Posted by *amdx* on April 3, 2010, 2:59 am

*> amdx wrote:*

*> > I think all our difference with mike boils down to the reference point*

and

*> > maybe some semantics. I kinda gave up on the argument.*

*> I don't feel semantics have place in battery, or AC polarity*

*> terminology. We're not discussing poetry or interpretation of prose.*

*> Either the terms are correct or not. It's not open to 'feelings'.*

*> I'll give this one more shot before dropping the topic.*

I'll give it my best shot.

I'll define the system 240v, 2 wires, no neutral. let me know if that is a

problem.

We'll start with your scenario as below.

>> If it were single phase connection of two 120 volt legs, the voltage

would

*>> be 240. In a single phase setup, both currents are at the same electrical*

*>> angle, so they add directly, 120 + 120 = 240.*

We'll start with a sinewave at 0 degrees and 0 Volts. Both wires, since they

are in phase.

As the sinewave starts to rise and gets to 30 degrees the voltage is 147

volts,

at 60 degrees the voltage has reached 260 volts and then at 90 degrees, 294

volts.

Now lets get out the oscilloscope, one lead on each wire, at 30 degrees the

voltage on

Line 1 has reached 85 volts and the voltage on Line 2 has reached 85 volts

also, because they're in phase

So the oscilloscope measures the potential difference between L1 and L2 and

gets 0 volts.

This continues through the whole cycle, since the are in phase there is no

potential difference.

If they are in phase, how can there be any potential difference to do work.

*If they are out of phase the real question is, at 30 degrees, does L1 go

negative 42.5 volts and

L2 go positive 42.5 volts. :-)

Mike (amdx)

*Depends on the reference point.

Posted by *amdx* on April 3, 2010, 3:37 am

*> > amdx wrote:*

*> >*

*> > > I think all our difference with mike boils down to the reference point*

*> and*

*> > > maybe some semantics. I kinda gave up on the argument.*

*> >*

*> >*

*> > I don't feel semantics have place in battery, or AC polarity*

*> > terminology. We're not discussing poetry or interpretation of prose.*

*> > Either the terms are correct or not. It's not open to 'feelings'.*

*> >*

*> > I'll give this one more shot before dropping the topic.*

*> >*

*> I'll give it my best shot.*

snip

See third graph and description.

http://www.nojolt.com/three_phase_and_single_phase_electric.shtml

See either drawing.

http://www.electricalknowledge.com/forum/archives/454.asp

See first graph and description

http://www.esubnet.com/fragment-electricity-primer.html

Mike (amdx)

Posted by *amdx* on April 6, 2010, 9:26 pm

*> > > I'll give this one more shot before dropping the topic.*

*> > >*

*> > I'll give it my best shot.*

mike

Where did ya go?

Was my argument persausive or did you just give up trying to

persaude me.

Mike (amdx)

Posted by *Josepi* on April 7, 2010, 4:08 am

Embarrased.

*> > > I'll give this one more shot before dropping the topic.*

*> > >*

*> > I'll give it my best shot.*

mike

Where did ya go?

Was my argument persausive or did you just give up trying to

persaude me.

Mike (amdx)

Posted by *m II* on April 7, 2010, 7:19 am

amdx wrote:

*> Where did ya go?*

*> Was my argument persausive or did you just give up trying to*

*> persaude me.*

This could go on forever, but it won't. This is really my last posting

on this topic.

Take a transformer secondary.

It makes 240 volts.

It has only ONE current flow in it.

Put a tap in the winding at exactly the mid point.

Measure the voltage in each half, moving the meter leads up in unison.

Both readings are identical and at the same phase angle.

Putting a centre tap on that winding has NOT reversed the current in

half the winding. The current is still the same as it was, at the SAME

angle all the way through the winding.

You are making things harder than they are. (-120 volts at 180 degrees)

***IS*** (120 volts at ZERO degrees). They are one and the same, now and

forever.

This is KEY:

******Any *two* wires in a single OR three phase circuit constitute a

SINGLE phase circuit. They have to. It's the LAW. Call your local

University. If you don't like their answer, Call God.******

Next, 208 volts phase to phase, in a three phase circuit, is obtained by

the result of 120 volts at zero degrees and 120 volts at 120 degrees.

There is 120 degrees between the rms peaks of the sine waves.

Try it. Break down the voltage to it's rectangular components.

120 volts at zero degrees equals 120 v + j 0

120 volts at 120 degrees equals 120 * (cos 120) +j 120 * sin 120 =

(-60 volts + j 103.92)

So, we have:

(120 + j 0)

-(-60 + j 103.92)

----------------

180+ j 103.92 Which is the resultant of the two vectors at 120 degrees

apart.

Now, re-convert back to polar notation. Pythagoras comes in handy.

180^2 + 103.92^2 = 43009

square root of 14399.36 = 208 volts.

Note that when the sine waves are the same peak value, 120 degrees

apart, multiplying the 120 line voltage by the square root of 3 also

gives you the 208 phase voltage

The newer 347 line voltage gives you 600 phase voltage. That voltage is

getting more popular for high rise building distributions. They now put

various small transformers in to feed office area 120 V needs.

In a Delta connection, the line voltage IS phase voltage and the root 3

is used to find current instead of voltage.

In a Delta connection, line current is root 3 times phase current.

Back to single phase. The centre tapped wire (neutral) in a three wire

system is NOT grounded because it's at zero potential. It is grounded

there in order to limit the maximum fault voltage to ground at the LINE

sides.

That screws up a lot of people. They mistakenly believe in erroneous and

quite fictitious, non existent, phase angles.

The only phase angles that exist in single phase system are caused by

lagging or leading power factors and show the relationship between

voltage and current.

Wake up, people...it's called single phase for a reason. Two phase and

three phase systems are birds of a completely different colour. Do your

homework.

mike

> amdx wrote:> > I think all our difference with mike boils down to the reference pointand

> > maybe some semantics. I kinda gave up on the argument.> I don't feel semantics have place in battery, or AC polarity> terminology. We're not discussing poetry or interpretation of prose.> Either the terms are correct or not. It's not open to 'feelings'.> I'll give this one more shot before dropping the topic.