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

[jumper]

??? Typo? Did you mean resistance instead of current. I agree that 'negligible' and 'near zero' are synonymous.



First, to the extent that the loads are balanced and cancel out current on the neutral, the current flows in exactly the path you describe. [EDIT: Not exactly the path you describe. Current travels from L1 to L2 without traveling at all on the shared neutral, other than at the node where it connects to the load neutrals.]

Second, the impedance of the neutral conductor is never actually zero. However negligible it is, it's enough to force some tiny amount of current to 'go the other way' and return through the L2 load conductor, and coil, just as you say. If the neutral develops a non negligible resistance then the change in current (and voltage!) on the other leg won't be non-negligible either. That's when it really will start to behave like a series circuit. But conversely, since the neutral impedance never entirely goes away, the series circuit behavior never entirely goes away either.

...

I fear this part of the discussion is a tangent. I believe it came up because buffalo tried to use 'series' to argue about 'phase'. That strikes me as a semantic game that I don't have a personal stake in. However, we should all be able to acknowledge that current can and sometimes will travel from L1 through a load, to the shared neutral node, and then through a load to L2 and back to the source, without traveling on the neutral. Using 'series' to describe that behavior seems reasonable enough to me.

No problem here.:thumbsup:

 

[jumper]

I know you know. It is just the series result would be an extreme exception as long as the tie to N is good. But I would agree it can happen.

Yep,ideal conditions, that was shown in the tutorial.

 

[jaggedben]

Does the load not effect the primary voltage in any way?[ /quote]Of course.

Yep.

Sorry, but please clarify.
Of course it does affect it? Or of course it does not?

 

[mivey]

I'll agree on that narrow point. What I liked about K8MHZ's post was that he seemed to come up with a method to measure the relative direction of the electromagnetic field that was objective, not relying on nomenclature. Consider the two points of the compass needles that point towards the Arctic when under the influence of Earth's magnetic field, and use that to define their direction. Now place those compass needles next to the source coils, one each. Do they point the same direction, or not? It would be nice to know if everyone on this thread can agree. Might help us nail down the 'basics' per jumper.

Btw it occurred to me that a CT meter amounts to much the same thing. There's a right way and a wrong way to set it up.

See my post about doing the same with a 120/208 system. The compass is then in conflict with what is proposed with a 120/240 system. Can't accept it in one case and deny it in another.

However, if you accept it as a guide, it does prove that the 120/240 system has a phase displacement like a 120/208 system has a phase displacement.

Sauce for the goose... If you can go against a compass for 120/208 then you can go against a compass for 120/240.

However, the compass has little to do with phase displacement anyway.

 

[mivey]

Sorry, but please clarify.
Of course it does affect it? Or of course it does not?

The load does affect the primary.

Kick on a heavy load and you will definitely see a portable generator react. A utility power system also reacts but to a lesser degree because it is usually relatively stiff. Usually.

add: I think he may have been making the point that you can have significant drop in one winding but not the other so they won't necessarily sum to zero, i.e. they are more than just copies of each other.

 

[jumper]

See my post about doing the same with a 120/208 system. The compass is then in conflict with what is proposed with a 120/240 system. Can't accept it in one case and deny it in another.

However, if you accept it as a guide, it does prove that the 120/240 system has a phase displacement like a 120/208 system has a phase displacement.

Sauce for the goose... If you can go against a compass for 120/208 then you can go against a compass for 120/240.

However, the compass has little to do with phase displacement anyway.

I posted graphs earlier showing both wave forms of the two systems. Clearly shows the same methodology employed. Got plenty of other pics to back it up also.

I am perfectly willing to be reasonable and see the difference in perspectives according to which reference we pick.

But the inconsistency/incorrect use of terms employed is really starting to irk me. Not you of course, I am just ranting before I go to the trenches. This is basic tranny analysis.

 

[mivey]

I posted graphs earlier showing both wave forms of the two systems. Clearly shows the same methodology employed. Got plenty of other pics to back it up also.

I am perfectly willing to be reasonable and see the difference in perspectives according to which reference we pick.

But the inconsistency/incorrect use of terms employed is really starting to irk me. Not you of course, I am just ranting before I go to the trenches. This is basic tranny analysis.

It is fascinating to me that such a simple thing as how voltage is defined is somehow brushed aside, forgotten, or something else. Truely fascinating. We have a lot of sharp folks here and that adds to the intrigue. It is an interesting study in how people react to information.

The basics of how a voltage difference is defined is covered precisely in any good physics text. You must pick a reference and no reference is any more valid than another. The physics work either way because that is simply how it works.

This stuff where voltage references are defined by some physical orientation is baseless. And where it really gets weird is the adamant stance that it must be so in one case by those who allow it to be different in another case. Such contradition but it goes by evidently unaware.

Inconsistent, like you said.

 

[jumper]

It is fascinating to me that such a simple thing as how voltage is defined is somehow brushed aside, forgotten, or something else. Truely fascinating. We have a lot of sharp folks here and that adds to the intrigue. It is an interesting study in how people react to information.

