty in common
usage. The generation is indeed a single electrical phase; the two
derived currents are out of phase (in time) with each other. "

I said about the same thing many posts ago. Is the 240V service in
use today
generally referred to as two phase? No. Is it the same as the
ancient two
phase system that was referred to that way? No, because there the
phases
differed by 90deg. What is the phase relationship between the two
hots in
today's 240V service? They have a phase difference of 180deg.


" No they, in fact, aren't. One is the negative of the other.

Which is the same as a time phase shift of pi radians.

To see so (in Matlab)

Matlab is wrong. "

Explain then how that is. If I have 3 signals that are 120 deg out
of
phase, krw agrees that consists of 3 phases. Apparently
he agrees that the ancient 2 phase system, where the phase difference
was 90deg, consists of 2 phases. So, why exactly if we have a system
where there are two conductors, one of which is 180deg out of phase
with the other, does it no longer qualify as consisting of 2 phases?

It's merely a special case of phase difference, where they happen to
be 180deg out of phase and one is the direct opposite of the other.
Try this mental experiment. Take two identical signals that are in
phase,
ie the phase difference is zero. Start adding phase shift, 1 deg at
a
time. Do you not now have a system with two phases? Continue
until you have 180 deg of phase shift. Why now are there not still
two phases?

Answer: In fact there are, it's just a special case where one can now
be called the opposite or negative of the other.

"Of course, because one "leads" the other by pi radians...

krw: Wrong, obviously. "

Actually it's absolutely correct. I also don't understand the
comment:

"Math engineering"

A core component of electrical engineering is math. Most of the
courses
are heavily math oriented. And the math engineers
use is the same as the math everyone else uses. And the phase
relationship
of two signals would be described the same by anyone using math.

krw: "Nope. Define CT as zero. The signals at each end are the same
but opposite
sign"

Geez, opposite sign is exactly how you get 180deg phase difference.


"Not "source", simply a demonstration of how the phase shift leads to
the
apparent negation of a sine wave.

Complete bull****. "


I'm a degreed Electrical Engineer, and it isn't BS to me. If you take
a signal centered
around zero volts, and another one in the same system that is also
centered around
zero volts, but is 180 deg out of phase and they share that common
zero volt referrence,
then:

One leads the other by 180deg
One lags the other by 180deg
One is the opposite of the other
One is the negative of the other.
You have two phases

That is exactly what you have with a 240V service. Is it generally
referred to as a two
phase system? No. Probably because it can be generated off of ONE
phase coming
from the power plant via a center tap transformer. But how I generate
it matters not a wit.
KRW, ask yourself this. You say you're an engineer. Here's a
simple test:

1 - I have a graph of what we all have
been describing, what I outlined above. Two sine waves on a graph,
both centered
around the zero voltage axis, both from the same system. One is
shifted by 90 deg
from the other. How many phases are there in this system?

2 - Same graph, but now one is shifted by 180 deg from the other. How
many phases
in this system?

3- Same graph, but now I have 3 sine waves, one shifted by 90, one by
180. How
many phases in this system?

My answer, and I think the answer from all other 3 who disagree with
you would be:

two
two
three

On Jan 16, 4:23*pm, wrote:
On Sun, 16 Jan 2011 14:22:42 -0500, Metspitzer
wrote:





On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman
wrote:

Metspitzer wrote:

It is considered single phase. *If you remove the center tap, you have
the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center, you
still have 240 total, but the fraction of 240 changes as you move the
center tap.

* *This sentence is the one that doesn't ring true.
* "The two insulated wires each carry 120 volts, but they are 180
degrees out of phase so the difference between them is 240 volts. "

Ok everyone. *Without any explanations included. *Weigh in on the
final answer. *In phase or 180 out? *You are allowed only yes or no.
Is the sentence in question correct?

I vote no.

no- Hide quoted text -

- Show quoted text -

Unbelievable. People are actually replying and answering this stupid
question
without apparently even realizing that the question already answered
itself. Did it not state: ""The two insulated wires each carry
120 volts, but they are 180
degrees out of phase "? Beyond that, it wants a yes or no answer to
something
that is mutually exclusive, ie "In phase or out?" How the hell do
you guys answer
that with a yes or no?

The problem some of you are having is understanding the difference
between
what something may be commonly called by those in the trade and the
engineering
concepts and definitions of systems, phase, etc.

And in the case of 240V service in your house, the answers you seek
a

Q What is the phase relationship of the two hots?
A They are 180deg out of phase with each other

Q Does it matter how that phase difference was achieved?
A No, from an electrical engineering perspective, we just need to look
at the voltage waveforms and current flow on the service cable. Plot
the waveform
on a graph paper and you have your answer.

Q Is this commony called a two phase system?
A No. Probably because it's created by a transformer that uses one of
the three
phases generated by the power plant.

On Mon, 17 Jan 2011 06:47:54 -0800 (PST), wrote:

On Jan 16, 4:23*pm, wrote:
On Sun, 16 Jan 2011 14:22:42 -0500, Metspitzer
wrote:





On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman
wrote:

Metspitzer wrote:

It is considered single phase. *If you remove the center tap, you have
the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center, you
still have 240 total, but the fraction of 240 changes as you move the
center tap.

* *This sentence is the one that doesn't ring true.
* "The two insulated wires each carry 120 volts, but they are 180
degrees out of phase so the difference between them is 240 volts. "

Ok everyone. *Without any explanations included. *Weigh in on the
final answer. *In phase or 180 out? *You are allowed only yes or no.
Is the sentence in question correct?

I vote no.

no- Hide quoted text -

- Show quoted text -

Unbelievable. People are actually replying and answering this stupid
question
without apparently even realizing that the question already answered
itself. Did it not state: ""The two insulated wires each carry
120 volts, but they are 180
degrees out of phase "? Beyond that, it wants a yes or no answer to
something
that is mutually exclusive, ie "In phase or out?" How the hell do
you guys answer
that with a yes or no?

The problem some of you are having is understanding the difference
between
what something may be commonly called by those in the trade and the
engineering
concepts and definitions of systems, phase, etc.

And in the case of 240V service in your house, the answers you seek
a

Q What is the phase relationship of the two hots?
A They are 180deg out of phase with each other

Q Does it matter how that phase difference was achieved?
A No, from an electrical engineering perspective, we just need to look
at the voltage waveforms and current flow on the service cable. Plot
the waveform
on a graph paper and you have your answer.

Q Is this commony called a two phase system?
A No. Probably because it's created by a transformer that uses one of
the three
phases generated by the power plant.

It was defined to me some 30 years ago, but what I came away with was
that it is "in phase" if the voltage and current reach peak and 0 at
the same instant. That is what I understand a single phase
transformer does. (Ignore capacitance and inductance)

wrote:

I'm a degreed Electrical Engineer, and it isn't BS to me. If you take
a signal centered
around zero volts, and another one in the same system that is also
centered around
zero volts, but is 180 deg out of phase and they share that common
zero volt referrence,
then:

One leads the other by 180deg
One lags the other by 180deg
One is the opposite of the other
One is the negative of the other.
You have two phases


Nobody I know would call 120/240 2-phase. You wouldn't buy a single core
transformer and specify whether it is in-phase or 180 degrees out of
phase. You don't get multiple phases out of a single transformer. If you
ask for a 2-phase transformer you will completely confuse the
transformer rep.

Analysis of real multiphase electricity commonly uses phasor analysis,
using SQR(-1).

A simple 120/240V system is single phase with the math handled with
*trivial* plus and minus signs. "2-phases" confuses trivial math.
Calling it 2-phase confuses communication with anyone who understands
multiphase power systems.

If 120/240 is 2-phase, then single phase has no particularly useful meaning.

If you tell a utility you want a 120/240V 2-phase service what will they
say? That is after they stop laughing.

--------------------
I never heard 120/240 called split phase either. A wiki article says it
is. But the article also says 120/240 "it is sometimes incorrectly
referred to as 'two phase'"

--
bud--

On Jan 17, 12:51*pm, bud-- wrote:
wrote:

I'm a degreed Electrical Engineer, and it isn't BS to me. *If you take
a signal centered
around zero volts, and another one in the same system that is also
centered around
zero volts, but is 180 deg out of phase and they share that common
zero volt referrence,
then:

One leads the other by 180deg
One lags the other by 180deg
One is the opposite of the other
One is the negative of the other.
You have two phases

Nobody I know would call 120/240 2-phase. You wouldn't buy a single core
transformer and specify whether it is in-phase or 180 degrees out of
phase. You don't get multiple phases out of a single transformer. If you
ask for a 2-phase transformer you will completely confuse the
transformer rep.

