May I ask a question about the single vs two phase stuff

[Ingenieur]

I wonder if i'm too old to go back to school now..... ~RJ~

never too old
got my grad degree at 55
classmates 1/2 my age

 

[Ingenieur]

Doesn't matter; one core, one phase.

Show me a three-phase transformer where all coils share one core leg.

wrong
3 phase are wound on a common core

 

[Ingenieur]

But which one can be shown instantaneously and which one requires the time factor? For 3ph, yes, there are three separate waves, but 1ph has only one, not two.

120/240/1 has 2 waveforms
1/0
1/180

can't believe that can't be grasped by many

 

[Ingenieur]

No and yes.

It's not grounded for the purpose of measuring from. I've never seen a rule that one test probe must be connected to the grounded conductor. I place my solenoid tester's probes to various points when troubleshooting.

it was rhetorical
that is why we ground it, and also to provide a gf earth return path for situations where the egc is not in the path and a true earth gf occurs

 

[jumper]

never too old
got my grad degree at 55
classmates 1/2 my age

I did not even start college till I was 34.

 

[Ingenieur]

Sure it is! That's more accurate than throwing in a "wait a half cycle and check it again."

no it is not
by any objective and quantifiable measure

 

[Ingenieur]

Because it isn't. It's one waveform that you're dividing into two of half the voltage by arbitrarily tapping the source in the center.

It's no different than using two 6v batteries in place of one 12v battery, and choosing to place a voltmeter probe on the jumper.

Now, if you choose, using the battery example with a meter probe on the jumper, to call that two sources at 180 degrees apart, I will still disagree, but I will also see your point.

dividing into 2, creating 2 phases at 0 and 180 deg :happyyes:

 

[Ingenieur]

Because it isn't. It's one waveform that you're dividing into two of half the voltage by arbitrarily tapping the source in the center.

It's no different than using two 6v batteries in place of one 12v battery, and choosing to place a voltmeter probe on the jumper.

Now, if you choose, using the battery example with a meter probe on the jumper, to call that two sources at 180 degrees apart, I will still disagree, but I will also see your point.

wrong
the DC example is not applicable
it is 2 waveforms, 0 and 180 degrees, call it opposite polarity if you like, but that is a consequence of the wave being 180 deg out of phase, not a '-1'

 

[GoldDigger]

And why is this a problem? It is a sine wave signal so of course it has a magnitude. No?

I have no problem with that. Just with the statement that the inverse waveform of a 120V L1-N supply cannot be the negative of the first because we also call it 120V and not -120V.

Sent from my XT1585 using Tapatalk

 

[jumper]

120/240/1 has 2 waveforms
1/0
1/180

The 120/240V 1P service is built by the two signals generated from the tranny set up,
however I still get 3 wave forms out of it. Had to that in.

But, I agree. 2 waveforms.

 

[jumper]

I have no problem with that. Just with the statement that the inverse waveform of a 120V L1-N supply cannot be the negative of the first because we also call it 120V and not -120V.

Sent from my XT1585 using Tapatalk

Got it. Thanks.

 

[jaggedben]

wrong
the DC example is not applicable
it is 2 waveforms, 0 and 180 degrees, call it opposite polarity if you like, but that is a consequence of the wave being 180 deg out of phase, not a '-1'

What's the difference? Also, we are using mathematical expressions to approximate what we see in the world. The voltages are not a 'consequence' of the math at this level of physics. It's the other way around.

I still don't think I received adequate responses to my post 241.

 

[jumper]

What's the difference? Also, we are using mathematical expressions to approximate what we see in the world. The voltages are not a 'consequence' of the math at this level of physics. It's the other way around.

I still don't think I received adequate responses to my post 241.

The difference is that at this point the discussion has moved beyond the battery analogy.

I actually use his exact post for a teaching tool.

But at this point the problem always goes back to this part of post 241 and the way we build it, measure it(pick a reference), and name it.

“It's been pointed out that in the physical world there are multiple ways to derive a 120/240V AC source with a waveform(s) resembling a sign wave.”

In short, same muddled mess as always and we have not even gotten into looking at the tranny from the primary windings perspective and the secondary noodle in power analysis.......

 

[LarryFine]

wrong
3 phase are wound on a common core

Yes, but each phase is on its own core leg:

 

[LarryFine]

120/240/1 has 2 waveforms
1/0
1/180

can't believe that can't be grasped by many

I certainly can grasp it, I just disagree.

 

[LarryFine]

it was rhetorical
that is why we ground it, and also to provide a gf earth return path for situations where the egc is not in the path and a true earth gf occurs

The choice to earth the neutral and the choice to measure from only it are two different things.

 

[LarryFine]

dividing into 2, creating 2 phases at 0 and 180 deg :happyyes:

To me, if it was two phases, it would be two regardless of the reference point.

 

[jaggedben]

To me, if it was two phases, it would be two regardless of the reference point.

:thumbsup:

 

[jaggedben]

120/240/1 can be viewed as 2 waveforms
1/0
1/180

can't believe that can't be grasped by many

FIFY

 

[jaggedben]

The difference is that at this point the discussion has moved beyond the battery analogy.

...

We're not relying on the battery analogy when stating that if voltage L1-N can be derived from sin(x) then voltage L2-N can be derived from -sin(x).