The basics of how a voltage difference is defined is covered precisely in any good physics text. You must pick a reference and no reference is any more valid than another. The physics work either way because that is simply how it works.

This stuff where voltage references are defined by some physical orientation is baseless. And where it really gets weird is the adamant stance that it must be so in one case by those who allow it to be different in another case. Such contradition but it goes by evidently unaware.

Inconsistent, like you said.

Yep.

And the darn terminology. And reading graphs out of context. And using non standard terms out of context. And using reference points for the scope as actual polarity of an AC signal. And using terms like additive for the secondary windings instead of series and parallel, additive and subtractive are used for polarity test of the primary and secondary! And saying center tap secondary when it is not! It is a multiwinding secondary! And split phase, anti phase, or two hemi phases are not NEC or IEEE defined systems. It is Single Phase!

And...I need to chill...

I feel better now.

 

[jwelectric]

On a discussion forum such as this one we have people with six years of math schooling trying to explain physics to a high school dropout.

If we take a two “D” cell flash light and connect a scope to it tapping the center of the two batteries we will see to voltages 180 degrees out of phase with each other but as we look at the batteries it is clear they are in series.

What if anything changes when we connect this same scope to a center tapped transformer? The numbers is all that changes

 

[GoldDigger]

Her we go again. It is not possible to have two DC sources "out of phase."

Sent from my XT1585 using Tapatalk

 

[jwelectric]

Her we go again. It is not possible to have two DC sources "out of phase."

Sent from my XT1585 using Tapatalk

you are correct but what will we see on the scope

 

[Besoeker]

If we take a two “D” cell flash light and connect a scope to it tapping the center of the two batteries we will see to voltages 180 degrees out of phase with each other but as we look at the batteries it is clear they are in series.

The topic is AC. The term "phase " doesn't apply to DC.

 

[jumper]

you are correct but what will we see on the scope

Mike we are beyond the battery analogy here.

It has its time and place, but pretty sure everyone in this rodeo/thread is past that.

All AC here.

 

[drktmplr12]

??? Typo? Did you mean resistance instead of current. I agree that 'negligible' and 'near zero' are synonymous.

i did mean resistance

First, to the extent that the loads are balanced and cancel out current on the neutral, the current flows in exactly the path you describe. [EDIT: Not exactly the path you describe. Current travels from L1 to L2 without traveling at all on the shared neutral, other than at the node where it connects to the load neutrals.]

Second, the impedance of the neutral conductor is never actually zero. However negligible it is, it's enough to force some tiny amount of current to 'go the other way' and return through the L2 load conductor, and coil, just as you say. If the neutral develops a non negligible resistance then the change in current (and voltage!) on the other leg won't be non-negligible either. That's when it really will start to behave like a series circuit. But conversely, since the neutral impedance never entirely goes away, the series circuit behavior never entirely goes away either.

i gave it some additional thought and will concede that for balanced loads it behaves like a series circuit and the current travels as I said it did not: from L1 through the load, to the neutral bar, trough L2 load, back to L2 without ever travelling on the shared neutral. the shared neutral will only supply or sink current to compensate for any imbalance in load.

I fear this part of the discussion is a tangent. I believe it came up because buffalo tried to use 'series' to argue about 'phase'. That strikes me as a semantic game that I don't have a personal stake in. However, we should all be able to acknowledge that current can and sometimes will travel from L1 through a load, to the shared neutral node, and then through a load to L2 and back to the source, without traveling on the neutral. Using 'series' to describe that behavior seems reasonable enough to me.

agreed.

 

[jumper]

Ideal series load.

Even some math.

Doesn’t change a thing.

 

[ggunn]

It was just a reference to vectors, phase angle, restive vs inductive and capacitive loads, phase shift, and more math with complex numbers. Really do not need to go there right now in my opinion.

ELI and ICE are acronyms.

“Remembering the phase difference

The mnemonic "ELI the ICE man" can be helpful in keeping track of the phase between the voltage and current in an AC circuit.

In a circuit with only an inductor and an AC power source, there is a 90o phase difference between the current and voltage - the voltage leads the current by 90o. This is the ELI part...with an inductor (L), the emf (E) is ahead of the current (I).

In a circuit with only a capacitor and an AC power source, there is also a 90o phase difference between the current and voltage - the voltage lags the current in this case. This is the ICE part...with an capacitor (C), the voltage emf (E) is behind the current (I).”

Of course, if you can remember that you cannot instantaneously change the voltage across a capacitor or the current through an inductor you don't need the mnemonic.

 

[ggunn]

The topic is AC. The term "phase " doesn't apply to DC.

Of course it does. DC is nothing more than very slow AC.

 

[ggunn]

@jaggedben: I fear this part of the discussion is a tangent.

Are you kidding? This whole discussion is a tangent!

 

[wwhitney]

Well they are not dependent then because they will practically never be exactly the same like you are thinking.

Certainly their idealizations are dependent. As to the actual waveforms in practice, they will deviate from any of the idealizations in this thread.

Cheers, Wayne

 

[Besoeker]

Ideal series load.

Even some math.

Doesn’t change a thing.

Interesting........