Analysis of real multiphase electricity commonly uses phasor analysis,
using SQR(-1).

A simple 120/240V system is single phase with the math handled with
*trivial* plus and minus signs. "2-phases" confuses trivial math.

Whether 2 phases confuses anyone or not has no bearing on the fact
that
there are two phases. I could describe many physical processes by
either
very simple terms or varying degrees of complexity. When looking at
electrical waveforms, that trivial plus and minus sign can equate to
being
described as 180deg out of phase.

I noticed you didn't specifically refute any of the statements:

One leads the other by 180deg
One lags the other by 180deg
One is the opposite of the other
One is the negative of the other.
You have two phases




Calling it 2-phase confuses communication with anyone who understands
multiphase power systems.

I never said to call it 2-phase power, nor do I recall anyone else
here really doing so.
A couple of us have said consistently that while you can view a 240V
service
as having two phases that are 180 deg out of phase with each other,
that
terminology is not commonly used to refer to the actual service.



If 120/240 is 2-phase, then single phase has no particularly useful meaning.

Let's get back to basics. The definition of phase and it's use in
electrical
engineering goes to the very roots of the discipline. IT doesn't
depend on
what terms people commonly call something. It doesn't depend on how
the
phases are generated. IT's not limited to only AC power systems.
I can take any linear system that has a sine wave going
into it and ask how many shifted sine waves of voltage are present
in that system and
what are their relationship to each other. I can ask a student to
plot the voltages
at various points in the system. Let's say I have a box with 3 wires
coming out.
Between A and C, there is one sine wave. Between B and C, there is an
identical sine wave, but it's shifted by 90deg. I ask, what is the
relationship
between them and how many different phases are present.

What would your answer be?

Now the same experiment, but with the sine waves shifted by 180deg
instead
of 90. Is the correct answer that it is now simply a plus and minus,
trivial
issue and there is only one phase present?




If you tell a utility you want a 120/240V 2-phase service what will they
say? That is after they stop laughing.

Again, neither I nor anyone else I believe, has called it "2 phase
service".
What common terms are used and what things really are, are two
different things.
If I told probably 1/4 of Americans that my son is a homosapien,
I'd get the same reaction because they don't even know what it means.
It doesn't make it untrue or not technically correct.



Unfortunately, I'm heading out for a few days. I'll have to pick back
up on this
later on.

On Jan 17, 12:27*pm, Metspitzer wrote:
On Mon, 17 Jan 2011 06:47:54 -0800 (PST), wrote:
On Jan 16, 4:23*pm, wrote:
On Sun, 16 Jan 2011 14:22:42 -0500, Metspitzer
wrote:

On Wed, 12 Jan 2011 20:54:48 -0600, Dean Hoffman
wrote:

Metspitzer wrote:

It is considered single phase. *If you remove the center tap, you have
the same thing on the primary as you do on the secondary.

If you chose to put the secondary tap anywhere but the center, you
still have 240 total, but the fraction of 240 changes as you move the
center tap.

* *This sentence is the one that doesn't ring true.
* "The two insulated wires each carry 120 volts, but they are 180
degrees out of phase so the difference between them is 240 volts. "

Ok everyone. *Without any explanations included. *Weigh in on the
final answer. *In phase or 180 out? *You are allowed only yes or no.
Is the sentence in question correct?

I vote no.

no- Hide quoted text -

- Show quoted text -

Unbelievable. * People are actually replying and answering this stupid
question
without apparently even realizing that the question already answered
itself. * *Did it not state: * ""The two insulated wires each carry
120 volts, but they are 180
degrees out of phase "? *Beyond that, it wants a yes or no answer to
something
that is mutually exclusive, ie "In phase or out?" * How the hell do
you guys answer
that with a yes or no?

The problem some of you are having is understanding the difference
between
what something may be commonly called by those in the trade and the
engineering
concepts and definitions of systems, phase, etc.

And in the case of 240V service in your house, the answers you seek
a

Q What is the phase relationship of the two hots?
A They are 180deg out of phase with each other

Q Does it matter how that phase difference was achieved?
A No, from an electrical engineering perspective, we just need to look
at the voltage waveforms and current flow on the service cable. *Plot
the waveform
on a graph paper and you have your answer.

Q Is this commony called a two phase system?
A No. *Probably because it's created by a transformer that uses one of
the three
phases generated by the power plant.

It was defined to me some 30 years ago, but what I came away with was
that it is "in phase" if the voltage and current reach peak and 0 at
the same instant. *That is what I understand a single phase
transformer does. *(Ignore capacitance and inductance)- Hide quoted text -

- Show quoted text -


What you are talking about is the relationship between voltage and
current.
If I put capacitance or inductance in a linear system, it changes the
phase
between the voltage and current. So, as you put it, they don't reach
peak or
zero at the same time. When plotted, the current and voltage are out
of
phase by a certain number of degrees. Whateve that shift is, you can
describe
it in degrees.

The phases under discussion here are pure voltage waveforms and are
present without even having a load. With a
240V service, you have identcial sine waves which are mirror images of
each other, between either hot and neutral. Take a sine wave and
shift
it by 180deg, ie one half cycle, and that is exactly what you have.
So, you
have two voltage waveforms that are 180 deg out of phase with each
other.
Hook up an oscilloscope and you can see it. Yet some are arguing
that this
then just becomes "it's just a negative", it's a case of plus and
minus, etc.
and can no longer be described as two phases which are 180 deg out of
phase.
Yet, there they are on an oscilloscope. Maybe someone can tell us
this:

I can see these two distinct phases on those 3 wires of the 240V
service with an oscilloscope.
With 3 phase, I could do the same thing on that service and see 3
different
phases, each seperated by 120 deg. Why is it that in the latter
case, those on
the other side of the argument here say there are 3 phases present,
but in the former,
there are but one, not the two on the oscilloscope? Posters dpb,
Jeff and David and myself
would describe both those services, their phases, in a consistent,
logical manner.


Usual disclaimer: I did not just say, nor have I ever said that a
240V service
is called a two phase service.

On 1/17/2011 6:26 AM spake thus:

David Nebenzahl wrote:

OK, I know this has devolved into a semantic argument, but you're
really giving us a distinction without a difference.

By now we all know that what is *called* 2-phase electric service
is that obsolete arrangement with one phase lagging the other by
90 . Fair enough.

But you really cannot argue that what one gets with a
center-tapped transformer actually is 2-phase current, regardless
of whether or not it is usually called that (yes, it's called
"split phase").

[snip]

My understanding is that the ancient two phase had a phase
difference of 90 deg, so there would also not be any time when there
is no voltage difference between the conductors.

I have to join dpb, David, and Jeff in saying that krw is totally
wrong.

[snip]

Thanks; I feel vindicated.

To throw out another example, I mentioned push-pull amplifiers in my
earlier reply. These are almost always preceded by a stage called a
phase splitter or phase inverter, which takes a signal and splits it
into two phases, one 180° from the other. Every electronics engineer in
the world would agree that this stage produces two distinct phases from
a single phase. Which is exactly what our center-tapped transformer does.

Again, just to make it crystal-clear, the electrical industry uses the
term "2-phase power" in a very specific way that does *not* include this
way of generating two phases. Nonetheless, it does generate two phases,
so technically speaking it is two-phase power.

Even if you would get laughed at by the power company for asking for a
2-phase transformer.

'K?


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

On 1/16/2011 8:36 AM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 09:27:59 -0500, Jeff Thies
wrote:

On 1/15/2011 6:30 PM, zzzzzzzzzz wrote:

On Sat, 15 Jan 2011 17:03:24 -0600, wrote:

zzzzzzzzzz wrote: ...

How thinketh thou so?

Math engineering
...

I didn't see the above mind-boggler earlier...

It (application of math) is pretty much the definition of
engineering...

What a bull****ter.

Do you have a degree in engineering? Most of the courses are math.
Been there, done that.

Yes. ...and 37 years experience as a design engineer.

A 180 degree (pi radians, one half circle) out of phase sine wave
is identical to an inverted sine wave. One half cycle is by
*definition* 180 degrees. The math, if you had any regard for it,
is very simple.

That's not the point. It is *ONE* phase that has been split in two by
a transformer's center tap. It is properly called "split-phase".
Two-phase is something entirely different, which if you didn't get
your "degree" from a Cracker Jax box, you'd know.

OK, I know this has devolved into a semantic argument, but you're really
giving us a distinction without a difference.

Bull****. The difference has been discussed here *MANY* times. You insist on
making the same old tired arguments.

By now we all know that what is *called* 2-phase electric service is
that obsolete arrangement with one phase lagging the other by 90°. Fair
enough.

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or not it
is usually called that (yes, it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

Look at it this way: with 3-phase service, there are 3 separate phase
conductors, each with 60-cycle AC starting at a different point: 0°,
120° and 240°, right? With the transformer, there are 2 conductors with
two phases: 0° and 180°. So how is this any different from the 3-phase
system (let's assume that the 3-phase setup comes with a common ground
conductor). One has the phases 120° apart, the other 180° apart. In both
cases, there are multiple conductors with different phases of the same
frequency current. Right? (You could just as well have 4 phases 90°
apart or 6 phases 60° apart, if you wanted to stretch the example.)

You seem to object to calling the center-tapped transformer "2-phase"
because you say that one side is just the inverse of the other (negative
when the other side is positive and vice versa), but hey, that's what
you get with a 180° phase shift, right? Can you say "push-pull amplifier"?

So just to be absolutely clear: a center-tapped transformer with all 3
conductors feeding circuits is not normally *called* "2-phase" power; it
is in fact, however, delivering 2-phase power.

I look forward to your argument to this.

Get a refund from Cracker Jax.

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or
not it is usually called that (yes, it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk sensibly
to this guy, at least for me.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

On Mon, 17 Jan 2011 17:03:30 -0800, David Nebenzahl
wrote:

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or
not it is usually called that (yes, it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk sensibly
to this guy, at least for me.
For what it's worth I agree with him. It is single phase. Calling it
anything else, other than perhaps split phase, is misleading and
in-accurate.

On Mon, 17 Jan 2011 17:03:30 -0800, David Nebenzahl
wrote:

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a center-tapped
transformer actually is 2-phase current, regardless of whether or
not it is usually called that (yes, it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk sensibly
to this guy, at least for me.

Another one who should get a refund from Cracker Jax.

On 1/17/2011 8:05 PM spake thus:

On Mon, 17 Jan 2011 17:03:30 -0800, David Nebenzahl
wrote:

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a
center-tapped transformer actually is 2-phase current,
regardless of whether or not it is usually called that (yes,
it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk
sensibly to this guy, at least for me.

For what it's worth I agree with him. It is single phase. Calling it
anything else, other than perhaps split phase, is misleading and
in-accurate.

Did you read my other replies? And trader4's replies (especially the
6:26 am one)?

Care to tell us how you figure that it's single phase? I'm interested in
hearing your reasoning.

Read his reply where he talks about adding phase shift a degree at a
time: that's the best explanation I've heard in this thread so far.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

wrote:
On Jan 17, 12:51 pm, bud-- wrote:
wrote:

I'm a degreed Electrical Engineer, and it isn't BS to me. If you take
a signal centered
around zero volts, and another one in the same system that is also
centered around
zero volts, but is 180 deg out of phase and they share that common
zero volt referrence,
then:
One leads the other by 180deg
One lags the other by 180deg
One is the opposite of the other
One is the negative of the other.
You have two phases
Nobody I know would call 120/240 2-phase. You wouldn't buy a single core
transformer and specify whether it is in-phase or 180 degrees out of
phase. You don't get multiple phases out of a single transformer. If you
ask for a 2-phase transformer you will completely confuse the
transformer rep.

Analysis of real multiphase electricity commonly uses phasor analysis,
using SQR(-1).

A simple 120/240V system is single phase with the math handled with
*trivial* plus and minus signs. "2-phases" confuses trivial math.

Whether 2 phases confuses anyone or not has no bearing on the fact
that
there are two phases. I could describe many physical processes by
either
very simple terms or varying degrees of complexity. When looking at
electrical waveforms, that trivial plus and minus sign can equate to
being
described as 180deg out of phase.

I noticed you didn't specifically refute any of the statements:

One leads the other by 180deg
One lags the other by 180deg
One is the opposite of the other
One is the negative of the other.
You have two phases

When the "phases" come from a single phase source (the utility
transformer), and one of the "phases" is the negative of the other,
calling them 2 phases makes no particular sense.

When I connect my 120-to-120V isolation transformer (for repairing
equipment) to one of the "phases" is the secondary the "A" phase or the
"B" phase?


If 120/240 is 2-phase, then single phase has no particularly useful meaning.

Let's get back to basics. The definition of phase and it's use in
electrical
engineering goes to the very roots of the discipline. IT doesn't
depend on
what terms people commonly call something. It doesn't depend on how
the
phases are generated. IT's not limited to only AC power systems.
I can take any linear system that has a sine wave going
into it and ask how many shifted sine waves of voltage are present
in that system and
what are their relationship to each other. I can ask a student to
plot the voltages
at various points in the system. Let's say I have a box with 3 wires
coming out.
Between A and C, there is one sine wave. Between B and C, there is an
identical sine wave, but it's shifted by 90deg. I ask, what is the
relationship
between them and how many different phases are present.

What would your answer be?

This, of course, comes from a multi-phase source.


Now the same experiment, but with the sine waves shifted by 180deg
instead
of 90. Is the correct answer that it is now simply a plus and minus,
trivial
issue and there is only one phase present?

The voltages come from a single phase source (the service transformer
primary is 2 wire). You get 2 phases from a single phase source?

The voltage on the secondary 2 wire combinations from that transformer
are locked into either a positive or negative relation to other 2 wire
combinations. When calculating currents in a 120/240V system with
resistive loads you use plus and minus signs. Calling it 2-phase adds
nothing useful and is not useful in calculations.

In the more general phasor calculations (which handle capacitance and
inductance), a 120/240V system is represented as +120 and -120V (both
"real").

Calling 120/240V "2-phase" makes as much sense as calling the old Edison
3-wire DC system 2-phase (at zero frequency).



Unfortunately, I'm heading out for a few days. I'll have to pick back
up on this
later on.

Have a good trip.

--
bud--

On 1/18/2011 9:49 AM bud-- spake thus:

wrote:

On Jan 17, 12:51 pm, bud-- wrote:

wrote:

I'm a degreed Electrical Engineer, and it isn't BS to me. If
you take a signal centered around zero volts, and another one
in the same system that is also centered around zero volts, but
is 180 deg out of phase and they share that common zero volt
referrence, then: One leads the other by 180deg One lags the
other by 180deg One is the opposite of the other One is the
negative of the other. You have two phases

Nobody I know would call 120/240 2-phase. You wouldn't buy a
single core transformer and specify whether it is in-phase or 180
degrees out of phase. You don't get multiple phases out of a
single transformer. If you ask for a 2-phase transformer you will
completely confuse the transformer rep.

Analysis of real multiphase electricity commonly uses phasor
analysis, using SQR(-1).

A simple 120/240V system is single phase with the math handled
with *trivial* plus and minus signs. "2-phases" confuses trivial
math.

Whether 2 phases confuses anyone or not has no bearing on the fact
that there are two phases. I could describe many physical
processes by either very simple terms or varying degrees of
complexity. When looking at electrical waveforms, that trivial
plus and minus sign can equate to being described as 180deg out of
phase.

I noticed you didn't specifically refute any of the statements:

One leads the other by 180deg One lags the other by 180deg One
is the opposite of the other One is the negative of the other.
You have two phases

When the "phases" come from a single phase source (the utility
transformer), and one of the "phases" is the negative of the other,
calling them 2 phases makes no particular sense.

When I connect my 120-to-120V isolation transformer (for repairing
equipment) to one of the "phases" is the secondary the "A" phase or
the "B" phase?

I guess I'd have to call that question a red herring.

In the case of a transformer such as you describe, presumably with no
center tap, then yes, there's only one phase. Only one set of conductors.

We're talking about something different: a center-tapped transformer,
such as the utility company uses to deliver what's typically called
"split-phase" power (i.e., 120-0-120).

There, you *do* have two phases.

The main objector in this discussion rejects this, apparently because
they don't consider the "inverse" of a phase (meaning a set of
conductors that's 180° out of phase with another set), to be a separate
phase. But it is.

It's just that this is not commonly *called* "2-phase power": that
refers to something else, specifically that obsolete system with one
phase 90° to the other that's been described here.

Again: the output of a center-tapped transformer, whatever its use, is
in fact 2 distinct and separate phases. But for some reason, it's not
called that.

Now, I look forward to *your* comments on my comments ...


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

On 1/17/2011 8:05 PM spake thus:

On Mon, 17 Jan 2011 17:03:30 -0800, David Nebenzahl
wrote:

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a
center-tapped transformer actually is 2-phase current,
regardless of whether or not it is usually called that (yes,
it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk
sensibly to this guy, at least for me.

For what it's worth I agree with him. It is single phase. Calling it
anything else, other than perhaps split phase, is misleading and
in-accurate.

Did you read my other replies? And trader4's replies (especially the
6:26 am one)?

Care to tell us how you figure that it's single phase? I'm interested in
hearing your reasoning.

Read his reply where he talks about adding phase shift a degree at a
time: that's the best explanation I've heard in this thread so far.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

Now, IF it was a 180 degree out of phase system instead of the
voltages of both adding, they would cancel. With the two lines
connected accross the load as above there would be NO current flow on
a straight resistive load without the neutral connected, because the
voltage would be the same at both ends of the string at the same time.
L1 and L2 would both be on the positive side of zero by the same
amount at the same time, and both be on the negative side of zero by
the same amount at the same time, so there would never be a potential
difference between the 2 lines, and therefor would never be a current
flow. Connecting the neutral would cause current to flow in both
loads, with the neutral carrying the full current of BOTH loads at the
same time.
And it would be IMPOSSIBLE to construct such a circuit using a simple
center tapped transformer, particularly a center tapped
autotransformer, which is the simplest way to illustrate the insanity
of it all.

If I grab my 240 volt Variac and center the moveable tap, connecting
120 volts between one end and the center tap I have 120 volts between
the center tap and either end, and 240 volts between the two ends.

It is single phase from one end to the other, no matter how you slice
it, and no matter how you attempt to twist it - and it is IDENTICAL to
the normal 120/240 domestic power as supplied throughout north america
and a large part of the rest of the world.

wrote:
On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

On 1/17/2011 8:05 PM spake thus:

On Mon, 17 Jan 2011 17:03:30 -0800, David Nebenzahl
wrote:

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a
center-tapped transformer actually is 2-phase current,
regardless of whether or not it is usually called that (yes,
it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk
sensibly to this guy, at least for me.

For what it's worth I agree with him. It is single phase. Calling it
anything else, other than perhaps split phase, is misleading and
in-accurate.

Did you read my other replies? And trader4's replies (especially the
6:26 am one)?

Care to tell us how you figure that it's single phase? I'm interested in
hearing your reasoning.

Read his reply where he talks about adding phase shift a degree at a
time: that's the best explanation I've heard in this thread so far.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

Now, IF it was a 180 degree out of phase system instead of the
voltages of both adding, they would cancel. With the two lines
connected accross the load as above there would be NO current flow on
a straight resistive load without the neutral connected, because the
voltage would be the same at both ends of the string at the same time.
L1 and L2 would both be on the positive side of zero by the same
amount at the same time, and both be on the negative side of zero by
the same amount at the same time, so there would never be a potential
difference between the 2 lines, and therefor would never be a current
flow. Connecting the neutral would cause current to flow in both
loads, with the neutral carrying the full current of BOTH loads at the
same time.
And it would be IMPOSSIBLE to construct such a circuit using a simple
center tapped transformer, particularly a center tapped
autotransformer, which is the simplest way to illustrate the insanity
of it all.

If I grab my 240 volt Variac and center the moveable tap, connecting
120 volts between one end and the center tap I have 120 volts between
the center tap and either end, and 240 volts between the two ends.

It is single phase from one end to the other, no matter how you slice
it, and no matter how you attempt to twist it - and it is IDENTICAL to
the normal 120/240 domestic power as supplied throughout north america
and a large part of the rest of the world.
Hi,
If you hook up dual trace 'scope on both end what do you see? Yheory vs.
real life situation can be different.

On Tue, 18 Jan 2011 13:11:16 -0700, Tony Hwang
wrote:



wrote:
On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

On 1/17/2011 8:05 PM spake thus:

On Mon, 17 Jan 2011 17:03:30 -0800, David Nebenzahl
wrote:

On 1/17/2011 3:50 PM zzzzzzzzzz spake thus:

On Sun, 16 Jan 2011 23:41:52 -0800, David Nebenzahl
wrote:

But you really cannot argue that what one gets with a
center-tapped transformer actually is 2-phase current,
regardless of whether or not it is usually called that (yes,
it's called "split phase").

Yes I can, and DID! It is *NOT* two-phase.

OK, folks, it's official; it's just not worth it trying to talk
sensibly to this guy, at least for me.

For what it's worth I agree with him. It is single phase. Calling it
anything else, other than perhaps split phase, is misleading and
in-accurate.

Did you read my other replies? And trader4's replies (especially the
6:26 am one)?

Care to tell us how you figure that it's single phase? I'm interested in
hearing your reasoning.

Read his reply where he talks about adding phase shift a degree at a
time: that's the best explanation I've heard in this thread so far.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

Now, IF it was a 180 degree out of phase system instead of the
voltages of both adding, they would cancel. With the two lines
connected accross the load as above there would be NO current flow on
a straight resistive load without the neutral connected, because the
voltage would be the same at both ends of the string at the same time.
L1 and L2 would both be on the positive side of zero by the same
amount at the same time, and both be on the negative side of zero by
the same amount at the same time, so there would never be a potential
difference between the 2 lines, and therefor would never be a current
flow. Connecting the neutral would cause current to flow in both
loads, with the neutral carrying the full current of BOTH loads at the
same time.
And it would be IMPOSSIBLE to construct such a circuit using a simple
center tapped transformer, particularly a center tapped
autotransformer, which is the simplest way to illustrate the insanity
of it all.

If I grab my 240 volt Variac and center the moveable tap, connecting
120 volts between one end and the center tap I have 120 volts between
the center tap and either end, and 240 volts between the two ends.

It is single phase from one end to the other, no matter how you slice
it, and no matter how you attempt to twist it - and it is IDENTICAL to
the normal 120/240 domestic power as supplied throughout north america
and a large part of the rest of the world.
Hi,
If you hook up dual trace 'scope on both end what do you see? Yheory vs.
real life situation can be different.
No it cannot in this case. What you see and how you interpret it CAN
be two different things, however.

On 1/18/2011 12:06 PM spake thus:

On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

Care to tell us how you figure that it's single phase? I'm
interested in hearing your reasoning.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

First of all, I give you points for a good example, a well-thought-out
reply and an A for effort here. But unfortunately, you're wrong. It's
pretty simple, really. Now let's see how well *I* do trying to explain why.

Using your example, if you did your experiment, everything would happen
just as you say it would. The 2 light bulbs connected between L1 and L2
would both light, and there would be no (or practically no) spark nor
change in their brightness if you connected and disconnected their
common connection to neutral. [1] So far, so good.

But your explanation is, well, wrong. Here's why:

L1 and L2 are, in fact, 180° out of phase, and therefore 2 separate
phases, with the neutral as the common between the two phases.

*IF* they werent'--IOW, if they were in phase, as you contend, then
there would be--could be--no current flow between them, ever. If they
were in phase, both L1 and L2 would be at their positive peak at the
same instant, at 0 volts at the same instant, and at their negative peak
at the same instant. Do you agree with this? (If this were the case,
then you could take 120 volts between either leg and neutral, but they
would be exactly in phase, so you couldn't do things like Edison
circuits, which depend on the two legs being 180° out of phase in order
to share the neutral, where the currents cancel because of the phase
difference.)

In order for there to be current flow between L1 and L2, one has to be
negative while the other is positive, and vice versa. With me here?

Now, if you just take L1 and L2 and forget about the neutral for a
second, then yes, that constitutes a single phase circuit of 240 volts
(nominal). No two phases there.

But if you consider L1, L2 *and* the neutral, then you definitely have
two phases, 180° apart. Consider the two sides (or phases) he one
goes from L1 to neutral, the other from L2 to neutral. Let's look at it
when L1 is at its positive peak; you have a positive potential between
L1 and neutral, right? At that same instant, L2 is at its negative peak,
so you have a *negative* potential between L2 and neutral. Am I not correct?

That, my friend, is the very definition of two completely separate and
distinct phases, right there in your very service panel.

I admit that things like this, simple as they may be, can be hard to
wrap one's head around. I have no problem with this one, but I get
confused by even simpler things. So you have my sympathies.

Does this change your perspective or not? Please rate this explanation
to our customer service representative.


[1] Ackshooly, this would depend on just how accurate the power
company's center tap is placed on their transformer. If the 2 sides are
out of balance by a few volts, you could get a tiny spark. Not sure what
their tolerances are here; probably pretty good, I'd guess.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

On Tue, 18 Jan 2011 13:26:24 -0800, David Nebenzahl
wrote:

On 1/18/2011 12:06 PM spake thus:

On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

Care to tell us how you figure that it's single phase? I'm
interested in hearing your reasoning.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

First of all, I give you points for a good example, a well-thought-out
reply and an A for effort here. But unfortunately, you're wrong. It's
pretty simple, really. Now let's see how well *I* do trying to explain why.

Using your example, if you did your experiment, everything would happen
just as you say it would. The 2 light bulbs connected between L1 and L2
would both light, and there would be no (or practically no) spark nor
change in their brightness if you connected and disconnected their
common connection to neutral. [1] So far, so good.

But your explanation is, well, wrong. Here's why:

L1 and L2 are, in fact, 180° out of phase, and therefore 2 separate
phases, with the neutral as the common between the two phases.

*IF* they werent'--IOW, if they were in phase, as you contend, then
there would be--could be--no current flow between them, ever. If they
were in phase, both L1 and L2 would be at their positive peak at the
same instant, at 0 volts at the same instant, and at their negative peak
at the same instant. Do you agree with this? (If this were the case,
then you could take 120 volts between either leg and neutral, but they
would be exactly in phase, so you couldn't do things like Edison
circuits, which depend on the two legs being 180° out of phase in order
to share the neutral, where the currents cancel because of the phase
difference.)

In order for there to be current flow between L1 and L2, one has to be
negative while the other is positive, and vice versa. With me here?

Now, if you just take L1 and L2 and forget about the neutral for a
second, then yes, that constitutes a single phase circuit of 240 volts
(nominal). No two phases there.

But if you consider L1, L2 *and* the neutral, then you definitely have
two phases, 180° apart. Consider the two sides (or phases) he one
goes from L1 to neutral, the other from L2 to neutral. Let's look at it
when L1 is at its positive peak; you have a positive potential between
L1 and neutral, right? At that same instant, L2 is at its negative peak,
so you have a *negative* potential between L2 and neutral. Am I not correct?
It is semantics, to a point. What you need to remember is it is NOT 2
separate power sources, as a real 2 phase or 3 phase (or any other
multi-phase) system is. What you have is a single source power. It is
generated as 3 "separate"phases by the power company, and each phase
of the 3 phase supply can be split off as a single phase. This single
phase is then "split" by center tapping the secondary of a
transformer.
This is CRITICAL in the definition of single/split phase vs 2 phase
power.
A 3 phase source is 3 separately generated power supplies,
synchronised but out of phase by an equal amount (equal to the result
of deviding 360 degrees by the number of phases) Each phase can be
separated from the other - and stand alone - and with 3 phase can be
connected delta or wye.
With 120/240 you COULD use 2 separate secondaries and connect them
either differetially or summarily (adding or subtracting) in for
either 240 or 0 volts, or in parallel. If paralleled they can also be
connected back to front, so to speak, which is effectively a short
circuit. A case could perhaps be made for calling THIS setup a 2 phase
system, but that would still be stretching things.


That, my friend, is the very definition of two completely separate and
distinct phases, right there in your very service panel.

Except as I have demonstrated they are NOT separate, and in the normal
"split phase" system, there is NO POINT where they ARE separate.

I admit that things like this, simple as they may be, can be hard to
wrap one's head around. I have no problem with this one, but I get
confused by even simpler things. So you have my sympathies.

And you have mine.

Does this change your perspective or not? Please rate this explanation
to our customer service representative.

Does not change my perspective at all.

[1] Ackshooly, this would depend on just how accurate the power
company's center tap is placed on their transformer. If the 2 sides are
out of balance by a few volts, you could get a tiny spark. Not sure what
their tolerances are here; probably pretty good, I'd guess.

And it depends a whole lot more on the "precision" of the incandescent
lamp manufacturer, as the load inballance is much more likely than the
power inballance.
It is not 2 phase, it is split phase.

David Nebenzahl wrote:
On 1/18/2011 9:49 AM bud-- spake thus:

wrote:

On Jan 17, 12:51 pm, bud-- wrote:

wrote:

I'm a degreed Electrical Engineer, and it isn't BS to me. If you
take a signal centered around zero volts, and another one in the
same system that is also centered around zero volts, but
is 180 deg out of phase and they share that common zero volt
referrence, then: One leads the other by 180deg One lags the other
by 180deg One is the opposite of the other One is the negative of
the other. You have two phases

Nobody I know would call 120/240 2-phase. You wouldn't buy a single
core transformer and specify whether it is in-phase or 180
degrees out of phase. You don't get multiple phases out of a single
transformer. If you ask for a 2-phase transformer you will
completely confuse the transformer rep.

Analysis of real multiphase electricity commonly uses phasor
analysis, using SQR(-1).

A simple 120/240V system is single phase with the math handled
with *trivial* plus and minus signs. "2-phases" confuses trivial
math.

Whether 2 phases confuses anyone or not has no bearing on the fact
that there are two phases. I could describe many physical
processes by either very simple terms or varying degrees of
complexity. When looking at electrical waveforms, that trivial
plus and minus sign can equate to being described as 180deg out of
phase.

I noticed you didn't specifically refute any of the statements:

One leads the other by 180deg One lags the other by 180deg One
is the opposite of the other One is the negative of the other. You
have two phases

When the "phases" come from a single phase source (the utility
transformer), and one of the "phases" is the negative of the other,
calling them 2 phases makes no particular sense.

When I connect my 120-to-120V isolation transformer (for repairing
equipment) to one of the "phases" is the secondary the "A" phase or
the "B" phase?

I guess I'd have to call that question a red herring.

It is a minor illustration that "2 phases" is not useful.

It makes no sense to say you get 2 phases out of what is obviously a
single-phase utility transformer.


In the case of a transformer such as you describe, presumably with no
center tap, then yes, there's only one phase. Only one set of conductors.

We're talking about something different: a center-tapped transformer,
such as the utility company uses to deliver what's typically called
"split-phase" power (i.e., 120-0-120).

There, you *do* have two phases.

From the wikipedia article
http://en.wikipedia.org/wiki/Split_phase
"it is sometimes incorrectly referred to as 'two phase'."
(The article also suggests split phase is not the best name because of
confusion with split-phase motors - which do start on 2-phases. I have
never heard "split-phase" used for a 120/240V service.)

You can invent your own language. Where is any reasonable source that
says a single phase transformer has 2 phases.


The main objector in this discussion rejects this, apparently because
they don't consider the "inverse" of a phase (meaning a set of
conductors that's 180° out of phase with another set), to be a separate
phase. But it is.

Not according to wikipedia.
Find a transformer manufacturer that says their single phase transformer
has secondaries that are 2 phases.


It's just that this is not commonly *called* "2-phase power": that
refers to something else, specifically that obsolete system with one
phase 90° to the other that's been described here.

Not *commonly* called 2-phase?
It is not *ever* called 2-phase. It is not a term used by any utility or
manufacturer.
It is a "single-phase" service, transformer, meter can, panel....


Again: the output of a center-tapped transformer, whatever its use, is
in fact 2 distinct and separate phases. But for some reason, it's not
called that.

Wow, progress. You are right - "it's not called that."

It is not called that because it makes no sense.
Voltages clearly comes from a single-phase transformer.
The voltages of any secondary windings are locked into plus or minus
relationships.
The secondary is trivially understood with plus and minus signs.
Calculations use plus and minus signs (not "phases").
Where inductance and capacitance are involved phasor analysis is used. A
120/240V service is characterized as +120 and -120.

It is not called that because it has no practical usefulness. (Except to
cause confusion.)

--
bud--

In ,
bud-- typed:
David Nebenzahl wrote:
On 1/18/2011 9:49 AM bud-- spake thus:

wrote:

....


Again: the output of a center-tapped transformer, whatever
its use, is in fact 2 distinct and separate phases. But
for some reason, it's not called that.

It's not called that because it is ONE phase coming from the powerco and is
split to make two 120Vac lines into the residence. Thus the proper term is
"split phase", not 2 phase. Although I hear 2 phase a lot, I know what
they'e talking about so it's NBD to me.


Wow, progress. You are right - "it's not called that."

It is not called that because it makes no sense.
Voltages clearly comes from a single-phase transformer.
The voltages of any secondary windings are locked into plus
or minus relationships.
The secondary is trivially understood with plus and minus
signs. Calculations use plus and minus signs (not "phases").
Where inductance and capacitance are involved phasor
analysis is used. A 120/240V service is characterized as
+120 and -120.
It is not called that because it has no practical
usefulness. (Except to cause confusion.)

Nah, it's just a bunch of egos here wanting to show how much they know and
hoping their guesses are right for the most part. This is a useless thread
with no useful information due to the interest in egoes rather than fact.
It's typical of this newsgroup for the last year or so in fact and does no
one any good. Post after post is filled with guesses and by gollies from
those who feel the need to confuse, not assist anyone.

HTH,

Twayne`

On Jan 18, 7:51*pm, wrote:
On Tue, 18 Jan 2011 13:26:24 -0800, David Nebenzahl





wrote:
On 1/18/2011 12:06 PM spake thus:

On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

Care to tell us how you figure that it's single phase? I'm
interested in hearing your reasoning.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

First of all, I give you points for a good example, a well-thought-out
reply and an A for effort here. But unfortunately, you're wrong. It's
pretty simple, really. Now let's see how well *I* do trying to explain why.

Using your example, if you did your experiment, everything would happen
just as you say it would. The 2 light bulbs connected between L1 and L2
would both light, and there would be no (or practically no) spark nor
change in their brightness if you connected and disconnected their
common connection to neutral. [1] So far, so good.

But your explanation is, well, wrong. Here's why:

L1 and L2 are, in fact, 180° out of phase, and therefore 2 separate
phases, with the neutral as the common between the two phases.

*IF* they werent'--IOW, if they were in phase, as you contend, then
there would be--could be--no current flow between them, ever. If they
were in phase, both L1 and L2 would be at their positive peak at the
same instant, at 0 volts at the same instant, and at their negative peak
at the same instant. Do you agree with this? (If this were the case,
then you could take 120 volts between either leg and neutral, but they
would be exactly in phase, so you couldn't do things like Edison
circuits, which depend on the two legs being 180° out of phase in order
to share the neutral, where the currents cancel because of the phase
difference.)

In order for there to be current flow between L1 and L2, one has to be
negative while the other is positive, and vice versa. With me here?

Now, if you just take L1 and L2 and forget about the neutral for a
second, then yes, that constitutes a single phase circuit of 240 volts
(nominal). No two phases there.

But if you consider L1, L2 *and* the neutral, then you definitely have
two phases, 180° apart. Consider the two sides (or phases) he one
goes from L1 to neutral, the other from L2 to neutral. Let's look at it
when L1 is at its positive peak; you have a positive potential between
L1 and neutral, right? At that same instant, L2 is at its negative peak,
so you have a *negative* potential between L2 and neutral. Am I not correct?

*It is semantics, to a point. What you need to remember is it is NOT 2
separate power sources, as a real 2 phase or 3 phase (or any other
multi-phase) system is. What you have is a single source power. It is
generated as 3 "separate"phases by the power company, and each phase
of the 3 phase supply can be split off as a single phase. This single
phase is then "split" by center tapping the secondary of a
transformer.
This is CRITICAL in the definition of single/split phase vs 2 phase
power.

It may be critical to the convention of what that 240V service is
commonly
called, but it doesn't alter the fact of how many distinct voltage
waveforms
are present. Going back to your example of the simple circuit with
two
balanced loads connected across the 240V hots, yes, in that case,
you have only one phase.
I cannot hook up an oscilloscope and see anything but one sine wave.
As soon as you introduce the neutral, now I can see TWO different sine
waves relative to the neutral, one being 180deg out of phase with the
other. That circuit can now be described as having two phases.

Suppose I take a black box that consists of various linear circuit
components
and is powered by a 120V AC outlet. Inside that box, I have a common
reference point.
I ask students in a first year electrical engineering course lab
experiment to
graph the voltages at circuit points A, B, and C relative to the
common
reference point. I have the circuit designed so that the waveform
at point B
lags the one at A by 30 degrees and the waveform at point C lags the
one at A
by 180 degrees. I ask thefollowing questions:

What is the phase relationship between waveforms A and B?

What is the phase realtionship between waveforms A and C?

How many different voltage phases are there in the black box
at points A, B, and C?

Do I need to know exactly how the voltages were generated, whether
it came from a wall outlet, battery/inverter, trnasformer etc to
answer any
of those questions?

What is your answer? Is it that there are 3 phases or is that there
can be only one, because it's originating from an outlet
that has only one phase?

If your answer is that there are 3 phases present, then continue to
the
next part. I have another black box that merely consists
of the 3 wire 240V service. The common reference
point is the neutral, point A is one hot, point B, the other hot.

What is the phase relationship between waveforms A and B?

How many phases are present?


Note the usual disclaimer. I did not just say, nor have I said
that the 240V service is commonly called two phase.

It's like I said earlier. If I went around telling people my
son is a homosapien, or if I referred to water as dihydrogen
oxide, it would be unusual and cause much
confusion, because a lot of people wouldn't even know what
it means. But that doesn change the fact that technically those
definitions and terminology are correct.

Also, Bud's argument asking to find a center tap transformer
manfacturer that calls their transformer two phase doesn't prove
anything. I could just as well ask to find a capacitor manufacturer
that
says their capacitor can generate a 90deg phase shift.





*A 3 phase source is 3 separately generated power supplies,
synchronised but out of phase by an equal amount (equal to the result
of deviding 360 degrees by the number of phases) Each phase can be
separated from the other - and stand alone - and with 3 phase can be
connected delta or wye.
*With 120/240 you COULD use 2 separate secondaries and connect them
either differetially or summarily (adding or subtracting) in *for
either 240 or 0 volts, or in parallel. If paralleled they can also be
connected back to front, so to speak, which is effectively a short
circuit. A case could perhaps be made for calling THIS setup a 2 phase
system, but that would still be stretching things.



This makes no sense at all. Why do I neeed 2 seperate secondaries?
You are getting all hung up on where the power comes from. The mere
presence of two voltage waveforms that are of different phases in a
circuit,
readily visible on an oscilloscope, is all that it takes to have two
phases
present.

Twayne wrote:
In ,
bud-- typed:
David Nebenzahl wrote:
On 1/18/2011 9:49 AM bud-- spake thus:

wrote:

...

Again: the output of a center-tapped transformer, whatever
its use, is in fact 2 distinct and separate phases. But
for some reason, it's not called that.

It's not called that because it is ONE phase coming from the powerco and is
split to make two 120Vac lines into the residence. Thus the proper term is
"split phase", not 2 phase. Although I hear 2 phase a lot, I know what
they'e talking about so it's NBD to me.

Wow, progress. You are right - "it's not called that."

It is not called that because it makes no sense.
Voltages clearly comes from a single-phase transformer.
The voltages of any secondary windings are locked into plus
or minus relationships.
The secondary is trivially understood with plus and minus
signs. Calculations use plus and minus signs (not "phases").
Where inductance and capacitance are involved phasor
analysis is used. A 120/240V service is characterized as
+120 and -120.
It is not called that because it has no practical
usefulness. (Except to cause confusion.)

Nah, it's just a bunch of egos here wanting to show how much they know and
hoping their guesses are right for the most part. This is a useless thread
with no useful information due to the interest in egoes rather than fact.
It's typical of this newsgroup for the last year or so in fact and does no
one any good. Post after post is filled with guesses and by gollies from
those who feel the need to confuse, not assist anyone.

HTH,

Twayne`


Perhaps like your "guesses and by gollies" about power factor correction
capacitors, using an oven neutral for a ground and class 2 power sources
which were confused and completely wrong.

This thread is excessively about semantics.

On Sat, 22 Jan 2011 08:54:39 -0800 (PST), wrote:

On Jan 18, 7:51Â*pm, wrote:
On Tue, 18 Jan 2011 13:26:24 -0800, David Nebenzahl





wrote:
On 1/18/2011 12:06 PM spake thus:

On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

Care to tell us how you figure that it's single phase? I'm
interested in hearing your reasoning.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

First of all, I give you points for a good example, a well-thought-out
reply and an A for effort here. But unfortunately, you're wrong. It's
pretty simple, really. Now let's see how well *I* do trying to explain why.

Using your example, if you did your experiment, everything would happen
just as you say it would. The 2 light bulbs connected between L1 and L2
would both light, and there would be no (or practically no) spark nor
change in their brightness if you connected and disconnected their
common connection to neutral. [1] So far, so good.

But your explanation is, well, wrong. Here's why:

L1 and L2 are, in fact, 180° out of phase, and therefore 2 separate
phases, with the neutral as the common between the two phases.

*IF* they werent'--IOW, if they were in phase, as you contend, then
there would be--could be--no current flow between them, ever. If they
were in phase, both L1 and L2 would be at their positive peak at the
same instant, at 0 volts at the same instant, and at their negative peak
at the same instant. Do you agree with this? (If this were the case,
then you could take 120 volts between either leg and neutral, but they
would be exactly in phase, so you couldn't do things like Edison
circuits, which depend on the two legs being 180° out of phase in order
to share the neutral, where the currents cancel because of the phase
difference.)

In order for there to be current flow between L1 and L2, one has to be
negative while the other is positive, and vice versa. With me here?

Now, if you just take L1 and L2 and forget about the neutral for a
second, then yes, that constitutes a single phase circuit of 240 volts
(nominal). No two phases there.

But if you consider L1, L2 *and* the neutral, then you definitely have
two phases, 180° apart. Consider the two sides (or phases) he one
goes from L1 to neutral, the other from L2 to neutral. Let's look at it
when L1 is at its positive peak; you have a positive potential between
L1 and neutral, right? At that same instant, L2 is at its negative peak,
so you have a *negative* potential between L2 and neutral. Am I not correct?

Â*It is semantics, to a point. What you need to remember is it is NOT 2
separate power sources, as a real 2 phase or 3 phase (or any other
multi-phase) system is. What you have is a single source power. It is
generated as 3 "separate"phases by the power company, and each phase
of the 3 phase supply can be split off as a single phase. This single
phase is then "split" by center tapping the secondary of a
transformer.
This is CRITICAL in the definition of single/split phase vs 2 phase
power.

It may be critical to the convention of what that 240V service is
commonly
called, but it doesn't alter the fact of how many distinct voltage
waveforms
are present. Going back to your example of the simple circuit with
two
balanced loads connected across the 240V hots, yes, in that case,
you have only one phase.
I cannot hook up an oscilloscope and see anything but one sine wave.
As soon as you introduce the neutral, now I can see TWO different sine
waves relative to the neutral, one being 180deg out of phase with the
other. That circuit can now be described as having two phases.

Suppose I take a black box that consists of various linear circuit
components
and is powered by a 120V AC outlet. Inside that box, I have a common
reference point.
I ask students in a first year electrical engineering course lab
experiment to
graph the voltages at circuit points A, B, and C relative to the
common
reference point. I have the circuit designed so that the waveform
at point B
lags the one at A by 30 degrees and the waveform at point C lags the
one at A
by 180 degrees. I ask thefollowing questions:

What is the phase relationship between waveforms A and B?

What is the phase realtionship between waveforms A and C?

How many different voltage phases are there in the black box
at points A, B, and C?

Do I need to know exactly how the voltages were generated, whether
it came from a wall outlet, battery/inverter, trnasformer etc to
answer any
of those questions?

What is your answer? Is it that there are 3 phases or is that there
can be only one, because it's originating from an outlet
that has only one phase?

If your answer is that there are 3 phases present, then continue to
the
next part. I have another black box that merely consists
of the 3 wire 240V service. The common reference
point is the neutral, point A is one hot, point B, the other hot.

What is the phase relationship between waveforms A and B?

How many phases are present?


Note the usual disclaimer. I did not just say, nor have I said
that the 240V service is commonly called two phase.

It's like I said earlier. If I went around telling people my
son is a homosapien, or if I referred to water as dihydrogen
oxide, it would be unusual and cause much
confusion, because a lot of people wouldn't even know what
it means. But that doesn change the fact that technically those
definitions and terminology are correct.

Also, Bud's argument asking to find a center tap transformer
manfacturer that calls their transformer two phase doesn't prove
anything. I could just as well ask to find a capacitor manufacturer
that
says their capacitor can generate a 90deg phase shift.





Â*A 3 phase source is 3 separately generated power supplies,
synchronised but out of phase by an equal amount (equal to the result
of deviding 360 degrees by the number of phases) Each phase can be
separated from the other - and stand alone - and with 3 phase can be
connected delta or wye.
Â*With 120/240 you COULD use 2 separate secondaries and connect them
either differetially or summarily (adding or subtracting) in Â*for
either 240 or 0 volts, or in parallel. If paralleled they can also be
connected back to front, so to speak, which is effectively a short
circuit. A case could perhaps be made for calling THIS setup a 2 phase
system, but that would still be stretching things.



This makes no sense at all. Why do I neeed 2 seperate secondaries?
You are getting all hung up on where the power comes from. The mere
presence of two voltage waveforms that are of different phases in a
circuit,
readily visible on an oscilloscope, is all that it takes to have two
phases
present.

Forget it.\People will believe what people will believe, and no amount
of explanation will get through.

On Jan 19, 1:32*pm, bud-- wrote:
David Nebenzahl wrote:
On 1/18/2011 9:49 AM bud-- spake thus:

wrote:

On Jan 17, 12:51 pm, bud-- wrote:

wrote:

I'm a degreed Electrical Engineer, and it isn't BS to me. *If you
take a signal centered around zero volts, and another one in the
same system that is also centered around zero volts, but
*is 180 deg out of phase and they share that common zero volt
referrence, then: One leads the other by 180deg One lags the other
by 180deg One is the opposite of the other One is the negative of
the other. You have two phases

Nobody I know would call 120/240 2-phase. You wouldn't buy a single
core transformer and specify whether it is in-phase or 180
degrees out of phase. You don't get multiple phases out of a single
transformer. If you ask for a 2-phase transformer you will
completely confuse the transformer rep.

Analysis of real multiphase electricity commonly uses phasor
analysis, using SQR(-1).

A simple 120/240V system is single phase with the math handled
with *trivial* plus and minus signs. "2-phases" confuses trivial
math.

Whether 2 phases confuses anyone or not has no bearing on the fact
that there are two phases. * I could describe many physical
processes by either very simple terms or varying degrees of
complexity. *When looking at electrical waveforms, that trivial
plus and minus sign can equate to being described as 180deg out of
phase.

I noticed you didn't specifically refute any of the statements:

One leads the other by 180deg One lags the other by 180deg One
is the opposite of the other One is the negative of the other. You
have two phases

When the "phases" come from a single phase source (the utility
transformer), and one of the "phases" is the negative of the other,
calling them 2 phases makes no particular sense.

When I connect my 120-to-120V isolation transformer (for repairing
equipment) to one of the "phases" is the secondary the "A" phase or
the "B" phase?

I guess I'd have to call that question a red herring.

It is a minor illustration that "2 phases" is not useful.

It makes no sense to say you get 2 phases out of what is obviously a
single-phase utility transformer.



In the case of a transformer such as you describe, presumably with no
center tap, then yes, there's only one phase. Only one set of conductors.

We're talking about something different: a center-tapped transformer,
such as the utility company uses to deliver what's typically called
"split-phase" power (i.e., 120-0-120).

There, you *do* have two phases.

*From the wikipedia articlehttp://en.wikipedia.org/wiki/Split_phase
"it is sometimes incorrectly referred to as 'two phase'."
(The article also suggests split phase is not the best name because of
confusion with split-phase motors - which do start on 2-phases. I have
never heard "split-phase" used for a 120/240V service.)

You can invent your own language. Where is any reasonable source that
says a single phase transformer has 2 phases.


How about this one:

http://www.allaboutcircuits.com/vol_2/chpt_9/4.html

"A pair of dots indicates like polarity.

Typically, the transformer will come with some kind of schematic
diagram labeling the wire leads for primary and secondary windings. On
the diagram will be a pair of dots similar to what is seen above.
Sometimes dots will be omitted, but when “H” and “X” labels are used
to label transformer winding wires, the subscript numbers are supposed
to represent winding polarity. The “1” wires (H1 and X1) represent
where the polarity-marking dots would normally be placed.

The similar placement of these dots next to the top ends of the
primary and secondary windings tells us that whatever instantaneous
voltage polarity seen across the primary winding will be the same as
that across the secondary winding. In other words, the phase shift
from primary to secondary will be zero degrees.

On the other hand, if the dots on each winding of the transformer do
not match up, the phase shift will be 180o between primary and
secondary, like this: (Figure below) "


Continue on in the above reference to the next section where the
transformer that has two secondary windings, and keep the above
discussion of phase in mind. They may not come right out and say it,
but clearly you can have transformer outputs that are out of phase
with each other, and hence, two distinct phases exist.

On Jan 22, 3:30*pm, wrote:
On Sat, 22 Jan 2011 08:54:39 -0800 (PST), wrote:
On Jan 18, 7:51*pm, wrote:
On Tue, 18 Jan 2011 13:26:24 -0800, David Nebenzahl

wrote:
On 1/18/2011 12:06 PM spake thus:

On Mon, 17 Jan 2011 22:14:37 -0800, David Nebenzahl
wrote:

Care to tell us how you figure that it's single phase? I'm
interested in hearing your reasoning.

OK, I'll take a crack at it. I'll attempt to keep it as simple as it
really is.

Go to your service pannel. Grab 2 100 watt incandescent bulbs and
connect them in series. Connect one end of the string to L1 (lets say
the red wire) and the other end of the string to L2 (lets say the
black wire). You now have a single phase 240 circuit.

Are you with me so far?
No dissagreement so far?

OK, now grab the white wire (common, neutral, transformer center tap)
and connect it to the junction between the two 100 watt bulbs.
Open and close the circuit bu connecting and disconnecting the white
wire. Put an ammeter on it if you like to see what is really
happening.

What do you see?
Is there ANY change to the behaviour of the circuit?
Do either of the lamps flicker when you connect and disconnect the
neutral?
Is there a spark on the white wire when you connect or disconnect it?
Does the ammeter show a current flow?
Have you made ANY change to the circuit by installing or removing the
neutral?
There is NO CHANGE - correct?
Are you still with me?

If there is no power flow on that third wire and you have not made any
measurable or noticeable change, what changes in the circuit to make
it a "2 phase" system?
Now you have my answer and my explanation.
There is NO CHANGE, so it is STILL a single phase system.
If you dissagree, I'd like you to explain it just as simply as I
explained my view.

First of all, I give you points for a good example, a well-thought-out
reply and an A for effort here. But unfortunately, you're wrong. It's
pretty simple, really. Now let's see how well *I* do trying to explain why.

Using your example, if you did your experiment, everything would happen
just as you say it would. The 2 light bulbs connected between L1 and L2
would both light, and there would be no (or practically no) spark nor
change in their brightness if you connected and disconnected their
common connection to neutral. [1] So far, so good.

But your explanation is, well, wrong. Here's why:

L1 and L2 are, in fact, 180° out of phase, and therefore 2 separate
phases, with the neutral as the common between the two phases.

*IF* they werent'--IOW, if they were in phase, as you contend, then
there would be--could be--no current flow between them, ever. If they
were in phase, both L1 and L2 would be at their positive peak at the
same instant, at 0 volts at the same instant, and at their negative peak
at the same instant. Do you agree with this? (If this were the case,
then you could take 120 volts between either leg and neutral, but they
would be exactly in phase, so you couldn't do things like Edison
circuits, which depend on the two legs being 180° out of phase in order
to share the neutral, where the currents cancel because of the phase
difference.)

In order for there to be current flow between L1 and L2, one has to be
negative while the other is positive, and vice versa. With me here?

Now, if you just take L1 and L2 and forget about the neutral for a
second, then yes, that constitutes a single phase circuit of 240 volts
(nominal). No two phases there.

But if you consider L1, L2 *and* the neutral, then you definitely have
two phases, 180° apart. Consider the two sides (or phases) he one
goes from L1 to neutral, the other from L2 to neutral. Let's look at it
when L1 is at its positive peak; you have a positive potential between
L1 and neutral, right? At that same instant, L2 is at its negative peak,
so you have a *negative* potential between L2 and neutral. Am I not correct?

*It is semantics, to a point. What you need to remember is it is NOT 2
separate power sources, as a real 2 phase or 3 phase (or any other
multi-phase) system is. What you have is a single source power. It is
generated as 3 "separate"phases by the power company, and each phase
of the 3 phase supply can be split off as a single phase. This single
phase is then "split" by center tapping the secondary of a
transformer.
This is CRITICAL in the definition of single/split phase vs 2 phase
power.

It may be critical to the convention of what that 240V service is
commonly
called, but it doesn't alter the fact of how many distinct voltage
waveforms
are present. * Going back to your example of the simple circuit with
two
balanced loads connected across the 240V hots, yes, in that case,
you have only *one phase.
I cannot hook up an oscilloscope and see anything but one sine wave.
As soon as you introduce the neutral, now I can see TWO different sine
waves relative to the neutral, one being 180deg out of phase with the
other. That circuit can now be described as having two phases.

Suppose I take a black box that consists of various linear circuit
components
and is powered by a 120V AC outlet. Inside that box, I have a common
reference point.
I ask students in a first year *electrical engineering course lab
experiment to
graph the voltages at circuit *points A, B, and C relative to the
common
reference point. * I have the circuit *designed so that the waveform
at point B
lags the one at A by 30 degrees and the waveform at point C lags the
one at A
by 180 degrees. *I ask thefollowing questions:

What is the phase relationship between waveforms A and B?

What is the phase realtionship between waveforms A and C?

How many different voltage phases are there in the black box
at points A, B, and C?

Do I need to know exactly how the voltages were generated, whether
it came from a wall outlet, battery/inverter, trnasformer etc to
answer any
of those questions?

What is your answer? *Is it that there are 3 phases or is that there
can be only one, because it's originating from an outlet
that has only one phase?

If your answer is that there are 3 phases present, then continue to
the
next part. * I have another black box that merely consists
of the 3 wire 240V service. * The common reference
point is the neutral, point A is one hot, point B, the other hot.

What is the phase relationship between waveforms A and B?

How many phases are present?

Note the usual disclaimer. *I did not just say, nor have I said
that the 240V service is commonly called two phase.

It's like I said earlier. * If I went around telling people my
son is a homosapien, or if I referred to water as dihydrogen
oxide, *it would be unusual and cause much
confusion, because a lot of people wouldn't even know what
it means. * But that doesn change the fact that technically those
definitions and terminology are correct.

Also, Bud's argument asking to find a center tap transformer
manfacturer that calls their transformer two phase doesn't prove
anything. * *I could just as well ask to find a capacitor manufacturer
that
says their capacitor can generate a 90deg phase shift.

*A 3 phase source is 3 separately generated power supplies,
synchronised but out of phase by an equal amount (equal to the result
of deviding 360 degrees by the number of phases) Each phase can be
separated from the other - and stand alone - and with 3 phase can be
connected delta or wye.
*With 120/240 you COULD use 2 separate secondaries and connect them
either differetially or summarily (adding or subtracting) in *for
either 240 or 0 volts, or in parallel. If paralleled they can also be
connected back to front, so to speak, which is effectively a short
circuit. A case could perhaps be made for calling THIS setup a 2 phase
system, but that would still be stretching things.

This makes no sense at all. * Why do I neeed 2 seperate secondaries?
You are getting all hung up on where the power comes from. *The mere
presence of two voltage waveforms that are of different phases in a
circuit,
readily visible on an oscilloscope, is all that it takes to have two
phases
present.

Forget it.\People will believe what people will believe, and no amount
of explanation will get through.- Hide quoted text -

- Show quoted text -

In other words, you won't answer a few basic, straightforward
questions about phase that go directly to the core of the discussion,
because to
do so is impossible without contradicting yourself. I think those of
us on the
other side of this have answered and addressed all your questions/
issues
with no problem.